Stacking efficiency of diselenadiazolyl pi-dimers. Consequences for electronic structure and transport properties

by Britten, James F.; Clements, Owen P.; Cordes, A. Wallace; Haddon, Robert C.; Oakley, Richard T.; Richardson, John F.

The preparation and crystal structure of 5-eyanofuran-2-[1,2,3,5-diselenadiazolyl], [RCN2Se2] (R = 5-cyanofuran), is reported. Crystal data for C6H2ON3Se2: monoclinic, space group P2(1), a = 7.1121(7), b= 20,541(2), c =20.923-(2) Angstrom. beta = 99.785(1)degrees, Z = 16. The crystal structure consists of diselenadiazolyl pi -dimer stacks running parallel to the x direction; the asymmetric unit consists of four pi -dimer units. The dimers are aligned into snakelike ribbons along the y direction, with consecutive dimers linked by head-to-tail CN-Se contacts. Each pi -dimer stack is bordered by two out-of-register stacks, but most interstack Se-Se contacts lie outside the van der Waals separation. Along the pi -dimer stacks, the intradimer Se-Se distances range from 3.183(10) to 3.294(1) Angstrom, and the interdimer Se-Se distances range from 3.826(1) to 3.945(1) Angstrom. Like other pi -dimer stacked diselenadiazolyls, [C6H2ON3Se2](2) is diamagnetic over the temperature range 4-380K. Variable temperature single-crystal conductivity measurements reveal a room-temperature conductivity near 10(-5) S cm(-1) and provide a calculated band gap of 0.72 eV. The structural results and transport properties are interpreted in the light of Extended Huckel band structure calculations.

Journal
Inorganic Chemistry
Volume
40
Issue
26
Year
2001
Start Page
6820
ISBN/ISSN
1520-510X; 0020-1669
DOI
10.1021/ic010678v