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ArticleHydrogen Bonding Propagated Phase Separation in Quasi-Epitaxial
Single Crystals: A Pd−Br Molecular Insulator
Takefumi Yoshida,* Shinya Takaishi,* Laurent Guérin, Tatsuhiro Kojima, Hiroyoshi Ohtsu,
Masaki Kawano, Tatsuya Miyamoto, Hiroshi Okamoto, Kenichi Kato, Masaki Takata, Yuka Hosomi,
Shoji Yoshida, Hidemi Shigekawa, Hisaaki Tanaka, Shin-ichi Kuroda, Hiroaki Iguchi, Brian K. Breedlove,Zhao-Yang Li, and Masahiro Yamashita*
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Cite This: Inorg. Chem. 2022, 61, 14067−14074

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sı Supporting Information*

ABSTRACT: In condensed matter, phase separation is strongly related to ferroelasticity,
ferroelectricity, ferromagnetism, electron correlation, and crystallography. These ferroics are importantfor nano-electronic devices such as non-volatile memory. However, the quantitative information
regarding the lattice (atomic) structure at the border of phase separation is unclear in many cases. Thus,
to design electronic devices at the molecular level, a quantitative electron−lattice relationship must be
established. Herein, we elucidated a PdII−PdIV/PdIII−PdIII phase transition and phase separation
mechanism for [Pd(cptn)2Br]Br2 (cptn = 1R,2R-diaminocyclopentane), propagated through a hydrogen-bonding network. Although
the Pd···Pd distance was used to determine the electronic state, the differences in the Pd···Pd distance and the optical gap between
Mott−Hubbard (MH) and charge-density-wave (CDW) states were only 0.012 Å and 0.17 eV, respectively. The N−H···Br···H−Nhydrogen-bonding network functioned as a jack, adjusting the structural difference dynamically, and allowing visible ferroelastic
phase transition/separation in a fluctuating N2 gas flow. Additionally, the effect of the phase separation on the spin susceptibility andelectrical conductivity were clarified to represent the quasi-epitaxial crystals among CDW−MH states. These results indicate that thephase transitions and separations could be controlled via atomic and molecular level modifications, such as the addition of hydrogenbonding.

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have reported superelastic organic molecules.8,9 A single crystalof 1,3-bis(4-methoxyphenyl)urea has been reported todemonstrate both superelasticity and ferroelasticity via singlecrystal-to-single-crystal twinning.8 However, crystallographic
boundaries with a significant NH···O hydrogen-bonding
network occur.8 Thus, there has been a surge of interest in
elastic phase separation over the last several years.
Tetracyanoquinodimethane (TCNQ) 10,11 and bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF)12,13 salts
have been used to demonstrate phase separation in organic
semiconductors via charge-transfer phase transitions (CTPTs).
Kumai et al. have reported a current-induced insulator−metaltransition in K-TCNQ,10 where the dimerized and partiallydimerized domains form an alternate phase separation alongthe π stacks due to lattice strain.11 Moreover, Pustogow et al.
have observed a metal-to-insulator transition for α-(BEDTTTF)2I3 using cryogenic scanning near-field optical microscopy, and they report that the phase transition and phase

INTRODUCTION
Phase separation in condensed matter, where multiple phases/
domains coexist in a single component, is intrinsically linked toferroelasticity, ferroelectricity, ferromagnetism, electron-correlation, and crystallography.1−13 Significantly, the compound
maintains several ferroelastic domains due to spontaneous
strain, which is induced by a chemical bond or an interaction
against the lattice strain that occurs during the phase transition.
In particular, physical properties have a direct effect on thestates at the interfaces between the phases. In addition,
external stimuli can be used to control some of the domains offerroics or multiferroics.3,4 As a result, scientists have creatednumerous compounds and analyzed the interfaces using avariety of techniques.1−13
Phase separation has been widely reported for metal oxides,
and it is frequently accompanied by ferroelasticity andferroelectricity.5,6 Wei et al. have reported that the phaseseparation in ferroelectric Pb(Zr0.1Ti0.9)O3 thin films can becontrolled by modifying the domain wall bending, type of
doping, polarization orientation, and the work functions ofadjacent electrodes.5 At the atomic scale, the ferroelastic
domains (walls) of oxides have been observed using atransmission electron microscope (TEM). Some oxides exhibit
micrometer-scale phase separation.7
Although phase separations in organic molecular solids are
relatively rare in comparison to metal oxides, Takamizawa et al.
© 2022 American Chemical Society

Received: June 15, 2022
Published: August 25, 2022

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separation were caused by the internal strain distribution in the
crystal.13 Despite the strong correlation between the lattice andthe electrons, α-(BEDT-TTF)2I3 has no crystallographic phaseboundaries.12,13 Although structural and orientational information has been reported, studies offering quantitative lattice(atomic) information have been limited. Thus, for themolecular design of the electronic devices, a quantitative
relationship between the lattice and the electrons should beestablished.1−3
Quasi-one-dimensional halogen-bridged metal (MX) complexes are excellent candidates for deciphering CTPT lattice−electron correlations.14−16 The MX chain comprises anisolated one-dimensional (1D) electronic system composedof the dz2 orbital of metal ions (M) and the pz orbital ofbridging halide ions (X),16 and an extended Peierls−Hubbard
model is used to explain the electronic states, in which thetransfer integral (t), the on-site and nearest neighbor-site
Coulomb repulsions (U and V, respectively), and theelectron−lattice interaction (S), all compete for energy.17,18
The Pd and Pt complexes with a −X···MII ···X−MIV−X···
Peierls distorted 1D structure are generally present in a mixedvalence charge-density-wave (MV−CDW) state due to a large
S value (S > U; Figure 1a). Moreover, Pd and Pt complexes in

