Supramolecular solid-state architectures formed by co-crystallization of melamine and 2-, 3- and 4-chlorophenylacetic acids

Abstract

A family of supramolecular complexes of melamine with chlorophenylacetic acid isomers using solvent-assisted and evaporation-based techniques has been prepared. Crystallization of melamine with 2-chlorophenylacetic acid yield hydrated ionic supramolecular complex (1), whereas crystallization of melamine with 3- and 4-chlorophenylacetic acids leads to formation of neutral supramolecular complexes (2, 3), all with base to acid ratio of 1:2. Within chlorophenylacetic acid isomers only in 2-chlorophenylacetic acid isomer as the stronger acid the proton transfer to melamine takes place. The crystal structures of supramolecular complexes have been determined. The supramolecular assembly is driven by the noncovalent interactions, most commonly by the hydrogen bonds. The components of the crystals interact via NH⋯O and OH⋯N with a graph of R22(8) forming respective ionic or neutral supramolecular complexes. All three supramolecular complexes studied interact each other via a pair of NH⋯O hydrogen bonds forming pseudo one-dimensional supramolecular chains along [1–10] and [−110] in 1 and along [010] in 2 and 3. Hirshfeld surface and analysis of 2D fingerprint plots have been analysed both quantitatively and qualitatively interactions governing the supramolecular organisation. The IR and Raman vibrational characterization of the supramolecular complexes 1–3 was supported by the spectra of their deuterated analogues.