Ching H Y Vincent, Clegg Jack K, Rendina Louis M
School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia.
Dalton Trans. 2007 Jun 7(21):2121-6. doi: 10.1039/b618668h. Epub 2007 Mar 30.
A series of platinum(II) complexes of the type Pt(NN)(pyB)22 (NN = bipy, phen; pyB = 3- or 4-pyridineboronic acid) were successfully prepared and fully characterised by 1D- and 2D-multinuclear NMR spectroscopy and ESI-MS. Using VT 1H NMR spectroscopy, rotational isomers for Pt(NN)(3-pyB)22 were identified and the free energies of activation for rotation of 3-pyB about the Pt-N bond were determined to be DeltaG++310) = 69.2 +/- 0.1 kJ mol(-1) and DeltaG++(305) = 66.0 +/- 0.1 kJ mol(-1) for Pt(bipy)(3-pyB)22 and Pt(phen)(3-pyB)22, respectively. The 3- and 4-pyB ligands readily deboronate in boiling H2O to afford Pt(NN)(py)22; the structure of Pt(phen)(py)2 (as its PF6- salt) was confirmed by X-ray crystallography. Preliminary thermal denaturation studies revealed only minimal interactions between Pt(NN)(pyB)22 and calf-thymus DNA and is attributed to hydroxylation of the boronic acid groups at pH 7.4 to afford the corresponding zwitterionic boronate species. This was confirmed by means of variable pH 1H and 11B{1H} NMR spectroscopy.
成功制备了一系列通式为Pt(NN)(pyB)₂₂（NN = 联吡啶、邻菲罗啉；pyB = 3 - 或4 - 吡啶硼酸）的铂(II)配合物，并通过一维和二维多核核磁共振光谱以及电喷雾电离质谱对其进行了全面表征。利用变温¹H核磁共振光谱，鉴定出了Pt(NN)(3 - pyB)₂₂的旋转异构体，对于Pt(联吡啶)(3 - pyB)₂₂和Pt(邻菲罗啉)(3 - pyB)₂₂，3 - pyB围绕Pt - N键旋转的活化自由能分别确定为ΔG‡(310) = 69.2±0.1 kJ mol⁻¹和ΔG‡(305) = 66.0±0.1 kJ mol⁻¹。3 - 和4 - pyB配体在沸腾的水中容易脱硼生成Pt(NN)(py)₂₂；通过X射线晶体学确定了[Pt(邻菲罗啉)(py)₂]²⁺（作为其PF₆⁻盐）的结构。初步的热变性研究表明，Pt(NN)(pyB)₂₂与小牛胸腺DNA之间只有极小的相互作用，这归因于在pH 7.4时硼酸基团的羟基化，生成了相应的两性离子硼酸酯物种。通过可变pH的¹H和¹¹B{¹H}核磁共振光谱证实了这一点。