Articlethe S value and the U value remains nearly constant in one
complex, causing the Pd complex to transition to the AV−MH
state, have been reported.31,32 In particular, [Pd(cptn)2Br]Br2(1) is the only system in the organic−inorganic hybrid
molecular solid in which MV−CDW and AV−MH states
coexist on the micrometer-order against the (±1 ± 1 0) planeover a broad temperature range (50−130 K).33 In addition,
without the use of a polarizer, a dynamic to-and-fro visible
phase transition/separation can be observed in a fluctuating N2
gas flow (Figure 1b−f, Movie S1: the brighter domain is in a
MH state and the darker domain is in a CDW state).
Furthermore, in scanning tunneling microscopy (STM)
images, a phase separation is observed at the nanoscale.34 In
this temperature range, 1 exhibits a typical ferroelastic phaseseparation, comprising a CDW−MH quasi-epitaxial single
crystal (close to homoepitaxial from the perspective of a single
crystal35,36). Typical ferroelastics have a large band gap (∼2.7eV) in an inorganic system.37 Xiong et al. have recently
reported an organic−inorganic organometallic semiconductor
with a narrow optical gap (ferrocenium tetrachloroferrate[Fe(Cp)2][FeCl4]) (1.61 eV).38 However, 1 has a gap of lessthan half (0.60 and 0.43 eV) that value and thus has thepotential to enable fast-response (to thermal, mechanical, andoptical stimuli) and low-gap optical devices. Although thedecrease in the energy gap also leads to difficulty in controlling
the transition, 1 can be controlled by a hydrogen-bonding
network.
To design molecular compounds with two or more phases ina single component, it is critical to understand the electron−
lattice correlation and phase separation in a CTPT. However,discussing the mechanism at the atomic level is complicatedbecause 1 in an MV−CDW state (at a higher temperature) has
a superstructure with diffused scattering and phase separation,39 making the extraction of structural information for eachcoexisting domain difficult. In this work, we determined thesuperstructure of an MV−CDW state using single-crystal X-ray
diffraction and the coexisting structures using synchrotron
powder X-ray diffraction. We showed that the PdII−PdIV/
PdIII−PdIII phase transition and phase separation mechanism
for [Pd(cptn)2Br]Br2 were propagated via a hydrogen-bonding
network. In addition, the effects of the phase separation on thephysical properties, such as spin susceptibility and conductivity, were clarified to better understand the behavior of
the CDW−MH quasi-epitaxial crystal.

Figure 1. (a) Electronic state of quasi-one-dimensional halogenbridged metal complexes. (b−f) Phase separation between MV−
CDW and AV−MH at 141 K in a fluctuated N2 gas flow (see Movie
S1).

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RESULTS AND DISCUSSION

Nanoscale Structure. To aid comprehension, we haveincluded a breakdown of the structure here (CCDC no.
1449578).33,39 Figure 2 and Table S1 show the crystal
structure and crystal data for 1 at 93 K (1 is in an AV−MH
state). The complex crystallized in the I222 space group with
the Pd ion in an elongated octahedral coordination sphere andthe Br anion bridging square planar Pd(cptn)2 moieties toform a linear chain along the a-axis (Figure 2a). The Pd−Pd
distance within the chain was determined to be 5.22 Å. These
chains formed a 2D sheet parallel to the ab plane via hydrogenbonding among free Br− counteranions and in-plane cptn
ligands via a N−H···Br···H−N hydrogen-bonding network
along the b axis (Figure 2b,c). These sheets were stacked along
the c axis via van der Waals interactions and C−H···Br···H−Chydrogen bonding (Figure S1).
Diffuse scattering at h = m + 0.5 (m is an integer) [itcontains additional structural information (superstructure)]

MV−CDW states have been extensively studied due to theirchemical and physical properties, which include intervalencecharge transfer from MII to MIV ions,19 overtone progression of
the resonance Raman mode,20,21 soliton and polaron
dynamics,22,23 and two-leg ladder and square tubular skeletonsformed by supramolecular assembly.24,25 In contrast, it has
been shown that Ni complexes have a −X−NiIII−X−NiIII−X−
1D structure and are in an averaged-valence Mott−Hubbard(AV−MH) state due to a large U value (U > S; Figure 1a).26
Moreover, intriguing physical properties, such as enormous
third-order nonlinear optical susceptibility,27 negative differential electrical conductivity,28 electrostatic carrier doping,29
and spin-Peierls transitions,30 have been reported.
Recently, several Pd complexes exhibiting MV−CDW to
AV−MH CTPT (Peierls transition), in which the decrease in
the Pd···Pd distances at low temperatures causes a decreases in14068

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ArticleFigure 3 depicts the sum of the diffuse scattering intensities
at various temperatures. Cooling reduced the intensity,

Figure 3. Sum of the diffuse scattering intensities at various
temperatures. Each plate represents a 2D sheet along the ab plane.
The green and yellow plates represent the CDW domains; since there
is almost no correlation among the 2D sheets along the c direction,
they are represented by different colors in the diagram. The whiteplates represent the MH domains.

whereas the width of the diffuse scattering did not change.
This behavior indicates that although the MV−CDW domain
shrinks, the structure and correlation length in the domain are
the same.
We measured the synchrotron powder X-ray diffraction
pattern (PXRD) of 1 in a temperature range to confirm theboundary between AV−MH and MV−CDW (Figure S4). For
the temperatures depicted in Figure 4, the diffraction peakFigure 2. Crystal structure of 1 at 93 K. (a) 1D chain structure, (b)stacking structure, and (c) hydrogen-bonding network. Gray: Pd,
Orange: Br, Blue: N, White: C, White(isotropy): H.

was observed in the MV−CDW state (higher temperature)(Figure S2). The three-dimensional-delta pair distributionfunction (3D-ΔPDF), a type of Patterson function, was used toanalyze diffuse scattering.39 In comparison to the structure in
the AV−MH state, the structure in the MV−CDW state differs
in three ways: (i) −Br···PdII ···Br−PdIV−Br··· Peierls distorted
1D structure; (ii) dimerization of Br− counteranion; and (iii)
local-ordering of C−H···Br···H−C hydrogen bonding.
(i) In the MV−CDW state, the structure contains −Br···PdII···Br−PdIV−Br··· units with a Peierls distorted 1D structure.
For the MV−CDW state, the electron−lattice interactions
cause the displacement of the bridged Br anion from thecenter. At 260 K, from 3D-ΔPDF, the PdII ···Br and Br−PdIV
distances were determined to be 2.76 and 2.49 Å, respectively(intrachain Pd−Pd distance was 5.25 Å).39 Correlations
between chains along the b axis correspond to the in-phaseordering of the −Br···PdII ···Br−PdIV−Br··· chains, whereas
correlations along the c axis have almost no charge ordering(Figure S3). (ii) The Br− counteranions dimerize along the aaxis with pairs of counteranions moving in the PdIV direction
by 0.035 Å (Figure S3).39 This is because the in-plane cptn
ligand has a long PdIV−N coordination distance and a short
PdII−N coordination distance, allowing it to attract and repel
Br− counteranions via N−H···Br···H−N hydrogen bonding.
The displacements of the Br− counteranions serve as thestarting point for phase transition propagation. (iii) Although
the C5 atom was disordered in the AV−MH state, it wasordered and shifted in the PdIV direction in the MV−CDW
state. This disorder occurs as a result of C5 atoms moving in
the PdIV direction due to C−H···Br···H−C hydrogen bonding(These Br− counteranions correlate with the adjacent MX
chain, as shown in Figure S1). As discussed in the Supporting
Information, there is no ferroelasticity along the c axis, which isconnected to the domain of the ab plane. However, it does
produce a weak correlation along the c axis.

