title: Multiconfiguration Self-Consistent Field Study on Formonitrile Imine and N-Substituted Nitrile Imines HCN2-R: Energy Component Analysis of the Pseudo-Jahn-Teller Effect.
abstract: Stable geometrical structures for formonitrile imine (1) and N-substituted nitrile imines HCN2-R (R = Li, BeH, BH2, CH3, CN, CCH, C6H5, NH2, OH, and F) (2-11) were examined by using the multiconfiguration self-consistent-field (MCSCF) method followed by second-order configuration interaction (SOCI) calculations and second-order multiconfiguration quasi-degenerate perturbation theory (MCQDPT2) calculations, together with the aug-cc-pVTZ basis sets. The results show that 1 suffers a pseudo-Jahn-Teller (JT) distortion from a linear C∞vstructure to a C1structure via a planar bent Csstructure. Each of the others is found to undergo pseudo-JT distortion from a symmetrical structure to a planar bent Csstructure for 2, 3, and 7 and to a C1structure for 4, 5, 6, 8, 9, 10, and 11. At the stationary structures of 1-11, the structural characteristics were briefly discussed in terms of allenic and propargylic. To elucidate the nature of pseudo-JT distortions, energy component analyses were carried out at the MCSCF+SOCI level of theory at all of the stationary structures for the relevant molecules. In most of the molecules examined, pseudo-JT stabilizations were classified into two groups, one in which the stability arises from a lowering of the energy of the attractive term Venand the other in which the stability results from a lowering of the energy of the repulsive terms Vnnand Vee. In addition to the above two groups, it was also found that the following three groups are responsible for the pseudo-JT stabilizations in a certain stage of the structural changes. Namely, one is a lowering of the energy of the term Veeobserved in 6, another is a lowering of the energy of the terms Veeand Venobserved in 9-11, and the other is a lowering of the energy of the terms Venand Vnnobserved in 10. These energetic behaviors were accounted in terms of an elongation or a contraction of the molecular skeleton, a migration of electrons from one part of the molecule to other parts, and the combined effects arising from these two factors.
authors.affiliation: Environmental Education Center, Miyagi University of Education , Sendai 980-0845, Japan.
authors.forename: Azumao
authors.initials: A
authors.lastname: Toyota
authors.affiliation: Environmental Education Center, Miyagi University of Education , Sendai 980-0845, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Muramatsu
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka Prefecture University , 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan.|The Research Institute for Molecular Electronic Devices (RIMED), Osaka Prefecture University , 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531, Japan.
authors.forename: Shiro
authors.identifier: http://orcid.org/0000-0003-1208-4574
authors.initials: S
authors.lastname: Koseki