Three [CuL2] Type Complexes with Halogen-Substituted Schiff Base Ligands Containing a Pyridine Group

Three mononuclear Schiff base copper(II) complexes, [Cu(L1)2] (1), [Cu(L2)2] (2) and [Cu(L3)2] (3) (HL1= 2,4-dichloro-6-[(2-chloro-3-pyridyl)iminomethyl]phenol, HL2 = 2,4-dibromo-6-[(2-chloro-3-pyridyl)-iminomethyl]phenol, HL3 = 2-bromo-4-chloro-6-[(2-chloro-3-pyridyl)iminomethyl]phenol), have been synthesized and characterized by elemental analyses, IR, UV–Vis spectra, and X-ray single crystal diffraction. X-ray structures reveal each crystal unit contains two molecules and the coordination environment around the copper(II) atom is tetracoordinated by two Schiff base ligands, showing a tetrahedron geometry with some distortion. Pairs of intermolecular C–H···X (X = Cl or Br), C–H···N and C–H···O hydrogen bonds form many hydrogen bonding rings and play a crucial role in stabilizing the crystal structures.