Synthesis, structural study and biological activity of new derivatives of chrysin containing a 2-mercaptopyridyl or 5-(trifluoromethyl)-2-mercaptopyridyl fragments

New derivatives of chrysin containing 2-mercaptopyridine (2a-2e) or 5-(trifluoromethyl)-2-mercaptopyridine (3a-3e) moieties were prepared from the reaction between bromides (1a-1e) and 2-mercaptopyridine or 5-(trifluoromethyl)-2-mercaptopyridine, respectively. Their structures were elucidated by NMR, IR and elemental analysis. The molecular structure of compounds 1a, 1c-1e, 2b-2e and 3a was determined by single-crystal X-ray diffraction studies. All rings in these structures are nearly coplanar and they showed an intramolecular hydrogen bond between the phenolic hydroxyl H atom and the carbonyl O atom that forms a six membered ring. The crystal packing also showed a wide variety of intermolecular contacts such as C-H⋯A, π-π, C-H⋯π and lone pair⋯π interactions which were supported by quantum theory of atoms in molecules (QTAIM), Hirshfeld surface, and fingerprint plot analyses. Biological activity of all compounds was tested in growth assays of the nematode Caenorhabiditis elegans. Compounds 2e, 3b and 3c inhibited larval development.