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

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Title: Mechanism of Formation of Copper(II) Chloro ComplexesRevealed by Transient Absorption Spectroscopy and DFT/TDDFT Calculations.
Authors: Mereshchenko, Andrey S.1, Olshin, Pavel K.1, Karabaeva, Kanykey E.1, Panov, Maxim S.1, Wilson, R. Marshall1, Kochemirovsky, Vladimir A.1, Skripkin, Mikhail Yu.1, Tveryanovich, Yury S.1, Tarnovsky, Alexander N.1
Source: Journal of Physical Chemistry B. Jul2015, Vol. 119 Issue 28, p8754-8763. 10p.
Subjects: Copper isotopes, Copper chlorides, Metal complexes, Density functional theory, Metal formability, Dissociation (Chemistry), Solvents
Abstract: Copper(II)complexes are extremely labile with typical ligand exchangerate constants on the order of 106–109M–1s–1. As a result, it isoften difficult to identify the actual formation mechanism of thesecomplexes. In this work, using UV–vis transient absorptionwhen probing in a broad time range (20 ps to 8 μs) in conjunctionwith DFT/TDDFT calculations, we studied the dynamics and underlyingreaction mechanisms of the formation of extremely labile copper(II)CuCl42–chloro complexes from copper(II)CuCl3–trichloro complexes and chlorideions. These two species, produced via photochemical dissociation ofCuCl42–upon 420 nm excitation into theligand-to-metal-charge-transfer electronic state, are found to recombineinto parent complexes with bimolecular rate constants of (9.0 ±0.1) × 107and (5.3 ± 0.4) × 108M–1s–1in acetonitrile anddichloromethane, respectively. In dichloromethane, recombination occursvia a simple one-step addition. In acetonitrile, where [CuCl3]−reacts with the solvent to form a [CuCl3CH3CN]−complex in less than20 ps, recombination takes place via ligand exchange described bythe associative interchange mechanism that involves a [CuCl4CH3CN]2–intermediate. In both solvents,the recombination reaction is potential energy controlled. [ABSTRACT FROM AUTHOR]
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Abstract:Copper(II)complexes are extremely labile with typical ligand exchangerate constants on the order of 106–109M–1s–1. As a result, it isoften difficult to identify the actual formation mechanism of thesecomplexes. In this work, using UV–vis transient absorptionwhen probing in a broad time range (20 ps to 8 μs) in conjunctionwith DFT/TDDFT calculations, we studied the dynamics and underlyingreaction mechanisms of the formation of extremely labile copper(II)CuCl42–chloro complexes from copper(II)CuCl3–trichloro complexes and chlorideions. These two species, produced via photochemical dissociation ofCuCl42–upon 420 nm excitation into theligand-to-metal-charge-transfer electronic state, are found to recombineinto parent complexes with bimolecular rate constants of (9.0 ±0.1) × 107and (5.3 ± 0.4) × 108M–1s–1in acetonitrile anddichloromethane, respectively. In dichloromethane, recombination occursvia a simple one-step addition. In acetonitrile, where [CuCl3]−reacts with the solvent to form a [CuCl3CH3CN]−complex in less than20 ps, recombination takes place via ligand exchange described bythe associative interchange mechanism that involves a [CuCl4CH3CN]2–intermediate. In both solvents,the recombination reaction is potential energy controlled. [ABSTRACT FROM AUTHOR]
ISSN:15206106
DOI:10.1021/acs.jpcb.5b03889