bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Metallofullerenes – Enabling Long-Lived Radical Ion Pair States
Authors: Guldi Dirk M.
Published: February 2020

The “holy grail” of artificial photosynthesis is the realization of long lived radical ion pair states that power catalytic centers and, consequently, the production of solar fuels. Notably, magnetic field effects, especially internal magnetic field effects, are rarely employed in this context. Here, we report on severalelectron donor-acceptor conjugates, in which the presence of the Lu3N cluster in electron donating Lu3N@Ih
-C80 exerts an appreciable electron nuclear hyperfine coupling on the charge transfer dynamics. As such, a fairly efficient radical ion pair intersystem crossing converts the initially formed singlet radical ion pair state, 1[(Lu3N@Ih
-C80)•+-PDI•-]/ 1[(Lu3N@Ih
-C80)•+-C60
•-], to the corresponding triplet radical ion pair state, 3[(Lu3N@Ih
-C80)•+-PDI•-] / 3[(Lu3N@Ih
-C80)•+-C60
•-]. Most notably, the radical ion pair state lifetime of the latter is up to 1000 times longer than that of the earlier.
(Invited) Temperature Works Against Symmetry but “Fortunately” It Does Not Always Win: The Example of Formation of Actinide Endohedral Metallofullerenes
Authors: Poblet Josep M. , Morales-Martinez Roser , Abella Laura , Rodriguez-Fortea Antonio , Zhuang Jiaxin , Chen Ning , Cai Wenting , Echegoyen Luis
Published: February 2020

For almost two decades, intensive work from experimental and theoretical groups has made it possible to advance in the understanding of structural and electronic properties of endohedral metallofullerenes and cluster metal fullerenes. Hence, several groups have proposed diverse rules related with the relative stability of fullerene cages.1-4 All of them considered the potential energy when they predict the stability of IPR and non-IPR isomers based on the ionic model, in which the guest transfers usually between three and six electrons to the hosting carbon cage. Those guidelines have explained why the highly symmetric C80(I
h) cage is the preferred fullerene when there is a transfer of six electrons, like in the well-known Sc3N@C80,4 or in many other examples, such as Lu3N@C80, La2@C80, Y3@C80, etc.5 In endohedral fullerenes with four or less electron transfer between host and guest, there is not a prevalent structure, like C80(I
h), and the diversity of captured carbon cages is larger, the theoretical prediction of the most abundant species to be formed in a K-H reactor being much more difficult. In addition to the relative potential energy, it is also necessary to consider the enthalpic and entropic contributions to the stability of the endohedral fullerenes. A systematic theoretical analysis for a series of A@C2n fullerenes with A = Th and U, in combination with accurate experimental characterization, have allowed us to show that the structures of A4+@C2n
4- species are different from those of cluster fullerenes, such as Sc2O4+@C2n
4-, Sc2S4+@C2n
4-or Sc2C2
4+@C2n
4-. Here, we will discuss on the electronic structure and the peculiarities in host-guest interactions and cage selection in actinide endohedral metallofullerenes. Our observations support that there is a thermodynamic control in the fullerene formation at the high temperatures in which the carbon cages are formed (>1500 K), which in many cases determines that the actinide captures chiral IPR and non-IPR isomers of low-symmetry, in contrast with cluster fullerene encapsulation where different carbon cages are selected.

References

1- Campanera, J. M.; Bo, C.; Poblet, J. M., Angew. Chem., Int. Ed.
2005,
44, 7230-7233

2- Rodríguez-Fortea, A.; Alegret, N.; Balch, A. L.; Poblet, J. M., Nature Chem.
2010,
2, 955.

3- Garcia-Borràs M., Osuna S., Swart M., Luis J.M., Solà M. Angew.
Chem. Int.. Ed.
2013, 52, 9275-9278.

4- Wang, Y.; Díaz-Tendero, S.; Martín, F. and Alcamí, M. J. Am. Chem. Soc.,
2016, 138, 1551–1560

5- Stevenson, S.; Rice, G.; Glass, T.; Harich, K.; Cromer, F.; Jordan, M. R.; Craft, J.; Hadju, E.; Bible, R.; Olmstead, M. M.; Maitra, K.; Fisher, A. J.; Balch, A. L.; Dorn, H. C., Nature
1999,
401, 55.

6- Popov, A. A.; Yang, S.; Dunsch, L., Chem. Rev.
2013,
113, 5989-6113.
High Regioselective Cycloaddtion of Sc3N@C78 with Aryl Oxiranes
Authors: Chen Muqing , Guan Runnan , Jin Fei , Yang Shangfeng
Published: February 2020

Endohedral metallofullerenes (EMFs) with entrapping atoms and clusters have many superior properties due to the electron transfer from inner clusters to outer carbon cages, enabling them numerous potential applications in the fields of single molecule magnet, energy conversion, nano devices. The chemical functionalization of endohedral metallofullerenes through attraching different functional groups onto fullerene cage is useful strategy to improve corresponding solubility and tune the electron structure of endohedral metallofullerenes. Due to lower cage symmetry of Sc3N@D3h
-C78 relative to that of Sc3N@Ih
-C80, the high regioseletive synthesis of Sc3N@D3h
-C78 derivatives have been a challenge in the fields of fullerene chemistry, howeer, is highly desired. Herein, we performed a photoreaction of Sc3N@Ih
-C78 with asymmetric aryl oxirane in the toluene solution, leading to only main product among the possible 34 isomers. The X-ray single crystal diffraction measurement shows the [6,6]-close addition pattern of Sc3N@Ih
-C78 derivative.
Hybrid Nanostructures for Electrochemical Reduction of Carbon Dioxide
Authors: Ozden Sehmus , Asset Tristan , Atanassov Plamen
Published: February 2020

