Trans-scale crystal dynamics for controlling kinetic responses in organic molecular systems

Domain: physics
Published: 2025-11-26
Editorial outcome: major_revision

Abstract
The origin and control of material dynamics are fundamental to understanding functional systems from molecular assemblies to engineered devices. The ability to actively control and directly visualize rapid chemical and structural changes in a single crystal remains a major challenge in solid-state chemistry, limiting our understanding of dynamic functions in molecular materials. Here, we report an anthracene-based molecular crystal platform that enables dual physical control of solid-state [4+4] photocycloaddition through temperature and light. Chemically engineered 1,8-bis(pentafluorophenyl)anthracene single crystals construct photoactive face-to-face π-stacks, allowing the reaction to be induced by visible-light irradiation. The crystals exhibit thermally switchable on/off reaction states controlled by the accumulation of lattice strain accelerated by heating. Furthermore, we observe the reaction and dynamics under various light sources, including UV, white LED, laser, and sunlight, demonstrating dual controllability by heat and light. Importantly, weak light irradiation with an LED enables direct observation of intermediate states in the single crystal, revealing a correlation between lattice strain and photoconversion rate. On these bases, we identify that the reaction kinetics depend on the light propagation direction and the relative orientation of the molecular transition dipole moment, providing a new parameter for directional photodynamic control. This trans-scale approach, integrating chemical molecular packing design, photo-thermal science, and anisotropic parameters, establishes a general strategy for tunable and observable crystal dynamics.

Introduction
The dynamics of life and matter arise from amplified cooperative and macro-scale crystalline structures via anisotropic packing with structural changes across molecular to aggregate scales, manifesting translational symmetry. Molecular-level physical responses are as density shifts, expansion, and contraction. Such systems enable thereby translated into macroscopic dynamics through rapid and the development of actuators, sensors, and manipulators that con- anisotropic volume changes. Therefore, photoresponsive molecular vert various forms of energy into controlled dynamics. Designing these crystals enable diverse operations through optical remote control. In this field, nanoscale photochemical reactions in crystals—such as artificial life systems requires interdisciplinary materials science and E–Z isomerization, intramolecular cycloaddition, and inter- physics approaches, incorporating trans-scale concepts that bridge molecular cycloaddition—have been widely demonstrated. the nano, meso, micro, and macro scales. Organic molecules, as Understanding the dynamics of these reactions is fundamental to fundamental units of material functionality, self-assemble into meso- elucidating the behavior of both living and artificial materials. However, crystal dynamics remain largely uncontrolled due to insufficient validation of ON/OFF switching based on molecular arrangement tunability and physical response factors, as well as the lack of direct observation of dynamic processes across nano-, meso-, and macro- scales—even though crystals are fully characterizable in terms of molecular structure, arrangement, orientation, and macroscopic shape. Thus, exploring trans-scale crystal dynamics not only satisfies academic curiosity but also drives progress toward the development of materials with finely controlled kinetic response systems. Here, we report trans-scale crystal dynamics for the interdisciplinary control of kinetic responses by chemically and physically designing the anthracene molecular arrangement within a single crystal. By utilizing the physical quantity of temperature and irradiated light to control dynamic response time, we have successfully interpreted the dynamic process through the gradual changes in the crystal structure. Building on these results, we have discovered a method for frequency based on the efficiency of the interaction between the electric field of light and the anisotropic molecular orientation within the crystal lattice.

Results
Chemical approaches for crystal dynamics
The importance of controlling crystal dynamics through photoactivation lies in the ability to construct reactive molecular assemblies that offer high reproducibility, along with a phase transition system that enables direct observation of dynamic processes. The [4+4] photocycloaddition of anthracene represents an ideal molecular system, wherein ON–OFF structural changes can be chemically and strategically induced by modifying the substituents. To achieve a photoinduced single-crystal-to-single-crystal phase transition in anthracene derivatives, precise control over bimolecular aggregation and crystal packing is essential. We targeted a face-to-face anthracene arrangement—favorable for photodimerization—by introducing substituents at the 1,8-positions along the short axis. The minimum face-to-face π-stacked structure required for the ON reaction has been identified based on data from the crystal structure database, previous literature, and our own study using molecular electrostatic potential maps. Electron-donating and electron-withdrawing groups were selected to tune intermolecular interactions, thereby steering the packing toward either face-to-face or edge-to-face conformations. 1,8-Bis(perfluorophenyl)anthracene (1) was prepared by direct arylation (75% yield), while 1,8-bis(4-fluorophenyl)anthracene (2), 1,8-bisphenylanthracene (3), 1,8-bis(4-methylphenyl)anthracene (4), and 1,8-bis(4-methoxyphenyl)anthracene (5) were synthesized by Suzuki–Miyaura cross-coupling (58–98% yields). Vapor diffusion or solvent evaporation afforded single crystals (1_CCDC:2456683, 2_CCDC:2456863, 3a_CCDC:2456867, 3b_CCDC:2456866, 4_CCDC:2456864, and 5_CCDC:2456865). Depending on the choice of electron-donating and electron-withdrawing groups, 1,8-diarylanthracene adopts either an ON (face-to-face) or OFF (edge-to-face) stacking structure in crystal.

1,8-Bis(pentafluorophenyl)anthracene (1) (Fig. 2a), which promotes selective face-to-face stacking through the introduction of electron-withdrawing groups and exhibits a characteristic optical absorption band, demonstrates ON behavior in crystal dynamics upon visible light irradiation. At 303 K, the centroid–centroid distances between the anthracene units in Unit 1 and Unit 2 are 3.818 and 4.667 Å, with corresponding overlap ratios of 41% and 33%, respectively. Notably, the centroid–centroid distance in Unit 1 is less than 4.2 Å, satisfying Schmidt’s criterion for [4+4] photocycloaddition. These results demonstrate that photodimerization occurs selectively at the Unit 1 site within a single crystal upon light irradiation. The resulting photodimer (1_PD) forms specifically at this position. Although the 1_PD crystals retain the original space group P2₁/c, Raman spectroscopy reveals changes in intra- and intermolecular vibrational modes, indicating modifications to both the chemical structure and crystal lattice. A Raman-active intramolecular vibrational mode at 329 cm⁻¹ was observed, arising from the C–C single bond formed through photodimerization. Furthermore, we demonstrate that the reverse transformation from crystalline 1_PD to crystalline 1 is feasible. This reversal was achieved by flash vacuum pyrolysis, in which specific molecular bonds are cleaved by a momentary high-temperature treatment. The results of this reverse reaction were also confirmed by NMR and single crystal structure analysis. These findings indicate that crystal dynamics can be reversibly controlled by the combined use of light and heat. These findings provide direct evidence for previously unobserved trans-scale crystal dynamics, governed by light-induced structural switching and kinetic control.

