synthesis and characterization of potentially biological active cyclometallated organoplatinum(ii) complexes

this work is presented in five parts. in the first part preparation of the starting complex [pt(c^n)cl(dmso)], 1, in which c^n = n(1),c(2?)-chelated, deprotonated 2-phenylpyridine, and dmso = dimethylsulfoxide, and its reaction with 1 equiv of the biphosphine ligands bis(diphenylphosphino)amine, dppa, or bis(diphenylphosphino)methane, dppm, to give the complex [pt(c^n)cl(dppa)], 2, or [pt(c^n)cl(dppm)], 3, respectively are described. careful 1- and 2d-nmr and conductivity measurements confirm that the structure of complexes 2 and 3 in solution is unusual neutral penta-coordinated. however, x-ray crystallography indicated that the solid state structure of each of the complexes 2 and 3 is comprised of a cationic platinum(ii) species having a common square-planar geometry with a cl- counter-anion. penta-coordinated molecules of complex 2 in solution also form a rare type of n-h???pt intermolecular hydrogen bonding. complexes [pt(c^n)(dppa)](pf6), 4, and [pt(c^n)(dppm)](pf6), 5, prepared by the reaction of complexes 2 and 3 with nh4pf6, having pf6- counter-anion with no coordinating ability, were ionic in solution and the n-h???pt intermolecular interaction in solution of complex 2 was vanished in the solution of complex 4. furthermore, the pharmacological effects of complexes 2 and 3 were evaluated in terms of their proteasome-inhibitory and apoptosis-inducing activities under in vitro and in vivo conditions. both complexes 2 and 3 showed significant proteasome-inhibitory activity against purified 20s proteasome, while complex 3 demonstrated superior inhibitory activity against cellular 26s proteasome. luminescent properties of both complexes 2 and 3 and their binding interaction with herring sperm dna has been investigated by fluorimeteric emission study using ethidium bromide (eb) as a fluoresce probe. our results strongly suggest that the ptii-containing biphosphine complexes that target the tumor proteasome have potential to be further investigated as potential anticancer drugs. in part two the starting complex 1 was reacted with either 1 or 0.5 equiv of 1,1-bis(diphenylphosphino)ferrocene, dppf, to give the cyclometalated diplatinum(ii) complex [pt2(c^n)2cl2(µ-dppf)], 7. complex 7 was fully characterized in detail in solution by using multinuclear nmr spectroscopy (1h, 13c, 31p, and 195pt) supported by a number of 2d nmr experiments, while the structure in solid state was determined by x-ray crystallography. cytotoxicity of the complex 7 was studied in three resisted human cancer cell lines derived from ovarian carcinoma(ch1), lung carcinoma(a549), and colon carcinoma (sw480) by means of the mtt assay (mtt = 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2h-tetrazolium bromide). part three describes reaction of complex 1 with 1 equiv of either 2-(diphenylphosphinoamino)pyridine , pph2nhpy, or 2-diphenylphosphino pyridine, pph2py, giving the complex [pt(c^n)(pph2nhpy)]cl, 8, or [pt(c^n)cl(pph2py-?1p)], 9, respectively. careful multinuclear 1d nmr spectroscopy (1h, 13c, 31p, and 195pt), 2d nmr and conductivity measurements show structure for complex 8 in solution is neutral penta-coordinated, while complex 9 is found to be neutral four coordinate. x-ray crystallography indicated that the solid state structure of complex 8 is comprised of a cationic platinum(ii) species having a common square-planar geometry with a cl- counter-anion. the complex 8 forms a rare type of intermolecular n-h???pt hydrogen bonding in solution. cytotoxicity properties of the complexes 8 and 9 were studied in three resisted human cancer cell lines. in part four, the reaction of complex 1 with 1 equiv of either 1,3,5-triaza-7-phosphaadamantane, pta, or triphenyl phosphine, pph3, to give the complex [pt(c^n)cl(pta)], 10, or [pt(c^n)cl(pph3)], 11, respectively, is described. multinuclear 1 and 2d nmr spectroscopy show the structures of complexes 10 or 11 in solution being neutral four coordinate. the x-ray crystallography indicated that the solid-state structure of complex 10 is comprised of a common square-planar geometry around platinum(ii). cytotoxicity of the complexes 10 and 11 were studied in three human cancer cell lines. part five describes the reaction of complex ptcl(dmso)2, in which dmso = dimethylsulfoxide, with nai to form starting complex cis/trans [pt2i4(dmso)2], 12. complex 12 was consequently reacted with 2 equiv of 2-(diphenylphosphinoamino)pyridine , pph2nhpy, p^n, to form complex [pti2(p^n)], 13. complex 13 was fully characterized by 1 and 2d multinuclear nmr, esi mass and elemental analysis. complex 13 is an unprecedented example of a platinum(ii) complex with simultaneous formation of intermolecular nh???i-pt and ch???i-pt h-bondings (with neighboring platinum center) and an intramolecular ch???pt hydrogen bonding in solid state. there are indications showing that the complex in solution probably forms different kinds of h-bonding interactions.