Dinuclear copper(II) complexes: Solvent dependent catecholase activity

Ligand‐Flexibility Controlled and Solvent‐Induced Nuclearity Conversion in CuII‐Based Catecholase Models: A Deep Insight Through Combined Experimental and Theoretical Investigations

“…However, if the d–d band remains intact (blue‐ or redshift may happen) intramolecular electron transfer should be the rate‐determining step. In our present case the d–d bands of all the complexes were observed to undergo a blue shift during the 2 h course of the catalytic reaction, suggesting the presence of Cu II species, so intramolecular electron transfer is assumed to be the rate‐determining step , . Dioxygen plays the key role for regeneration of the catalyst with its concomitant reduction of either kind: (i) two‐electron reduction to H 2 O 2 , or (ii) four‐electron reduction to water.…”

“…In our present case the d-d bands of all the complexes were observed to undergo a blue shift during the 2 h course of the catalytic reaction, suggesting the presence of Cu II species, so intramolecular electron transfer is assumed to be the rate-determining step. [49,31] Dioxygen plays the key role for regeneration of the catalyst with its concomitant reduction of either kind: (i) twoelectron reduction to H 2 O 2 , or (ii) four-electron reduction to water. We failed to detect any formation of I 3 spectroscopically ( Figure S21 in the Supporting Information) and so the possibility of dioxygen reduction to H 2 O 2 may be ruled out.…”

“…A number of factors that influence the catalytic activities of the model compounds have been identified. Solvent, pH of the medium and the nature of the model substrate are important external contributors, whereas Cu–Cu bond length,, stereoelectronic factors,, flexibility of the ligands and the coordination environment are the internal ones. However, the role of ligand flexibility has not yet been well explored.…”

“…[4][5][6][7] Reduced Schiff bases have been attracting special interest from coordination chemists recently be-[a] Scheme 1. Synthetic routes to the complexes.the model substrate are important external contributors, [30][31][32][33][34] whereas Cu-Cu bond length, [35,36] stereoelectronic factors, [37,38] flexibility of the ligands and the coordination environment are the internal ones. However, the role of ligand flexibility has not yet been well explored.…”

Catecholase activity of Mannich-based dinuclear CuII complexes with theoretical modeling: new insight into the solvent role in the catalytic cycle

“…5,6 As a consequence, the design of binucleating ligands has to satisfy a number of conditions such as metal-metal distance, steric, 4b,7 electronic 8 and bridging ligand features, 7a,9 redox potentials, 10 pH 5b,7b,9,11 and solvent properties. 12,13 In this study, we are particularly interested in developing a better understanding of the factors that affect the catalysis of dinuclear Cu II complexes towards the substrates 3,5-di-tert-butylcatechol (3,5-DTBC) and tetrachlorocatechol (TCC) 14 with the aid of DFT calculations. 15,16 We have synthesised two phenolic ''end-off'' compartmental Mannich-base ligands, 17c namely 2,6-bis[bis (2-methoxyethyl)aminomethyl]-4-chlorophenol (HL1), a conventional Mannichbase and 2-[bis (2-methoxyethyl)aminomethyl]-4-chlorophenol (HL2), a non-standard Mannich-base using the reported procedures of a controlled Mannich reaction.…”