Crystal Structure Correlations in the Photochemistry of Dimethyl 9-Phenyl-9,10-dihydro-9,10-ethenoanthracene-11,12-dicarboxylate

Article abstract of DOI:10.1107/S0108768193001144

A study of the photochemistry of the title 9-phenyldibenzobarrelene-11,12-diester (1) reveals the formation of a semibullvalene derivative, dimethyl 8b-phenyl-4b,8b,8c,8d-tetrahydrodibenzocyclopropapentalene-8c,8d-dicarboxylate (2), in acetone solution, with an additional cyclooctatetraene (COT) photoproduct, dimethyl 5-phenyldibenzocyclooctene-6,12-dicarboxylate (3), in acetonitrile, benzene and in solid-state photolysis.Crystal data: T = 294 K, Cu Kα, λ = 1.5418 Angstroem, C26H20O4, M_r = 396.44, (1), triclinic, P<*>1, a = 10.713 (1), b = 11.991 (1),c = 8.177 (1) Angstroem, α - 95.71 (1), β =- 105.14 (1), γ = 79.61 (1) deg, V = 995.9 (2) Angstroem³, Z = 2, D_x = 1.322 g cm^-3, F(000) = 416, μ = 6.8 cm^-1, R = 0.060 for 3069 reflections. (2), monoclinic, P2₁/n, a = 10.206 (3), b = 16.485 (1), c = 11.758 (4) Angstroem, β = 95.48 (2) deg, V = 1969.2 (8) Angstroem³, Z = 4, D_x = 1.337 g cm^-3, F(000) = 832, μ = 6.9 cm^-1, R = 0.039 for 2882 reflections. (3), triclinic, P<*>1, a = 11.074 (2), b = 25.298 (6), c = 7.668 (2) Angstroem, α = 94.22 (2), β = 94.53 (2), γ = 101.77 (2) deg, V = 2087.5 (8) Angstroem³, Z = 4 (two molecules per asymmetric unit), D_x = 1.261 g cm^-3, F(000) = 832, μ = 6.5 cm^-1, R = 0.039 for 4668 reflections.Compound (2) has a structure consistent with formation via normal di-?-methane reaction involving the triplet excited state, while formation of (3) provides another example of unexpected behaviour of the singlet excited state.