Probing Platinum Azido Complexes by 14N and 15N NMR Spectroscopy
Probing Platinum Azido Complexes by 14N and 15N NMR Spectroscopy
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DOI：
10.1002/chem.201101409
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发表时间：
2011-10-01
影响因子：
4.3
通讯作者：
Sadler, Peter J.
中科院分区：
文献类型：
--
作者：
Farrer, Nicola J.;Gierth, Peter;Sadler, Peter J.
金属叠氮化合物因其高能性质而引起人们的普遍兴趣，特别是铂叠氮化合物，因为它们作为光活化抗癌前药的潜力。然而，叠氮配体很难通过核磁共振光谱来探测，因为N-14具有四极性质，并且缺乏标量H-1偶联来通过极化转移来提高丰度较低的N-15的灵敏度。在这项工作中，我们报道了顺式、反式、顺-[铂(N-3)(2)(OH)(2)(NH3)](1)和反式、反式、反式[铂(N-3)(2)(OH)(2)(X)(Y)]的N-14和N-15核磁共振波谱研究，其中X=Y=NH3(2)；X=NH3，Y=py(3)(py=吡啶)；X=Y=py(4)；以及部分PtII前体。这些研究首次提供了配位络合物中叠氮基团的N-15核磁共振数据。我们讨论了叠氮配体和Am(M)ine配体的单键和三键J(N-15，PT-195)偶联。与其他金属叠氮化合物相比，铂-IV叠氮络合物中的N-14(α)(配位叠氮氮)信号非常宽(W-1/2约为2124赫兹)，这归因于N-14(α)原子上高度不对称的电场梯度。通过使用反振铃脉冲序列，快速获得了显示N-14(α)峰分辨率的N-14核磁共振谱(例如，1.5h，10mm2)。N-14(α)信号的线宽与溶剂的粘度相关。对于富含N-15的样品，可以直接检测叠氮N-15共振，这将允许随后进行一维N-15核磁共振波谱的光反应。T-1松弛时间：N-15为5.7-120ms，N-14为0.9-11.3ms。对(1)J(N-15，Pt-195)偶合常数的分析表明，叠氮配体在系列2-pic<；py<；NH3<；Cl-<；N-3(-)<；NO2-<；SCN-(2-pic=2-甲基吡啶)中具有中等强度的反式影响。此外，轴向的Cl-似乎比轴向的OH-配体对赤道的铂-IV-NH3键的削弱程度更大。
Metal azido complexes are of general interest due to their high energetic properties, and platinum azido complexes in particular because of their potential as photoactivatable anticancer prodrugs. However, azido ligands are difficult to probe by NMR spectroscopy due to the quadrupolar nature of N-14 and the lack of scalar H-1 coupling to enhance the sensitivity of the less abundant N-15 by using polarisation transfer. In this work, we report N-14 and N-15 NMR spectroscopic studies of cis,trans,cis-[Pt(N-3)(2)(OH)(2)(NH3)] (1) and trans,trans,trans-[Pt(N-3)(2)(OH)(2)(X)(Y)], where X = Y = NH3 (2); X = NH3, Y= py (3) (py= pyridine); X = Y= py (4); and selected PtII precursors. These studies provide the first N-15 NMR data for azido groups in coordination complexes. We discuss one-and three-bond J(N-15, Pt-195) couplings for azido and am(m) ine ligands. The N-14(alpha) (coordinated azido nitrogen) signal in the Pt-IV azido complexes is extremely broad (W-1/2 approximate to 2124 Hz for 4) in comparison to other metal azido complexes, attributable to a highly asymmetrical electric field gradient at the N-14(alpha) atom. Through the use of anti-ringing pulse sequences, the N-14 NMR spectra, which show resolution of the broad N-14(alpha) peak, were obtained rapidly (e. g., 1.5 h for 10 mm 4). The linewidths of the N-14(alpha) signals correlate with the viscosity of the solvent. For N-15-enriched samples, it is possible to detect azido N-15 resonances directly, which will allow photoreactions to be followed by 1D N-15 NMR spectroscopy. The T-1 relaxation times for 3 and 4 were in the range 5.7-120 s for N-15, and 0.9-11.3 ms for N-14. Analysis of the (1)J(N-15, Pt-195) coupling constants suggests that an azido ligand has a moderately strong trans influence in octahedral Pt-IV complexes, within the series 2-pic < py < NH3 < Cl- < N-3(-) < NO2- < SCN- (2-pic = 2-methylpyridine). In addition, an axial Cl- appears to weaken an equatorial Pt-IV-NH3 bond to a greater extent than an axial OH- ligand.