Thermal control of crystal dynamics
As crystal dynamics arise from the release of lattice strain accumulated during dimerization, thermal expansion or contraction of the unit cell induces the buildup of such strain. To investigate this, we performed variable-temperature single-crystal X-ray diffraction of crystal 1 from 103 to 303 K, evaluating atomic displacement parameters (U_eq) and crystallographic thermal expansion. With increasing temperature, two key changes were observed: (1) U_eq values of C9 and C10—atoms directly involved in anthracene photodimerization—increased, and (2) the reaction gap widened due to increased intermolecular distances (d_centroid-centroid, d_π-π, d_parallel) between Units 1 and 2. Expansion of the gap between π-stacks also induced anisotropic thermal expansion along the crystallographic c-axis and a reduction in the β angle. The temperature dependence of the photoreaction under white LED irradiation reveals that the crystal undergoes anisotropic deformation of the unit lattice as the temperature increases. It shows an “OFF: dormant state” between 103 and 203 K, during which no reaction occurs over 360 s, while a “ON: photoactive state” is observed between 253 and 353 K. Interestingly, the response time decreases with increasing temperature. Notably, under these conditions, crystal dynamics can be controlled in an ON–OFF manner by using temperature as a secondary physical parameter.

Optical control of crystal dynamics
The response time can also be modulated by photophysical parameters such as light intensity and wavelength. In contrast to white LED irradiation at room temperature (298 ± 5 K), UV light irradiation caused severe crystal collapse, including jumping, fragmentation, explosion, splintering, cracking, and splitting. Simultaneously, the emission color shifted from green to blue with increasing light exposure time. Single crystal X-ray structural analysis confirmed that the crystal obtained by UV irradiation (CCDC: 2483421) was structurally and chemically identical to the final product obtained by white LED irradiation, 1_PD. Similar behavior was observed under blue laser or sunlight exposure, though the response speed varied depending on the light source. Historically, the [4+4] photocycloaddition in crystals was proposed to require reactive sites to be within 4.2 Å of each other, and this was verified using UV light. Whereas crystal dynamics were previously accessible essentially under UV light, the discovery of systems responsive to visible light has enabled a more hierarchical and detailed understanding of photoinduced single-crystal-to-single-crystal phase transition-based dynamic processes. This UV-visible-driven dynamic crystal may exhibit varying phase transition ratios depending on the light wavelength. Powder X-ray diffraction measurements under UV irradiation at room temperature revealed that the diffraction intensity of the {020} reflection of crystalline 1 gradually disappeared with increasing irradiation time. This observation indicates a structural transition from crystalline 1 to crystalline 1_PD under UV irradiation. The {020} reflection from crystal 1 completely disappeared within approximately 210 s, demonstrating the quantitative transformation to crystal 1_PD. Under white LED irradiation, however, the phase transition (conversion) rate reached only about 50% within a comparable irradiation time. This difference arises from the higher absorption coefficient of UV light relative to visible light, confirming that the phase transition rate depends on the wavelength of the incident light. The absorption edge of one crystal, calculated from the fluorescence excitation spectrum, was found to be 470 nm, indicating a clear response to visible light.

Observation of intermediate states
While the mechanism of crystal dynamics was previously inferred by comparing crystal structures before and after the reaction, the stepwise photoreaction of the crystal, induced by white LED irradiation (a weak excitation light source) at room temperature, allows for direct observation of intermediate states, providing insights into the mechanism. The state corresponds to a mixed crystal 1·1_PD (x, y) with a nonstoichiometric composition, where crystals 1 and 1_PD coexist. The lattice parameter decreased linearly with increasing conversion ratio y. As unit 1 is progressively replaced by 1_PD, Vegard’s law predicts values of y as 0.87 and 0.92 at 480 and 540 s, respectively, based on the lattice constant a. The kinetics evaluated by the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation were determined to be k = 3.5 × 10⁻³ s⁻¹ and n = 1.3. Since n > 1, it was shown that 1_PD formed in the crystal acts as an autocatalyst for unreacted Unit 1. Photoinduced crystal dynamics based on the process of releasing the lattice strain stored by the photoproduct to the outside reveal the correlation between the conversion ratio of the intermediate state and the lattice strain (Δa/a_0, Δb/b_0, Δc/c_0) and the change in the lattice constants (Δa, Δb, Δc), leading to their control. While Δb/b_0 and Δc/c_0 change very little with increasing y, Δa/a_0 decreases significantly with increasing y, indicating that lattice strain accumulates in the crystallographic a-axis direction as the photoreaction progresses. At this constant temperature, photoinduced lattice deformation reduces the β angle like the heating process. The identification of this correlation between the conversion ratio and lattice strain supports the mechanism by which thermally controlled ON/OFF crystal dynamics and response speed are driven by the promotion of lattice strain storage as the temperature increases.

Directional photodynamic control in crystal
The origin of this dynamic process suggests that the orientational light absorption efficiency of the higher-order structure controls the reaction probability. The crystal structure reveals that the transition dipole moment (μ), which correlates with the absorption coefficient (allowed transition), is oriented along the short axis of anthracene for both Unit 1 and Unit 2. Thus, μ is oriented along the crystallographic b-axis. Because the interaction between μ and the incident electric field depends on their relative orientation, the optical absorption of the crystal is inherently anisotropic. This orientation of μ induces anisotropic optical absorption, as the efficiency of the interaction between the electric field and μ varies with the relative alignment (parallel or perpendicular) between the polarization of the incident light and μ. Light irradiation along the [010] direction results in isotropic light absorption, as the polarized light propagating in this direction is perpendicular to μ. In contrast, light irradiation along the [001] direction leads to anisotropic light absorption, as the polarized light in this direction is parallel to μ. To further explore the anisotropic nature of the reaction, we investigated the effect of light polarization on the [001] and [010] crystal planes using a white LED. Along the [010] direction, no color was observed regardless of the polarization angle, indicating isotropic light absorption for this orientation. In contrast, the [001] direction exhibited coloration at polarization angles of 0° and 180°, whereas no color appeared between 50° and 130°. These results qualitatively demonstrate anisotropic light absorption along the [001] direction, and the observed polarization dependence is consistent with the theoretically predicted orientation of μ. The photoreactive frequency factor and response time exhibit different dynamic behaviors depending on the crystal plane direction of light irradiation, due to the anisotropic molecular orientation and alignment of the molecular crystals. The frequency and response time of white LED irradiation on each plane of a single crystal were 39% of the total in the [001] direction, while they were 90% of the total in the [010] direction. These results statistically show that the [010] direction has a higher probability of occurrence than the [001] direction. The response times for the [001] direction ranged from 30 to 176 s, with a mean of 94 ± 35 s (mean ± SD, n = 90). In contrast, the response times for the [010] direction ranged from 5 to 121 s, with a mean of 34 ± 18 s (mean ± SD, n = 39). The response time is statistically shorter in the [010] direction than in the [001] direction. Since the strength of μ correlates with the efficiency of light absorption, both its direction and strength are important parameters for controlling the photoreaction rate in the solid phase. Designing both the direction and strength of μ offers the potential for even greater precision.

In summary, we have demonstrated that a trans-scale strategy, which combines appropriate physical parameters (temperature, light intensity, wavelength, and direction) with a chemical approach and a multiscale understanding of behavior from the nano- to meso- to macro-scale, can enable the control of crystal dynamics. This strategy may be applied to understanding the origin of photoreaction processes in living organisms and to controlling systems made of solid materials. Controlling physical functions based on the atomic–molecular coordinate information of a crystal structure represents a significant challenge in developing material-motion-responsive systems. We have already succeeded in providing the necessary physical parameters, which could lead to the discovery of operational dynamic devices spanning nano- to meso- to macro-scale response systems.

