title: Ethylenediamine-palladium(II) complexes with pyridine and its derivatives: synthesis, molecular structure and initial antitumor studies.
abstract: The synthesis of four mononuclear palladium complexes of general formula [Pd(en)Cl(L)]NO3 (en = ethylenediamine; L = pyridine (I), 4-methylpyridine (II), 4-hydroxypyridine (III) or 4-aminopyridine (IV) has been achieved. The structure of these compounds was studied by elemental analysis, IR, far-IR and 1H NMR; complex I was analyzed by X-ray diffraction. The crystal of [Pd(en)(pyridine)Cl]NO3 is monoclinic, space group P21/c (a = 7.990(2), b = 16.058(3), c = 9.846(2) A, beta = 103.81(3) degrees, Z = 4, R = 0.067, Rw = 0.066). The Pd(II) atom exhibits an approximately square planar coordination with bond lengths in the range 2.017-2.042 A for Pd-N and 2.320 A for Pd-Cl. In order to determine the donor strength of the aromatic pyridine ligands, the stability constants of binary complex ML2+ (M = [Pd(en) (H2O)2]2+; L = pyridine, 4-Me-pyridine, 4-OH-pyridine and 4-NH2-pyridine) were determined by potentiometric pH titration in aqueous solution (T = 25 degrees C, I = 0.1 mol l-1 NaNO3). The results show that the stability constants of the binary complexes systematically increase with increasing pKa of the pyridines. The above four palladium complexes, [Pt(en)(pyridine)Cl]NO3 and cis-diamminedichloroplatinum (II) (cis-DDP) were assayed for cytotoxicity in vitro against the human leukemia cell line HL-60, and compounds I, II, III and cis-DDP show significant cytotoxic activity against HL-60.
authors.affiliation: Department of Chemistry, Nankai University, Tianjin, People's Republic of China.
authors.forename: G
authors.initials: G
authors.lastname: Zhao
authors.forename: H
authors.initials: H
authors.lastname: Lin
authors.forename: P
authors.initials: P
authors.lastname: Yu
authors.forename: H
authors.initials: H
authors.lastname: Sun
authors.forename: S
authors.initials: S
authors.lastname: Zhu
authors.forename: X
authors.initials: X
authors.lastname: Su
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D018360:Crystallography, X-Ray; D004354:Drug Screening Assays, Antitumor; D004355:Drug Stability; D018922:HL-60 Cells; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D010165:Palladium / Q000737:chemistry / Q000494:pharmacology; D011725:Pyridines / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D009942:Organometallic Compounds; D011725:Pyridines; D010165:Palladium