Figure 4. PXRD pattern of the peak of the (2 0 0) plane of 1 (a) at
various temperatures and (b) at 92 K during the cooling process.

corresponds to the (2 0 0) plane. A single peak (without any
shoulder peak) was observed between 120 and 300 K, and an
additional shoulder peak appeared between 92 and 100 K.
These single and shoulder peaks correspond to the Pd···Pddistances of the MV−CDW and AV−MH, respectively. The
single and shoulder peaks at (2 0 0) were deconvoluted into
two peaks in the ratio of 3:1 (CDW/MH) (this ratio was
calculated using bulk sample, and this tendency might notalways match the behavior of a single crystal because it was
obtained as an average of several crystals) At 92 K, the unit
cells were fit to be CDW (a: 5.231, b: 6.960, and c: 22.623 Å)
and MH (a: 5.219, b: 6.967, and c: 22.607 Å) using the Le Bailmethod (R = 4.47%, Figure S5; see the methods section). The
difference in the Pd···Pd distances in the MH and CDW states(|Δa|) was only 0.012 Å. This value is less than that reported
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for the Pd complex with alkyl chain (∼0.03 Å).31 In addition,
the distance between the chains along the b axis increased from
the MV−CDW to AV−MH states. These findings confirmedthat there is only a slight difference in the value of unit cellparameters between the MV−CDW and AV−MH states.
STM images are shown in Figure 5. We observed atomicscale phase separation between the MV−CDW and AV−MH

Articleflow (Movies S2 and S3 at 135 K). The front and back sides of
the crystals have similar striped domains (Movies S2 and S3 at
135 K). These findings indicate that the domain of the striped
pattern is correlated with the depth direction (see Supporting
Information before Figure S9 and Table S2). Moreover, thedomain shape of each crystal is memorized, and as will be
described later, can be changed by an external force.
Propagation Mechanism for the Phase Transition.
From PXRD and optical conductivity measurements, there wasa decrease in the Pd−Pd distance of 0.013 Å induced by thetransition from the CDW to MH state and a 0.2 eV optical gap
fluctuation. To comprehend the ferroelastic phenomena, wemust consider two dimensions: (i) microscopic and (ii)macroscopic. In other words, there are specific trends along thea and b axes when the averaged structures around thecounteranions are compared at room temperature (∼300 K)(MV−CDW) and 93 K (AV−MH) (Figure 6).

Figure 5. STM image of 1 at 113 K. The blue, black, and green dottedlines indicate the AV−MH state, the MV−CDW state, and theboundary between them, respectively.

domains over an area of 25 nm × 25 nm. Bright spots wereobserved on the PdIV site in the MV−CDW domain and on
the PdIII site in the AV−MH domain (Figure S6).34 Although
the difference in the CDW Pd(IV−ρ)−Br···Pd(II+ρ) and MH
PdIII−X−PdIII electronic states is small (ρ is almost 1), twodomains with clear borders were observed at 113 K. On theother hand, the Ni−Pd heterojunction system has threedomains, where the intermediate domain cannot be distinguished whether MV−CDW or AV−MH.40 These heterojunction interface differences may require attention in
fabricating devices. The borderline is not parallel to the (1 10) plane that is observed in the macroscale structure, as shownin Figure S7, but it is parallel to the (1 0 0) or (0 1 0) plane at
the nanoscale and is adjacent to the defects. These findings
indicated that the defects act as nanoscale anchors for thedomain wall. At the same time, we observed quasi-epitaxial
growth at the nanoscale between the MV−CDW and AV−MH
states.
Macroscale Structure. Figure S7 shows optical images ofa single crystal of 1 on the substrate at various temperatures. At
temperatures between 50 and 130 K, there is a phaseseparation between the bright and dark domains, whoseborder is parallel to the (110) plane. In addition, the bright anddark domains were assigned to MV−CDW and AV−MH
states, respectively, using Raman spectroscopy.33 In Figure S8,
the ratio of the AV−MH domain is plotted (the optical images
in Figure S7 were used to calculate this ratio, where the brightand dark domains correspond to the CDW and MH states,
respectively). A thin crystal in a N2 gas flow at 141 K (±2 K)
underwent dynamic phase transitions between MV−CDW andAV−MH states with a striped domain (Movie S1; the colors in
Figure S7 and the movie are different due to the use ofdifferent cameras and light sources). On the other hand, at agiven temperature, the phase separation in the crystals on thesubstrate was static because the thermal conductivity of 1 issufficient to follow the surrounding environment. In addition,
the pattern was basically independent of the direction of the

Figure 6. Hydrogen bonding structure of 1 (a), (c) at RT, and (b),(d) at 93 K. (a) and (b) Gray: Pd, Orange: Br, Blue: N, White: H. (c)and (d) Gray: Pd, Red: bridged Br, Purple: Br counteranion, Blue: N,
White: H.

(i) At room temperature, the N(A)···Br···N(B) angle was
100.59°, whereas it was 100.40° at 93 K. A comparison of theMV−CDW and MH states indicated that both the Pd···Pddistance (a direction) and the N(A)···Br···N(B) angle
increased and the interchain (b axis) distance decreased. In
the AV−MH state, the converse occurred, as confirmed by thetemperature dependence of the unit cell (Figure S10). Thus, inthe MV−CDW state, there is spontaneous strain along the adirection, whereas in the AV−MH state, there is spontaneous
strain along the b direction. These strains act as stresses on theoverall thermal strain of the crystal. Therefore, the NH···Br···
HN hydrogen bond adjusts and propagates the strain along thea and b directions during the transition, similar to a jack. In the
MV−CDW state, Br counteranions are shifted by 0.035 Å
along the a direction. Therefore, the structural change is highly
complicated. The polarities of Nδ−−Hδ+ bond generally follow
the order (PdII···)Nδ−−Hδ+ < (PdIII···)Nδ′−−Hδ′+ < (PdIV···)Nδ″−−Hδ″+. Dimerization of the Br− counteranion may be
induced by the difference in the Nδ−−Hδ+···Br−···Hδ+−Nδ−hydrogen bonding, as determined from the 3D-ΔPDF results.
When a chain transitions to the AV−MH state, thePd(II→III)NH···Br hydrogen bond strengthens and its bondlength decreases, whereas the Pd(IV→III)NH···Br hydrogenbond weakens and its bond length increases. Subsequently,
the Br− anion migrates toward the center. At this point, the14070

