School of Chemistry and Physics, University of KwaZulu-Natal, Scottsville, 3209, Pietermaritzburg, South Africa.
Dalton Trans. 2014 Feb 14;43(6):2549-58. doi: 10.1039/c3dt52272e. Epub 2013 Dec 6.
The rate of substitution of the chloride ligand by three bio-relevant nucleophiles, thiourea (Tu), N,N-dimethylthiourea (Dmtu) and N,N,N,N-tetramethylthiourea (Tmtu), in the complexes: 1,3-bis(2-pyridylimino)isoindoline platinum(II) chloride (Pt2), 1,3-bis(2-pyridylimino)benz(f)isoindoline platinum(II) chloride (Pt3) and 1,3-bis(1-isoquinolylimino)isoindoline platinum(II) complex (Pt4) was investigated under pseudo first-order conditions as a function of concentration and temperature using stopped-flow and UV-Visible spectrophotometry. Computational modeled data of bis(pyridylimino)3,4-pyrrolate platinum(II) chloride (Pt1) were incorporated in the study for comparison. The observed pseudo first-order rate constants for substitution reactions obey the rate law kobs = k2[Nu]. High negative activation entropies and second-order kinetics for the displacement reactions all support an associative mode of activation. The reactivity is dependent on stabilization of the LUMO energy and inversely proportional to the number of phenyl rings added irrespective of the site of attachment. The electron density on the ligand moiety plays a significant role in the substitution behavior of the platinum(II) complexes, as supported by DFT descriptors {electrophilicity index (ω) and chemical hardness (η)}.
三种生物相关亲核试剂，硫脲（Tu）、N,N-二甲基硫脲（Dmtu）和 N,N,N,N-四甲基硫脲（Tmtu），在配合物中的氯离子配体的取代率：1,3-双（2-吡啶亚氨基）异吲哚啉铂(II) 氯化物（Pt2）、1,3-双（2-吡啶亚氨基）苯（f）异吲哚啉铂(II) 氯化物（Pt3）和 1,3-双（1-异喹啉亚氨基）异吲哚啉铂(II) 配合物（Pt4），在停流和紫外可见分光光度法下，在准一级条件下，作为浓度和温度的函数进行了研究。还将双（吡啶亚氨基）3,4-吡咯烷酸铂(II) 氯化物（Pt1）的计算模拟数据纳入研究进行比较。取代反应的观察到的准一级速率常数符合速率定律 kobs = k2[Nu]。取代反应的高负活化熵和二级动力学都支持缔合活化模式。反应性取决于 LUMO 能量的稳定性，与添加的苯基环的数量成反比，而与附着的位置无关。配体部分的电子密度在铂(II) 配合物的取代行为中起着重要作用，这得到了 DFT 描述符{电负性指数（ω）和化学硬度（η）}的支持。
