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

• DOI: 10.1021/cm960545l
• Publication Date: 2002-07-26T05:07:11Z
• Authors: T. M. Barclay; A. W. Cordes; C. D. MacKinnon; R. T. Oakley; R. W. Reed
• Keywords: Monoclinic crystal system; Triclinic crystal system; Quinoline

The synthesis of dicyanooligothiophenes NC(C4H2S)nCN (n = 3−6) is reported. For n 3, 4, and 5 the dinitriles are generated by treatment corresponding dibromo compounds with copper(I) cyanide in quinoline. 6 preparation involves Ni-catalyzed coupling 5-bromo-2,2':5',2''-terthiophene-5''-carbonitrile. structures all four dicyano derivatives have been determined X-ray crystallography. space group monoclinic C2/c, a 18.363(7), b 11.8356(9), c 30.666(4) Å, β 102.15(2)°, V 6515(3) Å3, Z 20. 4 triclinic P1̄, 7.3254(9), 7.8658(6), 8.1813(8) α 64.706(8), 76.059(8), γ 76.692(8)°, 409.29(7) 1. 13.633(4), 11.706(5), 37.073(8) 90.22(2)°, 5929(3) 12. 6, P21/a, 13.8962(14), 5.9100(16), 14.0798(16) 98.446(4)°, 1143.8(4) 2. In molecules approximately planar, all-trans thiophene rings. oligomers linked into ribbonlike arrays intermolecular CN- - -H contacts. these ribbons stacked coplanar layers (π-stacks). packed herringbone motif very similar to that observed H(C4H2S)6H (α-6T). UV−visible spectra 2−6) recorded, shifts π−π* excitation energies relative those found other α,ω-disubstituted oligothiophenes interpreted light MNDO calculations. Extended Hückel band structure calculations on 6) indicate substantial interactions; both well-developed 2-dimensional electronic structures.