Methods
Materials
Solvents and reagents were purchased from Tokyo Chemical Industry Co., Sigma-Aldrich Co., LLC, Kanto Chemical Co., Inc., and FUJIFILM Wako Pure Chemical. 1 was prepared by direct arylation. Purified water was obtained using an ion exchange method (Pureline WL200, Yamato Scientific). The ion exchanger resin cartridge (CPC-P) had a capacity of 2 L and contained activated carbon. The water sample had a conductivity of 0.04 × 10⁻⁴ S/m.

Equipment
¹H and ¹³C NMR spectra were recorded on a JEOL JNM-ECZ400S spectrometer and Bruker Ascend-400 spectrometers. Ultraviolet-visible (UV–vis) absorption spectroscopy was performed using a JASCO V-650 spectrophotometer. Fluorescence excitation and photoluminescence (PL) spectroscopy were conducted using a JASCO FP-8300 fluorescence spectrophotometer. Optical microscopy images and movies were acquired using a SHIMADZU Moticam 1080BMH equipped with a UV lamp (365 nm, 66 mW), a microscopic photoluminescence (µ-PL) spectroscopy system with a blue laser (405 nm, 5 µW), and a KEYENCE VHX-S8000 equipped with a white LED (4 mW). Light source spectra were measured using a Color Compass MFA. The power of the light sources was measured using a Field Mate laser power meter with a PM10 power sensor. Single-crystal X-ray diffraction measurements were performed using a Rigaku XtaLAB Synergy-S/Mo system (MoKα radiation, λ = 0.71073 Å) equipped with a HyPix-600HE photon counting detector and processed using the Olex2 software package. Powder X-ray diffraction (XRD) measurements were carried out using a Rigaku SmartLab diffractometer with graphite-monochromatized CuKα radiation (λ = 1.5418 Å). Raman spectroscopy was conducted using a HORIBA Jobin-Yvon LabRAM HR800 spectrometer, employing an Nd:YAG laser (λ = 532 nm) as the excitation source. An area of approximately 30 µm on the sample was irradiated through a D2 filter using a 50× objective lens. A microscope-compatible cooling/heating stage (Linkam model 10002L) was used under a nitrogen atmosphere over the temperature range of 103 K–353 K.

Single-crystal X-ray diffraction analysis
The reduction and correction of the diffraction data were performed using the CrysAlisPro program. The structure was solved with the ShelXT structures solution program using Intrinsic Phasing. The structure was refined with the ShelXL refinement package using Least Squares minimization. Any alerts in the CIF should be carefully addressed with the guidance of a crystallographer when necessary. The occupancies of the molecules were refined based on electron densities using the free variables. The crystallographic refinement process includes the handling of disordered molecules. All non-hydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms were placed in idealized positions and refined as rigid atoms with the relative isotropic displacement parameters.

Theoretical calculations
All density functional theory (DFT) calculations were performed using Becke’s three-parameter hybrid exchange function and the Lee-Yang-Paar correlation function (B3LYP) with a default threshold of 6–31+G(d,p) basis set as implemented in Gaussian 16 Revision B.01. TD-DFT vertical excitation energy calculations were carried out for the anthracene dimers extracted from crystal structures using long-range corrected hybrid functional with damped dispersion correction (ωB97X-D). The electrostatic potential maps, highest-energy occupied, and lowest-energy unoccupied molecular orbitals were plotted using GaussView 6.0. The orientation of the transition μ was evaluated by TD-DFT calculations. Using dummy atoms to define the x, y, and z axes, the dipole vector was found to lie along the short axis of the anthracene framework.

JMAK equation
Photochemical reaction in a single crystal was modeled using the JMAK equation.

y = 1 − e⁻(kt)n (1)

where y is the conversion ratio for the 1_PD, k is the reaction ratio constant, t is the irradiation time, and n is the Avrami exponent (reaction order).

