Structural studies of `push–pull' butadienes

Abstract

Compound (I), ethyl 2-cyano-5-dimethylamino-3- methyl-2,4-pentadienoate, C₁₁H₁₆N₂O₂, M_r = 208.26, monoclinic, P2₁/n, a = 7.679(2), b = 13.368 (2), c = 11.756 (2) Å, β = 92.62 (2)°, V = 1205.5 (4) ų, Z = 4, D_x = 1.15 g cm^-3, λ(Cu Kα) = 1.5418Å, μ = 6.15cm^-1, F(000)=448, T=293K, R=0.062 for 1721 unique reflections. Compound (II), 4,4-bis(methylthio)-2-phenyl- 1,3-butadiene- 1,1- dicarbonitrile, C₁₄H₁₂N₂S₂, M_r=272.38, triclinic, P1̅, a = 8.833 (1), b = 9.419 (2), c = 9.520 (1) Å, α = 106.77 (1), β = 93.14 (1), ᵞ = 109.61(1)°, V= 704.2 (2) ų, Z = 2, D_x = 1.28 g cm^-3, λ(Cu Kα) = 1.5418 Å, μ = 32.29 cm^-1, F(000) = 284, T = 293 K, R = 0.062 for 2059 unique reflections. Compound (III), ethyl 2-cyano-5-dimethylamino-3-phenyl-2,4- pentadienoate, C₁₆H₁₈N₂O₂, M_r=270.33, mono- clinic, C2/c, a = 17.468 (1), b= 13.753 (4), c= 15.218 (1) Å, β = 125.49 (1)°, V = 2976.7 (9) ų, Z = 8, D_x = 1.21 g cm^-3, λ(Cu Kα)= 1.5418Å, μ = 6.12 cm^-1, F(000)=1152, T = 293 K, R = 0.055 for 2211 unique reflections. Compound (IV), 4-dimethylamino-4-methylthio-3-phenyl-l,3- butadiene-1,1-dicarbonitrile, C₁₅H₁₅N₃S, M_r = 269.36, monoclinic, P2₁/n, a = 9.951 (1), b – 10.040 (1), c = 14.764 (2) Å, β = 98.67 (1)°, V = 1458.9 (2) ų Z = 4, D_x = 1.23 g cm^-3, λ(Cu Kα) = 1.5418 Å, μ = 18.37 cm ^-1, F(000) = 568, T = 293 K, R = 0.052 for 2479 unique reflections. The influence of different electron donor-acceptor pairings on the molecular geometry is discussed.