Producing fuels by reduction of carbon dioxide (CO2) is one of the key solutions that would be a groundbreaking impact not only on global energy also environmental sustainability. The success of this revolutionary technology depends on products that forms from reduction of CO2. Therefore it is important to develop effective catalytic materials for facilitating the CO2 reduction process. However, current catalysts do not have high efficiency and good selectivity. These existing catalysts are leading to multiple products. Major reported CO2 reduction catalysts are limited with two-electron reduced products that results formation of CO and formate. The formation of hydrocarbon products that have multiple proton and electron transfers is still one of the major scientific challenges that needs to be addressed. Currently, there is no identified catalyst that can facilitate CO2 reduction to selective hydrocarbon fuels with good efficiency due to the minute mechanistic understanding. Here, we will discuss tuning the hybrid structure of metal-oxide nanoparticles and two-dimensional (2D) layered materials as an efficient and selective CO2 reduction electrocatalyst with the density functional theory calculations, which reveals the unusual electrocatalytic properties of hybrid structure creating intrinsic chemical and electronic coupling and assist to understand the mechanism beyond the process.
Potential Applications of Layered Double Hydroxides in Membrane-Based Separation and Anti-Corrosion
Authors: Liu Yi
Published: February 2020

Layered double hydroxides (LDHs) are representative of inorganic layered compounds consisting of positively charged brucite-like sheets and charge compensating anions located in interlayer galleries. The high length-to-width ratio, uniform gallery height, flexible chemical compositions, active surface functionality and unique calcination properties of LDHs have inspired us to explore their potentials in gas separation. In the presentation we demonstrated that LDHs not only enabled to effectively separate hydrogen-containing gas mixtures relying on the uniform interlayer galleries, but also could serve as efficient perch, active heterogeneous nucleation center and qualified single metal source of MOF crystals for the preparation of high performance MOF membranes.

In addition, potential applications of LDHs in anti-corrosion were further explored. Relying on the dense in-plane structure of LDHs, preferentially c-oriented NiAl-CO3 LDH coatings were prepared showing excellent anti-corrosion performance. In addition, well-intergrown MOF coatings exhibiting excellent anti-corrosion performance could be in situ grown on Al substrates further by simple solvothermal treatment of ZnAl-CO3 LDH buffer layers. To sum up, full utilization of both microstructural and physicochemical properties of LDHs had greatly expanded their potential applications in membrane-based separation and anti-corrosion.
Charge Generation in Monolayer Transition Metal Dichalcogenides
Authors: Blackburn Jeffrey L. , Sulas Dana , Yun Seok Joon , Lee Young Hee , Vigil-Fowler Derek , Reid Obadiah , Miller Elisa M.
Published: February 2020

At the monolayer level, many layered 2D transition metal dichalcogenides (TMDCs) are direct bandgap semiconductors in which photo-excitation creates strongly bound excitons. To incorporate these excitonic semiconductors into solar energy harvesting and conversion devices, it is critical to dissociate excitons to produce long-lived free charge carriers. There are still many open questions regarding the fundamental steps of exciton dissociation and subsequent recombination of charge carriers within 2D TMDCs. These include the roles of defects and traps in localizing charges, the types of interfaces that facilitate fast charge separation and slow recombination, and the role of charge diffusion/delocalization in overcoming the Coulomb binding energy following charge separation. In this talk, I will discuss our efforts at answering some of these questions using a number of 2D TMDC model systems and interfaces. We observe long-lived charge generation in certain neat 2D TMDCs that can be related to specific growth-related defects. Charge generation can also be enhanced by creating interfaces with the appropriate energetics for separating electrons and holes, and the lifetime of the charge-separated state is tied to the degree to which the carrier(s) can escape the interface through diffusion and/or delocalization. These studies provide insight into harnessing the potential of monolayer 2D TMDCs in solar energy harvesting and solar fuels applications.
(Invited) (sSNOM) Imaging of 2D Encapsulated Ga Layered Metal
Authors: Rotkin Slava V.
Published: February 2020

Plasmonic properties of newly discovered class of 2‐dimensional materials (2DM): one‐to‐few monolayer thick metals synthesized using confinement heteroepitaxy (CHet)1 will be discussed. Optical properties of 2DM are modulated at the ultimate scale of (a few) nanometers, thus the characterization also requires a similar spatial resolution. Scattering‐type scanning near‐field optical microscope (sSNOM) allowed us to reveal surface impedance of the 2D‐Ga layers coated with bilayer graphene. 2D‐Ga has extremely large optical contrast due to high density of states, resulting in ultimate light‐matter interactions within an atomic layer. 2D‐Ga was shown to not cover the surface uniformly, leaving the valleys of lower contrast. sSNOM data has been analyzed with two novel algorithms: impedance clustering (revealing metal encapsulation) and photonic decay curves (via 3D sSNOM mapping). Photonic decay is directly related to surface plasmonic density of states, the quantity of interest for nanophotonics applications of 2D‐metals.

Author acknowledges Mr. M. Blades for help with data processing, Dr. T. Gokus (Neaspec) – for sSNOM instrumentation, and Prof. J. Robinson (PSU) – for CHet material synthesis. This research was partially supported by the NSF ECCS‐1509786, and Penn State Quantum Characterization Infrastructure initiative.

[1] N.Briggs, B.Bersch, A.De La Fuente Duran, Y.Wang, A.Li, C.Navarro, J.Robinson, EP03.15.03 : Two‐Dimensional Monoelemental Materials via Confinement Heteroepitaxy, MRS Fall Meeting, Boston MA, 11/25‐30/2018.

