bluuebunny/crossref_metadata_2025_split huggingface dataset:
Switchable Anode and Cathode Materials for Water Splitting Under Alkaline Conditions
Authors: O'Mullane Anthony Peter 
Published: July 2021

The ability to store energy from intermittent renewable energy sources is a significant challenge that can be addressed by generating hydrogen as a storage medium via electrochemical water splitting. To ensure the production of hydrogen at scale, there is an urgent need to develop new cost-effective catalyst materials that are active yet stable. There has been a significant research effort in this area for both the hydrogen evolution reaction (HER) at the cathode and the more sluggish oxygen evolution reaction (OER) at the anode where the latter limits the overall efficiency of an electrolysis cell. In particular, transition metal based electrocatalysts containing chalcogenides (S and Se) or phosphorous have been extensively reported as bifunctional electrocatalysts for overall water splitting. However there remains the question as to whether the pristine material is truly bifunctional with regards to inherent activity for both the HER and the OER which has implications for their use in commercial electrolysers.
In this talk I will summarise our recent work on the concept of bifunctional electrodes for overall water splitting. The importance of catalyst characterization post reaction is demonstrated to elucidate the true nature of the active material that is responsible for electrocatalytic activity and how the surface chemistry and crystallinity of the catalyst changes. The implications of this in developing bifunctional catalysts for electrolysers integrated with intermittent energy sources that may be subject to rapid start up and shut down conditions is also discussed. Finally demonstration of electrocatalysts that can be switched between the OER and HER under an accelerated stress test without loss of activity is presented.
Beta-Substituent and Metal Effect on Their Structures and Electrochemical Properties
Authors: Hiroto Satoru 
Published: July 2021

Three-dimensional π-conjugated molecules have received extensive attention in many chemical research areas due to their interesting structure and unique characteristics. In particular, twisted π-conjugated systems have been focused on for potential applications to solution processible organic materials. To date, numerous twisted organic molecules such as twistacenes have been synthesized. Under these situations, we found that oxidation of beta-amino substituted porphyrins provided highly twisted porphyrin dimers in excellent yield. Sequential use of amination and oxidation of 5,10,15,20-tetramesitylporphyrins afforded highly twisted porphyrin oligomers. The structures of the dimers proved dependent on substituents at porphyrin periphery. This time, we succeeded in the synthesis of beta-substituted porphyrin oligomers by using the oxidative dimerization protocol. Introduction of more bulky substituents at meso-positions on oxidation process provided the corresponding twisted porphyrin dimers with larger twisted angles. As a result, beta-substituents induced more distortion of porphyrin oligomers. In addition, electrochemical analysis revealed the distortion caused reduction of electronic communications between each porphyrin unit. We also found beta-methyl substituted porphyrin oligomer exhibited solvent-dependent and temperature dependent optical property. Theoretical calculations as well as electrochemical measurements suggested that conformational change by solvent and temperature caused change of absorption spectrum of the tetramer. Such conformational change dependent on solvent is quite rare for porphyrin oligomers and that should lead to novel stimuli-responsive porphyrin oligomers.
Secondly, we also investigated the central metal effect on the electrochemical properties and structures of the dimers. The central Ni(II) metal can be readily removed by treatment of concentrated sulfonic acid. Insertion of Zn(II) and Cu(II) metals induced planarization of porphyrin planes, resulting in smaller twisting angle of the corresponding dimers. In the case of the Cu(II) complex, the presence of magnetic interactions between two porphyrin units were revealed by temperature dependent magnetic susceptibility measurements. In this presentation, we will disclose the structural characterizations of these dimers and would like to show the relationship between electrochemical properties and the conformations of porphyrin dimers.

