Molecular orbital study on qu artet molecules with trigonal axis of symmetry

Kazunari Yoshizawa, Masashi Hatanaka, Akihiro Ito, Kazuyoshi Tanaka, Tokio Yamabe

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The ESR spectrum of the randomly oriented cationic triradical of 1,3,5-tris(diphenylamino)benzene (TDAB) is shown to agree well with the theoretical prediction of a quartet (5 = 3/2) molecule. The electronic structures of non-Kekulé-type isoelectronic molecules 1,3,5-trimethylenebenzene (TMB) and 1,3,5-triaminobenzene trication (TAB3+) are discussed by means of the ab initio molecular orbital (MO) method in the unrestricted Hartree-Fock scheme. In TMB the quartet State with planar D3h geometry is predicted to lie 26.1 kcal/mol below the lowest doublet State with a planar C2V geometry in which one of the methylene groups has a longer C-C bridge bond connecting the phenyl ring. Moreover, in TAB3+ the quartet State with planar D3h also lies 16.9 kcal/mol below the lowest doublet State with an orthogonal geometry where one of the amino groups is twisted out of the molecular plane. These quartet ground states result from the nearly threefold-degenerate Orbitals consisting of the nonbonding MOs. In addition, the quartet-doublet Splitting energy of TDAB is investigated using the semiempirical AM1 method.

Original languageEnglish
Pages (from-to)323-332
Number of pages10
JournalMolecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals
Issue number1
Publication statusPublished - Aug 1 1993
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

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