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Inorganic Chemistrypubs.acs.org/IC(PdIV···)NH···Br and (PdII···)NH···Br hydrogen bond lengths
increase and decrease in the neighboring chains, respectively.
These structural modifications to the ligands perturbate the dz2
orbitals of the Pd ion (the dz2 = d(2z2−x2−y2) orbital also
contributes to the xy plane). Furthermore, this perturbationinduces a phase transition in the subsequent chains. As a result,hydrogen bonding is critical for phase separation andtransition.
(ii) The differences in a (|Δa|) and b (|Δb|) axes of theMV−CDW and AV−MH states were calculated to be 0.012
and 0.007 Å, respectively, using PXRD data at 92 K. The sumsof these differences were 0.24 and 0.14 μm in a complete
crystal (∼100 μm which corresponds to approximately 2.0 ×
104 units for each axis) (eq S1). Contrastingly, the difference in|Δc| between CDW and MH at 92 K was calculated to be 0.016
Å. In the case of the c axis, the sum of difference was 7.2 nm for
a complete crystal (∼10 μm which corresponds to approximately 4.5 × 103 units for each axis) (eq S1). These
differences immediately relax if each domain is in paraelastics.
Each domain, however, alleviates the strain by moving thedomain wall. This behavior is typical of the ferroelastic domain.
The total spontaneous strain was calculated as stotal =(sa(CDW → MH)2 + sb(CDW → MH)2 + sc(CDW → MH)2)1/2 = 0.0026,
where |sa(CDW → MH)| = |(aMH − aCDW)/aCDW| = 0.0023, |sb(CDW → MH)| = |(bMH − bCDW)/bCDW| = 0.0010, and |sc(CDW → MH)| = |(cMH − cCDW)/cCDW| = 0.0007. These values
are comparable to those reported for typical ferroelastics.41,42
The domain wall corresponding to the (1 1 0) plane of eachdomain [dCDW = (aCDW2 + bCDW2)1/2 = 8.707 Å, dMH = (aMH2 +bMH2)1/2 = 8.705 Å] has almost no epitaxial strain.42
The interactions between cptn ligands are weak along the caxis, where the flexible alkylene ring may release the epitaxial
strain. In addition, by applying external strain, the domain wall
can be eliminated (Figure 7, Movie S4. The crystal was

Articleat various temperatures are shown in Figure 8. The ECT in the
MV−CDW state corresponds to CT from an occupied band of

Figure 8. ECT vs T plots of 1 at various temperatures.

the PdII dz2 orbital to an unoccupied band of the PdIV dz2
orbital and is defined as 2S−U, where S is proportional to thePd···Pd distance. Moreover, ECT in the MH state corresponds
to CT from the occupied lower Hubbard band of the PdIII dz2
orbital to the unoccupied upper Hubbard band of the PdIII dz2
orbital and is defined as U, where U is on-site Coulomb
repulsion energy.23 The ECT decreased gradually from 0.66 to
0.60 eV between 300 and 150 K and abruptly decreased from0.60 to 0.43 eV between 150 and 100 K. Then, ECT was nearly
constant at 0.43 eV between 100 and 10 K; this value isconsistent with the previously reported value (∼0.45 eV).43
This small ECT value or U value is attributed to the dz2 orbital
expansion induced by the weak ligand field of the in-plane
ligands. These results indicate that a CDW-to-MH transition
occurs between 150 and 100 K, and that the difference in ECTvalues for CDW and MH is at least 0.17 eV.
Figure S12a shows the temperature dependence of the spin
susceptibility in 1, as determined by electron spin resonance.
We observed a clear change in the spin susceptibility at
approximately 150 K. In the low-temperature phase, a Curielike behavior was observed, as shown by the dashed curve.
These Curie spins could arise from the chain ends or thesegments containing odd number of spins in the PdIII MH state(S = 1/2) because of antiferromagnetic interaction. Contrastingly, spin susceptibility decreased remarkably at the hightemperature phase, demonstrating the dominance of thenonmagnetic PdII−PdIV CDW state. Considering the entropyof the spin (CDW state < MH state), the spin should havehigh entropy in the high-temperature phase. In contrast, theMX complexes have high spin entropy (MH state) in the lowtemperature phase because the structural change (decrease in
the Pd···Pd distances) occurring in this phase is dominant in
the CDW-to-MH transition of Pd-based MX complexes.44 At
the intermediate temperature region of 200−100 K, the spin
susceptibility changed significantly with blunt hysteresis due tothe formation of the phase separation. 1/χ versus T plots for 1
are shown in Figure S12b. The spin concentration below 100
K is calculated as 0.36%, which is higher than that of reported
Pd-based MX complexes (∼0.14%).31,43
In Figure 9, the electrical conductivities (σ) of 1 and[Pd(chxn)2Br]Br2 at various temperatures (T) are plotted. At
300 K, the conductivity of 1 was 10−2 S cm−1, which is thesecond highest value of all Pd-based MX compounds43
reported so far and significantly higher than that offerrocenium tetrachloroferrate [∼10−6 S cm−1 (AC)].38 Thishigher conductivity is facilitated by the lower band gap and 2D
sheet structure, wherein the defects can be bypassed whenelectron conduction occurs through a one-dimensional chain.

