Conformation of acyclic derivatives of 1,1,4,4-tetraphenyl-1,3-butadiene

The structures of three functionally different acyclic derivatives of 1,1,4,4-tetraphenyl-1,3-butadiene, dimethyl 2,3-bis(diphenylmethylene)-1,4-butanedioate, C₃₂H₂₆O₄, 2,3-bis(diphenylmethylene)-1,4-butanedioic acid diethanol solvate, C₃₀H₂₂O₄.2C₂H₆O, and 2,3-bis(bromomethyl)-1,1,4,4-tetraphenyl-1,3-butadiene, C₃₀H₂₄Br₂, have been determined characterizing the preferred conformational mode of this moiety in the solid state. The diphenylmethylene groups adopt a syn conformation with respect to the central bond of the butadiene segment, the C=C - C=C torsion angles about this bond varying within 48-49○. In the observed structures, two of the phenyl rings are almost parallel to one another and partly overlap. The different crystalline environments seem to have little effect on the overall molecular conformation.