Triplet spin excitons in tris(dimethylamino)cyclopropenium 2,3-dichloro-5,6-dicyanobenzoquinonide

Abstract

The title compound (TDAC-DDQ) crystallizes in the monoclinic space group P21/n, with cell parameters a = 9.852 (3), b = 16.180 (6), c = 12.152 (3) Å, β = 104.14 (2)°, V = 1875.8 Å3, and Z = 4 (Rw = 0.051). Planar diamagnetic TDAC+ (X+) and paramagnetic DDQ- (A-) form two magnetically inequivalent ...X+A-A-X+... stacks. Electron paramagnetic resonance (EPR) of the DDQ- dimers indicates a singlet-triplet gap of 0.25 eV and fine structure constants of D = 215 G and E = 21 G, typical of (DDQ-)2 systems and consistent with solution spin densities. But the incorporation of TDAC+ within the stack immobilizes the triplet spin exciton, with an upper bound of 1 MHz for the hopping between magnetically inequivalent DDQ- dimers. © 1987 American Chemical Society.