Koichi Mogi

Theoretical study of low-lying electronic states of TiCl and ZrCl

Low-lying electronic states of TiCl and ZrCl were investigated by the complete active space SCF (CASSCF), multi-reference singly and doubly excited configuration interaction (MRSDCI), and multi-reference coupled pair approximation (MRCPA) calculations using the model core potential (MCP) method. Relativistic effects were incorporated in the MCP and basis sets for Zr at the level of Cowan and Griffin’s quasi-relativistic Hartree–Fock method. The 4Φ state was found to be the ground state of TiCl, whereas the 2Δ state was the ground state of ZrCl at all levels of calculation. Two low-lying excited states were very close in energy to the ground state. The excited 4Σ− and 2Δ states of TiCl were higher than the ground state by 0.102 eV and 0.458 eV, respectively, and the excited 4Φ and 4Σ− states of ZrCl were higher by 0.094 eV and 0.110 eV, respectively, at the MRCPA level. The calculated values of re(2.319 A) and ωe(382 cm−1) for the ground 4Φ state of TiCl are quite close to the values of re(2.351 A) and ωe(...

Hole-burning spectroscopy and ab initio calculations for the aniline dimer

Abstract The mass-resolved spectrum indicates that only one conformation contributes to sharp peaks observed in the S 1 ←S 0 resonance two-photon ionization (R2PI) spectrum. However, geometry optimizations at the MP2/cc-pVDZ level suggest that two conformational isomers are stable: a head-to-head conformation with a single NH⋯N hydrogen bond and a head-to-tail conformation with double NH 2 ⋯π hydrogen bonds. The calculations show that the head-to-tail conformation is more stable by 1.18 kcal mol −1 .

Effects of intermolecular interaction on proton tunneling: Theoretical study on two-dimensional potential energy surfaces for 9-hydroxyphenalenone-CO2/H2O complexes

The effects of binding of CO2 or H2O with 9-hydroxyphenalenone (9HPO) on proton tunneling in the S0 state have been theoretically investigated. High-level ab initio calculations predict that CO2 is van der Waals-bonded to the C=O⋯OH moiety of 9HPO in the most stable structure. This planar structure is more stable than the nonplanar structure where CO2 is bonded above the aromatic rings of 9HPO. In the 9HPO–H2O complex, H2O is hydrogen-bonded to the carbonyl group in the most stable structure. Two-dimensional potential energy surfaces (PESs) for 9HPO–CO2 and 9HPO–H2O have been calculated with the reaction surface method, and the contour plots of PESs for the complexes are compared with those for the 9HPO monomer. The binding of CO2 with 9HPO induces slight asymmetry in the double-minimum potential well, whereas the asymmetry of the PES is very large for the binding of H2O. The transition state energy for 9HPO–CO2 drastically decreases to be about a half that of 9HPO, while that for 9HPO–H2O is only slightl...

Experimental and theoretical aspects of the haptotropic rearrangement of diiron and diruthenium carbonyl complexes bound to 4,6,8-trimethylazulene.

The haptotropic rearrangement of dinuclear metal carbonyl species on the conjugate pi-ligand of (micro2,eta3:eta5-4,6,8-trimethylazulene)M2(CO)5 [M = Fe (3) and Ru (4)] was investigated in detail both experimentally and theoretically. The complexes, 3 and 4, were synthesized and characterized by spectroscopy and crystallography. The spin saturation transfer technique of 1H NMR was used to measure the rate constant k of the haptotropic isomerization between the two enantiomers of 3 and 4, from which thermodynamic parameters were determined: (3; deltaS(double dagger) = -7 +/- 1 cal K(-1) mol(-1), deltaH(double dagger) = 22 +/- 1 cal mol(-1), deltaG(double dagger)373 = 25 +/- 1 cal mol(-1)), (4; deltaS(double dagger) = 7 +/- 1 cal K(-1) mol(-1), deltaH(double dagger) = 25 +/- 1 cal mol(-1), deltaG(double dagger)373 = 23 +/- 1 cal mol(-1)). DFT calculations (the B3LYP, B1B95 and PBE1PBE methods) were also carried out using the CEP-31G and cc-pVDZ as the basis set of the transition metal and other elements, respectively, by which both ground state and transition state structures were optimized for the haptotropic rearrangement of 3 and 4. The potential energy surface for these reactions suggests that the reaction involves the conversion of the coordination mode from micro2eta3,eta5- (ground state) to micro2,eta1,eta5- (transition state). Mechanistic consideration, in particular that of differences in transition states between the diiron and diruthenium complexes, is also described.

Theoretical study of low lying electronic states of GdO

Low lying electronic states of GdO have been investigated by complete active space SCF (CASSCF) and multireference singly and doubly excited configuration interaction (MRSDCI) calculations using the model core potential (MCP) method. The 4f electrons of Gd were included explicitly in the valence space. Relativistic effects were incorporated in the MCP and basis sets for Gd at the level of Cowan and Griffins quasirelativistic Hartree—Fock method. The 9Σ− state (f7σ) was the ground state, and excited states, 9Δ, 9Π, 29Σ−, 7Σ−, 7Δ, 7Π, and 27E−, lay between 0 ∼ 22 300 cm−1. The energy separations for these states agreed well with available experimental values. Calculated GdO bond lengths and vibrational frequencies for these states are in the ranges of 1.81–1.85 Å and of 800–880 cm−1, respectively. Mulliken population analysis showed that the gross population of the 4f orbitals was 7.1 e for all these states, and that the 4f electrons were strongly localized on Gd atom. The effective charge distribution was approximated to be Gd+O−. The σ and π bonding orbitals were mainly formed by Gd 5d and O 2p orbitals.