Figure 1
Modification of Conductive Electrodes with Two-Dimensional Materials
Authors: Velický Matěj , Dryfe Robert AW , Novoselov Kostya S , Abruña Héctor D.
Published: February 2020

A full understanding of how the electrochemical properties of two-dimensional (2D) materials depend on their structure and surrounding environment is critical for their successful implementation in electrochemistry-related technologies. Although this understanding is currently limited, the complex and tunable electronic structure of 2D materials suggests that a large landscape of possibilities exists in optoelectronics, energy storage/conversion, and photocatalysis.1

Here we show that modification of conductive electrodes with sub-nanometer thick 2D materials leads to a reciprocal interaction between the electrode and the 2D material. This interaction can be viewed as a chemical passivation of the electrode surface by the 2D material, alongside the endowment of the 2D material with the electronic properties of the conductive substrate. We will present two examples of this approach in the context of electrochemistry. First, we will discuss hexagonal boron nitride (hBN) on graphite, which represents a wide-gap tunneling barrier on a semimetallic substrate (Figure). We will examine the dependence of the electrochemical tunneling current and the electron transfer kinetics on the number of hBN layers. Second, we will discuss molybdenum disulfide (MoS2) on gold, which represents a semiconducting (1.9 eV bandgap) barrier on a metallic substrate. We will show that a single layer of MoS2 effectively passivates the surface chemistry of the underlying Au substrate, and that in turn, the Au increases the density of the electronic state of the MoS2, rendering it metallic.2

These findings show that a tunable electrochemical response can be achieved by modification of conductive substrates with 2D materials, either through the nature or thickness of the 2D material. Our results can be exploited in future research and applications in areas such as electrode modification, electrochemical switching or surface passivation.

Velický M. and Toth P. S., Appl. Mater. Today 8,
2017,68-103.

Velický M. et al., ACS Nano 12,
2018, 10463-10472.

Figure 1
(Invited) Atomically Precise Graphene Nanoribbons: From Synthesis to Applications
Authors: Sinitskii Alexander
Published: February 2020

Atomically precise graphene nanoribbons (GNRs) are at the forefront of nanocarbon research and hold great promise for electronic and optoelectronic applications. Theoretical studies have shown that narrow GNRs possess interesting electronic and magnetic properties that strongly depend on the nanoribbon’s width and edge structure. GNRs with different structures can be synthesized with atomic precision and fine-tuned properties by coupling properly designed molecular precursors and planarization of the resulting polymers.

In this talk, I will discuss our efforts on designing and synthesizing new atomically precise GNRs for electronic applications. First, I will describe a scalable bottom-up solution approach for atomically precise GNRs that is based on Yamamoto coupling of pre-synthesized molecular precursors followed by cyclodehydrogenation using Scholl reaction. This approch can be applied to the synthesis of a variety of GNRs, including pristine and nitrogen-doped GNRs with the chevron structure. Then, I will demonstrate that the electrical conductivity of atomically precise chevron GNRs can be improved by their lateral extension. Two types of new laterally extended chevron GNRs (eGNRs) were synthesized in solution, and their high structural quality was confirmed by a number of characterization techniques, including high-resolution scanning tunneling microscopy and Raman spectroscopy combined with a computational analysis. Optical spectroscopy and scanning tunneling spectroscopy showed that lateral extension of chevron GNRs resulted in the decrease of their electronic bandgap.

We developed a procedure for processing eGNRs into uniform thin films that exhibit improved electrical conductivity compared to similar films of regular chevron GNRs. The eGNR films were employed in gas sensors that showed very high responsivity to low molecular weight alcohols compared to similar sensors based on benchmark graphitic materials, such as graphene and graphene oxide. Finally, we demonstrated the first electronic nose system based on atomically precise GNRs that could reliably recognize analytes of nearly the same chemical nature, such as methanol and ethanol. Overall, this talk will demonstrate the entire path from designing new atomically precise GNRs with improved properties to their bottom-up synthesis, characterization, processing and implementation in electronic devices.
(Invited) Electronic Structure and Raman Fingerprint of Atomically Precise Graphene Nanoribbons – a Key for Integration in Devices.
Authors: Senkovskiy Boris V. , Lindfors Klas , Fischer Felix R. , Grueneis Alexander
Published: February 2020

Graphene nanoribbons (GNRs) are a novel tunable material that combines the best attributes of graphene and carbon nanotube worlds. We present our recent results on the electronic, optical and vibrational properties of atomically precise GNRs, particularly, pristine and boron-doped armchair graphene nanoribbons of N = 7 carbon atoms width (7-AGNRs and B-7AGNRs). Spatially aligned GNRs are synthesized by bottom-up approach on stepped Au surface. Using angle-resolved photoemission spectroscopy (ARPES) we reveal energy band dispersion of these systems. ARPES data allow us to determine the energies of one-dimensional sub-bands and the effective masses of charge carriers, which are important for charge transport characterization. Using ultra-high vacuum Raman spectroscopy we probe phonons of air-sensitive B-7AGNRs in situ and reveal the existence of characteristic splittings and red-shifts of vibration modes due to the presence of boron atoms. We perform transfer of 7-AGNRs on to the insulating substrate, which allows tuning and probing their optical response. Particularly, bright photoluminescence in 7-AGNRs is controllably induced by defect-engineering. Finally, we partially transform N=7 to narrow-gap N=14 AGNRs via lateral edge fusion on large-area surface. The band structure of 14-AGNRs is visualized by ARPES. Raman fingerprint allows easy identification of type and orientation of GNRs on both metallic and insulating substrates. The fused GNRs are also integrated in the field-effect transistor.

