Insight into the conformational selectivity of cobalt(iii) complexes with a tetradentate salen-type Schiff base ligand and their biorelevant catalysis: a combined experimental and theoretical study

Abstract

Salen-based octahedral trans metallo-salen complexes with monodentate co-ligands may exist as several conformational isomers including stepped and umbrella shaped conformations. However, the factors governing the selective isolation of a particular...

Chemical fixation of atmospheric CO2 in tricopper(ii)-carbonato complexes with tetradentate N-donor ligands: reactive intermediates, probable mechanisms, and catalytic and magneto-structural studies

“…We have been exploring catechol oxidase (CAO) (Scheme 1a) and phenoxazine synthase (PHS) (Scheme 1b) activities using different first row transition metal complexes in aerobic conditions. 48–53 The former is a dicopper type-III enzyme that catalyzes a variety of catechols to the corresponding quinones, while the latter involves the oxidative coupling of o -aminophenols to produce phenoxazinone chromophore, a component of naturally occurring antineoplastic agent actinomycin D, 54 which is used clinically for the treatment of a wide range of cancers. 55–57 Under ambient conditions, several transition metal complexes have shown CAO and PHS activities, modelling the functions of these metalloenzymes; however, physio-mechanistic investigations with different nuclearities, especially for phenoxazinone synthase, are limited.…”

“…We have been developing coordination compounds with different Schiff base ligands derived from one end-protected triamine N , N -dimethyldipropylenetriamine and pyridine-2-carboxaldehyde or salicylaldehyde or their derivatives, and have observed the versatile coordination adaptabilities of these ligands. 51–53,89–94 As a part of our ongoing study, we report herein three N 4 /N 3 O donor ligands ( L 1 , L 2 and HL 3 ) derived from the Schiff base condensation reaction of N , N -dimethyldipropylenetriamine with pyridine-2-carboxaldehyde or its derivative or salicylaldehyde (Scheme 2), and their copper( ii ) complexes with different nuclearities, [Cu 3 ( L 1 ) 3 (μ 3 -CO 3 )](ClO 4 ) 3 ( 1 ), [Cu 3 ( L 2 ) 3 (μ 3 -CO 3 )](ClO 4 ) 3 ( 2 ) and [Cu(L 3 )(ClO 4 )] ( 3 ). The magnetic correlation of 1 and 2 has been established with similar tri-nuclear copper( ii ) complexes.…”