Figure 7. Images of a single crystal of 1. (a) At 110 K, (c) at 100 K
before push, and (d) at 100 K after push. (b) Schematic illustration of
the thermal shrinking of the single crystal and its elastic force(spontaneous strain).

manually pushed using the needle at 100 K). Initially, the roleof hydrogen bonding in the bulk appears ambiguous.
Nonetheless, when considering nanoscale functionality, thesum of the innumerable hydrogen bonds promotes phaseseparation in the bulk.
Physical Properties. The charge transfer energy (ECT;
optical gap is calculated from the reflectivity spectra of 1 atvarious temperatures, shown in Figure S11) versus T plots of 1
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Inorganic Chemistrypubs.acs.org/IC(PAL) (λ = 0.700 Å). The synchrotron powder-crystal X-ray
diffraction data were collected on the BL02B2 Beamline in SPring-8(λ = 1.000 Å). The Le Bail analysis48 was performed using the Rietica
program package (old version). Temperature dependence of STM
was analyzed using an Omicron LT-STM with an electrochemicallyetched W tip. The Fourier transform infrared spectra of single crystal
were measured in reflectance mode using a JASCO FT/IR 6700
spectrometer in conjunction with an IRT-5000 microscope unit.
Polarized reflectivity spectra in the UV−Vis−NIR range wereacquired using a custom-built spectrometer equipped with a 25 cm
grating monochromator and an optical microscope. Temperature
regulation was accomplished using a Janis ST-300 cryostat equippedwith a ZnSe window. The Kramers−Kronig transformation was used
to convert the obtained reflectivity spectra to optical conductivity
spectra. A Quantum Design PPMS MODEL 6000 was used todetermine the electrical conductivity.

Figure 9. Electrical conductivities (σ) of 1 and [Pd(chxn)2Br]Br2 atvarious temperatures.

The conductivity of 1 then decreased upon cooling, which istypical for semiconductors. In ln(σ) versus T−1 × 103 plots(Arrhenius plots), the activation barrier (Ea) is nearly constantat 145 meV compared to 227 meV for [Pd(chxn)2Br]Br2 at
low temperatures. There are shoulder peaks near 6.5 and 10
K−1 × 103 (∼150 and ∼100 K), which appear to reduce Ea.
Although this behavior could be explained by the fact that the
crystals are quasi-heterojunctions, it is still being investigated.
Because the optical gaps for the MV−CDW and AV−MH
states are 0.4 and 0.6 eV, respectively, and the difference
between them is small (∼0.2 eV), the interface may be highly
conductive.
Ferroelastic phase separation induces the behavior of thephysical properties.45−49 Hence, it would be advantageous if
the physical properties of the compound could be spontaneously controlled via molecular design.

■

ASSOCIATED CONTENT* Supporting Information
sı

The Supporting Information is available free of charge athttps://pubs.acs.org/doi/10.1021/acs.inorgchem.2c02078.
Crystal data, structural information, PXRD data, STM
images, images of crystal, optical data, and magnetic
properties (PDF)
Phase separation between MV−CDW and AV−MH at
141 K in a fluctuated N2 gas flow (MP4)
Imaging of a single crystal at 135 K (MP4)
Imaging of a single crystal at 135 K (MP4)
Imaging of a single crystal at 110 K (MP4)■■

CONCLUSIONSIn this study, for the first time, we elucidated the mechanism of
PdII−PdIV/PdIII−PdIII phase transition and the phase separation mechanism of 1 at the atomic and molecular levels usingsynchrotron X-ray techniques. The N−H···Br···H−N hydrogen bonds propagated the strain that induced the transition
like a jack. The dynamic to-and-fro visible phase transition/
separation was derived from spontaneous strain and temperature fluctuations. The differences in the Pd···Pd distance andoptical gap of the AV−MH and MV−CDW were only 0.012 Å
and 0.17 eV, respectively. These differences could be
elucidated only via methods such as X-ray diffraction using a
synchrotron radiation source. In addition, the effects of thephase separation on the physical properties, such as spin
susceptibility and electrical conductivity, were clarified tounderstand the behavior of CDW−MH quasi-epitaxial crystal.
Finally, the phase separation was caused by ferroelasticity
through the hydrogen-bonding network, and it could becontrolled by applying an external force. These findings imply
that spin magnetic susceptibility and electrical conductivity canbe manipulated as well. We expect that these results will enable
the design of more rational molecular devices.

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ArticleAUTHOR INFORMATION

Corresponding Authors

Takefumi Yoshida − Department of Chemistry, Graduate
School of Science, Tohoku University, Sendai, Miyagi 9808578, Japan; Present Address: Innovation ResearchCenter for Fuel Cells, The University of ElectroCommunications, Chofu, Tokyo 182-8585, Japan;
orcid.org/0000-0003-3479-7890;
Email: takefumi.yoshida.b7@tohoku.ac.jp
Shinya Takaishi − Department of Chemistry, Graduate Schoolof Science, Tohoku University, Sendai, Miyagi 980-8578,
Japan; orcid.org/0000-0002-6739-8119;
Email: shinya.takaishi.d8@tohoku.ac.jp
Masahiro Yamashita − Department of Chemistry, Graduate
School of Science, Tohoku University, Sendai, Miyagi 9808578, Japan; School of Materials Science and Engineering,
Nankai University, Tianjin 300350, China;
Email: yamasita.m@gmail.com
Authors

Laurent Guérin − Institut de Physique de Rennes, Rennes
Cedex 35042, France
Tatsuhiro Kojima − Department of Chemistry, Graduate
School of Science, Osaka University, Toyonaka, Osaka 5600043, Japan; orcid.org/0000-0002-1313-8987
Hiroyoshi Ohtsu − Department of Chemistry, School of
Science, Tokyo Institute of Technology, Tokyo 152-8550,
Japan; orcid.org/0000-0002-2911-3151
Masaki Kawano − Department of Chemistry, School of Science,
Tokyo Institute of Technology, Tokyo 152-8550, Japan;
orcid.org/0000-0001-9886-4226
Tatsuya Miyamoto − Department of Advanced Materials
Science, Graduate School of Frontier Sciences, The Universityof Tokyo, Kashiwa 277-8561, Japan