Figure 1
Progress in Boron Subnaphthalocyanines (BsubNcs) –Targeting Bay Position Halogenation and Avoiding It and Its Electrochemical Impact
Authors: Bender Timothy P , Holst Devon , Kronik Leeor , Hildebrand Mariana 
Published: July 2021

For some time, our group has been focused on the molecular design, synthesis and application of derivatives of boron subphthalocyanines (BsubPcs) and subnaphthalocyanines (BsubNcs), which are compounds with a chelated central boron atom and an extensive p-conjugated macrocyclic ligand. Our focal point continues to be balanced between the basic and applied chemistry of the BsubPcs and BsubNcs, their physical properties (electrochemistry included) and their application as light emitting, light absorbing and electronic conducting materials in organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs)/organic solar cells (OSCs) respectively; the basic electrochemical and photophysical properties being critical to these applications.
For this presentation, I will focus on our progress on the development of BsubNcs. In the past we have shown that BsubNcs end up being a mixed allowed composition based on bay-position halogenation that was formed randomly during the reaction of BCl3 with 2,3-dicyanonaphthalene at temperature on forming the BsubNcs. The random bay-position halogenation has been shown to be impactful in a positive way within OPV devices, negative within OLED devices and also has electrochemical variations. However given it is random halogenation, it is desirable to truly understand its impact systematically.
I will outline how the use of BBr3 for the formation of the BsubNcs impacts the outcome, also enables random bay-position halogenation and does enable the first example of the bay-position halogenated BsubNcs to be separable.
From a basic chemistry perspective, I will then highlight that we have progressed on blocking the random bay-position halogenation by developing a method to entirely avoid the bay-position halogenation. I will outline the approach and show the first basic characterization of non-bay-position halogenated BsubNc and the relative characteristics of the associated BsubNcs. Electrochemical comparison of the BsubNcs will also be outlined and also spectroelectrochemistry characterization.
We have also applied computational modelling to look at the relative impact of the random bay-position halogenation. We have found that the frequency of halogenation has a larger impact on the predicted HOMO/LUMO energy levels than does the random halogen positioning and will be discussed.
I will also outline our approach to accelerated development of BsubNcs whereby their molecular design and synthesis is first justified through a re-adopted computational model. I will show how we calibrate several levels of computational modelling relative to and against a firm set of experimental data. I will then move onto several examples of how we have developed BsubNcs for their application in organic electronic devices utilizing this method.

Figure 1
Mechanistic Studies on the Reactions between Cobalamins and the Biological Signaling Molecule Nitroxyl (HNO)
Authors: Brasch Nicola E , Polaczek Justyna , Cink Ruth B , Subedi Harishchandra , van Eldik Rudi 
Published: July 2021

The N-hydroxysulphonamide Piloty’s acid, PhSO2NHOH, was first reported in the scientific literature over a century ago. N-hydroxysulphonamides have recently attracted considerable attention, due to their propensity to spontaneously decompose to cleanly release nitroxyl (HNO) upon deprotonation of the parent molecule. Like its well-established cousin nitric oxide (NO), HNO is a biological signaling molecule with a rich redox chemistry. Furthermore therapeutics that generate HNO in vivo show considerable promise in treating cardiovascular disease including congestive heart failure, through mechanisms unique to HNO. HNO reacts primarily with metal centres and thiols (protein thiol residues and small molecular weight thiols) in biological systems.
The cobalt-containing vitamin B12 macrocycle is a cofactor for numerous enzymes in humans and bacteria. Detailed mechanistic studies on the reactions of Piloty’s acid with all three oxidation states of vitamin B12 – Co(I), Co(II) and Co(III) – will be presented, and reveal a complex and rich coordination chemistry for this simple triatomic molecule.
Synthesis, Spectral and Electrochemical Studies of β-Trisubstituted Porphyrins and Monobenzoporphyrins
Authors: Bulbul Amir Sohel , Sankar Muniappan 
Published: July 2021

Meso-Tetraarylporphyrins having electron-withdrawing substituents viz. nitro, formyl, acyl, or bromo groups is the key precursor to expand the chemistry of β-functionalized porphyrins.1 These β-functionalized porphyrins have been utilized in nonlinear optics, anion sensing, gas storage, photodynamic therapy (PDT), and dye-sensitized solar cells (DSSC).2 Modulating the degree of π-conjugation and introducing suitable donor-acceptor substituents at β-positions result red-shifted electronic spectral features, low HOMO-LUMO gap and high ground state dipole moment which are essentials for enhanced nonlinear optical behavior. Benzoporphyrin derivatives are currently under investigation as photosensitizers for PDT.3 Herein, we synthesized unsymmetrically functionalized trisubstituted porphyrins and monobenzoporphyrins in one step and characterized by various spectroscopic techniques viz. UV-vis, fluorescence, NMR, MALDI-TOF mass spectrometry and electrochemical studies.
The synthesized trisubstituted porphyrins and monobenzoporphyrins were significantly red-shifted as compared to their precursor porphyrins. Further, these porphyrins exhibited a large anodic shift in reduction and cathodic shift in oxidation potentials due to extended π-conjugation and electron-withdrawing β-substituents. In this presentation, we will present the facile synthesis, photophysical and intriguing electrochemical redox properties of π-extended porphyrins.

