The crystal structure of the 1:1 complex between N,N'-dimethyl-4,4'-bipyridylium diiodide and quinol

The complex is monoclinic, space group P21/c, with a=6-817 (1), b=7.897 (1), c= 19-351 (2) /~,, ,8= 102.7 (1) °, Z=2. The structure was solved by the heavy-atom method and refined by block-diagonal, least-squares calculations to a final R of 0.036 for 2204 reflexions. Each quinol molecule is hydrogen bonded to two Iions with O . . . Idistances 3.457 (3) A, and each Iis 0.68 A out of the quinol plane. Such centrosymmetric quinol. 2Iunits are stacked alternately with centrosymmetric bipyridylium ions in infinite columns along b. The tilt of these units is such that each pyridine ring has a quinol molecule lying over or under it on one side (with a dihedral angle between the two rings of 3.4 ° and an average perpendicular separation of 3"38 A) and an Iion on the other side (perpendicular distance from the ring 3.73 A) almost directly above or below the N atom at a distance of 3.736 (3) A. This arrangement is indicative of charge-transfer interaction between both quinol and Ias donors and the bipyridylium ion as acceptor.