Near‐Infrared Light‐Driven Hydrogen Evolution from Water Using a Polypyridyl Triruthenium Photosensitizer

In order to realize artificial photosynthetic devices for splitting water to H₂ and O₂ (2 H₂O+hν→2 H₂+O₂), it is desirable to use a wider wavelength range of light that extends to a lower energy region of the solar spectrum. Here we report a triruthenium photosensitizer [Ru₃(dmbpy)₆(μ‐HAT)]⁶⁺ (dmbpy=4,4′‐dimethyl‐2,2′‐bipyridine, HAT=1,4,5,8,9,12‐hexaazatriphenylene), which absorbs near‐infrared light up to 800 nm based on its metal‐to‐ligand charge transfer (¹MLCT) transition. Importantly, [Ru₃(dmbpy)₆(μ‐HAT)]⁶⁺ is found to be the first example of a photosensitizer which can drive H₂ evolution under the illumination of near‐infrared light above 700 nm. The electrochemical and photochemical studies reveal that the reductive quenching within the ion‐pair adducts of [Ru₃(dmbpy)₆(μ‐HAT)]⁶⁺ and ascorbate anions affords a singly reduced form of [Ru₃(dmbpy)₆(μ‐HAT)]⁶⁺, which is used as a reducing equivalent in the subsequent water reduction process.     

4,7‐Bis(4‐pyridyl­ethynyl)‐2,1,3‐benzo­thia­diazo­le and its dipyridinium diperchlorate

The title compound, C₂₀H₁₀N₄S, and its dipyridinium salt, 4,4′‐(2,1,3‐benzo­diazol‐4,7‐diyl­diethynyl)­dipyridinium diperchlorate, C₂₀H₁₂N₄S²⁺·2ClO₄^?, display bond alternation in the 2,1,3‐benzo­thia­diazo­le rings, which suggests their quinonoid character. The dipyridinium dication mol­ecules stack along the a axis and form a dimer with short S?N interheteroatom contacts [3.146 (4) Å] between the two 1,2,5‐thia­diazo­le rings. The dimer is surrounded by the perchlorate anions with which it forms a large number of intermolecular N—H?O and C—H?O hydrogen bonds.     

Formation of Defect-Spinel Phase in CdSnO3

A spinel-type structure was found in cadmium stannate CdSnO₃ prepared by thermal decomposition of the hydroxostannate CdSn(OH)₆ at 550–800°C. Its occurrence depends strongly on the precipitation conditions of CdSn(OH)₆ from CdCl₂ and Na₂Sn(OH)₆ aqueous solutions. In the (Cd_1–xCa_x)SnO₃ system, the spinel phase appears in the composition range of 0.0 ≤ x ≤ 0.35. The experimental results suggest the presence of cation vacancies in the spinel octahedral sites.     

Application of 1,2,3,5,6,7-hexahydropyrrolizinium perchlorate in the synthesis of 7a-substituted hexahydro-1h-pyrrolizines

The method for preparing 7a-substituted hexahydro-1H-pyrrolizines 2 from 1,2,3,5,6,7-hexahydropyrrol-izinium Perchlorate (3) was investigated, by which introduction of a wide variety of functionalities on C(7a) could be achieved easily.     

Maximum Caliber: a variational approach applied to two-state dynamics

We show how to apply a general theoretical approach to nonequilibrium statistical mechanics, called Maximum Caliber, originally suggested by E. T. Jaynes [Annu. Rev. Phys. Chem. 31, 579 (1980)], to a problem of two-state dynamics. Maximum Caliber is a variational principle for dynamics in the same spirit that Maximum Entropy is a variational principle for equilibrium statistical mechanics. The central idea is to compute a dynamical partition function, a sum of weights over all microscopic paths, rather than over microstates. We illustrate the method on the simple problem of two-state dynamics, A<-->B, first for a single particle, then for M particles. Maximum Caliber gives a unified framework for deriving all the relevant dynamical properties, including the microtrajectories and all the moments of the time-dependent probability density. While it can readily be used to derive the traditional master equation and the Langevin results, it goes beyond them in also giving trajectory information. For example, we derive the Langevin noise distribution rather than assuming it. As a general approach to solving nonequilibrium statistical mechanics dynamical problems, Maximum Caliber has some advantages: (1) It is partition-function-based, so we can draw insights from similarities to equilibrium statistical mechanics. (2) It is trajectory-based, so it gives more dynamical information than population-based approaches like master equations; this is particularly important for few-particle and single-molecule systems. (3) It gives an unambiguous way to relate flows to forces, which has traditionally posed challenges. (4) Like Maximum Entropy, it may be useful for data analysis, specifically for time-dependent phenomena.     

Aryne reaction with trifluoromethyl ketones in three modes: C-C bond cleavage, [2+2] cycloaddition and O-arylation

Trifluoromethyl ketones were found to be coupled with arynes in three modes depending upon their substitution patterns, namely C-C bond cleavage, [2+2] cycloaddition and O-arylation.     

Molecular Spintronics Based on Single‐Molecule Magnets Composed of Multiple‐Decker Phthalocyaninato Terbium(III) Complex

Unlike electronics, which is based on the freedom of the charge of an electron whose memory is volatile, spintronics is based on the freedom of the charge, spin, and orbital of an electron whose memory is non‐volatile. Although in most GMR, TMR, and CMR systems, bulk or classical magnets that are composed of transition metals are used, this Focus Review considers the growing use of single‐molecule magnets (SMMs) that are composed of multinuclear metal complexes and nanosized magnets, which exhibit slow magnetic‐relaxation processes and quantum tunneling. Molecular spintronics, which combines spintronics and molecular electronics, is an emerging field of research. Using molecules is advantageous because their electronic and magnetic properties can be manipulated under specific conditions. Herein, recent developments in [LnPc]‐based multiple‐decker SMMs on surfaces for molecular spintronic devices are presented. First, we discuss the strategies for preparing single‐molecular‐memory devices by using SMMs. Next, we focus on the switching of the Kondo signal of [LnPc]‐based multiple‐decker SMMs that are adsorbed onto surfaces, their characterization by using STM and STS, and the relationship between the molecular structure, the electronic structure, and the Kondo resonance of [TbPc₂]. Finally, the field‐effect‐transistor (FET) properties of surface‐adsorbed [LnPc₂] and [Ln₂Pc₃] cast films are reported, which is the first step towards controlling SMMs through their spins for applications in single‐molecular memory and spintronics devices.     

Local crystal structure of nano-manganese-oxide gold adsorbent

The local crystal structure of dried and deuterated nano-manganese-oxide powder samples was studied via atomic pair distribution function analysis of X-ray and neutron powder diffraction data. The protonated sample shows ultrahigh efficiency as a gold adsorbent even from ppt-level aqueous solutions such as seawater. We show that the nano-manganese-oxide particles have an R-MnO₂-type local crystal structure. The possible role of the protons on the surface of the nano-particles is discussed.