Bowles, S. E.; Dooley, B. M.; Benedict, J. B.; Kaminsky, W.; Frank*, N. L. The Competing Roles of Topology and Spin Density in the Magnetic Behavior of Spin Delocalized Radicals: Donor-Acceptor Annelated Nitronyl Nitroxides Polyhedron 2009 28, 9-10, 1704-1709 (JUN 22 2009). DOI: 10.1016/j.poly.2008.10.056 (Conference: 11th International Conference on Molecule-Based Magnets (ICMM 2008) Location: Florence, ITALY Date: SEP 21-24, 2008)
Electron donor-acceptor interactions in organic D-A dyads lead to a lowering of the orbital (HOMO-LUMO)gap, important for appdlications in organic electronics. Donor-acceptor interactions in thienyl substituted benzimidazole-nitronyl nitroxides (TBNN) leads to NIR absorption (1000 nm) that exhibits solvatochromism consistent with HOMO-SOMO charge transfer. The TBNN radicals form highly disordered slipped pi-stacks in the solid state that give rise to antiferromagnetic interactions consistent with 1D chain interactions with J = -2 to -10 cm(-1) depending on substitution. The weak exchange parameters are attributed to packing disorder due to topology of a planar radical.