Synthesis, structural, physico-chemical and biological properties of new palladium(II) complexes with 2,6-dimethyl-4-nitropyridine

This paper describes the synthesis and properties of two new palladium(II) complexes with 2,6-dimethyl-4-nitro-pyridine (dmnp): mononuclear [Pd(dmnP)(2)Cl-2] and dinuclear [Pd-2(dmnP)(2)Cl-4]. Complexes were characterized on the basis of chemical and chromatographic analyses, MS and conductometric measurements, as well as by IR and NMR (H-1 and C-13) spectral studies. The crystal structures of ligand and mononuclear complex, trans-dichlorobis(2,6-dimethyl-4-nitro-pyridine)palladium(11), were determined by three-dimensional X-ray methods. The crystals of both compounds are monoclinic, space groups P2(1)/c with a= 19.075(4), b = 5.419(1), c = 15.045(3) Angstrom and beta = 108.15(3)degrees for (dmnp), and a = 7.544(2), b = 14.509(3), c = 8.032(2) Angstrom and beta = 90.32(3)degrees for [Pd(dmnP)(2)Cl-2]. In the (dmnp) there are two crystallographically independent molecules in the unit cell. The nitro groups and methyl C atoms are coplanar with the ring plane. The hydrogen bond of the type C-H... 0 links the molecules into pairs around center of symmetry. These dimers are held together by contacts of the van der Waals type. In the crystal structure of [Pd(dmnP)(2)Cl-2] the I'd atom lies on an inversion center and is four-coordinated by two pyridine N atoms and by two Cl atoms in trans positions. The coordination geometry is square-planar, with Pd-N and Pd-Cl distances of 2.033(2) and 2.311(1) Angstrom, respectively. The two pyridine rings are mutually parallel, but they are twisted from the PdN2Cl2 coordination plane by about 88.5degrees. The preliminary assessments of anti-tumor properties of both complexes and ligand were evaluated as in vitro anti-proliferative activity in four human cancer cell lines: SW707 (adenocarcinoma of the rectum), T47D (breast cancer), HCV (bladder cancer) and A549 (non-small cell lung carcinoma). The [Pd(dmnP)(2)Cl-2] exhibits strong cytotoxic activity against all cell lines whereas the free ligand and dinuclear [Pd2(dmnP)(2)Cl-4] are only moderate active. (C) 2004 Elsevier Inc. All rights reserved.