CH⋯S hydrogen bonds as the organising force in 2,3-thienyl- and phenyl- or 2,3-dithienyl-substituted propenoic acid aggregates studied by the combination of FT-IR spectroscopy and computations

Various propenoic acid stereoisomers 2,3-disubstituted with thienyl and/or phenyl groups were synthesised and their aggregation behaviour was studied both in solution and in the solid state by experimental (mid-range FT-IR spectroscopy) and computational (semiempirical and ab initio) methods. Experimental approach embraced the identification of potential hydrogen bonding sites through finding the relevant IR bands and monitoring their displacement upon increasing the acid concentration in solution and on going from solution to the solid state. In solution OH⋯O hydrogen bonds were only found providing short-range ordering, while in the solid state CH⋯S hydrogen bonds were identified. Hydrogen bonding sites could be assigned and relevant aggregate models could be built. Molecular modelling allowed obtaining good estimates for hydrogen bond lengths and angles and visualisation of the geometric arrangements.