Solid-state effects of monofluorophenyl substitution in dithiadiazolyl radicals: Impact on S···S and S···N interactions and their classification via Hirshfeld surfaces and fingerprint plots

Abstract

Ortho- and para-fluorophenyl 1,2,3,5-dithiadiazolyl (DTDA) radicals were synthesised and structurally characterised in the solid-state. This enables the well-known molecular origins of the electrical conductivity properties in this series of molecules to be studied, specifically S···S conduction pathways.This work includes the first report of monofluorophenyl DTDA crystal structures, filling an important gap in the literature to complement the many structural records of di-, tri-, tetra- and pentafluorophenyl DTDA analogues. This report also overturns previous thinking that monofluoro-substitution in these phenyl DTDA compounds does not influence the supramolecular chemistry; indeed, we demonstrate that singular fluorine is indeed structurally (and therefore property) directing as per their di-, tri-, tetra- and pentafluorinated relatives. In particular, the S···S and S···N interactions that control the electrical conductivity in DTDAs are distinct in these mono-fluorophenyl DTDAs.Hirshfeld surfaces were employed to clarify the nature and extent of these interactions. Their ability to exploit the very sensitive features of surface topologies in order to identify S···S and S···N intermolecular interactions is important since these interactions are much more subtle than, say, classical hydrogen-bonding.Furthermore, we demonstrate that Hirshfeld surfaces can classify the entire set of intermolecular interactions for a compound via a fingerprint plot. This affords the instant recognition of a given type of DTDA supramolecular network. In turn, barcodes can be generated from these fingerprint plots which quantify the percentage contribution of atom pairs that are involved in intermolecular interactions within DTDAs. The predictive potential of such classification within the field of molecular design is shown via a comparison of our fingerprint plots with those of DTDAs from previous studies.