Figure 1. Molecular structures, absorption spectral profile and cyclic voltammograms of synthesized porphyrins.

References:

Moura, N. M. M. et al,
J. Porphyrins Phthalocyanines
15, 2011, 652-658.

(a) Senge, M. O. et al,
Eur. J. Org. Chem.
2011, 5797-5816. (b) Sankar, M. et al, Chem. Commun.
41, 2012, 6481-6483. (c) Kumar, R. et al,
Inorg. Chem., 53, 2014, 12706-12719. (d) Higashino, T. et al,
Dalton Trans.
44, 2015, 448-463. (e) Sankar, M. et al, ACS Appl. Energy Mater.
1, 2018, 2793-2801. (f) Dar, T. A. et al,
Green Chem.
21, 2019, 1757-1768.

(a) de-Torres, M. et al,
Chem. Commun.
51, 2015, 2855-2858. (b) Zhang, X. et al, ACS Nano
12, 2018, 4630-4640. (c) Grover, N. et al,
Inorg. Chem.
58, 2019, 2514-2522.

Figure 1
Photochemical Reactivities and Photodynamic Effects of an Organorhodium Phthalocyanine
Authors: Murata Kei , Saibe Yuki , Misawa Ryuji , Ikeuchi Yoshiho , Ishii Kazuyuki 
Published: July 2021

The light-triggered uncaging of bioactive molecules is attractive for a new type of photodynamic therapy (PDT) as it enables the tumor-selective cell attack in various mechanism of action. In particular, photochemical release of formaldehyde is promising as they exhibit cytotoxicity by the alkylation and crosslinking of biological tissues.[1] Meanwhile, methyl-cobalt porphyrinic compounds are known to give formaldehyde by the homolytic cleavage of a metal-carbon bond under visible light irradiation in the presence of molecular oxygen.[2] However, there has been no report on the photochemical formation of formaldehyde under irradiation of red light which shows high permeability toward biological tissues. In this study, the organometallic phthalocyanine complexes possessing a group 9 metal center were synthesized, and their photophysical properties, photochemical reactivities and photodynamic effects were investigated under red light irradiation.
Through the screening of reaction conditions, the methyl-rhodium phthalocyanine complex (1) was found to give formaldehyde by irradiation of pulsed laser of red light in the presence of oxygen. The laser-power dependency on the conversion rate indicated that the metal-carbon bond of 1 is activated through the stepwise, two-photon excitation. In order to realize the photochemical formation of formaldehyde in biological environment, 1 was encapsulated into a liposome of 1,2-Dipalmitoyl-sn-glycero-3-phosphorylcholine (DPPC). By irradiation of red light, the liposomal 1 released formaldehyde in water under air. Finally, the phototoxicity and cytotoxicity of liposomal 1 toward HeLa cells were investigated. The HeLa cells treated by liposomal 1 were successfully killed by light irradiation, indicating that 1 exhibits the photodynamic effect.
References
[1] Huang, H.; Hopkins, P. B. J. Am. Chem. Soc.
1993, 115, 9402-9408.
[2] Dolphin, D.; Johnson, A. W.; Rodrigo, R. J. Chem Soc.
1964, 3186-3193.
Host-Guest Chemistry of Porphyrins in Liquid Crystalline Macrocycles
Authors: Tanaka Kentaro 
Published: July 2021

Structurally well-defined macrocyclic molecules have great potential to accommodate specific guest molecules in the hollow. Recently, we have reported a series of macrocycles which are composed of four carbazoles connected with four salphen ligands1, four dibenzothiophenes connected with four salen ligands2, or four diindrocarbazoles connected with four salphen ligands3 (MC1, MC2 and MC3, respectively). The macrocycles with appropriate peripheral alkyl chains and their tetranuclear metal complexes with square planar metal ions showed thermotropic columnar liquid crystalline properties1,2. These macrocycles stacked to form columns inside the fluid materials. Especially, the giant macrocycle MC3 contained a square hollow with a diagonal of 2.5 nm. This giant macrocycle has the largest inner cavity among known discrete shape-persistent macrocycles that exhibit thermotropic LC properties. The size and shape of the hollow structure make it interesting for molecular inclusion applications. For example, MC3 molecule can accommodate a tetrapyridylporphyrin inside the hollow to afford a planar conjugate, and the conjugate showed liquid crystalline behavior.