Data availability
All data that support the findings of this study are presented in the Manuscript and Supplementary Information or are available from the corresponding author upon request. The X-ray crystallographic coordinates for structures reported in this study have been deposited at the Cambridge Crystallographic Data Center (CCDC), under deposition numbers 2456683, 2456863, 2456867, 2456866, 2456864, and 2456865. These data can be obtained free of charge from The Cambridge Crystallographic Data Center via www.ccdc.cam.ac.uk/data_request/cif. Crystal dynamic movies are available as follows; https://doi.org/10.5281/zenodo.15694836.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This manuscript presents a compelling interdisciplinary study on trans-scale crystal dynamics in anthracene derivatives, demonstrating innovative control of solid-state kinetics through chemical design and physical parameters (light direction, temperature). The work provides valuable mechanistic insights into photoinduced lattice strain and anisotropic responses. While scientifically sound and suitable for publication, minor revisions are required to enhance clarity, rigor, and presentation consistency.\n1. In the manuscript, the crystal dynamics in photoreaction processes of crystal 1 was comprehensively studied. However, crystal 2-5 as control samples were rarely mentioned. The authors should add some discussion to explain the meanings of each crystal reported in the article.\n2. The severe crystal collapse observed under UV light compared to visible light/LED is attributed to the light wavelength. However, UV light sources often have significantly higher photon energies and potentially higher intensities (power densities) than the visible light sources used (white LED, blue laser, sunlight). The manuscript does not report the incident light intensities/power densities for the different sources used in these comparative experiments. The authors should reconsider this issue.\n3. In the temperature dependence of the photoreaction, the authors claimed that：“each temperature point represents the average response time of up to three crystals“. Such sample size is not enough for statistical experiment, which is recommended to be increased to 10 or more.\n4. Spelling mistake: “Date ware” (Fig.4 caption) → “Data were”\n5. please confirm the format of the references.\n6. Some literature (Research 2024, 7, 0411; Adv. Sci. 2025, 12, e09088) should be added to reflect the research breadth of the work.", "reviewer_2": "The manuscript presents an interesting study on anthracene-based crystals that show stimuli-responsive behavior through light-induced dimerization. Although this is a well-known photochemical reaction and have been previously used as a solid platform for exploring dynamic structural changes in the solid state, in this manuscript the authors introduce a dual control mechanism—using both heat and light—to modulate the crystal’s response, allowing the visualization of intermediate states, which is a notable achievement.\nHowever, despite these strengths, the manuscript has several issues that make it unsuitable for publication in a high-impact journal in its current form:\nComments\n1) The abstract lacks specificity and fails to clearly state the focus on anthracene derivatives or highlight the key findings—namely, dual control and intermediate state visualization. Instead, it relies on vague references to biological systems, which are not directly relevant and overgeneralize the study’s implications. It should be rewritten accordingly.\n2) The rationale behind the selection and design of the anthracene derivatives is not explained. Although several anthracene derivatives are synthesized and characterized, in the manuscript their specific roles are unclear. A schematic framework is needed to clarify how these derivatives contribute to the study’s objectives.\n3) As the author notes, identifying the relative orientation between light propagation and the molecular transition dipole moment as a control parameter in the photodynamic process is potentially significant. However, this concept is underdeveloped in the manuscript. To substantiate its importance, the authors should provide more robust theoretical/experimental evidence than simple statistics.\n4) Several figures in the Supporting Information are either incorrectly referenced or not well integrated into the main text. This weakens the clarity and coherence of the experimental narrative. Proper cross-referencing and clearer integration are needed to improve consistency and readability throughout the manuscript. For example, in page 3 the authors mention: “Raman spectroscopy reveals changes in intra- and intermolecular vibrational modes (Supplementary Fig. 18), indicating modifications to both the chemical structure and crystal lattice (Supplementary Figs. 19–21 and Supplementary Table 8)”. On the one hand, Supplementary Fig. 18 presents only two Raman spectra without any accompanying discussion of the observed differences, which limits its usefulness in supporting the claims made in the main text. On the other hand, Supplementary Figs. 19–20 primarily focus on the solid-state retro reaction, including thermal analysis (DSC and TGA), the experimental setup, and NMR characterization of the final product—none of which directly support the discussion on changes in chemical structure or crystal lattice. This misalignment highlights the need for more accurate and purposeful cross-referencing of the supplementary materials. Considering the substantial volume of Supporting Information provided, and to improve overall readability and coherence, the manuscript should be carefully revised to ensure that each supplementary figure and table is clearly and correctly cited in context, and that the integration of this material meaningfully supports the corresponding sections of the main text.\n5) The authors study the transformation under different light sources; however, these reactions appear to proceed more rapidly and, in some cases, lead to the rapid breakdown of the crystals. It remains unclear whether the final phases obtained under these alternative light sources are the same as those formed under white LED light. The authors should clarify whether the photoproducts are structurally and chemically identical across different irradiation conditions, and, if not, provide a discussion on the observed differences and their implications.\nIn summary: While the results are of scientific interest a more focused presentation and clearer methodological framing are needed to meet the standards of a high-impact journal.", "reviewer_3": "In the manuscript titled “Trans-scale crystal dynamics for controlling kinetic responses in organic molecular systems”, Hino et al. report temperature-dependent, photoinduced crystal dynamics in anthracene derivative crystals.\nA key highlight of the study is the controlled modulation of crystal behavior through the relative orientation between the light propagation direction and the molecular transition dipole moment.\nThe work is intriguing and of have relevance to the field of dynamic molecular crystals. However, I recommend major revision before the manuscript can be considered for publication. The following points should be addressed to improve clarity, completeness, and presentation:\n1. The abstract is too general and lacks a concise summary of the actual experimental work carried out. Instead of briefly stating the methodology or system studied, the abstract reads more like a conclusion. This diminishes clarity for readers attempting to understand the work from the outset.\n2. The manuscript lacks a systematic description. For instance, it is not clearly stated how many anthracene derivatives were synthesized and studied, or the rationale behind their selection. The use of abbreviations should also be defined clearly at the beginning. From Figure 1 and the Supplementary Information (SI), it appears that five derivatives were investigated, but this should be clearly presented in the main text.\n3. There is excessive referencing to the SI, which makes reading cumbersome. For example:\nThe sentence: “Depending on the choice of substituents, 1,8-diarylanthracene adopts either an ON (face-to-face) or OFF (edge-to-face) stacking structure (Supplementary Tables 1–6)” directs the reader across six different supplementary tables. A consolidated explanation in the main text summarizing this trend would help.\nSimilarly, the statement: “The minimum face-to-face π-stacked structure required for the ON reaction has been identified based on data from the crystal structure database, previous literature, and our own study using molecular electrostatic potential maps (Fig. 1a and Supplementary Figs. 1–13)” references 13 supplementary figures. Such heavy dependence on SI should be minimized by integrating key insights and summaries into the main text.\n4. The sentence: “The discovery of crystal dynamics driven by visible light overcomes previous limitations related to light wavelength, enabling a more hierarchical and in-depth understanding of the dynamic process.” is unclear and should be elaborated. What limitations were previously imposed by light wavelength, and how does visible light resolve them?\n5. The manuscript would benefit from a more detailed explanation of what exactly constitutes the ON and OFF states in terms of molecular stacking and crystal structure. These structural transitions are central to the work but are only briefly mentioned.