[TDNQ][CoCp*2] and [TDNQ]3[CoCp2]2; Radical Anions of a 1,2,5-Thiadiazolo-naphthoquinone
datasetposted on 01.06.2011, 00:00 by Ian S. Morgan, Michael Jennings, Alessandro Vindigni, Rodolphe Clérac, Kathryn E. Preuss
The first crystal structure of a quinone[1,2,5]thiadiazole radical anion is presented. Reduction of naphtha[2,3-c][1,2,5]thiadiazole-4,9-dione (TDNQ) with outersphere electron transfer agents, decamethylcobaltocene (CoCp*2) and cobaltocene (CoCp2), by slow mixing of solutions, generates two species: [TDNQ][CoCp*2] and [TDNQ]3[CoCp2]2, respectively. The [TDNQ][CoCp*2] is soluble in a wide variety of organic solvents, whereas [TDNQ]3[CoCp2]2 is generally insoluble. The radical anion oxidation state, TDNQ•, in [TDNQ][CoCp*2] is confirmed by lengthened C–O bond distances in the (solvated) crystal structure, as compared to neutral TDNQ, shifting of the ν(C–O) stretch in the IR absorption spectrum, and the presence of a solution electron paramagnetic resonance (EPR) signal. In the [TDNQ]3[CoCp2]2 species, copacking of single-molecule radical anions, TDNQ•, and bimolecular radical anion units, (TDNQ)2•, with cobaltocenium cations is observed. The magnetic measurements highlight the presence of dominating antiferromagnetic interactions between TDNQ• and (TDNQ)2• spins in this cobaltocene salt.