New zinc(II), palladium(II) and platinum(II) complexes of dl-piperidine-2-carboxylic acid; X-ray crystal structure of trans-[Zn2(μ-Ca)2(Hpa)2Cl6] and anticancer activity of some complexes

New complexes of dl-piperidine-2-carboxylic acid (dl-H2pa), [Zn(Hpa)(AcO)(H2O)2], trans-[Zn2(μ-Ca)2(Hpa)2Cl6], [M(bpy)(Hpa)]Cl and [M(pa)(PPh3)2] (M(II) = Pd, Pt) have been prepared and characterized on the basis of elemental analyses, molar conductivity and thermal measurements, IR, Raman, UV–Vis, NMR (1H and 31P) and mass spectroscopy. dl-Piperidine-2-carboxylic acids act as bidentate ligands, through the carboxyl oxygen and cyclic nitrogen atoms. The crystal structure of trans-[Zn2(μ-Ca)2(Hpa)2Cl6], obtained from the addition of ZnCl2 to dl-H2pa in either hard tap water or presence of CaCl2, has been determined by X-ray diffraction. It crystallizes in a triclinic lattice with space group symmetry P1. The complex has two zinc atoms in tetrahedral geometry, each ligated by a carboxyl oxygen and three chlorine atoms. The other carboxyl oxygen atoms from the two Hpa− ligands are bridged by two calcium atoms, i.e., there are two Zn(Hpa−)Cl3 units bridged by two calcium atoms. The free dl-H2pa and its complexes, trans-[Zn2(μ-Ca)2(Hpa)2Cl6], [Pd(bpy)(Hpa)]Cl and [M(pa)(PPh3)2] (M(II) = Pd, Pt) have been tested against the serous ovarian cancer ascites, OV 90 cell line.