H. Mizouchi et al., DESIGN OF DONOR OLIGOMERS TO PRODUCE PARALLEL SPINS UPON ELECTRON-TRANSFER, Journal of the American Chemical Society, 117(11), 1995, pp. 3260-3269
Donor oligomers that give parallel spins upon electron transfer (ET) a
re designed. Tetrathiafurvalenes (TTFs) or tetraselenafulvalenes (TSFs
) are linked with bonds > C=Y (Y = CH2, O, S, C(CN)(2)) that yield dyn
amic spin polarization (DSP) in favor of parallel spins between cation
radicals of adjacent donors. Donors in these oligomers are not linked
by planar because of steric hindrance. Planar oligomers are designed
by adding a -S- bridge in the linkage of two donors. Oligomers linked
with a metaphenylene group are also examined. pi electronic structures
are calculated by the Pariser-Parr-Pople (PPP) model in the unrestric
ted Hartree-Fock (UHF) approximation using the Mataga-Nishimoto (M-N)
or Ohno potential. Dications of all the dimers have the triplet UHF gr
ound state. The DSPs, and consequently the singlet-triplet energy gaps
(S-T gaps), are much larger in the M-N potential than the Ohno one. T
he S-T gaps are much larger in the planar dimers than in the nonplanar
ones. Cation radicals of trimers and tetramers have quartet and quint
et UHF ground states, respectively. Donor abilities and orbital energy
gaps of oligomers and their cation radicals are studied.