Crystal structures and photochemistry of triphenylphosphine oxide complexes of ethyl hydrogen 9,10-dihydro-9,10-ethenoanthracene-11,12-dicarboxylate

Abstract

The detailed course of the photochemical rearrangement reactions of dibenzobarrelenedicarboxylates has been studied by crystal structure analyses of two complexes of triphenylphosphine oxide (1) with the monoester ethyl hydrogen 9,10-dihydro-9,10-ethenoanthracene-11,12-di-carboxylate (2), and by correlation of the crystal structure data with photochemical behaviour. Crystal data: T = 294 K, Cu Kα, λ = 1.54178 A. (1.2), C 18 H 15 OP.C 20 H 16 O 4 , M r = 598.63, P1, a = 13.501(1), b = 14.845(1), c = 8.5190(6)A, α = 102.21(1), β = 98.68 (1), γ = 68.70 (1)°, Z = 2, R = 0.039 for 4546 reflections with I > 3σ(I); (1.2).0.5toluene, C 18 H 15 OP.C 20 H 16 O 4 .0.5C 7 H 8 , M r = 644.71, P2 1 /n, a = 8.546(2), b = 28.164(5), c = 14.368(2)A, β = 98.81(2)°, Z = 4, R = 0.052 for 3462 reflections. Both crystals contain pairs of molecules linked by O-H...O hydrogen bonds, with dimensions and conformations similar to those of previously studied analogues. In the unsolvated crystal the ester group of the monoester is fully conjugated with the C(11)=C(12) double bond [C=C-C=O torsion angle = -179.6(2)°, cos 2 (angle) = 1.0], but the acidic group is non-conjugated [109.0(3)°, 0.11]. In the toluene solvate the opposite is the case, the ester group being non-conjugated [110.5(5)°, 0.12], and the acid group conjugated [-13.8 (6)°, 0.94]. The different amounts of photoproducts formed in the solid-state photolyses can be correlated with these conformational differences.