Synthesis and characterization of square planar and square pyramidal copper(II) compounds with tridentate Schiff bases: Formation of a molecular zipper via H-bonding interaction

Three copper(II) compounds, [Cu(L1)(H2O)2]NO3 (1), [Cu(L1)(N3)]·2H2O (2), and [Cu(L2)Cl2] (3), where HL1 = 2-[(pyridine-2-ylmethylene)-amino]-phenol and L2 = (2-methoxy-phenyl)-pyridin-2-ylmethylene-amine are tridentate Schiff-base ligands, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy, Thermo-gravimetric study and single-crystal X-ray diffraction. Compound 1 crystallizes in triclinic space group P1¯ with cell dimensions a = 7.725(5), b = 9.140(5), c = 11.162(5), α = 102.229(5), β = 104.330(5) and γ = 104.710(5), whereas compounds 2 and 3 crystallize in monoclinic space groups P21/c and P21/n respectively with cell dimensions of a = 10.2111(3), b = 6.6366(2), c = 20.8098(5), β = 101.851(2) (for 2) and a = 7.9914(1), b = 18.2591(3), c = 9.5695(2), β = 91.384(1) (for 3). In compound 1, copper(II) center exhibits a distorted square pyramidal geometry while in case of compound 2, copper(II) acquires square planar geometry. The geometry of copper(II) in compound 3 is intermediate between square pyramid and a structure, which is known as ‘inverse square pyramid’. A zipper like infinite chain was formed in compound 2 via hydrogen bonding network between the complex moiety, azide and enclathrated water molecules.