VINYLOGOUS TETRATHIAFULVALENE (TTF) PI-ELECTRON DONORS AND DERIVED RADICAL CATIONS - ESR SPECTROSCOPIC, MAGNETIC, AND X-RAY STRUCTURAL STUDIES

The properties of new 2,2'-ethanediylidene(1,3-dithiole) derivatives 5 , 6, and 8-11 are reported, Cyclic voltammetric studies establish that they are efficient donor molecules, with the extended conjugation res ulting in stabilization of dications, relative to tetrathiafulvalene T TF (1). Radical cations are generated by oxidation of the neutral comp ounds with trifluoroacetic acid or anhydrous silver perchlorate in dic hloromethane, and their ESR and proton ENDOR spectra are reported. The bulk. of the spin population resides in the central S2C=C-CC=CS2 part of the pi-system. The X-ray crystal structure of donor 6 reveals that the 2,2'-ethanediylidene(1,3-dithiole) framework is planar. Donor 6 f orms a crystalline 1:1 charge-transfer complex with TCNQ, the X-ray cr ystal structure of which shows a mixed stack structure. A solution of this complex in acetonitrile exhibits ESR spectra of both radical ions , 6(.+) and TCNQ(.-). Static susceptibility data are reported for TCNQ complexes of some of these donors.