\n6. It is stated that UV light irradiation caused dramatic physical responses such as jumping, fragmentation, explosion, splintering, cracking, and splitting. But no detailed mechanism or conditions under which these movements occur is provided. Moreover, the photographic evidence (e.g., in the SI) is insufficient to clearly distinguish these effects.\n7. The statement that “the crystal may exhibit varying phase transition ratios depending on the light wavelength” is not substantiated with any mechanistic explanation or data discussion. The authors should clarify the origin of this behavior.\n8. Crucial details such as the intensity (power density) of the light sources used (UV, white LED, laser) are not provided. These are essential for reproducibility and understanding the kinetics.\n9. Among three crystals irradiated, only one shows cracking. The authors should discuss why the other two did not respond similarly. Could crystal size or morphology be influencing the mechanical response? A brief analysis or hypothesis on size-dependence would add value.\n10. The manuscript states that the transition dipole moment is oriented along the crystallographic b-axis. However, a more detailed explanation is needed on how μ is calculated or estimated from the crystal structure.\n11. The manuscript focuses on the direction of the transition dipole moment but does not discuss how its magnitude might influence the photoinduced response. A brief discussion of whether higher μ would correlate with stronger or faster response would be useful, especially in the context of designing molecules for better dynamic behavior."}, "author_response": "Point-by-Point Response to the Reviewers\nTo all Reviewers\nWe sincerely thank the reviewers for their insightful comments and constructive feedback on our study.\nFollowing their valuable suggestions, we have carefully revised the manuscript to enhance its clarity and\nrigor. We hope that the reviewers will find our responses and revisions satisfactory.\n・Revised parts were highlighted by Yellow.\nTo the Reviewer: 1\nThis manuscript presents a compelling interdisciplinary study on trans-scale crystal dynamics in anthracene\nderivatives, demonstrating innovative control of solid-state kinetics through chemical design and physical\nparameters (light direction, temperature). The work provides valuable mechanistic insights into photoinduced\nlattice strain and anisotropic responses. While scientifically sound and suitable for publication, minor\nrevisions are required to enhance clarity, rigor, and presentation consistency.\n==== > Thank you for your understanding and your thoughtful review comments below.\n1. In the manuscript, the crystal dynamics in photoreaction processes of crystal 1 was comprehensively\nstudied. However, crystal 2-5 as control samples were rarely mentioned. The authors should add some\ndiscussion to explain the meanings of each crystal reported in the article.\n==== > We thank the reviewer for their insightful comments. Anthracene derivatives (1–5) reported here were\ndesigned and selected to identify the chemical control factors necessary for inducing face-to-face structures\n(Fig. 1). These substituent-induced assembly structures are not merely variations of crystal engineering;\nrather, they represent a branching point in crystal functions that govern the active (ON) and inactive (OFF)\nstates of intermolecular photoreactions. Phenyl substitution introduces steric effects that favor the formation\nof face-to-face and edge-to-face arrangements between anthracene units. In contrast, the electronic effects of\naryl substituents systematically shift the competitive balance of molecular assemblies, with increased electron-\naccepting properties promoting the selective formation of ON structures. Conversely, electron-donating\nsubstituents on the aryl groups contribute to the formation of OFF structures, underscoring the effectiveness of\nthis chemical strategy for material design and functional control. Furthermore, as shown in Supplementary\nFig. S15, we investigated the ground-state electrostatic potentials of compounds 1–5. The results indicate that\nelectron-accepting substituents generate a negative relative charge density on the hydrogen atoms of the\nanthracene ring and along the short axis. This suggests that the electrostatic potential of the anthracene core\nplays a decisive role in guiding effective aggregate formation during molecular assembly. To strengthen the\ndiscussion, we have incorporated this evidence, along with comparative analyses and experimental data, into\nthe revised manuscript and Supplementary Information. Please see Pages 3-4 (Subtitle: Chemical approaches\nfor crystal dynamics) in highlighted manuscript and Fig. 1.\n2. The severe crystal collapse observed under UV light compared to visible light/LED is attributed to the light\nwavelength. However, UV light sources often have significantly higher photon energies and potentially higher\nintensities (power densities) than the visible light sources used (white LED, blue laser, sunlight). The\nmanuscript does not report the incident light intensities/power densities for the different sources used in these\ncomparative experiments. The authors should reconsider this issue.\n==== > The irradiation intensity/power density of each light source was specified, and the calculation method\nis described in the Supplementary Information (Supplementary Fig. S18). As shown in Fig. 3d, the following\nlight sources were used: UV light (365 nm, 3 mW/cm2), blue laser (405 nm, 8 W/cm2), white LED (470 nm, 3\nmW/cm2), and sunlight (20–23 mW/cm2). Despite their comparable intensities/power densities, significant\ncrystal collapse was observed under UV irradiation compared with visible light (white LED). This behavior\nreflects differences in photon absorption efficiency and the resulting strain gradients within the crystal.\nIn addition to the strong absorption of UV light by the reactants, the photoproducts also absorb within the\nsame wavelength range. This overlap induces a steep strain gradient between the crystal surface and interior,\nleading to rapid crystal dynamics. By contrast, visible light (white LED) is more weakly absorbed by the\nreactants, and the strain arising from photoproducts accumulates gradually, resulting in a slower response of\nthe crystal dynamics. To strengthen the discussion, we have incorporated this rationale, along with supporting\nexperimental data, into the revised manuscript and Supplementary Information. Please see following revised\nfigure.\nRevised figure (Fig.3)\n3. In the temperature dependence of the photoreaction, the authors claimed that：“each temperature point\nrepresents the average response time of up to three crystals“. Such sample size is not enough for statistical\nexperiment, which is recommended to be increased to 10 or more.\n==== > We investigated the average response time and its standard deviation (SD) as the number of samples\nincreased at each temperature point (Fig. 3c). These experiments were conducted over a 5-minute observation\nperiod, during which a response of up to eight crystals was observed at the lowest temperature of 253 K\n(Supplementary Figs. S31-35). Accordingly, when the parameter for each temperature point was set to\n“maximum 8 crystals,” the average response time became progressively shorter with increasing temperature,\nconsistent with the previous experiments (Fig. 3c). The revised Supplementary Material has been updated to\npresent the response of “maximum 8 crystals” in greater detail, and the original figure has been replaced with\nthe revised version. Please see following revised figure.\nRevised figure (Fig.3)\n4. Spelling mistake: “Date ware” (Fig.4 caption) → “Data were”\n==== > Based on your feedback, we have fixed the issue.\n5. please confirm the format of the references.\n==== > We have addressed the formatting issues in the references section, specifically including \"all authors\nwith 5 or fewer names in the reference list\" and correcting the wording of \"book citations.\"\n6. Some literature (Research 2024, 7, 0411; Adv. Sci. 2025, 12, e09088) should be added to reflect the\nresearch breadth of the work.\n==== > Thank you for the reference. We have incorporated the proposed reference on photoreactions in single\ncrystals (Adv. Sci. 2025, 12, e09088) into the manuscript. This reference provides valuable background\ninformation and helps broaden the appeal of this work to readers interested in crystal dynamics.\nTo the Reviewer: 2\nThe manuscript presents an interesting study on anthracene-based crystals that show stimuli-responsive\nbehavior through light-induced dimerization. Although this is a well-known photochemical reaction and have\nbeen previously used as a solid platform for exploring dynamic structural changes in the solid state, in this\nmanuscript the authors introduce a dual control mechanism—using both heat and light—to modulate the\ncrystal’s response, allowing the visualization of intermediate states, which is a notable achievement.\nHowever, despite these strengths, the manuscript has several issues that make it unsuitable for publication in a\nhigh-impact journal in its current form:\n==== > Thanks for your understanding of our research contents and your constructive comments below.\n1) The abstract lacks specificity and fails to clearly state the focus on anthracene derivatives or highlight the\nkey findings—namely, dual control and intermediate state visualization. Instead, it relies on vague references\nto biological systems, which are not directly relevant and overgeneralize the study’s implications. It should be\nrewritten accordingly.\n==== > We would like to express our sincere gratitude to the reviewers for their constructive suggestions.