Novel Dinuclear Platinum(II) Complexes Containing Mixed Nitrogen鈥揝ulfur Donor Ligands

详细信息    查看全文

• 作者：Stephanie Hochreuther ; Ralph Puchta ; Rudi van Eldik
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：December 19, 2011
• 年：2011
• 卷：50
• 期：24
• 页码：12747-12761
• 全文大小：675K
• 年卷期：v.50,no.24(December 19, 2011)
• ISSN：1520-510X

文摘

A series of novel dinuclear platinum(II) complexes were synthesized containing a mixed nitrogen鈥搒ulfur donor bidentate chelate system in which the two platinum centers are connected by an aliphatic chain of variable length. The bidentate chelating ligands were selected to stabilize the complex toward decomposition. The pK_a values and reactivity of the four synthesized complexes, namely, [Pt₂(S¹,S⁴-bis(2-pyridylmethyl)-1,4-butanedithioether)(OH₂)₄]⁴⁺ (4NSpy), [Pt₂(S¹,S⁶-bis(2-pyridylmethyl)-1,6-hexanedithioether)(OH₂)₄]⁴⁺ (6NSpy), [Pt₂(S¹,S⁸-bis(2-pyridylmethyl)-1,8-octanedithioether)(OH₂)₄]⁴⁺ (8NSpy), and [Pt₂(S¹,S¹⁰-bis(2-pyridylmethyl)-1,10-decanedithioether)(OH₂)₄]⁴⁺ (10NSpy), were investigated. This system is of special interest because only little is known about the substitution behavior of dinuclear platinum complexes that contain a bidentate chelate that forms part of the aliphatic bridging ligand. Moreover, the ligands as well as the dinuclear complexes were examined in terms of their cytotoxic activity, and the 10NSpy complex was found to be active. Spectrophotometric acid鈥揵ase titrations were performed to determine the pK_a values of all the coordinated water molecules. The substitution of coordinated water by thiourea was studied under pseudo-first-order conditions as a function of nucleophile concentration, temperature, and pressure, using stopped-flow techniques and UV鈥搗is spectroscopy. The results for the dinuclear complexes were compared to those for the corresponding mononuclear reference complex [Pt(methylthiomethylpyridine)(OH₂)₂]²⁺ (Pt(mtp)), by which the effect of the increasing aliphatic chain length of the bridged complexes could be investigated. The results indicate that there is a clear interaction between the two platinum centers, which becomes weaker as the chain length between the metal centers increases. Furthermore, differences and similarities of the N,S-system were compared to the corresponding dinuclear N,N-system studied previously in our group. In addition, quantum chemical calculations were performed to support the interpretation and discussion of the experimental data.