Ab Initio Computations of the Geometrical, Electronic, and Vibrational Properties of the Ground State, the Anion Radical, and the N,N‘-Dihydro Cation Radical of 4,4‘-Bipyridine Compared to Transient Raman Spectra
摘要:
The geometrical and electronic structures, the force constants, the vibrational frequencies, and the potential energy distributions for various isotopomers of 4,4'-bipyridine (44BPY) in the ground state S-0 and for the corresponding anion radical 44BPY(.-) and N,N'-dihydro cation radical 44BPYH(2)(.+) have been computed by the 3-21G(+*) ab initio method, with the RHF formalism for the ground state S-0 and with the ROHF formalism for the ionic species. The theoretical results have been compared to the available vibrational data. The very good agreement between calculations and experiment has allowed the determination of the conformations of the S-0 state and of the ion radicals. The ground state is characterized by an aromatic structure in which the two pyridyl rings are linked in a twisted conformation, and the ionic species present a quinoidal planar distortion, more marked in the cation radical than in the anion radical.
Ab Initio Computations of the Geometrical, Electronic, and Vibrational Properties of the Ground State, the Anion Radical, and the N,N‘-Dihydro Cation Radical of 4,4‘-Bipyridine Compared to Transient Raman Spectra
摘要:
The geometrical and electronic structures, the force constants, the vibrational frequencies, and the potential energy distributions for various isotopomers of 4,4'-bipyridine (44BPY) in the ground state S-0 and for the corresponding anion radical 44BPY(.-) and N,N'-dihydro cation radical 44BPYH(2)(.+) have been computed by the 3-21G(+*) ab initio method, with the RHF formalism for the ground state S-0 and with the ROHF formalism for the ionic species. The theoretical results have been compared to the available vibrational data. The very good agreement between calculations and experiment has allowed the determination of the conformations of the S-0 state and of the ion radicals. The ground state is characterized by an aromatic structure in which the two pyridyl rings are linked in a twisted conformation, and the ionic species present a quinoidal planar distortion, more marked in the cation radical than in the anion radical.
One-step exchange-labelling of pyridines and other N-heteroaromatics using deuterium gas: catalysis by heterogeneous rhodium and ruthenium catalysts
作者:Efstathios Alexakis、John R. Jones、William J.S. Lockley
DOI:10.1016/j.tetlet.2006.05.106
日期:2006.7
A wide range of pyridines and other nitrogen heteroaromatics can be labelled with deuterium at room temperature and pressure by isotopic exchange with deuterium gas in THF in the presence of rhodium black, ruthenium black or 5% rhodium on alumina. The labelling is rapid, isotope efficient and applicable to both electron-rich and electron-poor substrates. In a few cases, a degree of reduction accompanies the exchange. (c) 2006 Elsevier Ltd. All rights reserved.