Reference:

[1] S. Kawano, Y. Ishida, and K. Tanaka, J. Am. Chem. Soc.
2015, 137, 2295.
[2] Kawano, S.; Hamazaki, T.; Suzuki, A.; Kurahashi, K.; Tanaka, K. Chem. Eur. J., 2016, 22, 15674-15683.
[3] Kawano, S.; Kato, M.; Somiya, S.; Nakayama, M.; Onoe, J.; Tanaka, K. Angew. Chem. Int. Ed.,
2018, 57, 167–171.

Figure 1
DFT Investigation of Porphyrin Aggregates
Authors: Sabuzi Federica , Stefanelli Manuela , Monti Donato , Conte Valeria , Galloni Pierluca 
Published: July 2021

Owing the attractive potential applications of porphyrin assemblies in photocatalysis, sensors and material science, nowadays studies concerning porphyrin aggregation are largely diffused. These chromophores can organize in elaborated architectures by an assorted set of non-covalent interactions (i.e. π–π stacking, H-bonding, metal coordination, hydrophobic effect, and electrostatic forces) between the tetrapyrrolic macrocycles, mostly in J-or H-aggregated species, where the aromatic platforms are stacked side by side and face to face, respectively. UV-vis spectroscopy allows the identification of the porphyrin arrangement within the aggregates, through the modified spectral features of the porphyrin monomer following the interaction among the porphyrin units. Despite plenty of experimental investigations dealing with the self-organization of porphyrin both in solution and at the solid state, computational studies are still limited.
In this communication, a computational examination of the different porphyrin aggregation approaches will be presented, taking into account the amphiphilic [5-{4-(3-trimethylammonium)propyloxyphenyl}-10,15,20-triphenylporphyrin] chloride, whose aggregation behavior has been previously experimentally investigated. In particular, the definition of appropriate functionals to study and characterize porphyrin aggregates, to get more insights on the kind of the interactions responsible for the formation of the specific noncovalent systems (J-, H-, T- or cation-π aggregates) experimentally observed will be proposed.
Fig. 1. Optimized geometry of H-type (left) and cation-π (right) dimers of [5-{4-(3-trimethylammonium)propyloxyphenyl}-10,15,20-triphenylporphyrin] chloride in water, with WB97XD functional and 6-31G(d) basis set.

Figure 1
Using the Electrode Potential to Orient Single Molecules in Nanoscale Electrical Junctions and Determine Charge Transport Mechanism
Authors: Borguet Eric 
Published: July 2021

Charge transport through and between molecules is central to important processes in nature. Studying the conductivity of single molecules can contribute to a better understanding of charge transport, and also help to develop building blocks of molecular electronics, light harvesting devices, etc. We measure the conductivity of molecules using the Scanning Tunneling Microscope break-junction (STM-BJ) method that utilizes repeatedly formed circuits where one or a few molecules are trapped between two electrodes, at least one of which has nanoscale dimensions. The statistical analysis of thousands of measurements yields the conductance of single molecules.
One particular interest is the role of the molecule-electrode contact and orientation in charge transport. In the simplest analysis this contact can present a substantial barrier to charge injection, which can have important consequences in devices such as dye sensitized semiconductor nanoparticle solar cells. Our most recent developments include controlling the orientation of the molecule in the junction using the electrode potential so that we can measure conductance along different molecular axes, accessing elements of the anisotropy of the molecular conductance tensor. Specifically, when the molecule is oriented flat, with the molecular plane parallel to the electrode surface, charge transport is measured perpendicular to the molecular plane. Furthermore, the electrode dependence of the molecular conductivity provides insight into the transport mechanism. This approach can be applied to molecules that do not have suitable molecular anchoring groups for traditional STM-BJ measurements, and allows us to determine the importance of anchoring groups in charge transport in molecular junctions.
High Aspect Ratio TiO2 Nanotube Layers Obtained in a Short Time
Authors: Alijani Mahnaz , Sopha Hanna , Ng Siow Woon , Macak Jan M. 
Published: July 2021

