Extended Open-Chain Polyenides as Versatile Delocalized Anion Ligands for Metal Chain Clusters

Although small cyclic- and open-chain unsaturated hydrocarbon anions such as cyclopentadienide and open-chain pentadienide are used as the strongly electron-donating auxiliary ligands for metal complexes, more extended π-conjugated unsaturated hydrocarbon anions have rarely been used in coordination chemistry, despite their potential ability to serve as the multiply bridging π-ligands for metal clusters. This work reports isolation of metal chain clusters bearing the multi-dentate, open-chain extended unsaturated hydrocarbon anion ligands. The extended open-chain π-conjugated polyenyl ligands could effectively stabilize oxidized palladium chains, including an unprecedented [Pd₄]⁴⁺ chain.     

Expansion of Photostable Luminescent Radicals by Meta-Substitution

Polychlorinated pyridyldiphenylmethyl radicals having substituents meta to the position bearing the carbon-centered radical (α-carbon) are synthesized. All of them are stable in ambient conditions in solutions and fluorescent in cyclohexane. The fluorescence of the radicals with bromo, phenyl, 4-chlorophenyl, or 2-pyridyl substituents are enhanced in chloroform, while the emission of the radicals with 2-thienyl or 2-furyl substituents are quenched in chloroform. DFT and TD-DFT calculations indicate that the first doublet excited states of the former are locally excited, while the first doublet excited states of the latter are charge transfer states from the π-electron-donating substituent to the accepting radical. The latter also show much higher photostability under 370-nm light irradiation compared with the first reported photostable fluorescent radical, (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical (PyBTM), with pronounced bathochromic shifts of the fluorescence.     

岩石节理粗糙面的分形几何特性与剪切强度关系的实验研究

自然形成的岩石节理面的表面形状具有分形特性，利用分形理论来描述岩石节理的粗糙特性，并确立与岩石节理面的剪切力学特性间的关系对于指导岩体工程设计，和管理具有重要一研究利用开发设计的三维激光测距仪在精确测定岩石节理面的表面形状４ 基础上，依据变量图法建立了 岩石节理面的     

Heterometallic d8–d10 Coupling of Rh(I) and M(0) (M=Pd,Pt) in a Sandwich Framework of π-Conjugated Ligands

A heterometallic M−M′ bond formation is a key to construct atomically precise bimetallic clusters and materials. However, it is sometimes not straightforward to construct a heterometallic M−M′ bond through conventional methods including redox condensation. Here, we found that a sandwich framework of π-conjugated unsaturated hydrocarbon ligands provides a unique coordination environment that facilitates unusual coupling of d⁸ Rh^I and d¹⁰ M⁰ (M=Pd, Pt). The molecular orbital analysis showed that the electron-accepting ability of the sandwich framework through back-donation allows the formation of a dσ-type Rh−Pd bond in a (d–d)¹⁸ electron system.     

Stereoselective anti-SN2′ Mitsunobu reaction of α-hydroxy-α-alkenylsilanes

A novel silyl group-directed anti-S_N2′ reaction of allylic alcohols under Mitsunobu reaction conditions is described. The Mitsunobu reaction of α-hydroxy-α-alkenylsilanes with a TBS or TIPS group gave the anti-S_N2′ product, in which regio- and stereochemical outcomes of the reaction depended on the steric bulkiness of the silyl group.     

Reorganization energy of supramolecular donor–acceptor dyad of octaethylporphyrin isomers and axial-coordinated acceptor: Experimental and computational study

The internal reorganization energy (λ_V) of photoinduced electron transfer (ET) in the supramolecular donor–acceptor dyads of 2,3,7,8,12,13,17,18-octaethylporphinatozinc(II) (ZnOEP) and electron acceptor ligands was compared with those of structural isomers, 2,3,7,8,11,12,17,18-octaethylhemiporphycenatozinc(II) (ZnHPc) and 2,3,6,7,12,13,16,17-octaethylporphycenatozinc(II) (ZnPcn). First, ET process of the supramolecular donor–acceptor dyads of ZnOEP was investigated by means of the transient absorption spectroscopy mainly. The formation of supramolecular dyads was confirmed by absorption spectral change, from which the association constant was estimated. The ET process was confirmed by the observation of radical cation of ZnOEP during the laser flash photolysis. The ET rates of these dyads are in the order of ZnOEP > ZnHPc > ZnPcn, when the driving forces for ET are similar to each other. From the free energy dependence of ET rates, the λ_V values of OEP and its isomers were estimated. The estimated λ_V value was in the order of ZnOEP < ZnHPc < ZnPcn. This tendency was reproduced by calculation at B3LYP/6-31G(d) and BHandHLYP/6-31G(d) levels. The origin of this tendency was discussed on the basis of the structural change during the ET process.