Laboratory of Inorganic and General Chemistry, Department of Chemistry, University of Ioannina, 451 10 Ioannina, Greece.
Dalton Trans. 2014 Apr 14;43(14):5409-26. doi: 10.1039/c3dt53594k.
The GIAO-PBE0/SARC-ZORA(Pt)∪6-31+G(d)(E) (E = main group element) computational protocol without including relativistic and spin-orbit effects is offered here for the accurate prediction of the (195)Pt NMR chemical shifts of a series of cis-(amine)2PtX2 (X = Cl, Br, I) anticancer agents (in total 42 complexes) and cis-diacetylbis(amine)platinum(II) complexes (in total 12) in solutions employing the Polarizable Continuum Model (PCM) solvation model, thus contributing to the difficult task of computation of (195)Pt NMR. Calculations of the torsional energy curves along the diabatic (unrelaxed) rotation around the Pt-N bond of the cis-(amine)2PtX2 (X = Cl, Br, I) anticancer agents revealed the high sensitivity of the (195)Pt NMR chemical shifts to conformational changes. The crucial effect of the conformational preferences on the electron density of the Pt central atom and consequently on the calculated δ(195)Pt chemical shifts was also corroborated by the excellent linear plots of δ(calcd)((195)Pt) chemical shifts vs. the natural atomic charge Q(Pt). Furthermore, for the accurate prediction of the (195)Pt NMR chemical shifts of the cis-bis(amine)Pt(II) anticancer agents bearing carboxylato- as the leaving ligands (in total 8) and a series of octahedral Pt(IV) antitumor agents (in total 20 complexes) the non-relativistic GIAO-PBE0/SARC-ZORA(Pt)∪6-31+G(d)(E) computational protocol performs best in combination with the universal continuum solvation model based on solute electron density called SMD for aqueous solutions. Despite neglecting relativistic and spin orbit effects the agreement of the calculated δ(195)Pt chemical shifts with experimental values is surprising probably due to effective error compensation. Moreover, the observed solvent effects on the structural parameters of the complexes probably overcome the relativistic effects, and therefore the successful applicability of the non-relativistic GIAO-PBE0/SARC-ZORA(Pt)∪6-31+G(d)(E) computational protocol in producing reliable δ(calcd)((195)Pt) chemical shifts could be understood. In a few cases (e.g. the dihydroxo Pt(IV) complexes) the higher deviations of the calculated from the experimental values of δ(195)Pt chemical shifts are probably due to the fact that the experimental assignments refer to a different composition of the complexes in solutions than that used in the calculations, and different hydrogen bonding and formation of dimeric species.
本文提供了一种不考虑相对论和自旋轨道效应的 GIAO-PBE0/SARC-ZORA(Pt)∪6-31+G(d)(E)（E = 主族元素）计算协议，用于准确预测一系列顺式（胺）2PtX2（X = Cl、Br、I）抗癌药物（共 42 个配合物）和顺二乙酰基双（胺）铂（II）配合物（共 12 个）的（195）Pt NMR 化学位移。采用极化连续体模型（PCM）溶剂化模型，对溶液中（195）Pt NMR 进行了计算，这对（195）Pt NMR 的计算任务具有重要意义。对顺式（胺）2PtX2（X = Cl、Br、I）抗癌药物中 Pt-N 键非弛豫（未松弛）旋转的扭转能曲线的计算表明，（195）Pt NMR 化学位移对构象变化非常敏感。构象变化对 Pt 中心原子电子密度的关键影响，以及由此对计算得到的δ（195）Pt 化学位移的影响，也得到了δ（195）Pt 化学位移与自然原子电荷 Q（Pt）之间极好的线性关系的证实。此外，对于带有羧基作为离去配体的顺式双（胺）Pt（II）抗癌药物（共 8 个）和一系列八面体 Pt（IV）抗肿瘤药物（共 20 个配合物）的（195）Pt NMR 化学位移的准确预测，非相对论 GIAO-PBE0/SARC-ZORA（Pt）∪6-31+G（d）（E）计算协议与基于溶质电子密度的通用连续体溶剂化模型 SMD 结合使用效果最佳，适用于水溶液。尽管忽略了相对论和自旋轨道效应，但与实验值的吻合令人惊讶，这可能是由于有效误差补偿。此外，观察到的溶剂效应对配合物结构参数的影响可能超过了相对论效应，因此可以理解非相对论 GIAO-PBE0/SARC-ZORA（Pt）∪6-31+G（d）（E）计算协议在产生可靠的δ（calcd）（195）Pt 化学位移方面的成功适用性。在某些情况下（例如二羟基 Pt（IV）配合物），计算得到的δ（195）Pt 化学位移与实验值之间的偏差较大，这可能是由于实验值指的是配合物在溶液中的组成与计算中使用的不同，以及不同的氢键和二聚体形成。