\nFollowing their suggestions, we have revised the abstract to focus on anthracene derivatives and clarify the\nmain achievements, such as \"dual control and visualization of intermediate states.\"\nRevised Abstract:\nThe origin and control of material dynamics are crucial for understanding functional systems, yet direct\nvisualization of rapid changes in single crystals has remained challenging. We report an anthracene-\nbased molecular crystal platform that enables dual physical control of solid-state [4+4]\nphotocycloaddition through temperature and light. Chemically designed 1,8-\nbis(pentafluorophenyl)anthracene crystals formed photoactive face-to-face π-stacks, allowing visible-\nlight-induced reactions. The crystals exhibited thermally switchable on/off states, governed by lattice\nstrain accumulation. Weak LED light irradiation enabled direct observation of intermediate states in\n[4+4] photocycloaddition process, revealing a correlation between lattice strain and photoconversion\nrate. Moreover, reaction kinetics depended on light propagation direction and molecular transition\ndipole orientation, introducing a new anisotropic control parameter. This trans-scale approach,\nintegrating molecular packing design, photo-thermal control, and directional anisotropy, offers a\ngeneral strategy for tunable and observable crystal dynamics.\n132 words (<150 words)\n2) The rationale behind the selection and design of the anthracene derivatives is not explained. Although\nseveral anthracene derivatives are synthesized and characterized, in the manuscript their specific roles are\nunclear. A schematic framework is needed to clarify how these derivatives contribute to the study’s objectives.\n==== > We thank the reviewer for their insightful comments. Anthracene derivatives (1–5) were designed and\nselected to identify the chemical control factors necessary for inducing face-to-face structures (Fig. 1).\nPhotoinduced structural transitions in anthracene crystals proceed via photodimerization of the face-to-face\npacking motif. However, achieving photodimerization in single crystals requires precise control of molecular\norientation and alignment to bring reactive sites into proximity. In this study, we successfully induced face-to-\nface structures by introducing electron-withdrawing groups along the short axis of anthracene. We believe\nthese findings provide valuable molecular design guidelines for crystal dynamics and will contribute to the\nfurther development of this research field. To strengthen the discussion, we have incorporated this schematic\ndiagram into the revised manuscript. Please see Pages 3-4 (Subtitle: Chemical approaches for crystal dynamics) in highlighted manuscript. Please see following new figure.\nAdded figure (Fig. 1)\n3) As the author notes, identifying the relative orientation between light propagation and the molecular\ntransition dipole moment as a control parameter in the photodynamic process is potentially significant.\nHowever, this concept is underdeveloped in the manuscript. To substantiate its importance, the authors should\nprovide more robust theoretical/experimental evidence than simple statistics.\n==== > We appreciate the opportunity to clarify the correlation between the light transmission direction\n(polarization) and the molecular transition dipole moment (μ) in the crystal. Organic crystals adopt anisotropic\nmolecular arrangements, allowing μ to be oriented in specific directions depending on the aggregation state.\nThis orientation of μ leads to anisotropic optical absorption, since the efficiency of interaction between the\nelectric field and μ depends on their relative orientation (parallel vs. perpendicular) to the polarization of\nincident light (Angew. Chem. 2020, 132, 4486–4493; Chem. Eur. J. 2023, 29, e202302351). This provides\nfurther evidence for the anisotropy observed in the response time and frequency of the crystal dynamics.\nQuantum chemical calculations (TD-DFT calculation) indicate that μ in bimolecular aggregates is aligned\nalong the anthracene minor axis (Supplementary Fig. 46). Consistently, single-crystal X-ray diffraction\nanalysis and indexing of crystal morphology (Supplementary Fig. 50) revealed that μ is oriented along the\ncrystallographic b-axis (Supplementary Fig. 51). Experimental support for this assignment was obtained by\nexamining the polarization dependence of incident white LED light for different crystal plane orientations\n([001] and [010]) (Supplementary Fig. 52). Specifically, white light irradiation along the [010] direction\nexhibited no color regardless of polarization, suggesting isotropic absorption in this plane. By contrast, the\nirradiation along the [001] direction showed color at polarization angles of 0° and 180°, but not between 50°\nand 130°. This qualitatively demonstrates anisotropic absorption along [001] due to the in-plane orientation of\nμ on 001 facet, with polarization directions consistent with the theoretically predicted orientation of μ. We\nhope this additional information will help clarify that the relative configuration of polarization and μ is a key\ncontrolling parameter for crystal dynamics. To strengthen the discussion, we have incorporated this\ncomparative analysis, experimental data, and references into the revised manuscript and Supplementary\nInformation. Please see Pages 7-8 (188-, 195-) in highlighted manuscript. Please see following new figure.\nRevised figure (Fig. 52 in SI)\n4) Several figures in the Supporting Information are either incorrectly referenced or not well integrated into\nthe main text. This weakens the clarity and coherence of the experimental narrative. Proper cross-referencing\nand clearer integration are needed to improve consistency and readability throughout the manuscript.\n==== > Thank you very much for your constructive comments. We regret unable to cite properly due to the\nlarge amount of additional information. We have checked and revised everything to improve the consistency\nand readability of the entire manuscript. We have also minimized excessive citations.\nFor example, in page 3 the authors mention: “Raman spectroscopy reveals changes in intra- and\nintermolecular vibrational modes (Supplementary Fig. 18), indicating modifications to both the chemical\nstructure and crystal lattice (Supplementary Figs. 19–21 and Supplementary Table 8)”. On the one hand,\nSupplementary Fig. 18 presents only two Raman spectra without any accompanying discussion of the\nobserved differences, which limits its usefulness in supporting the claims made in the main text. On the other\nhand, Supplementary Figs. 19–20 primarily focus on the solid-state retro reaction, including thermal analysis\n(DSC and TGA), the experimental setup, and NMR characterization of the final product—none of which\ndirectly support the discussion on changes in chemical structure or crystal lattice. This misalignment\nhighlights the need for more accurate and purposeful cross-referencing of the supplementary materials.\nConsidering the substantial volume of Supporting Information provided, and to improve overall readability\nand coherence, the manuscript should be carefully revised to ensure that each supplementary figure and table\nis clearly and correctly cited in context, and that the integration of this material meaningfully supports the\ncorresponding sections of the main text.\n==== > We thank the reviewer for their careful attention to detail. In response to their comments, we have\ncorrected the issues regarding references and the integration of Supplementary Information into the text. The\nchanges in intramolecular and intermolecular vibrational modes observed by Raman spectroscopy in this\nstudy provide spectroscopic evidence that photoirradiation induces chemical structural transformations in the\ncrystal, leading to subsequent structural transitions. A previous study reported that Raman spectroscopy\nmeasurements during solid-state photoreactions of 9-methylanthracene revealed the appearance of a new\nintramolecular band near 330 cm-1, attributed to photodimer formation (J. Raman Spectrosc. 2017, 48, 271–\n277). To further clarify this point, we performed quantum chemical calculations to analyze the vibrational\nmodes of the photoproduct 1 . The Supplementary Information (Supplementary Fig. 21) has been updated\nPD\naccordingly. The results show a Raman-active intramolecular vibrational mode at 329 cm-1, arising from the\nnewly formed C–C single bond upon photodimerization. This provides theoretical support for the two\nexperimentally observed Raman spectra. Furthermore, we demonstrate that the reverse reaction from crystal\n1 back to crystal 1 is possible. This process is likely based on flash vacuum pyrolysis, in which specific\nPD\nmolecular bonds are cleaved under instantaneous high-temperature treatment (Chem. Rev. 2006, 106, 12,\n4868–4884). These results suggest that crystal dynamics can, in principle, be driven reversibly through the\ncombined use of light and heat. To improve the consistency and readability, we incorporated these\nexperimental data into the revised manuscript (Pages 4-5 (100-)) and Supplementary Information.\nRevised figure (Fig. 21 in SI)\n5) The authors study the transformation under different light sources; however, these reactions appear to\nproceed more rapidly and, in some cases, lead to the rapid breakdown of the crystals. It remains unclear\nwhether the final phases obtained under these alternative light sources are the same as those formed under\nwhite LED light. The authors should clarify whether the photoproducts are structurally and chemically\nidentical across different irradiation conditions, and, if not, provide a discussion on the observed differences\nand their implications.