Spin-spin coupling between the two unpaired electrons in cross-conjugated tetrathiafulvalene dication radicals

Spin-spin interactions were examined for bis(tetrathiafulvalenyl) (TTF) der ivatives bridged with a 1,1-vinyl group (2,2-diphenyl, 1: 2,2-fluorenyliden e, 2; and 2,2-dimethyl, 3). The chemical oxidation of these cross-conjugate d TTFs using AgClO4 yielded characteristic seven-line ESR spectra, indicati ng the exchange interactions between the unpaired electrons on each TTF moi ety. Compounds 2 and 3, in addition, exhibited fine structures and half-fie ld resonances in the frozen solutions, which evidence the tripler interacti on in the solid state, even with a twisted geometry of the molecular config uration. These findings substantiate the possibility of spin-spin interacti ons or triplet ground states predicted for some TTF oligomers. Copyright (C ) 2000 John Wiley & Sons, Ltd.