Isomeric and Isostructural Oligothienylsilanes–Structurally Similar, Physicochemically Different: The Effect of Interplay between C–H···C(π), S···C(π), and Chalcogen S···S Interactions

Abstract

The solid state and solution properties of tris(2-thienyl)methylsilane, I, tetrakis(2-thienyl)silane, III, and their positional isomers bearing 3-thienyl groups (II and IV) were investigated and compared. The tris(thienyl)silanes (I, II) crystallize in different space groups, but their respective structural motifs are very comparable. In turn, the tetrathienyl isomers are isostructural. Furthermore, in all studied systems the same set of C–H···C(π), S···C(π), S···S, C–H···S interactions are engaged in supramolecular structure formation. These interactions are interchangeable as thienyl rings (excluding structure II) are affected by 2-fold positional disorder. Despite the high level of structural similarity, the studied thienylsilanes show very different physicochemical behavior: (1) much higher melting points and larger enthalpies of fusion for II (mp = 71.3 °C, ΔH = 20.9 kJ mol–1) and IV (mp = 221.2 °C, ΔH = 29.1 kJ mol–1) with respect to their isomeric counterparts I (mp = 28.6 °C, ΔH = 16.0 kJ mol–1) a...