Solid State and Solution Conformation of Di-2-thienyl Telluride: X-Ray Structure and Dipole Moment Studies

Abstract

The crystal and molecular structure of di-2-thienyl telluride was determined by X-ray analysis. Crystal (monoclinic) data were: a = 9.526(4), b = 6.252(4), c - 16.302(5) Å; β = 97.29(3)°, Z = 4, space group P21/c. Hydrogen bonds are absent and only van der Waals forces are determining crystal packing. The Cring-Te bond distances suggest little conjugation of Te atom with the rings. Comparisons with published structures for Car-X-Car (X = chalcogen) type molecules revealed that the C (l)-Te-C(5) angle takes the lowest value (95.6°) in the molecule understudy. The remaining bond lengths and angles are close to standard values. The molecular conformation found in the crystal is “butterfly-like” , with thienyl ring planes nearly perpendicular to the C(l)-Te-C(5) plane and the S atoms distal to each other. Dipole moment was measured for di-2-thienyl telluride in benzene solution (μ = 1.18 D at 30°). This value, which was interpreted via classical vector addition method in terms of rotation angles about C(l)-Te and C(5)-Te bonds, showed that the molecular conformation found in the crystalline state is retained in solution.