SOLID-STATE INTERMOLECULAR INTERACTIONS IN CYANOFUNCTIONALIZED DISELENADIAZOLYL DIMERS

The preparation and crystal and molecular structure of the monofunctional 1,2,3,5-diselenadiazolyl radical [RCN2Se2] (R = 3,5-dicyanophenyl) are described. Crystals of [(CN)2C6H3CN2Se2] are triclinic, space group P1BAR, a = 7.197(2), b = 10. 753 (3), c = 13.345(5) angstrom, alpha = 88.00(3)-degrees, beta = 82.05(2)-degrees, gamma = 81.00(2)-degrees, MW = 31 1. 1, Z = 4. The structure consists of stacked arrays of radical dimers laced together by networks of short CN --- Se contacts, but the steric bulk of the organic ligand leads to a pairwise aggregation of [CN2Se2] columns. These structural features are compared with those observed in related dimers, and the results interpreted in the light of extended Huckel band calculations on a series of model structures. The results provide a qualitative correlation between the size and dimensionality of the intermolecular Se --- Se network and the degree of crystal orbital dispersion.