Synthesis and crystal structures of three rigidly linked donor–acceptor systems designed to test the effect of bridge configuration on the dynamics of long-range intramolecular electron transfer processes

Abstract

The synthesis and single crystal X-ray structures of three rigid bichromophoric systems are described, namely the dicyanovinyl derivatives of 7,12-dimethoxydodecahydro-1,4:6,13-dimethanopentacen-15-one, 3, 8,13-dimethoxyhexadecahydro-1,4:5,16:6,17:7, 14-tetramethanohexacen-17-one, 4 and 6,11-dimethoxy-4b, 12b-dimethyldodecahydro-4,13;5,12-dimethano-2H-indeno-[5′,6′:3′,4′]cyclo-buta[1′,2′:3,4]cyclobuta[1,2-b]anthracen-2-one 5. Compounds 3 and 4 were synthesized from dimethanonaphthacene 8via Diels–Alder reaction with tetrachlorodimethoxycyclopentadiene 9(in the case of 3) and via successive Diels–Alder reactions, firstly with hexachlorocyclopentadiene, 14, and then with 9, in the case of 4. The synthesis of 5 was achieved through ring expansion of the dichloroketene [2 + 2] cycloadduct formed from 21. Differences in the rates of photoinduced intramolecular electron transfer in 3–5, compared with those for 1 and 2, are rationalized in terms of the differing configurations of the hydrocarbon bridges in these systems, as revealed by X-ray crystallography.