Crystal structures and cytotoxicity of isopropylamine Pt(II) complexes: A trinuclear squarato-bridged [Pt3(μ2-C4O4)3(H2NPri)6] · 3H2O and a mononuclear cis-[Pt(NO3)2(H2NPri)2

Abstract

Crystals of a novel platinum(II) complex with squarato ligand, [Pt3(μ2-C4O4)3(H2NPri)6]·3H2O (1) (H2NPri=ipa), have been isolated from the aqueous solution of cis-[Pt(H2O)2(H2NPri)2]SO4 and barium squarate. Slow evaporation of methanol solution of cis-[Pt(NO3)2(H2NPri)2] (2) resulted in crystallization of nitrato complex.The single crystal X-ray diffraction method was used to determine structures of 1 and 2. Complex 1 crystallizes in a triclinic space group P1¯ with a=11.17380(10)Å, b=14.4535(2)Å, c=14.8010(2)Å, α=86.0901(10)°, β=78.4343(11)°, γ=69.1915(5)°, and complex 2 in a monoclinic space group P21/n, with a=10.1161(2)Å, b=9.9188(2)Å, c=13.3766(2)Å, β=102.7360(7)°. The X-ray structure analysis revealed that three platinum atoms in 1 are connected with three squarates which adopt bis(unidentate) binding modes. The squarato ligands span relatively long intramolecular Pt⋯Pt distances (4.8842(3)–5.2699(3)Å). A pair of cis positioned isopropylamine ligands completes a square planar coordination sphere of each Pt(II) ion. The square–planar coordination of complex 2 consists of two cis positioned isopropylamine ligands and two nitrato ligands.The results of cytotoxicity assay of trimer 1, monomer 2 and cis-diamminedichloroplatinum(II) (cisplatin) performed on human bladder tumor cell line T24 provide evidence that complex 2 is less cytotoxic compared to cisplatin and that the survival of tumor cells after exposure to 1 was minimally reduced.