Influence of anionic co-ligands on the structural diversity and catecholase activity of copper(ii) complexes with 2-methoxy-6-(8-iminoquinolinylmethyl)phenol

Abstract

A novel dinuclear copper(II) complex, [Cu 2 L 2 (m 1,1 -N 3 ) 2 ] (1), and a mononuclear copper(II) complex, [CuL(NCO)] (2), have been synthesized from a planar tridentate ligand 2-methoxy-6-(8iminoquinolinylmethyl)phenol (HL) together with pseudohalides as coligands, and the solid state structures were determined by X-ray crystallography. Structural characterizations reveal that the geometry of centrosymmetrically related copper(II) centers in 1 is square pyramidal while it is square planar in 2. The impact of the structural diversity was found on their catechol oxidase mimicking activity. Strongly bridging azide ions being substitutionally inert mean complex 1 is inactive towards the catecholase activity, while mononuclear analogue 2 exhibits moderately strong catechol oxidase activity.The ESI-MS positive spectrum of a mixture of complex 2 and 3,5-DTBCH 2 shows a peak corresponding to both superoxo and substrate bound species, Na[CuL(O 2 )(3,5-DTBCH)] + , suggesting that both the dioxygen and substrate simultaneously coordinated to the metal center in the catalytic cycle. Most importantly, complex 2 not only represents the mononuclear class of copper(II) compounds that are rarely visited for the study of catecholase mimicking activity but also the first example of a mononuclear square planar complex exhibiting catechol oxidase activity.Scheme 1 Route to the syntheses of complexes 1 and 2.This journal is

A Highly Selective “On‐Off‐On” Optical Switch for Sequential Detection of Cu2+and S2−Ions Based on 2, 6‐Diformyl‐4‐methyl Phenol and Catecholase Activity by Its Copper Complex

“…The mononuclear L–Cu complex show the significant catalytic activity towards 3,5‐di‐ tert‐ butylcatechol (3,5‐DTBC) ,. This substrate (3,5‐DTBC) with bulky tertbutyl substituent's on the ring has low quinine‐catechol reduction potential making it easy to oxidize to the corresponding o‐quinone(3,5‐DTBQ).…”

Triazine based Mn (II) and Mn (II)/Ln (III) complexes: Synthesis, characterization and catecholase activities

“…Finally, catecholase enzyme mimetic properties of the complexes for 3,5-DTBC → 3,5-DTBQ conversion in the presence of air oxygen were investigated by spectrophotometric method. Homo-dinuclear Mn (II) complexes (1,4) were found to catalyse the conversion of 3,5-DTBC → 3,5-DTBQ with turnover numbers of 37.25 and 35.78 h −1 (k cat ), respectively. Mononuclear Eu (III) and La (III) complexes did not exhibit detectable catecholase activity.…”

“…The ligands (H 2 L 1 and H 2 L 2 ) were reacted with Mn (II), La (III) or Eu (III) salts to yield corresponding metal complexes (1)(2)(3)(4)(5)(6). In the complexes, the ligands can accommodate the metal ions via coordination bonds in a provided cavity of the ligands with N 3 O 2 donor sets (pyridin-diimine nitrogens and phenolic oxygen atoms).…”

“…The time-dependent (over 1 h) UV-Vis. spectral change for the complexes (1,4,(7)(8)(9)(10) at 400 nm was carried out in MeOH at room temperature. For catalyst-substrate mixture the rates were obtained from the initial slope of ΔA 400nm vs. time plots and analyzed by Michaelis-Menten to calculate turnover numbers (k cat ) ( Figure 11 & Table 3).…”

“…Studies on the synthesis and characterization of coordination complexes have been increasing due to their potential use of these compounds in a variety of fields such as catalysis, adsorption, storage, magnetism, molecular recognition, fluorescence, and sensor. [1][2][3] The choice of metal ion and ligand ensures that these compounds exhibit multifunctional properties. Different coordination geometries and oxidation numbers make them possible to use in different applications.…”