Variable non-covalent interactions in the crystals of a series of 4-Y-benzyl pyrrolidine-1-carbodithioates: Y = Cl, Br, I, Me and NO2

Abstract

A series of five S-benzyl esters of pyrrolidine dithiocarbamate, differing only in the substituent in the 4-position of the benzyl group, i.e. (CH₂CH₂)₂NC(S)SCH₂C₆H₄-4-Y for Y = Cl, Br, I, Me and NO₂ (1–5), have been investigated by crystallographic and computational chemistry techniques, including analyses of the calculated Hirshfeld surfaces and the calculation of interaction energies. Remarkable differences in molecular conformations, e.g. almost 90° differences in the C–S(thioether)–C(methylene)–C torsion angles, are related to packing effects as revealed through unrestricted geometry-optimisation calculations. The influence of the remote substituent, Y, upon the molecular packing is crucial with four different packing patterns elucidated. In the chlorine derivative, 1, Cl⋯Cl contacts feature between layers having C–H⋯π interactions. In each of the isomorphous bromine (2) and iodine (3) derivatives, X⋯S halogen-bonding is detected within linear supramolecular chains which assemble into layers through phenyl-C–H⋯S(thione), methylene-C–H⋯π(phenyl) and off-set phenyl-π⋯π(phenyl) stacking. Layers are also evident in the methyl species, 4, with directional pyrrolidine-C–H⋯π(phenyl) and π(phenyl)⋯π(phenyl) interactions apparent between molecules. In the three-dimensional architecture of nitro derivative 5, methylene-C–H⋯π(phenyl) and long phenyl-C–H⋯O(nitro) interactions are discerned. The X⋯S halogen-bonding is more significant for 3cf.2 based on geometric criteria and calculated interaction energies.