Synthesis, spectroscopic, magnetic and biological activity studies of copper(II) complexes of an antipyrine Schiff base

The Schiff base, 4-(2-pyrrolylmethylideneamino)antipyrine (HPAP), (1), and its copper(II) complexes were synthesized and characterized by elemental analysis and by physical and spectral methods such as i.r., u.v.-vis., H-1-n.m.r., C-13-n.m.r. and e.s.r. as well as by molar conductance and magnetic moment determinations. Both the bis-ligand, [(HPAP)(2)Cu]X-2 (4, 5), [(PAP)(2)Cu] (6), and the dimer, [(PAP)Cu](2)X-2 (2, 3), complexes were isolated. In these complexes, the Schiff base acts as a bidentate or tridentate neutral or monobasic ligand. Interaction of the isolated [(PAP)Cu](2)Cl-2 (2), with strong coordinating organic bases was studied and the resultant adducts, [(PAP)CuLs]Cl; Ls = pyridine (7), alpha-picoline (8), beta-picoline (9), gamma-picoline (10) or n-propylamine (11), were isolated and characterized. Biological activity screening was studied and an activity correlation coefficients matrix was constructed for HPAP and the copper(II) complexes against gram-positive, gram-negative and fungi species. The copper content, structure of the complex as well as the degree of exposure of the metal center control the biological activity of the isolated complexes.