Exchange Interaction of 5,5‘-(<i>m</i>- and <i>p</i>-Phenylene)bis(10-phenyl-5,10-dihydrophenazine) Dications and Related Analogues
作者:Eriko Terada、Toshihiro Okamoto、Masatoshi Kozaki、Miyuki Eiraku Masaki、Daisuke Shiomi、Kazunobu Sato、Takeji Takui、Keiji Okada
DOI:10.1021/jo051791w
日期:2005.11.1
5,5'-(m-Phenylene)bis[(10-aryl-5,10-dihydroplienazine) dications, 3a(2+) and 3b(2+) and their p-analogues 4a(2+) and 4b(2+), 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 (vertical bar Delta m(s)vertical bar = 2) showed that these dications had singlet ground states with Delta E-ST/k(B) = -27 to -21 K for the m-isomer 3(2+) and with Delta E-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 3a(2+) and 4a(2+) and for (m- and p-phenylene)bisphenothiazine dications 1(2+) and 221 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, Delta E-TMO = vertical bar HOMO(alpha) - (HOMO - 1)(alpha)vertical bar. The calculated J values were negative in the order of 10 K for the m-dications (J/k(B) = -14.7 K for 12+, -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 1J1 values for the p-dications are qualitatively consistent with the experimental Delta E-ST (2J) values.