In the last two decades, anodic TiO2 nanotube (TNT) layers have gained considerable attention for both their unique physical and chemical properties practical applications [1-3].
One of the key parameters that characterize TNT layers is the aspect ratio, which is the ratio between the TNT layer thickness and the nanotube diameter. In particular, TNT layers with a high aspect ratio (HAR) due to their 1D ordered structure, an exceptional morphology and a high surface area, have a great potential in different applications, such as filtration and micro-photo reactors [4,5]. In the last decade, ethylene glycol (EG)-based electrolytes containing small amounts of NH4F and H2O [6] were the most widely used electrolytes to produce high-aspect ratio TNT layers. However, using these electrolytes very long anodization times i.e., several hours or up to several days [7], are needed. Apparently, the synthesis of long and extremely robust HAR TNT layers in a relatively short time remains very challenging until now. Recently, it has been shown that the addition of lactic acid (LA) to EG-based electrolytes can shift the dielectric breakdown potential to significantly higher potentials due to the strong adsorption of lactic acid on TiO2 during the anodization [8]. Thus, considerably higher anodization potentials and increased electrolyte temperatures can be employed and HAR TNT layers can be obtained within less than one hour of anodization.
In this presentation we will demonstrate that HAR TNT layers can be obtained within short anodization times using an optimized anodization protocol. The key feature is the use of NH4F/H2O/EG electrolytes containing LA with optimized electrolyte [9].
Experimental details and some recent anodization results will be presented and discussed.
References:
[1] J.M. Macak et al., small. 2007, 300-304,3.
[2] J.M. Macak et al., Curr. Opin. Solid State Mater. 2007, 3-8,11.
[3] R. Poulomi, et al., Nanoscale. 2010, 45-59, 2.
[4] G. Cha, et al., Electrochim. Acta
2020, 302-310, 258.
[5] Z. Xuemei, et al., ACS Catalysis
2017, 3210-3235, 7.
[6] K. Lee et al., Chem. Rev.
2014, 9385-9454, 114.
[7] S.P. Albu et al., Phys. Status Solidi RRL.
2007 R65-R67, 1.
[8] S. So et al., J. Am. Chem. Soc.
2012, 11316-11318, 134.
[9] M. Alijani et al., Electrochim. Acta
2020, submitted.
Key Challenges Towards Scalability of Niobium Based Materials for Lithium-Ion Battery Technology
Authors: Santhanam Sumithra , Zhang Wanwei , Wu Jianshen , Pezin Joris , El Ouatani Loubna , Groombridge Alexander S. 
Published: July 2021

Next generation high energy density and ultrafast charging lithium-ion battery technology requires fast charging anodes with high capacity, low volume expansion during cycling and moderate operating voltage. Li4Ti5O12 (LTO) is the only commercially available anode material that has the ability to safely fast charge in 5 mins with minimal expansion on intercalation of lithium-ions. However, it suffers from poor energy density and low capacity (<160 mAh/g) and poor electronic, ionic conductivities. Echion Technologies Ltd has developed “Mixed Niobium Oxide” -based anodes that it has commercialised to solve these issues, offering the ability to fast-charge in under 5 mins and maintain a long lifetime, with double the volumetric capacity of LTO materials (>640 mAh/cm3). In general, mixed niobium oxide materials [1,2] are intrinsically insulating and require improvement in electronic conductivity (by materials/particle engineering) for minimising impedance effects at the cell level. Material parameters (particle morphology, size distribution, microstructure), degradation mechanism and ageing of anodes play a vital role towards scalability of optimised materials for commercial devices and tailored applications. The different scalable synthesis techniques, processing parameters and their effect on material characteristics, electrochemical performances will be discussed in this talk. The critical challenges faced by industry towards scalability of materials and commercial devices will also be reviewed.
[1] Jian-Tao Han et.al., Chem. Mater., 23 (2011) 2027-2029.
[2] M. Bini et.al., Chemistry Select., 4, 19 (2019) 5656-5661.