Schiff base derived from 2-hydroxy-1-naphthaldehyde and liquid-assisted mechanochemical synthesis of its isostructural Cu(II) and Co(II) complexes

The Schiff base ligand derived from 2-hydroxy-1-naphthaldehyde, namely 1-[(2-biphenylamino)methylen]naphthalen-2(1H)-one (1) and its corresponding Cu(II) and Co(II) complexes (2 and 3, respectively) were synthesized and characterised by means of IR spectroscopy, thermal analysis and also by powder and single crystal X-ray diffraction. The mononuclear complexes have been obtained by a conventional solution-based method as well as by a mechanochemical method, i.e. by liquid-assisted grinding. The molecule of 1 is not planar and the keto-amino tautomer was detected from the molecular geometry consideration. The discrete molecules are pi-stacked in the [100] direction and connected by weak intermolecular interactions. Compounds 2 and 3 are isostructural. The form of the copper atom coordination polyhedron is irregular square planar while the form of the cobalt atom coordination polyhedron is irregular tetrahedral. Both complexes form 1D chains in the [010] direction by weak C-H center dot center dot center dot O and C-H center dot center dot center dot C interactions.