title: Mechanism of Formation of Copper(II) Chloro Complexes Revealed by Transient Absorption Spectroscopy and DFT/TDDFT Calculations.
abstract: Copper(II) complexes are extremely labile with typical ligand exchange rate constants on the order of 10(6)-10(9) M(-1) s(-1). As a result, it is often difficult to identify the actual formation mechanism of these complexes. In this work, using UV-vis transient absorption when probing in a broad time range (20 ps to 8 μs) in conjunction with DFT/TDDFT calculations, we studied the dynamics and underlying reaction mechanisms of the formation of extremely labile copper(II) CuCl4(2-) chloro complexes from copper(II) CuCl3(-) trichloro complexes and chloride ions. These two species, produced via photochemical dissociation of CuCl4(2-) 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 ± 0.1) × 10(7) and (5.3 ± 0.4) × 10(8) M(-1) s(-1) in acetonitrile and dichloromethane, respectively. In dichloromethane, recombination occurs via a simple one-step addition. In acetonitrile, where [CuCl3](-) reacts with the solvent to form a [CuCl3CH3CN](-) complex in less than 20 ps, recombination takes place via ligand exchange described by the associative interchange mechanism that involves a [CuCl4CH3CN](2-) intermediate. In both solvents, the recombination reaction is potential energy controlled.
authors.affiliation: †Institute of Chemistry, Saint-Petersburg State University, 198504 Saint-Petersburg, Russian Federation.
authors.forename: Andrey S
authors.initials: AS
authors.lastname: Mereshchenko
authors.affiliation: †Institute of Chemistry, Saint-Petersburg State University, 198504 Saint-Petersburg, Russian Federation.
authors.forename: Pavel K
authors.initials: PK
authors.lastname: Olshin
authors.affiliation: ‡Department of Chemistry and the Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, United States.
authors.forename: Kanykey E
authors.initials: KE
authors.lastname: Karabaeva
authors.affiliation: †Institute of Chemistry, Saint-Petersburg State University, 198504 Saint-Petersburg, Russian Federation.
authors.forename: Maxim S
authors.initials: MS
authors.lastname: Panov
authors.affiliation: ‡Department of Chemistry and the Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, United States.
authors.forename: R Marshall
authors.initials: RM
authors.lastname: Wilson
authors.affiliation: †Institute of Chemistry, Saint-Petersburg State University, 198504 Saint-Petersburg, Russian Federation.
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Kochemirovsky
authors.affiliation: †Institute of Chemistry, Saint-Petersburg State University, 198504 Saint-Petersburg, Russian Federation.
authors.forename: Mikhail Yu
authors.initials: MY
authors.lastname: Skripkin
authors.affiliation: †Institute of Chemistry, Saint-Petersburg State University, 198504 Saint-Petersburg, Russian Federation.
authors.forename: Yury S
authors.initials: YS
authors.lastname: Tveryanovich
authors.affiliation: ‡Department of Chemistry and the Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, United States.
authors.forename: Alexander N
authors.initials: AN
authors.lastname: Tarnovsky
mesh_terms: D003300:Copper / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*
chemical_list: D003300:Copper; C029892:cupric chloride