title: Exchange interaction of 5,5'-(m- and p-phenylene)bis(10-phenyl-5,10-dihydrophenazine) dications and related analogues.
abstract: [structures: see text] 5,5'-(m-Phenylene)bis[(10-aryl-5,10-dihydrophenazine) dications, 3a2+ and 3b2+, and their p-analogues 4a2+ and 4b2+, were prepared, and their exchange interaction was investigated. The EPR spectra of these dications at 123 K in a butyronitrile matrix showed the population of a triplet state. The temperature dependence of the EPR signal intensity (absolute value(delta m(s)) = 2) showed that these dications had singlet ground states with deltaE(ST)/k(B) = -27 to -21 K for the m-isomer 3(2+) and with deltaE(ST)/k(B) = -10 to -8 K for the p-isomer 4(2+). Theoretical calculation of the exchange interaction J for these dications at the orthogonal torsion angle geometries was carried out for 3a2+ and 4a2+ and for (m- and p-phenylene)bisphenothiazine dications 1(2+) and 2(2+) using the broken-symmetry approach for the singlet states. A good correlation was observed between the calculated J and a MO-energy term in the triplet state, deltaE(TMO) = absolute value(HOMO(alpha) - (HOMO - 1)(alpha)). The calculated J values were negative in the order of 10 K for the m-dications (J/k(B) = -14.7 K for 1(2+), -11.5 K for 3a(2+)), but much smaller negative values were found for the p-isomers (J/k(B) = -0.9 K for 2(2+), -0.8 K for 4a2+). The smaller absolute value(J) values for the p-dications are qualitatively consistent with the experimental deltaE(ST) (2J) values.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Terada
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Okamoto
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Kozaki
authors.forename: Miyuki Eiraku
authors.initials: ME
authors.lastname: Masaki
authors.forename: Daisuke
authors.initials: D
authors.lastname: Shiomi
authors.forename: Kazunobu
authors.initials: K
authors.lastname: Sato
authors.forename: Takeji
authors.initials: T
authors.lastname: Takui
authors.forename: Keiji
authors.initials: K
authors.lastname: Okada