EXPERIMENTAL SECTION[Pd(cptn)2Br] Br2 (1) was synthesized using the same procedure as
described previously.33 X-ray diffraction patterns of single crystals
were collected using a Bruker APEX-II diffractometer equipped withan APEX II CCD detector and a JAPAN Thermal Engineering Co.,
Ltd. Cryo system DX-CS190LD. The synchrotron single-crystal X-ray
diffraction data were collected on the NW2A Beamline in the Photon
Factory Advanced Ring of the High Energy Accelerator Research
Organization (KEK, Proposal no. 2014G008), the Swiss-Norwegian
Beamlines (SNBL) in European Synchrotron Radiation Facility(ESRF), and the 2D Beamline in Pohang Accelerator Laboratory14072

https://doi.org/10.1021/acs.inorgchem.2c02078
Inorg. Chem. 2022, 61, 14067−14074

Inorganic Chemistrypubs.acs.org/IC

Hiroshi Okamoto − Department of Advanced Materials
Science, Graduate School of Frontier Sciences, The Universityof Tokyo, Kashiwa 277-8561, Japan; orcid.org/00000003-2807-5277
Kenichi Kato − RIKEN SPring-8 Center, Sayo-gun, Hyogo
679-5148, Japan
Masaki Takata − Institute of Multidisciplinary Research for
Advanced Materials, Tohoku University, Sendai 980-8577,
Japan
Yuka Hosomi − Faculty of Pure and Applied Sciences,
University of Tsukuba, Tsukuba 305-8573, Japan
Shoji Yoshida − Faculty of Pure and Applied Sciences,
University of Tsukuba, Tsukuba 305-8573, Japan
Hidemi Shigekawa − Faculty of Pure and Applied Sciences,
University of Tsukuba, Tsukuba 305-8573, Japan;
orcid.org/0000-0001-9550-5148
Hisaaki Tanaka − Department of Applied Physics, Graduate
School of Engineering, Nagoya, University, Nagoya 4648603, Japan; orcid.org/0000-0003-3503-6161
Shin-ichi Kuroda − Department of Applied Physics, Graduate
School of Engineering, Nagoya, University, Nagoya 4648603, Japan
Hiroaki Iguchi − Department of Chemistry, Graduate Schoolof Science, Tohoku University, Sendai, Miyagi 980-8578,
Japan; orcid.org/0000-0001-5368-3157
Brian K. Breedlove − Department of Chemistry, Graduate
School of Science, Tohoku University, Sendai, Miyagi 9808578, Japan; orcid.org/0000-0003-1419-577X
Zhao-Yang Li − School of Materials Science and Engineering,
Nankai University, Tianjin 300350, China; orcid.org/
0000-0002-0952-9862(3) Fiebig, M.; Lottermoser, T.; Fröhlich, D.; Goltsev, A. V.; Pisarev,
R. V. Observation of coupled magnetic and electric domains. Nature
2002, 419, 818−820.
(4) Kagawa, F.; Horiuchi, S.; Minami, N.; Ishibashi, S.; Kobayashi,K.; Kumai, R.; Murakami, Y.; Tokura, Y. Polarization Switching
Ability Dependent on Multidomain Topology in a Uniaxial Organic
Ferroelectric. Nano Lett. 2014, 14, 239−243.
(5) Wei, X.-K.; Sluka, T.; Fraygola, B.; Feigl, L.; Du, H.; Jin, L.; Jia,
C.-L.; Setter, N. Controlled Charging of Ferroelastic Domain Walls in
Oxide Ferroelectrics. ACS Appl. Mater. Interfaces 2017, 9, 6539−6546.
(6) Fan, Z.; Xue, F.; Tutuncu, G.; Chen, L.-Q.; Tan, X. Interaction
Dynamics Between Ferroelectric and Antiferroelectric Domains in a
PbZrO3-Based Ceramic. Phys. Rev. Appl. 2019, 11, 064050.
(7) Hu, Y.; You, L.; Xu, B.; Li, T.; Morris, S. A.; Li, Y.; Zhang, Y.;
Wang, X.; Lee, P. S.; Fan, H. J.; Wang, J. Ferroelastic-switching-driven
large shear strain and piezoelectricity in a hybrid ferroelectric. Nat.
Mater. 2021, 20, 612−617.
(8) Sasaki, T.; Sakamoto, S.; Takasaki, Y.; Takamizawa, S. A
Multidirectional Superelastic Organic Crystal by Versatile Ferroelastical Manipulation. Angew. Chem., Int. Ed. 2020, 132, 4370−4373.
(9) Takamizawa, S.; Takasaki, Y. Versatile Shape Recoverability of
Odd-Numbered Saturated Long-Chain Fatty Acid Crystals. Cryst.
Growth Des. 2019, 19, 1912−1920.
(10) Kumai, R.; Okimoto, Y.; Tokura, Y. Current-Induced InsulatorMetal Transition and Pattern Formation in an Organic ChargeTransfer Complex. Science 1999, 284, 1645−1647.
(11) Okimoto, Y.; Kumai, R.; Saitoh, E.; Izumi, M.; Horiuchi, S.;
Tokura, Y. Spectroscopic study of stripe pattern formation induced bycurrent injection in a charge-transfer complex. Phys. Rev. B: Condens.
Matter Mater. Phys. 2004, 70, 115104.
(12) Sasaki, T.; Yoneyama, N.; Suzuki, A.; Kobayashi, N.; Ikemoto,Y.; Kimura, H. Real Space Imaging of the Metal−Insulator Phase
Separation in the Band Width Controlled Organic Mott System κ(BEDT-TTF)2Cu[N(CN)2]Br. J. Phys. Soc. Jpn. 2005, 74, 2351−
2360.
(13) Pustogow, A.; McLeod, A. S.; Saito, Y.; Basov, D. N.; Dressel,
M. Internal strain tunes electronic correlations on the nanoscale. Sci.
Adv. 2018, 4, No. eaau9123.
(14) Yoshida, T.; Takaishi, S.; Kumagai, S.; Iguchi, H.; Mian, M. R.;
Yamashita, M. Observation of charge bistability in quasi-onedimensional halogen-bridged palladium complexes by X-ray absorption spectroscopy. Dalton Trans. 2019, 48, 11628−11631.
(15) Matsuzaki, H.; Iwata, M.; Miyamoto, T.; Terashige, T.; Iwano,K.; Takaishi, S.; Takamura, M.; Kumagai, S.; Yamashita, M.;
Takahashi, R.; Wakabayashi, Y.; Okamoto, H. Excitation-PhotonEnergy Selectivity of Photoconversions in Halogen-Bridged Pd-Chain
Compounds: Mott Insulator to Metal or Charge-Density-Wave State.
Phys. Rev. Lett. 2014, 113, 096403.
(16) Yamashita, M.; Okamoto, H., Material Designs and New Physical
Properties in MX- and MMX-Chain Compounds; Springer: Berlin, 2012.
(17) Nasu, K. Extended Peierls-Hubbard Model for One-Dimensional N-Sites N-Electrons System. I. Phase Diagram by Mean Field
Theory. J. Phys. Soc. Jpn. 1983, 52, 3865−3873.
(18) Weber-Milbrodt, S. M.; Gammel, J. T.; Bishop, A. R.; Loh, E. Y.
Two-band model for halogen-bridged mixed-valence transition-metal
complexes. II. Electron-electron correlations and quantum phonons.
Phys. Rev. B: Condens. Matter Mater. Phys. 1992, 45, 6435−6458.
(19) Clark, R. J. H.; Kurmoo, M. Electronic and resonance Raman
spectra of mixed-valence linear-chain complexes of platinum with 1,3diaminopropane. Inorg. Chem. 1980, 19, 3522−3527.
(20) Clark, R. J. H.; Frank, M. L.; Trunble, W. R. Resonance Raman
spectra and excitation profiles of the mixed valence compound
wolffram’s red [PtII(C2H5NH2)4][PtIV(C2H5NH2)4Cl2]Cl44H2O.
Chem. Phys. Lett. 1976, 41, 287−292.
(21) Clark, R. J. H. Nyholm Lecture. Synthesis, structure, andspectroscopy of metal−metal dimers, linear chains, and dimer chains.
Chem. Soc. Rev. 1990, 19, 107−131.

