The valence ionization potentials of F2O and Cl2O have been determined by photoelectron spectrometry, and the results are compared with the predictions of ab initio and approximate LCAO SCF calculations. The first PES band shows vibrational structure which is assigned to ν1 for F2O, and to both ν1 and ν2 for (Cl2O). These frequencies all show slight increases over the corresponding values for the ground states of the neutral molecules.

Variable-temperature l H n.m.r. data are presented for the square-planar Ni'I complexes, [{Me,M (pz),),Ni] ( M = Ga or B, and pz = pyrazolyl, N,C,H,), and stereochemical nonrigidity for the molecules in solution is invoked to account for the spectral changes observed. Activation energies obtained for the suggested interconversion processes are 46 for the gallium and 67 kJ mo1-I for the boron complex. The CuII complexes, [{Me,M(pz),),Cu] (M = Ga or B), and [{Me,Ga(dmpz),),Cu] (dmpz = 3.5-dimethylpyrazolyl, N2C5H,), have been studied by electronic absorption spectroscopy, ESCA, and e.s.r. spectroscopy. Data have been interpreted to provide tentative one-electron orbital sequences for copper in these complexes. The colour change observed from solid to solution for square-planar [(Me,Ga(pz),),Cu] has been interpreted in terms of a tetrahedral distortion of the square-planar CuN, chromophore in solution. The e.s.r. results for the pseudotetrahedral complex, [(Me,Ga-(dmpz),),Cu],indicate substantial d-p mixing in the ground state.

No abstract

The first ionization potential in the photoelectron spectra of CH3SH (9.42 eV) and (CH3)2S (8.65 eV) as in H2S (10.47 eV) corresponds to ionization of a lone-pair electron, and, although there is a small interaction in the C-S bond, the inductive effect is thought to cause the considerable shift to lower energy. In contrast to these molecules and -toluenethiol (first I.P., 9.25 eV) the sulfur lone pair in thiophenol exhibits a considerable amount of ir interaction with the adjacent benzene ring. The higher I.P.'s of CH3SH and (CH3)2S have been assigned, and it is shown that ionization occurs more readily from orbitals situated mainly in the C-S bond than the S-H bond.

Ordinary third-order Rayleigh-Schrödinger perturbation theory is used to evaluate vertical ionization potentials of closed-shell molecules. The method is tested with double-zeta calculations on H2O, CH2, NH3, H2CO, and F2O. The results are compared with the ΔSCF method and discussed. On the basis of our calculations, we confirm the suggested alternative assignment for the photoelectron spectrum of F2O, instead of the original assignment based on Koopmans' theorem.