Syntheses,characterisations and X-ray crystal structures of 5,5′-bis(diphenylphosphino)2,2′-bithiophene derivatives,Ph 2 (X)P(C 4 H 2 S) 2 P(X)Ph 2 (X = O,S and CH 3 + · I − )

Abstract

Phosphine-substituted oligothiophenes are interesting third-order nonlinear materials. Both their linear and nonlinear optical properties can be altered by varying the group attached to the nonbonding pair of electrons on the phosphorus atoms, the number of phosphine groups attached to the oligothiophene and the number of repeat units in the oligothiophene. In this article, we report the syntheses, multinuclear NMR spectroscopic characterizations and X-ray crystal structures for three derivatives of 5,5′-bis(diphenylphosphino)-2,2′-bithiophene, Ph₂(X)P(C₄H₂S)₂P(X)Ph₂ (X = −, 1) in which X is O (2), S (3) and CH₃⁺ · I⁻ (4). The X-ray crystal structures exhibit significantly different π–π stacking, suggesting that these compounds could have significantly different nonlinear optical properties in the solid state.