Structure of the charge-transfer salt 2,2',5,5'-tetraselenafulvalene-7,7,8,8-tetrecyano-p-quinodimethane (TSeF-TCNQ)

2,2',5,5'-Tetraselenafulvalene-7,7,8,8-tetracyano-p-quinodimethane (1/1), TSeF-TCNQ, C6H4Se4.C12H4N4, M(r)=596.13, monoclinic, P2(1)/c, a=12.5038 (4), b=3.8724 (2), c=18.5031(7)Angstrom, beta=104.131 (3)degrees, V=868.9 Angstrom(3), T=297 K, Z=2, F(000)=560, D-x= 2.28 Mg m(-3), lambda(CuK alpha)=1.5418 Angstrom, mu=115.7 cm(-1) R(F)=0.018, wR(F)=0.030 for 1393 unique reflections with sigma(F-2)>3F(2). The crystals are isostructural with the corresponding tetrathiafulvalene salt, TNF-TCNQ, with both cations and anions arranged in segregated stacks parallel to b. There are Se ... N distances of 3.17 and 3.18 Angstrom along a, between cation and anion stacks, and H .... H distances of 2.58 Angstrom along c, between neighboring cation stacks, all shorter than the corresponding distances in TTF-TCNQ.