\n==== > The final product obtained under white LED irradiation was identified as the photodimer 1 .\nPD\nHowever, it remained unclear whether the products generated under different light sources were identical to\nthat obtained under white LED light. To address this issue, we carried out X-ray diffraction measurements\nunder UV irradiation. Powder X-ray diffraction at room temperature revealed a gradual disappearance of the\n{020} reflection of crystalline 1 with increasing irradiation time (Supplementary Fig. 40), suggesting a\nstructural transition from crystalline 1 to crystalline 1 under UV light. To further clarify this point, we\nPD\nperformed single-crystal X-ray structural analysis. The crystals obtained under UV irradiation (CCDC\nreference number: 2483421) were identified as 1 and confirmed to be structurally and chemically identical\nPD\nto the final product obtained under white LED light. We believe these additional experiments enhance the\nclarity and accuracy of our identification of the final product under different light sources. Please see Page 6\n(147-) in highlighted manuscript.\nAdded figure (Fig. 40 in SI)\nIn summary: While the results are of scientific interest a more focused presentation and clearer\nmethodological framing are needed to meet the standards of a high-impact journal.\n==== > We would like to express my sincere gratitude for the evaluation and comments on this research.\nBased on the valuable advice, we have carefully revised the paper to provide a more focused description of the\nresearch results and organize the methodology.\nTo the Reviewer: 3\nIn the manuscript titled “Trans-scale crystal dynamics for controlling kinetic responses in organic molecular\nsystems”, Hino et al. report temperature-dependent, photoinduced crystal dynamics in anthracene derivative\ncrystals.\nA key highlight of the study is the controlled modulation of crystal behavior through the relative orientation\nbetween the light propagation direction and the molecular transition dipole moment.\nThe work is intriguing and of have relevance to the field of dynamic molecular crystals. However, I\nrecommend major revision before the manuscript can be considered for publication. The following points\nshould be addressed to improve clarity, completeness, and presentation:\n==== > Thanks for your understanding of the content and your constructive comments below.\n1. The abstract is too general and lacks a concise summary of the actual experimental work carried out.\nInstead of briefly stating the methodology or system studied, the abstract reads more like a conclusion. This\ndiminishes clarity for readers attempting to understand the work from the outset.\n==== > Considering that the abstract was too general, we have specifically included the experimental subjects\nand main results (such as dual control of crystal dynamics by heat and light, and direct observation of\ncrystallographic intermediate states) in the abstract. We hope that this revision will address the reviewer's\nconcerns and more clearly convey the outline and novelty of our research.\nRevised Abstract:\nThe origin and control of material dynamics are crucial for understanding functional systems, yet direct\nvisualization of rapid changes in single crystals has remained challenging. We report an anthracene-\nbased molecular crystal platform that enables dual physical control of solid-state [4+4]\nphotocycloaddition through temperature and light. Chemically designed 1,8-\nbis(pentafluorophenyl)anthracene crystals formed photoactive face-to-face π-stacks, allowing visible-\nlight-induced reactions. The crystals exhibited thermally switchable on/off states, governed by lattice\nstrain accumulation. Weak LED light irradiation enabled direct observation of intermediate states in\n[4+4] photocycloaddition process, revealing a correlation between lattice strain and photoconversion\nrate. Moreover, reaction kinetics depended on light propagation direction and molecular transition\ndipole orientation, introducing a new anisotropic control parameter. This trans-scale approach,\nintegrating molecular packing design, photo-thermal control, and directional anisotropy, offers a\ngeneral strategy for tunable and observable crystal dynamics.\n132 words (<150 words)\n2. The manuscript lacks a systematic description. For instance, it is not clearly stated how many anthracene\nderivatives were synthesized and studied, or the rationale behind their selection. The use of abbreviations\nshould also be defined clearly at the beginning. From Figure 1 and the Supplementary Information, it appears\nthat five derivatives were investigated, but this should be clearly presented in the main text.\n==== > A systematic description of the anthracene derivatives and definitions of abbreviations have been\nadded to the text. It should first be emphasized that the activity or inactivity of intermolecular photoreactions\nin crystals is determined by the association mode and crystal structure of the compound. To clarify the\nunderlying chemical factors, five anthracene derivatives were designed and selected to identify structural\nfeatures that promote face-to-face arrangements. This study demonstrates that the introduction of electron-\nwithdrawing groups provides an effective chemical strategy for inducing face-to-face structures, which are a\nprerequisite for photodimerization. Please see Pages 3-4 (Subtitle: Chemical approaches for crystal dynamics)\nof highlighted manuscript and following new figure.\nAdded figure (Fig. 1)\n3. There is excessive referencing to the SI, which makes reading cumbersome. For example:\nThe sentence: “Depending on the choice of substituents, 1,8-diarylanthracene adopts either an ON (face-to-\nface) or OFF (edge-to-face) stacking structure (Supplementary Tables 1–6)” directs the reader across six\ndifferent supplementary tables. A consolidated explanation in the main text summarizing this trend would\nhelp.\n==== > To avoid excessive SI dependence, we have made the relationship and tendency between the\nsubstituents and bimolecular structures correspond to Fig. 1c. Please see Pages 4 (76-) in highlighted\nmanuscript.\nSimilarly, the statement: “The minimum face-to-face π-stacked structure required for the ON reaction has\nbeen identified based on data from the crystal structure database, previous literature, and our own study using\nmolecular electrostatic potential maps (Fig. 1a and Supplementary Figs. 1–13)” references 13 supplementary\nfigures. Such heavy dependence on SI should be minimized by integrating key insights and summaries into\nthe main text.\n==== > To focus on the main points, we have narrowed down the citations to those that are particularly\nrelevant.\n4. The sentence: “The discovery of crystal dynamics driven by visible light overcomes previous limitations\nrelated to light wavelength, enabling a more hierarchical and in-depth understanding of the dynamic process.”\nis unclear and should be elaborated. What limitations were previously imposed by light wavelength, and how\ndoes visible light resolve them?\n==== > Previously, [4+4] photocycloaddition reactions (photodimerization) in solids were largely limited to\nultraviolet light (Chem. Soc. Rev., 2023, 52, 3098–3169). This limitation is attributed to the near-UV\nabsorption bands of anthracene derivatives, which exhibit very low absorption efficiency in the visible light\nrange. Moreover, UV light-induced crystal dynamics often lead to rapid crystal collapse, making it difficult to\ncapture gradual changes in lattice strain. In this study, we overcame the previous wavelength limitation by\nextending the π-conjugation of anthracene via aryl substitution on the short axis, thereby enhancing visible-\nlight absorption and inducing a photoreactive crystal structure. Crystal 1 undergoes efficient\nphotodimerization under white light (visible light), enabling direct visualization of intermediate states during\nthe structural transition. This approach overcomes the previous UV light-dependence and allows direct\nobservation of lattice strain changes, which is crucial for elucidating the origin of crystal dynamics. We hope\nthat these explanations address the reviewer’s concerns and more clearly communicate the significance of our\nresearch. Please see Page 6 (143-) of highlighted manuscript.\n5. The manuscript would benefit from a more detailed explanation of what exactly constitutes the ON and\nOFF states in terms of molecular stacking and crystal structure. These structural transitions are central to the\nwork but are only briefly mentioned.\n==== > We appreciate the opportunity to clarify the dual control (ON/OFF) of crystal dynamics. First, we\nnote that crystal dynamics is driven by the external release of lattice strain accumulated in the crystal as a\nresult of photoreaction. Both heating and photoreaction were found to decrease the lattice axis angle β (Fig.\n3a), indicating that the accumulation of lattice strain due to photoreaction is accelerated by heating. The\ntemperature-dependent lattice strain was characterized by X-ray diffraction measurements. Temperature-\nvariable single-crystal X-ray analysis of crystal 1 between 103 K and 303 K revealed an elongation of the π-\nstacking distance and an increase in molecular volume with increasing temperature. These molecular stacking\ndisplacements induced lattice deformations, resulting in a decrease of the axis angle β. To clarify the\ntemperature dependence of molecular stacking and crystal structure, we compared the crystal structures at 103\nK and 303 K. The updated Supplementary Information (Supplementary Fig. 30) clearly visualizes these\ndifferences in crystal structures based on molecular stacking displacements. We believe that these additional\ncomparisons enhance the clarity and accuracy of the correlation between the ON/OFF states and the molecular\nstacking and crystal structures. To further enrich the discussion, we have incorporated this rationale,\ncomparative analysis, and experimental data into the revised manuscript and Supplementary Information.