Supramolecular assembly of 2-aminobenzothiazole and N-[(2-oxo-2H-1- benzopyran-3-yl)carboxyl]phenethylamide donor-acceptor complex. A comparative study

In this paper the synthesis and solid state characterization of the donor-acceptor (D-A) complex between 2-aminobenzothiazole (ABT) and N-[(2-oxo-2H-1-benzopyran-3-yl)carboxyl]phenethylamide is reported. A comparison is performed with other aminobenzothiazole-coumarin complexes reported earlier and the results are analyzed in the context of crystal engineering. A common feature of these structures is the presence of a building block formed by pair-wise self complementary NH⋯N interactions between two molecules of ABT, defining an R₂² (8) motif. The complete three-dimensional supramolecular arrangement is achieved by both strong (NH⋯O) and weak (CH⋯X, X = O, aryl) H-bonding interactions which define an A⋯D⋯D'⋯A' hydrogen bonded tetrameric unit, which packs through π-stacking interactions. The resulting donor-acceptor assemblies present two patterns of alternated stacking: D-A and D-A-A'-D'. Finally, the factors ruling the supramolecular isomerism exhibited by these complexes and the nature of the interactions are discussed and supported by ab initio theoretical calculations.