References:

[1] B.V. Senkovskiy, et al. Nano Lett. 2017, 17, 4029–4037

[2] B.V. Senkovskiy et al. 2D Materials 2018, 5, 035007

[3] B.V. Senkovskiy, et al. ACS Nano 2018, 12, 7571–7582

Corrections were made to this article on 6 March 2020. A typo was removed from author Felix R. Fischer's name.
(Invited) Application of Impedance Spectroscopy for Perovskite Solar Cells
Authors: Murakami Takurou N
Published: February 2020

Perovskite solar cells (PSCs) have reached over 20% efficiency. However, there is still room for improvement of the reproducibility of the solar cell performance in the PSCs. Also, PSCs still have unknown properties such as a hysteresis of I-V curve, effects of the porous layers in the electron transporting layer, and effects of aging. Characterization of the PSCs is essential to understand the electronic properties of the materials and their interfaces in PSCs. Currently, the general architecture for an efficient PSC with n–i–p configuration can be summarized as follows: transparent conductive oxide (TCO) as the electron-collecting layer / n-type semiconductor for the electron-transporting layer (ETL) / perovskite as the intrinsic material / p-type semiconductor for the hole-transporting layer (HTL) / metal as the hole-collecting layer. The photovoltaic performances of PSCs without an ETL or HTL are inferior to those with the standard PSC structure, indicating the important role of charge selection and transportation in the ETL and HTL. Impedance spectroscopy is powerful method for measurement of the resistance components and the capacitance in the electronics devices and is often used for characterizations of the PSCs. However, impedance spectra in PSCs are mostly used for supporting the presumption in the results without verification of the spectra assignment. On the other hand, there are reports to verify the impedance spectra of PSCs with the complexity equivalent circuits. Interpretation of the impedance spectra for PSCs with simple equivalent circuits is significant for the accurate characterization of PSC as a general method.

In this research, we prepared the model PSCs including the layer with different thickness and measured the impedance spectra of the model PSCs to understand the correspondence between the PSC architecture and spectra.
(Invited) Single Particle Spectro-Electrochemistry
Authors: Link Stephan
Published: February 2020

A surface plasmon in a metal nanoparticle is the coherent oscillation of the conduction band electrons leading to both absorption and scattering as well as strong local electromagnetic fields. These fundamental properties have been exploited in many different ways, including for example surface enhanced spectroscopy and sensing, photothermal cancer therapy, and color display generation. Plasmons are both sensitive antennas to amplify and record spectroscopic signals but also convert the incident photon energy into excited charge carriers. The latter can be exploited for chemical redox reactions at the nanoparticle surface. To eliminate heterogeneities caused by nanoparticle size and shape, we have developed an electrochemical approach to monitor the plasmon resonance of individual nanoparticles while applying electrochemical potentials to charge the particles, change the surrounding electrolyte double layer, and assist in redox reaction as the metal nanoelectrode Fermi level is tuned. In this talk I will present our recent progress especially with respect to understanding how plasmons can be utilized beyond sensing in electrochemical redox reactions.
(Invited) Beta, Beta-Functionalized Push-Pull Opp-Dibenzoporphyrins As Sensitizers for Dye-Sensitized Solar Cells: The Role of the Phenylethynyl Bridge
Authors: Wang Hong , Hu Yi , D'Souza Francis
Published: February 2020

Significant progress has been made on dye-sensitized solar cells sensitized by push-pull porphyrins in recent years.1-3 An effective way to significantly enhance power conversion efficiencies of porphyrin dyes is through installation of push (electron-donating) and pull (electron-withdrawing) groups at porphyrin meso-positions.4-6 In this presentation, we present a different strategy to install push and pull groups at porphyrin beta-positions. Three series of novel opp-dibenzoporphyrins were prepared using this strategy. Our studies show significant push-pull effects for these porphyrins.7 DFT calculations suggest that the inclusion of ethynylphenyl bridge between the donating group and porphyrin core significantly segregate the frontier orbitals, which is a much-favored feature for sensitizers in DSSC. The electronic and optical properties of these pi-extended porphyrins were measured using UV-Vis spectroscopy, life-time and steady state fluorescence spectroscopy, cyclic voltammetry and transient spectroscopy. Their photovoltaic performances were tested in dye-sensitized solar cells.

Reference

T. Higashino and H. Imahori, Dalton Trans., 2015, 44, 448-463.

M. Urbani, M. Gratzel, M. K. Nazeeruddin and T. Torres, Chem. Rev., 2014, 114, 12330-12396.

L. L. Li and E. W. Diau, Chem. Soc. Rev., 2013, 42, 291-304.

A. Yella, H.-W. Lee, H. N. Tsao, C. Yi, A. K. Chandiran, M. K. Nazeeruddin, E. W.-G. Diau, C.-Y. Yeh, S. M. Zakeeruddin and M. Grätzel, Science, 2011, 334, 629-634.

S. Mathew, A. Yella, P. Gao, R. Humphry-Baker, B. F. Curchod, N. Ashari-Astani, I. Tavernelli, U. Rothlisberger, M. K. Nazeeruddin and M. Gratzel, Nat. Chem., 2014, 6, 242-247.

