Synthesis of a solid chelating ligand for the formation of efficient heterogeneous catalysts is highly desired in the fields of organic transformation and solar energy conversion. Here, we report the surfactant-directed self-assembly of a novel periodic mesoporous organosilica (PMO) containing 2,2'-bipyridine (bpy) ligands within the framework (BPy-PMO) from a newly synthesized organosilane precursor [(i-PrO)3Si-C10H6N2-Si(Oi-Pr)3] without addition of any other silane precursors. BPy-PMO had a unique pore-wall structure in which bipyridine groups were densely and regularly packed and exposed on the surface. The high coordination ability to metals was also preserved. Various bipyridine-based metal complexes were prepared using BPy-PMO as a solid chelating ligand such as Ru(bpy)2(BPy-PMO), Ir(ppy)2(BPy-PMO) (ppy = 2-phenylpyridine), Ir(cod)(OMe)(BPy-PMO) (cod = 1,5-cyclooctadiene), Re(CO)3Cl(BPy-PMO), and Pd(OAc)2(BPy-PMO). BPy-PMO showed excellent ligand properties for heterogeneous Ir-catalyzed direct C-H borylation of arenes, resulting in superior activity, durability, and recyclability to the homogeneous analogous Ir catalyst. An efficient photocatalytic hydrogen evolution system was also constructed by integration of a Ru-complex as a photosensitizer and platinum as a catalyst on the pore surface of BPy-PMO without any electron relay molecules. These results demonstrate the great potential of BPy-PMO as a solid chelating ligand and a useful integration platform for construction of efficient molecular-based heterogeneous catalysis systems.

Silicon nanomaterials are encouraging candidates for application to photonic, electronic, or biosensing devices, due to their size-quantization effects. Two-dimensional silicon nanosheets could help to realize a widespread quantum field, because of their nanoscale thickness and microscale area. However, there has been no example of a successful synthesis of two-dimensional silicon nanomaterials with large lateral size and oxygen-free surfaces. Here we report that oxygen-free silicon nanosheets covered with organic groups can be obtained by exfoliation of layered polysilane as a result of reaction with n-decylamine and dissolution in an organic solvent. The amine residues are covalently bound to the Si(111) planes. It is estimated that there is ca. 0.7 mol of residue per mole of Si atoms in the reaction product. The amine-modified layered polysilane can dissolve in chloroform and exfoliate into nanosheets that are 1-2 microm wide in the lateral direction and with thicknesses on the order of nanometers. The nanosheets have very flat and smooth surfaces due to dense coverage of n-decylamine, and they are easily self-assembled in a concentrated state to form a regularly stacked structure. The nanosheets could be useful as building blocks to create various composite materials.

Boron clusters are proposed as a new concept for the design of magnesium-battery electrolytes that are magnesium-battery-compatible, highly stable, and noncorrosive. A novel carborane-based electrolyte incorporating an unprecedented magnesium-centered complex anion is reported and shown to perform well as a magnesium-battery electrolyte. This finding opens a new approach towards the design of electrolytes whose likelihood of meeting the challenging design targets for magnesium-battery electrolytes is very high.

The aromatic excimers of benzene, naphthalene, anthracene, pyrene, and perylene are systematically investigated using the multiconfiguration quasi-degenerate perturbation theory (MCQDPT) method, which is one of high-level ab initio quantum chemical methods. The reference configuration space for MCQDPT is carefully designed for an appropriate description of the target electronic state with a tractable computational cost. The dimers with eclipsed parallel arrangement are investigated. The basis set dependence of the selected spectroscopic parameters is examined for the benzene and naphthalene dimers, and that of the excimer binding energy is found to be significant. In contrast, the equilibrium intermolecular distance and excimer fluorescence energy are less sensitive to the size of the basis sets used, and they agree with the corresponding experimental values, even with a nonextensive basis set size. The calculated spectroscopic parameters for anthracene, pyrene, and perylene dimers are also in good agreement with the experimental results. The electronic properties of the excimers are discussed in relation to those of the corresponding monomers. The wave functions of the excimers are analyzed in detail to clarify the origin of the attractive nature between the two monomers.

This investigation elucidates the electrochemical reaction process occurring within lithium-sulfur battery cells in detail, which has been unclear even after a half century of study primarily due to the very high reactivity of the polysulfide species. The polysulfide intermediates were deactivated by organic conversion - benzylization, and LC/MS and NMR analyses were first applied. The results demonstrate that the second voltage plateau in the discharge profile, which is the most important step in practical use because of its constant voltage, is dominated by the reduction of the Li2S3 intermediate. The first voltage plateau and the transition state between the plateaus, in which the voltage varies with the capacity, are associated with multiple reactions including the decomposition of S8 into Li2Sx (x = 1 to 7) and the transformation of Li2Sy (y = 4 to 8) into Li2Sz (z = 1 to 3). It is also revealed that longer polysulfide species, Li2Si (i = 6 to 8), are responsible for the redox shuttle phenomenon, which causes serious capacity degradation.

