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首页> 外文期刊>Bulletin of the Chemical Society of Japan >Proton NMR Investigation of the Stoichiometry,Stability,and Exchange Kinetics of Tl~+ Complexes with Hexacyclen and Hexamethylhexacyclen in N,N-Dimethylformamide Solutions.Observation of a Three-Site Exchange Process
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Proton NMR Investigation of the Stoichiometry,Stability,and Exchange Kinetics of Tl~+ Complexes with Hexacyclen and Hexamethylhexacyclen in N,N-Dimethylformamide Solutions.Observation of a Three-Site Exchange Process

机译：N，N-二甲基甲酰胺溶液中Tl〜+与六环素和六甲基六环素配合物的化学计量，稳定性和交换动力学的质子NMR研究。三点交换过程的观察

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摘要

~1H NMR spectroscopy was used to investigate the Stoichiometry,stability,and exchange kinetics and mechanism of ligand interchange for Tl~+ complexes with hexacyclen(HCY)and hexamethylhexacyclen(HMHCY)in dimethyl-formamide(DMF)solution.In both cases,a stable complex with a 1:1 Stoichiometry was formed in solution.A complete line-shape analysis was used to evaluate the mean exchange times and exchange rates.The two-site chemical exchange between Tl~+ and HCY proceeded via a dissociative ligand-interchange mechanism in the temperature range 250-310 K.However,the ~1H NMR spectra of the T1~+-HMHCY complex system in DMF,in about the same temperature range,revealed the predominance of a three-site exchange process in the system.The type of exchange was dependent on the T1~+/HMHCY mole ratio,pho.At pho < 1,ligand exchange occurs via a dissociative mechanism,while at pho > 1,a bimolecular metal exchange is the predominate mechanism.In this case,the main factors controlling the exchange rates are the conformational rearrangement of the ligand during a concerted partial decomplexation of a Tl~+ cation and partial complexation of a second one.The activation parameters(E_a,DELTA H,DELTA S,and DELTA G)for the exchange processes(i.e.the ligand exchange,metal exchange,and the conformational change of the complex)were determined and compared with those for a two-site exchange for the Tl~+-HCY system.
机译：〜1H NMR光谱用于研究二甲基甲酰胺（DMF）溶液中Tl〜+与六环素（HCY）和六甲基六环素（HMHCY）的Tl〜+配合物的化学计量，稳定性，配位交换和机理。在溶液中形成了化学计量比为1：1的稳定配合物，使用完整的线形分析来评估平均交换时间和交换速率.Tl〜+和HCY之间的两点化学交换是通过解离配体交换进行的机理是在250-310 K的温度范围内进行的。然而，在大约相同的温度范围内，DMF中T1〜+ -HMHCY复杂系统的〜1H NMR光谱显示了该系统中三点交换过程的优势。交换类型取决于T1〜+ / HMHCY摩尔比pho。在pho <1时，配体交换通过解离机理发生，而在pho> 1时，双分子金属交换是主要机理。控制汇率的主要因素重新协调Tl〜+阳离子的部分解配和第二个阳离子的部分配合时配体的构象重排。交换过程的活化参数（E_a，DELTA H，DELTA S和DELTA G）确定了交换，金属交换和配合物的构象变化，并将其与Tl〜+ -HCY系统的两点交换进行了比较。

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