G. Di Carlo, A. O. Biroli, F. Tessore, S. Caramori and M. Pizzotti, Coord. Chem. Rev., 2018, 358, 153-177.

Y. Hu, S. Yellappa, M. B. Thomas, R. G. W. Jinadasa, A. Matus, M. Shulman, F. D'Souza and H. Wang, Chem Asian J, 2017, 12, 2749-2762.
(Invited) Nanostructured Copper and Copper Alloys for CO2 Reduction
Authors: Gewirth Andrew A. , Hoang Thao Thi Huong , Chen Xinyi S. , Kenis Paul J.A.
Published: February 2020

Electrodeposition of Cu/Ag or Cu/Sn alloy films from plating baths containing 3,5-diamino-1,2,4-triazole (DAT) as an inhibitor exhibit high surface area and high CO2 reduction activities. EXAFS shows that the codeposited alloy films are homogenously mixed. An alloy film containing 6% Ag exhibits the best CO2 reduction activities activity with a Faradaic Efficiency (FE) for C2H4 product formation reaching 60% at -0.7 V vs. RHE, a FE for C2H5OH formation reaching 25% at -0.7 V vs. RHE, among the highest reported for this activity. Raman studies show that the origin of the high activity is the stabilization of a Cu2O overlayer along with stabilization of the CO intermediate by the Ag or Sn incorporated in the alloy with the exact speciation a function of the interplay between the added metal and the Cu surface.
Formation and Isolation of a Four-Electron-Reduced Porphyrin
Authors: Kojima Takahiko , Suzuki Wataru , Kotani Hiroaki , Ishizuka Tomoya , Shiota Yoshihito , Yoshizawa Kazunari
Published: February 2020

Porphyrins are well known as 18π conjugated aromatic macrocycles with high stability and also as redox-active compounds exhibiting reversible multi-redox processes. In this study, we demonstrated that the two-electron reduction of a diprotonated dodecaphenylporphyrin derivative by Na2S2O4 in DMSO afforded the corresponding isophlorin (Iph) selectively. Formation of Iph was confirmed by spectroscopic measurements and the isolation of tetra-methylated Iph. Further two-electron reduction of Iph was examined using excess Na2S2O4 in DMSO to obtain an unprecedented four-electron reduced porphyrin (IphH2
), which was successfully characterized by spectroscopic analysis and X-ray crystallography. IphH2
showed a unique conformation and could be oxidized to reproduce the starting porphyrin by the chemical oxidation, allowing us to establish a proton-coupled four-electron reversible redox system.
Synthesis and Applications of Monobenzoporphyrins
Authors: Kumar Sandeep , Sankar Muniappan
Published: February 2020

Porphyrins are one of the most abundant macrocyle found in nature [1] which is playing a vital role in biological and material applications [2]. The push-pull porphyrins are used in dye-sensitized solar cells (DSSCs), nonlinear optics (NLO), ion-sensing and catalysis etc [3]. In this regard, MTPP(Benzo)CHO (M = Cu, Zn, Ni and Co) were prepared from the dibromo β-formyl porphyrin using Heck coupling followed by electrocyclization [4] for NLO applications. Further, cyanoacetic acid appended antipodal Zn(II) benzoporphyrin (Figure 1) was synthesized from β-formyl monobenzoporphyrin using Knoevenagel condensation reaction in order to utilize for DSSC application.

The UV-Visible absorption spectra of the ZnTPP(Benzo)CHCCNCOOH and the MTPP(Benzo)CHO (M = Cu, Zn, Ni and Co) and MTPPBr2CHO (M = Cu, Zn, Ni and Co) were compared, which show a red-shifted Soret and Q bands as compared to precursor porphyrins. Also, we have studied the electrochemical redox properties of both ZnTPP(Benzo)CHO and ZnTPP(Benzo)CHCCNCOOH. These porphyrins exhibited a cathodic shift in the first redox potentials as compared to ZnTPPBr2CHO. Similarly, CuTPP(Benzo)CHO exhibited a positive shift in the first oxidation potential and a negative shift in the first reduction potential as compared to CuTPPBr2CHO (Figure 1). In this presentation, we will describe the synthesis, spectral and redox properties of monobezoporphyrin derivatives and their application in DSSC.

Figure 1: Molecular structures of synthesized porphyrins and their comparative Cyclic voltammograms in CH2Cl2 using TBAPF6 as supporting electrolyte at 298 K.

References

1. Shao, S.; Rajendiran, V.; Lovell, J. F. Chem. Rev.
2017. 379, 99.

2. D. R.; Summerville, D. A.; Basolo, F. Chem. Rev. 1979, 79, 139.

3. (a) Kumar, R.; Sudhakar, V.; Prakash, K.; Krishnamoorthy, K.; Sankar, M. ACS Appl. Energy Mater.
2018, 1, 2793. (b) Prakash, K.; Sudhakar, V.; Krishnamoorthy, K.; Sankar, M. Dyes Pigm.
2019, 160, 386. (c) Prakash, K.; Manchanda, S.; Sudhakar, V.; Sharma, N.; Sankar, M.; Krishnamoorthy, K. Dyes Pigm.
2017, 147, 56. (d) Yadav, P.; Kumar, R.; Saxena, A.; Butcher, R. J.: Sankar, M. Eur. J. Inorg. Chem.
2017, 26, 3269. (e) Sonkar, P. K.; Prakash, K.; Yadav, M. Ganesan, V.; Sankar, M.; Gupta, R.; Yadav, D. K. J. Mater. Chem. A 2017, 5, 6263.

4. (a) Jinadasa, R. G. W.; Fang, Y.; Deng, Y.; Deshpande, R.; Jiang, X.; Kadish, K. M.; Wang, H. RSC Adv., 2015, 5, 51489. (b) Jiao, L.; Hao, E.; Fronczek, F. R.; Vicente, M. H.; Smith, K. M. 2006 ,37, 3900.

