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

The reaction of N,N'-dimethylimidazolidine-2-selone (4) with TCNQ affords l ustrous dark crystals with elemental analysis corresponding to the formula 4.(TCNQ)(1.167). X-Ray crystal structure determination shows that this comp ound is formed by discrete [4(2)](2+) dications, in which two oxidized imid azolidine molecules are bonded through an -Se-Se- bridge [2.5187(7) Angstro m]. These dications interact on one side with a third disordered molecule o f 4 (occupancy factor 0.5) via Se ... Se soft interactions of 2.715(4) and 2.899(4) Angstrom to give almost linear -Se-Se ... Se- arrangements [Se(2)- Se(1)... Se(3), 177.64(6)degrees and Se(2)-Se(1)... Se(3a), 167.89(5)degree s]. The unit cell contains six imidazolidine molecules bearing a total of f our positive charges, balanced by four negative charges distributed on seve n TCNQ molecules, stacked in two dimers and a trimer. Structural data sugge st that the negative charges are unevenly distributed on the TCNQ molecules . Single crystal infrared spectra also suggest the presence of at least thr ee differently charged TCNQ's, and in addition indicate a room temperature optical gap of similar to 0.3 eV, placing this compound among wide bandgap semiconductors (sigma = 3.45 x 10(-3) S cm(-1)). Cyclic voltammetry of 4 is discussed in comparison with those of previously studied imidazoline-2-sel one derivatives (1-3), and shows that for this donor the achievement of a m ixed valence compound with TCNQ is possible in MeCN.