Complete contact information is available at:https://pubs.acs.org/10.1021/acs.inorgchem.2c02078
Author Contributions

The manuscript was written through contributions of all
authors.
Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS
This work was partially supported by JSPS KAKENHI grants
JP19H05631, JP20K15293, and JP21H04988 and the National
Natural Science Foundation of China (NSFC, 22150710513).
The synchrotron single-crystal X-ray diffraction data werecollected on the NW2A Beamline in the Photon Factory
Advanced Ring of the High Energy Accelerator Research
Organization (KEK, Proposal no. 2014G008), the SNBL in
ESRF, and on the 2D Beamline in PAL. The synchrotron
powder-crystal X-ray diffraction data were collected on theBL02B2 Beamline in SPring-8. P. M.Y. acknowledges the
support of the 111 project (B18030) from China.

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ArticleREFERENCES(1) Cowburn, R. P.; Welland, M. E. Room Temperature Magnetic
Quantum Cellular Automata. Science 2000, 287, 1466−1468.
(2) Koyama, T.; Chiba, D.; Ueda, K.; Kondou, K.; Tanigawa, H.;
Fukami, S.; Suzuki, T.; Ohshima, N.; Ishiwata, N.; Nakatani, Y.;
Kobayashi, K.; Ono, T. Observation of the intrinsic pinning of amagnetic domain wall in a ferromagnetic nanowire. Nat. Mater. 2011,
10, 194−197.
14073

https://doi.org/10.1021/acs.inorgchem.2c02078
Inorg. Chem. 2022, 61, 14067−14074

Inorganic Chemistrypubs.acs.org/IC

Article(37) Farokhipoor, S.; Noheda, B. Conduction through 71̊ Domain
Walls in BiFeO3 Thin Films. Phys. Rev. Lett. 2011, 107, 127601.
(38) Zhang, H.-Y.; Hu, C.-L.; Hu, Z.-B.; Mao, J.-G.; Song, Y.; Xiong,
R.-G. Narrow Band Gap Observed in a Molecular Ferroelastic:
Ferrocenium Tetrachloroferrate. J. Am. Chem. Soc. 2020, 142, 3240−
3245.
(39) Guérin, L.; Yoshida, T.; Zatterin, E.; Simonov, A.; Chernyshov,D.; Iguchi, H.; Toudic, B.; Takaishi, S.; Yamashita, M. Elucidating 2D
Charge-Density-Wave Atomic Structure in an MX−Chain by the 3DΔPair Distribution Function Method**. ChemPhysChem 2022, 23,No. e202100857.
(40) Wakizaka, M.; Kumagai, S.; Wu, H.; Sonobe, T.; Iguchi, H.;
Yoshida, T.; Yamashita, M.; Takaishi, S. Macro- and atomic-scaleobservations of a one-dimensional heterojunction in a nickel andpalladium nanowire complex. Nat. Commun. 2022, 13, 1188.
(41) Aizu, K. Determination of the State Parameters andFormulation of Spontaneous Strain for Ferroelastics. J. Phys. Soc.
Jpn. 1970, 28, 706−716.
(42) Carpenter, M. A.; Salje, E. H.; Graeme-Barber, A. Spontaneous
strain as a determinant of thermodynamic properties for phasetransitions in minerals. Eur. J. Mineral. 1998, 10, 621−691.
(43) Mian, M. R.; Iguchi, H.; Takaishi, S.; Murasugi, H.; Miyamoto,T.; Okamoto, H.; Tanaka, H.; Kuroda, S.-i.; Breedlove, B. K.;
Yamashita, M. Multiple-Hydrogen-Bond Approach to Uncommon
Pd(III) Oxidation State: A Pd-Br Chain with High Conductivity and
Thermal Stability. J. Am. Chem. Soc. 2017, 139, 6562−6565.
(44) Yamashita, M.; Takaishi, S. Stabilization of Pd(iii) states in
nano-wire coordination complexes. Chem. Commun. 2010, 46, 4438−
4448.
(45) Xu, C.; Mao, J.; Guo, X.; Yan, S.; Chen, Y.; Lo, T. W.; Chen,
C.; Lei, D.; Luo, X.; Hao, J.; Zheng, C.; Zhu, Y. Two-dimensional
ferroelasticity in van der Waals β’-In2Se3. Nat. Commun. 2021, 12,3665.
(46) Ju, C.; Yang, J.-C.; Luo, C.; Shafer, P.; Liu, H.-J.; Huang, Y.-L.;
Kuo, H.-H.; Xue, F.; Luo, C.-W.; He, Q.; Yu, P.; Arenholz, E.; Chen,
L.-Q.; Zhu, J.; Lu, X.; Chu, Y.-H. Anomalous Electronic Anisotropy
Triggered by Ferroelastic Coupling in Multiferroic Heterostructures.
Adv. Mater. 2016, 28, 876−883.
(47) Stinson, H. T.; Sternbach, A.; Najera, O.; Jing, R.; Mcleod, A.
S.; Slusar, T. V.; Mueller, A.; Anderegg, L.; Kim, H. T.; Rozenberg,
M.; Basov, D. N. Imaging the nanoscale phase separation in vanadium
dioxide thin films at terahertz frequencies. Nat. Commun. 2018, 9,3604.
(48) Agar, J. C.; Damodaran, A. R.; Okatan, M. B.; Kacher, J.;
Gammer, C.; Vasudevan, R. K.; Pandya, S.; Dedon, L. R.; Mangalam,
R. V. K.; Velarde, G. A.; Jesse, S.; Balke, N.; Minor, A. M.; Kalinin, S.
V.; Martin, L. W. Highly mobile ferroelastic domain walls incompositionally graded ferroelectric thin films. Nat. Mater. 2016,
15, 549−556.
(49) Le Bail, A. Whole Powder Pattern Decomposition Methods andApplications: A Retrospection. Powder Diffr. 2005, 20, 316−326.