Figure 1
Hydrogen and Oxygen Evolution Reactions Catalyzed By Metal Porphyrins and Corroles
Authors: Cao Rui
Published: February 2020

Catalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are key steps involved in artificial photosynthesis for solar-energy conversion for the production of clean, carbon-free, and renewable energy sources, and thus they are considered to be appealing ways to eliminate the energy and environmental problems caused by burning fossil fuels. Extensive efforts have been made to develop efficient and robust catalysts for these two processes. Research on mononuclear metal complexes has attracted increasing attention recently because not only they are capable of catalyzing HER and OER as efficiently as multinuclear metal complexes, but also there are several advantages in synthesis and mechanism studies by using single site catalysts. In this talk, we will introduce hydrogen and oxygen evolution reactions catalyzed by single site metal porphyrins and corroles.
Vitamin B12 - a Bioinspired Catalyst for Organic Reactions
Authors: Gryko Dorota
Published: February 2020

Nature constructs and decomposes complex molecules with the help of enzymes and light as the ultimate energy source. However, despite enzyme’s fundamental benefits, their industrial application can be limited by their availability, instability towards certain reaction conditions, cost, scale, lack of suitable enzyme etc. A complementary approach to sustainable methodologies relies on the formation or cleavage of chemical bonds using bioinspired methods (methods imitating the efficient and elegant designs of biology) and recruiting light, the most abundant free energy source.

Vitamin B12 - a cofactor of many enzymes seems inspirational.[1,2] This type of catalysis has been successfully translated into the laboratory and used in a small collection of reactions.[2, 3] The advantage of using vitamin B12 as a catalyst lays in the complete stability of the central cobalt ion and by the definition it is nontoxic. It has also been well documented that the reaction mechanism usually follows a radical pathway, bringing a new dimension to this already interesting field.

Along this line, we have developed new vitamin B12-catalyzed reactions involving reduction of Co(III) to Co(I) or Co(II) and subsequent reactions with electrophiles or radicals. Under light irradiation vitamin B12 derivative unusually catalyzes a new olefinic sp2 C-H alkylation reaction, with diazo reagents as a carbene source, instead of the expected cyclopropanation, acylation of activated olefins. Light-induced vitamin B12-catalyzed methods are also suitable for C-O bond cleavage.

These key findings emphasize the unique feature of vitamin B12 as a catalyst to achieve something unachievable with other methoologies or to find a greener approach.

Banerjee, R. Chemistry and Biochemistry of B12, John Wiley & Sons, Inc, 1999

K. ó Proinsias, M. Giedyk, D. Gryko, Chem. Soc. Rev.
2013, 42, 6605-6619.

Giedyk, M.; Fedosov, S.; Gryko, D. Chem.
Commun.
2014, 50, 4674-4676.

Figure 1
Bright Quadruplex Nanostructures Using Masked Porphyrin Lanterns
Authors: Jayawickramarajah Janarthanan , Pathak Pravin , Vik Ryan S
Published: February 2020

DNA-based self-assembly, that incorporates numerous dyes, is an attractive modality to construct 2D and 3D nanoscale structures with photonic properties. Such assemblies have potential applications in multiple arenas, including as nanoscale optical waveguides for photonic circuits, synthetic light-harvesting materials, and signal enhanced fluorescent devices. However, densely arranged dyes tend to aggregate (especially in water) leading to attenuated photophysical properties. Additionally, increasing dye density can substantially compromise the DNA assembly mode due to competing hydrophobic interactions. In this seminar we will illustrate a “tether, mask, and assemble” strategy that first incorporates the porphyrin dye onto DNA and then masks the dye (forming a porphyrin lantern state wherein detrimental aggregation is negated) and finally assembles the DNA into bright nanostructures. We particularly focus on using versatile, guanine-rich, sequences that can form cyclic and cylindrically arranged porphyrin lanterns.
Main Group Element Containing Porphyrins in Construction of Photoanodes
Authors: Poddutoori Prashanth K
Published: February 2020

Recently, we reported several ‘axial-bonding’ type Donor-Acceptor systems using porphyrins that contain main group elements at the center of the porphyrin. Among these porphyrins, aluminum(III) porphyrin (AlPor) and phosphorus(V) porphyrin (PPor) are unique in term of their structural, electronic and redox properties. For example, both porphyrins form axial bonds, which allow us to build axially linked multicomponent Donor-Acceptor systems. Moreover, their redox properties are unique, AlPor has moderate potentials whereas PPor has very positive potentials, and they are easy to tune. We successfully exploit these properties to build high-potential photoanodes by using the AlPor or PPor in combination with suitable redox centers and semiconductor nanoparticles. Optical and electrochemical studies suggest that newly designed “Donor-Porphyrin-MO2” (M = Ti(IV) or Sn(IV)) photoanodes are excellent candidates for construction of solar cells and photoelectrochemical cells for production of solar fuels. Here we discuss some of our recent work on such supramolecular systems.

References:

1. Interfacial electron transfer in photoanodes based on phosphorus(V) porphyrin sensitizers co-deposited on SnO2 with Ir(III)Cp* water oxidation precatalyst. Poddutoori, P. K.; Thomsen, J. M.; Milot, R. L.; Sheehan, S. W.; Negre, C. F. A.; Garapati, V. K. R.; Schmuttenmaer, C. A.; Batista, S.; Brudvig, G. W.; van der Est, A. J. Mater. Chem. A
2015,
3, 3868.

2. Interfacial Electron Transfer Followed by Photooxidation in N,N-Bis(p-anisole)aminopyridine–Aluminum(III) Porphyrin–Titanium(IV) Oxide Self-Assembled Photoanodes. Lim, G. N.; Poddutoori, P. K.; Hedstrom, S.; Batista, V. S.; D’Souza, F.; van der Est, A. Phys. Chem. C
2017,
121
, 14484.

