Oligothiophenes End-Capped by Nitriles. Preparation and Crystal Structures of α,ω-Dicyanooligothiophenes NC(C4H2S)nCN (n = 3−6)

The synthesis of dicyanooligothiophenes NC(C4H2S)nCN (n = 3−6) is reported. For n = 3, 4, and 5 the dinitriles are generated by treatment of the corresponding dibromo compounds with copper(I) cyanide in quinoline. For n = 6 the preparation involves the Ni-catalyzed coupling of 5-bromo-2,2‘:5‘,2‘‘-terthiophene-5‘‘-carbonitrile. The structures of all four dicyano derivatives have been determined by X-ray crystallography. For n = 3, the space group is monoclinic C2/c, with a = 18.363(7), b = 11.8356(9), c = 30.666(4) A, β = 102.15(2)°, V = 6515(3) A3, Z = 20. For n = 4 the space group is triclinic P1, a = 7.3254(9), b = 7.8658(6), c = 8.1813(8) A, α = 64.706(8), β = 76.059(8), γ = 76.692(8)°, V = 409.29(7) A3, Z = 1. For n = 5 the space group is monoclinic C2/c, with a = 13.633(4), b = 11.706(5), c = 37.073(8) A, β = 90.22(2)°, V = 5929(3) A3, Z = 12. For n = 6, the space group is monoclinic P21/a, with a = 13.8962(14), b = 5.9100(16), c = 14.0798(16) A, β = 98.446(4)°, V = 1143.8(4) A3, Z = 2. In all four ...