(22) Okamoto, H.; Yamashita, M. Solitons, Polarons, and Excitonsin Quasi-One-Dimensional Halogen-Bridged Transition Metal Compounds. Bull. Chem. Soc. Jpn. 1998, 71, 2023−2039.
(23) Takaishi, S.; Kawakami, D.; Yamashita, M.; Sasaki, M.;
Kajiwara, T.; Miyasaka, H.; Sugiura, K.-i.; Wakabayashi, Y.; Sawa,
H.; Matsuzaki, H.; Kishida, H.; Okamoto, H.; Watanabe, H.; Tanaka,
H.; Marumoto, K.; Ito, H.; Kuroda, S.-i. Dynamical Valence
Fluctuation at the Charge−Density−Wave Phase Boundary in
Iodide-Bridged Pt Compound [Pt(chxn)2I]I2. J. Am. Chem. Soc.
2006, 128, 6420−6425.
(24) Kawakami, D.; Yamashita, M.; Matsunaga, S.; Takaishi, S.;
Kajiwara, T.; Miyasaka, H.; Sugiura, K.-i.; Matsuzaki, H.; Okamoto,H.; Wakabayashi, Y.; Sawa, H. Halogen-Bridged PtII/PtIV MixedValence Ladder Compounds. Angew. Chem., Int. Ed. 2006, 45, 7214−
7217.
(25) Kobayashi, A.; Kitagawa, H. Mixed-Valence Two-Legged MXLadder Complex with a Pair of Out-of-Phase Charge-Density Waves.
J. Am. Chem. Soc. 2006, 128, 12066−12067.
(26) Toriumi, K.; Wada, Y.; Mitani, T.; Bandow, S.; Yamashita, M.;
Fujii, Y. Synthesis and crystal structure of a novel one-dimensional
halogen-bridged nickel(III)-X-nickel(III) compound, {[Ni(R,Rchxn)2Br]Br2}. J. Am. Chem. Soc. 1989, 111, 2341−2342.
(27) Kishida, H.; Matsuzaki, H.; Okamoto, H.; Manabe, T.;
Yamashita, M.; Taguchi, Y.; Tokura, Y. Gigantic optical nonlinearity
in one-dimensional Mott-Hubbard insulators. Nature 2000, 405,
929−932.
(28) Kishida, H.; Ito, T.; Nakamura, A.; Takaishi, S.; Yamashita, M.
Current oscillation originating from negative differential resistance in
one-dimensional halogen-bridged nickel compounds. J. Appl. Phys.
2009, 106, 016106.
(29) Takaishi, S.; Yamashita, M.; Matsuzaki, H.; Okamoto, H.;
Tanaka, H.; Kuroda, S.-i.; Goto, A.; Shimizu, T.; Takenobu, T.; Iwasa,
Y. One-Dimensional Bromo-Bridged NiIII Complexes [Ni(S,Sbn)2Br]Br2 (S,S-bn=2S,3S-diaminobutane): Synthesis, Physical
Properties, and Electrostatic Carrier Doping. Chem. - Eur. J. 2008,
14, 472−477.
(30) Takaishi, S.; Tobu, Y.; Kitagawa, H.; Goto, A.; Shimizu, T.;Okubo, T.; Mitani, T.; Ikeda, R. The NQR Observation of SpinPeierls Transition in an Antiferromagnetic MX-Chain Complex[NiBr(chxn)2]Br2. J. Am. Chem. Soc. 2004, 126, 1614−1615.
(31) Takaishi, S.; Takamura, M.; Kajiwara, T.; Miyasaka, H.;
Yamashita, M.; Iwata, M.; Matsuzaki, H.; Okamoto, H.; Tanaka, H.;
Kuroda, S.-i.; Nishikawa, H.; Oshio, H.; Kato, K.; Takata, M. ChargeDensity-Wave to Mott−Hubbard Phase Transition in Quasi-OneDimensional Bromo-Bridged Pd Compounds. J. Am. Chem. Soc. 2008,
130, 12080−12084.
(32) Yamashita, M. Next Generation Multifunctional Nano-Science
on Advanced Metal Complexes with Quantum Effect and Nonlinearity. Bull. Chem. Soc. Jpn. 2021, 94, 209−264.
(33) Yoshida, T.; Takaishi, S.; Iguchi, H.; Okamoto, H.; Tanaka, H.;
Kuroda, S.-i.; Hosomi, Y.; Yoshida, S.; Shigekawa, H.; Kojima, T.;
Ohtsu, H.; Kawano, M.; Breedlove, B. K.; Guérin, L.; Yamashita, M.
Optically Visible Phase Separation between Mott-Hubbard andCharge-Density-Wave Domains in a Pd-Br Chain Complex.
ChemistrySelect 2016, 1, 259−263.
(34) Yuka, H.; Shoji, Y.; Atsushi, T.; Takefumi, Y.; Shinya, T.;
Osamu, T.; Masahiro, Y.; Hidemi, S. Temperature dependence ofPeierls−Hubbard phase transition in [Pd(cptn) 2 Br]Br 2 studied byscanning tunneling microscopy. Jpn. J. Appl. Phys. 2016, 55, 08NB16.
(35) Wang, L.; King, I.; Chen, P.; Bates, M.; Lunt, R. R. Epitaxial
and quasiepitaxial growth of halide perovskites: New routes to highend optoelectronics. APL Mater. 2020, 8, 100904.
(36) Zhang, H.; Qin, M.; Chen, Z.; Yu, W.; Ren, Z.; Liu, K.; Huang,J.; Zhang, Y.; Liang, Q.; Chandran, H. T.; Fong, P. W. K.; Zheng, Z.;
Lu, X.; Li, G. Bottom-Up Quasi-Epitaxial Growth of Hybrid
Perovskite from Solution Process�Achieving High-Efficiency Solar
Cells via Template-Guided Crystallization. Adv. Mater. 2021, 33,
2100009.
14074

https://doi.org/10.1021/acs.inorgchem.2c02078
Inorg. Chem. 2022, 61, 14067−14074