Figure 1
Charged Porphyrin Metal Complexes As Building Units of Ion-Pairing Assemblies and Materials
Authors: Maeda Hiromitsu
Published: February 2020

π-Electronic ions with appropriate geometries and peripheral substituents provide assemblies through interactions between building subunits, resulting in fascinating electronic properties. Structures and properties of the assemblies can be controlled by the combined negatively and positively charged species in the assemblies. Thus far, diverse ion-responsive π-electronic systems and π-electronic ions have afforded dimension-controlled ion-pairing assemblies as crystals, supramolecular gels, and thermotropic liquid crystals (LCs).[1,2] Highly ordered arrangement of charged species has been found to be a key factor to exhibit the enhanced performance as fascinating electronic materials. In fact, ion pairs of porphyrin-AuIII complexes as π-electronic cations, prepared with the combination of various anions including a π-electronic anion, formed dimension-controlled assemblies as thermotropic liquid crystals, whose ionic components were highly organized by electrostatic and π–π stacking interactions.[3–5]

References

A recent review: Haketa, Y.; Maeda, H.Bull. Chem. Soc. Jpn.
2018, 91,420.

Recent examples: a) Maeda, H.;Takeda, Y.; Haketa, Y.; Morimoto, Y.; Yasuda, N. Chem. Eur. J.
2018, 24, 8910; b) Kaname, S.; Haketa, Y.; Yasuda, N.; Maeda, H. Org. Lett.
2018, 20, 3268; c) Maeda, H.; Okubo, T.; Haketa, Y.; Yasuda, N. Chem. Eur. J.
2018, 24, 16176; d) Yamakado, R.; Ishibashi, H.; Motoyoshi, Y.; Yasuda, N.; Maeda, H. Chem. Commun.
2019, 55, in press.

Haketa, H.; Bando, Y.; Sasano, Y.; Tanaka, H.; Yasuda, N.; Hisaki,I.; Maeda, H.to be submitted.

Assemblies of anionic porphyrins: Sasano, Y.; Yasuda, N.; Maeda, H. to be submitted.

As related species, chiral metal complexes of dipyrrins, with half structures of porphyrin, have exhibited long lifetime photo-excited triplet states: Hirata, G.; Kobayashi, Y.; Yasuda, N.; Maeda, H. to be submitted.
(Invited) Synthesis and Properties of All SWCNT Metallic Nanotube Wire
Authors: Lashmore David , Bystricky Pavel , Bulmer John
Published: February 2020

Copper and aluminum wire conductors are the principal means of conducting electricity. However, they add weight, possess poor fatigue and corrosion resistance and suffer from electromigration under severe conditions. Carbon nanotube (CNT) conductors have long been thought able to replace metals but still fall short of copper in electrical conductivity. CNT wires have so far displaced metal conductors in only a few high value-added applications. In this presentation, we outline an approach to create CNT conductors that address copper shortcomings. These carbon-based wires are made by a new high rate process to grow all metallic (armchair) CNT single wall tubes which are spun into wire in situ within the reactor all in one step, thereby keeping air away from the contacting surfaces of the tubes. We discuss a model of growth in terms of entropy of formation and radiation induced sympathetic vibration.

In all other CNT yarn formation methods known to us, multistep processes are required which add cost or omit spinning. This latter process is necessary to add strength and improve conductivity. The innovations described in this talk include (1) methods for synthesis of nearly all metallic single chirality carbon nanotubes, and (2) the in situ spinning of these nanotubes within the reactor to a finished wire.

We describe their properties determined by Raman, TGA, and structure by SEM and TEM. The conductivity of CNT wires depends on CNT alignment, surface contamination, control over the interfaces (Schottky barriers), and density. Yarns made from nanotubes of exactly the same diameters are also expected to pack well in the wire and provide better properties than the more typical random and larger diameters sometimes made.

The combination of Boronite’s approach to create all CNT wire from uniform nanotubes with metallic chirality with the increasing commercial pressure to reduce weight, increase strength, and operational temperature, opens up commercial opportunities for very lightweight wiring in applications from aircraft to rotating machinery used at high temperatures. Weight saving in a variety of products is especially important for aircraft, cars, and even for large electric systems required to deliver very high current pulses. Boronite has also developed a unique method for infiltrating CNT spun yarn with copper, silver or aluminum to create electromigration resistant materials that can carry extreme currents.
Mechanistic Insights into the Initial Stages of Chloride Enhanced Depassivation of Chromium Oxide Film, a Density Functional Theory Study
Authors: Sarfo Kofi Oware , Murkute Pratik , Isgor O. Burkan , Tucker Julie , Árnadóttir Líney , Zhang Yongfeng
Published: February 2020

The formation of a passive film of metal oxides, such as chromium (e.g. Cr2O3) has been shown to play a key role in the corrosion resistance of stainless steels. Understanding the surface chemistry of these oxide surfaces, in different conditions, provides an essential insight into the stability and functionality of the protective layers. Aggressive ions, such as chlorides, are often part of the solution surrounding stainless steel, but these ions can lead to a breakdown of the oxide film and loss of protection for the metal surface. Here, we used density functional theory to investigate the interactions of Cl and adsorbed water with α-Cr2O3 (0001) passive film to better understand these breakdown mechanisms. Previous studies have suggested the Cr passive film (Cr2O3) is terminated by a mixture of hydroxyls and adsorbed water in aqueous solution, so mixed hydroxylated/water terminated surfaces are included in our study. The chloride (Cl) interaction was modeled by Cl substitution with hydroxyls and subsurface insertion of Cl via exchange with oxygen (O). These have been proposed to be the initial steps of Cl induced breakdown of the passive film. The effect of Cl surface concentration on substitution and insertion was also calculated from 1/6ML to a monolayer coverage. Competitive adsorption of Cl by substitution with OH and H2O is more favorable at the low Cl coverages but becomes less favorable at higher coverages while the insertion of Cl is unfavorable at lower coverages but becomes favorable at monolayer coverage. This implies that Cl can penetrate into the film at high Cl concentrations suggesting a Cl concentration dependent depassivation.
Mechanistic Study of Environmentally-Friendly Zr-Based and Hybrid Nano-Coating Surface Conversion Treatment
Authors: Liu Xiaoyang , Vonk Donald , Tong Xiao , Ravel Bruce , Halada Gary P. , Foster Kate , Petrash Stanislas , Chen-Wiegart Yu-chen Karen
Published: February 2020

