Mechanism of Formation of Copper(II) Chloro Complexes Revealed by Transient Absorption Spectroscopy and DFT/TDDFT Calculations

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• 作者：Andrey S. Mereshchenko ; Pavel K. Olshin ; Kanykey E. Karabaeva ; Maxim S. Panov ; R. Marshall Wilson ; Vladimir A. Kochemirovsky ; Mikhail Yu. Skripkin ; Yury S. Tveryanovich ; Alexander N. Tarnovsky
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：July 16, 2015
• 年：2015
• 卷：119
• 期：28
• 页码：8754-8763
• 全文大小：472K
• ISSN：1520-5207

文摘

Copper(II) complexes are extremely labile with typical ligand exchange rate constants on the order of 10⁶鈥?0⁹ M^鈥? s^鈥?. As a result, it is often difficult to identify the actual formation mechanism of these complexes. In this work, using UV鈥搗is transient absorption when probing in a broad time range (20 ps to 8 渭s) in conjunction with DFT/TDDFT calculations, we studied the dynamics and underlying reaction mechanisms of the formation of extremely labile copper(II) CuCl₄^{2鈥?/sup> chloro complexes from copper(II) CuCl₃鈥?/sup> trichloro complexes and chloride ions. These two species, produced via photochemical dissociation of CuCl₄2鈥?/sup> upon 420 nm excitation into the ligand-to-metal-charge-transfer electronic state, are found to recombine into parent complexes with bimolecular rate constants of (9.0 卤 0.1) 脳 107 and (5.3 卤 0.4) 脳 108 M鈥? s鈥? in acetonitrile and dichloromethane, respectively. In dichloromethane, recombination occurs via a simple one-step addition. In acetonitrile, where [CuCl₃]鈭?/sup> reacts with the solvent to form a [CuCl₃CH₃CN]鈭?/sup> complex in less than 20 ps, recombination takes place via ligand exchange described by the associative interchange mechanism that involves a [CuCl₄CH₃CN]2鈥?/sup> intermediate. In both solvents, the recombination reaction is potential energy controlled.}