Reaction of N,N’-dimethylimidazolidine-2-selone (4) with TCNQ. Characterisation and X-ray crystal structure of the mixed-valence compound 4·(TCNQ)1.167

The reaction of N,N'-dimethylimidazolidine-2-selone (4) with TCNQ affords lustrous dark crystals with elemental analysis corresponding to the formula 4?(TCNQ)1.167. X-Ray crystal structure determination shows that this compound is formed by discrete [42]2z dications, in which two oxidized imidazolidine molecules are bonded through an ±Se±Se± bridge [2.5187(7) AÊ ]. These dications interact on one side with a third disordered molecule of 4 (occupancy factor 0.5) via Se¼Se soft interactions of 2.715(4) and 2.899(4) AÊ to give almost linear ±Se±Se¼Se± arrangements [Se(2)±Se(1)¼Se(3), 177.64(6)³ and Se(2)±Se(1)¼Se(3a), 167.89(5)³]. The unit cell contains six imidazolidine molecules bearing a total of four positive charges, balanced by four negative charges distributed on seven TCNQ molecules, stacked in two dimers and a trimer. Structural data suggest that the negative charges are unevenly distributed on the TCNQ molecules. Single crystal infrared spectra also suggest the presence of at least three differently charged TCNQ's, and in addition indicate a room temperature optical gap of y0.3 eV, placing this compound among wide bandgap semiconductors (s~3.4561023 S cm21). Cyclic voltammetry of 4 is discussed in comparison with those of previously studied imidazoline-2-selone derivatives (1±3), and shows that for this donor the achievement of a mixed valence compound with TCNQ is possible in MeCN.