The naphthalene molecule has two important lowest-lying singlet excited states, denoted (1)La and (1)Lb. Association of the excited and ground state monomers yields a metastable excited dimer (excimer), which emits characteristic fluorescence. Here, we report a first computational result based on ab initio theory to corroborate that the naphthalene excimer fluorescence is (1)La parentage, resulting from inversion of (1)La and (1)Lb-derived dimer states. This inversion was hypothesized by earlier experimental studies; however, it has not been confirmed rigorously. In this study, the advanced multireference (MR) theory based on the density matrix renormalization group that enables using unprecedented large-size active space for describing significant electron correlation effects is used to provide accurate potential energy curves (PECs) of the excited states. The results evidenced the inversion of the PECs and accurately predicted transition energies for excimer fluorescence and monomer absorption. Traditional MR calculations with smaller active spaces and single-reference theory calculations exhibit serious inconsistencies with experimental observations.

Boron clusters are proposed as a new concept for the design of magnesium-battery electrolytes that are magnesiumbattery-compatible, highly stable, and noncorrosive. A novel carborane-based electrolyte incorporating an unprecedented magnesium-centered complex anion is reported and shown to perform well as a magnesium-battery electrolyte. This finding opens a new approach towards the design of electrolytes whose likelihood of meeting the challenging design targets for magnesium-battery electrolytes is very high.The possibility of developing a rechargeable magnesium battery has been a topic of great interest for several decades. [1] Magnesium batteries are particularly attractive owing to their high theoretical capacity (3832 mA h cm À3 ) as well as the low cost and high abundance of Mg metal as compared to Li. [1,2] Additionally, Mg possesses an important safety advantage over Li in that Mg metal is not prone to dendrite formation. [3] However, before Mg batteries can see practical application, several challenges must be overcome, including the identification of a suitable solvent/electrolyte combination.[2] It has proven particularly challenging to identify such a system for magnesium-based batteries owing to the tendency of many common electrolytes to form nonconductive ion-blocking layers at the electrode surface.[4] Thus, any solvent/electrolyte combination used in a Mg battery must be stable across the entire potential window at which the battery operates.This requirement is particularly problematic for the design of high-voltage battery systems, for which an electrolyte candidate must be stable to both Mg metal (À2.37 V versus the normal hydrogen electrode, NHE) and the cathode-active material selected, which should ideally operate near + 1 V (vs. NHE). Furthermore, previous research has suggested that Mg metal is reactive toward many common polar solvents and electrolyte anions.[5] In fact, the majority of previously reported electrolyte systems have been limited to highly inert ethereal solvents, such as tetrahydrofuran (THF).[6] This limitation makes the design of electrolyte materials quite difficult, as a successful candidate must be highly soluble in these nonpolar solvents in addition to being electrochemically robust. As a result, only a handful of potential electrolytes are known to be compatible with Mg anodes. [6] Recent studies at the Toyota Research Institute of North America have demonstrated Mg(BH 4 ) 2 to be a highly competent electrolyte for magnesium-battery applications. [7] This electrolyte was the first non-organomagnesium electrolyte compatible with Mg metal and provided excellent electrochemical performance in glyme. In tandem with further research into this system, we sought to pursue potential routes to materials with enhanced oxidative stability as compared to the observed oxidation onset potential of 1.7 V (vs. Mg on Pt) for Mg(BH 4 ) 2 .High oxidative stability is crucial for the development of Mg batteries for operation with future high-voltage cathodes. Although organo...

This paper describes the physicochemical properties of a rhenium (Re) complex [Re(bpy)(CO) Cl] immobilized on a bipyridine-periodic mesoporous organosilica (BPy-PMO) acting as a solid support. The immobilized Re complex generated a metal-to-ligand charge transfer absorption band at 400 nm. This wavelength is longer than that exhibited by Re(bpy)(CO) Cl in the polar solvent acetonitrile (371 nm) and is almost equal to that in nonpolar toluene (403 nm). The photocatalytic activity of this heterogeneous Re complex was lower than that of a homogeneous Re complex due to the reduced phosphorescence lifetime resulting from immobilization. However, the catalytic activity was enhanced by the co-immobilization of the ruthenium (Ru) photosensitizer [Ru(bpy) ] on the PMO pore surfaces. Quantum chemical calculations suggest that electron transfer between the Ru and Re complexes occurs through interactions between the molecular orbitals in the pore walls. These results should have applications to the design of efficient heterogeneous CO reduction photocatalysis systems.