Chemical conversion coatings can improve both anti-corrosion and adhesion properties in a wide range of applications. Due to the environmental and health issues of traditional chromate and phosphate coatings, more research has been carried out to develop environment-friendly and cost-effective chemical conversion coating. In this study, the coating formation mechanism of zirconium-based conversion coating and zirconium-polymer-based hybrid coating applied on carbon steel has been investigated. For zirconium-based coating, the kinetics of coating formation was characterized by the growth of the cluster size, as assessed by high-resolution SEM imaging; the evolution of the chemical composition was studied by Synchrotron X-ray Absorption Near Edge Spectroscopy (XANES) and X-ray Photoelectron Spectroscopy (XPS). Furthermore, the processing-structure-property correlation of an improved zirconium-based organic-inorganic “hybrid” coating was investigated. In both systems, corrosion tests have been carried out to understand the potential effects of post-coating processes. Overall, the study sheds light on the mechanism of the zirconium-based and hybrid coating formation, advancing the development of novel anti-corrosion technologies.
Super Slipery Coating By ZnO Based on Aluminum and Its Anti-Corrosion Performance
Authors: Liu Jingyuan
Published: February 2020

Similar to the “lotus leaf effect”, super-hydrophobic surfaces have excellent self-cleaning characteristics and corrosion resistance. However, in the process of droplet condensation on a rough surface, the droplets on the surface can transform from the Wenzel-Cassie state to the Wenzel state, leading to failure of the superhydrophobic effect and greatly reduced corrosion resistance of the alloy surface. Aizenberg et al. first proposed the concept of a slippery liquid-infused porous surface (SLIPS), where lubricating oil is poured into the porous surface for preparation of super-slippery surfaces; a dynamic oil film forms on the surface, solving the problem of super-hydrophobic failure. Since then, research has been focused on mimicking nature and trying to fabricate such surfaces artificially. In this paper, double-layer zinc oxide was synthesized on an aluminum substrate by a sol-gel and hydrothermal method. The aluminum sheet coated with zinc oxide was infiltrated into the Dupon Krytox GPL104 lubricating oil for 2h to obtain an aluminum-based double-layer super-slippery surface. The surface has all the properties of a SLIPS, repelling all simple and complex liquids (including water, milk, coffee, juice, ink, and others); it also exhibits good anti-corrosion and antifouling properties. The corrosion resistance of the surface was tested by electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl aqueous solution (simulated seawater test); the result was four orders of magnitude higher than that of an untreated aluminum sheet. It shows good corrosion resistance, and the corrosion resistance did not change significantly after three months. This provides potential application prospects for aluminum alloy corrosion protection.
Anodic Polarization Behavior of Iron in Phosphoric Acid Solution Under the Action of Magnetic Field
Authors: Tang Yuanjie , Cai Shuangwei , Ning Fei , Ling Sichun , Zhang Kun , Ma Jiarong , Lu Zhanpeng , Yu Chengbing
Published: February 2020

The effect of magentic field on anodic dissolution, passivation and dissolution-passivation transition of iron in sulfuric acid solutions have been investigated. The change of anodic dissolution in the dissolution-passivation transition region and the resultant shrinkage of the passive region due to applied magnetic field have been reported. Uneven dissolution of iron electrode after anodic dissolution in sulfuric acid solutions have been reported. In the represent work, the effect of magnetic field on anodic behavior of iron in 0.5 mol/L phosphoric acid is investigated. Potentiodynamic polarization curves and potentiostatic polarization measurements are conducted at 0T and 0.4T. The anodic polarization curves at 0T and 0.4T are shown in Fig. 1, and the electrode surfaces after the measurements are shown in Fig. 2. The anodic polarization curve at 0T exhibits typical anodic dissolution, dissolution-passivation transition, steady passivation and transpassivation behavior. There is no sgnificant effect of magentic field on the active dissolution at potentials lower than Emax, 0T. Magnetic field moves the dissolution-passivation transition potential to a more noble potential therefore narrows the steady passivation range. There is no passive range in the anodic polarizaiton curve at 0.4T, showing only the drastic drop of current at Emax, 0.4T and then an increase of current soon. There is a quasi-linear potential-current density relationship in a wide potential range, i.e. -0.45 to 0.90V(SCE) at 0T, and -0.45 to 1.85V (SCE). The electrode surfaces after the potentiodynamic polarization measurements up to 2.0V(SCE) at 100 mV/min are observed, indicating severe anodic dissolution. The uneven electrode surface shows the locally accelerated anodic dissolution at the left and right edges of the electrode. From the center of the electrode along the horizontal direction to the edge, the uneven dissolution of the electrode surface presents an aggravating tendency. The results are consistent with thoese observed for iron in sulfuric acid at 0.4T magnetic field. When potentiostatic polarization starts at 1.2V at 0T, passive state can be reached and the further applied 0.4T magnetic field decreased the measured current density, showing the potential-dependent rate determining step and the resultant magnetic field effect on selective electrochemical processes.

Figure 1