\nAdded figure (Fig. 30 in SI)\n6. It is stated that UV light irradiation caused dramatic physical responses such as jumping, fragmentation,\nexplosion, splintering, cracking, and splitting. But no detailed mechanism or conditions under which these\nmovements occur is provided. Moreover, the photographic evidence (e.g., in the SI) is insufficient to clearly\ndistinguish these effects.\n==== > To avoid confusion, we have added a description of an additional jumping mechanism under UV light\nirradiation to the Supplementary Information (Supplementary Fig. 37). The diverse responses observed under\nUV light, shown in Fig. 3d and Supplementary Fig. 37, arise from the accumulation of lattice strain due to\nphotodimerization. The different modes of stress release give rise to complex crystal responses. When\nphotodimerization proceeds unevenly within the crystal, the lattice strain becomes biased in one direction,\ngenerating a driving force that causes the crystal to jump. When stress is concentrated on a specific crystal\nplane, localized fracture occurs, forming cracks. Furthermore, when stress simultaneously exceeds the\ncohesive strength of the crystal lattice in multiple regions, the crystal partially collapses, resulting in local\nfracture. Finally, if photodimerization occurs rapidly throughout the crystal, causing a large volume change\nand overwhelming the stress-relaxation capacity, the crystal fractures all at once, leading to explosive\nscattering of fragments (total fracture). However, the conditions required to independently achieve jumps,\nfractures, explosions, or crack formation remain unclear. In future work, we plan to investigate the relative\norientation of the UV light propagation direction (polarization) and the molecular transition dipole moment,\naiming to achieve precise control over these responses.\nAdded figure (Fig. 37 in SI)\n7. The statement that “the crystal may exhibit varying phase transition ratios depending on the light\nwavelength” is not substantiated with any mechanistic explanation or data discussion. The authors should\nclarify the origin of this behavior.\n==== > As you pointed out, the original manuscript lacked sufficient mechanistic explanation and supporting\ndata for the wavelength-dependent phase transition rate. To address this, we have provided additional\nexplanations and supplementary data. Specifically, powder X-ray diffraction measurements under room-\ntemperature UV irradiation showed that the {020} reflection from crystal 1 completely disappeared after\napproximately 210 seconds, indicating a quantitative transformation to crystal 1 (Supplementary Fig. 40). In\nPD\ncontrast, under white LED irradiation, the phase transition (conversion) rate remained at approximately 50%\nover a similar irradiation period. This difference is attributed to the higher absorption coefficient of UV light\ncompared with visible light, confirming that the phase transition rate depends on the light wavelength.\nHowever, UV irradiation also induces responses such as fracture, explosion, and cracking, making it\nimpossible to determine the phase transition rate from single-crystal X-ray analysis of the same crystal. We\nhope that these explanations address the reviewer’s concerns and more clearly convey the mechanism\nunderlying the wavelength-dependent phase transition rate. Please see Page 6 (147-) in highlighted\nmanuscript.\nAdded figure (Fig. 40 in SI)\n8. Crucial details such as the intensity (power density) of the light sources used (UV, white LED, laser)\nare not provided. These are essential for reproducibility and understanding the kinetics.\n==== > Thank you very much for your valuable comment. Following your suggestion, we have revised Fig.\n3d (caption) to clarify:\n\"Optical microscopy images of crystal 1 under UV light (365 nm, 3 mW/cm²), blue laser (405 nm, 9 W/cm²),\nwhite LED (470 nm, 3 mW/cm²), and sunlight (20–23 mW/cm²) at 298 ± 5 K.\"\n9. Among three crystals irradiated, only one shows cracking. The authors should discuss why the other two\ndid not respond similarly. Could crystal size or morphology be influencing the mechanical response? A brief\nanalysis or hypothesis on size-dependence would add value.\n==== > Our initial observations showed that only one of three crystals exposed to sunlight for 10 minutes\nexhibited a crack, while the other two remained intact (Fig. 3d). This difference may have been due to\ninsufficient light exposure time. In a follow-up experiment, after exposing the crystals to sunlight for 1 hour,\nall crystals exhibited clear collapse (Supplementary Fig. 39b). These results suggest that the response time of\ncrystal dynamics depends on both internal factors (e.g., crystal size and morphology) and external factors\n(e.g., wavelength and exposure time). Notably, even among three crystals derived from the same crystal\nstructure, only one exhibited a crack after 10 minutes of sunlight exposure. These observations motivated us\nto perform a statistical analysis of the response time and frequency of crystal dynamics under white LED\nirradiation. The rationale, comparative analysis, and experimental data are provided in the Supplementary\nInformation.\nAdded figure (Fig. 39 in SI)\n10. The manuscript states that the transition dipole moment is oriented along the crystallographic b-axis.\nHowever, a more detailed explanation is needed on how μ is calculated or estimated from the crystal structure.\n==== > We apologize for the insufficient description in our previous manuscript. The direction of the\ntransition dipole moment (μ) was estimated based on crystal structure and electronic structure analyses.\nSpecifically, we first performed TD-DFT calculations on the bimolecular aggregate (Unit 1 and Unit 2) of\ncrystal 1 to identify the major electronic transitions corresponding to the absorption bands. The μ associated\nwith the S₀–S₂ transition was found to lie along the short axis of the anthracene skeleton, determined by\ndefining the obtained x, y, and z coordinates using dummy atoms. Next, we aligned the molecular orientation\nobtained from single-crystal X-ray structure analysis to the crystal coordinate system and projected on this\nmolecular axis onto the crystal axes (Supplementary Fig. 46). As a result, we confirmed that the μ direction\nprimarily coincides with the crystallographic b-axis (Supplementary Fig. 51). In this revised manuscript, we\nhave added this analysis procedure to the Methods section and Supporting Information. We believe that this\nclarification demonstrates that our estimation method is based on a combination of TD-DFT calculations and\ncrystallographic orientation analysis. Please see Pages 10 (270-) in highlighted manuscript.\n11. The manuscript focuses on the direction of the transition dipole moment but does not discuss how its\nmagnitude might influence the photoinduced response. A brief discussion of whether higher μ would correlate\nwith stronger or faster response would be useful, especially in the context of designing molecules for better\ndynamic behavior.\n==== > While this paper has focused on the directionality of the transition dipole moment (μ), we would like\nto add that its magnitude is also important. In general, the magnitude of μ is proportional to the absorption\nefficiency, and molecules with a larger μ will generate more photoexcited states or photoproducts under the\nsame irradiation conditions. As a result, photoreactions and structural transitions in the crystal are promoted,\nsuggesting that the response of crystal dynamics is strong and appears quickly. Therefore, considering both\nthe \"direction\" and \"magnitude\" of μ is an important guideline for dynamic crystal design. Please see Page 8\n(212-) in highlighted manuscript."}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors have carefully addressed all my issues and I suggest the acceptance of this manuscript in Nature Communications.", "reviewer_2": "The authors have satisfactorily addressed my concerns. I recommend acceptance of the manuscript in its current form.", "reviewer_3": "The manuscript titled “Trans-scale crystal dynamics for controlling kinetic responses in organic molecular systems” by Hayashi et al. has been thoroughly revised. The authors have addressed all the comments raised by the reviewers.\nHowever, my comment regarding the excessive dependence on the Supporting Information appears to have been misunderstood. Earlier, the authors had cited numerous SI figures and tables within a single explanation, whereas in the revised version they have removed these citations altogether. My suggestion was not to eliminate references to the Supporting Information, but rather to combine a maximum of two to three related figures or tables in one explanation so that the reader does not lose track while going through the SI. The authors may wish to revisit this point.\nWith this minor revision, I would recommend acceptance of the manuscript for publication in Nature Communications."}, "author_response": ""}]

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