US EPA

3708307 

Journal Article 

Syntheses, structures and catecholase activity of two cobalt(III) complexes derived from N,N '-ethylenebis(3-ethoxysalicylaldiimine): A special host-guest system from a special ligand 

Chakraborty, P; Mohanta, S 

2015 

1 

Inorganica Chimica Acta
ISSN: 0020-1693
EISSN: 1873-3255 

435 

38-45 

10.1016/j.ica.2015.06.007 

WOS:000359325600006 

The work in this report deals with syntheses, crystal structures, catechol oxidase activity and ESI-MS (positive) studies of two mononuclear cobalt(III) compounds [(CoLOEt-e)-L-III(N-3)(2)superset of(H3O+)]center dot 2MeOH (1) and [(CoLOEt-en)-L-III(NCS)(H2O)]center dot DMF center dot H2O (2), where H2LOEt-en is N,N'-ethylenebis(3-ethoxysalicylaldiimine). The metal center in both the compounds occupies N(imine)(2)O(phenoxo)(2) compartment. Two apical coordination positions are occupied by one anionic ligand (thiocyanate) and one neutral ligand (water) in 2 but by two anionic ligands (azide) in 1. The extra negative charge in [(CoLOEt-e)-L-III(N-3)(2)] is balanced by an oxonium ion (H3O+), which is trapped in the O(phenoxo)(2)O(ethoxy)(2) compartment to result in the formation of host-guest species [(CoLOEt-e)-L-III(N-3)(2)superset of(H3O+)] in 1. Both the compounds show catechol oxidase activity (1 in MeCN, 2 in DMF) as monitored by the UV-Vis spectroscopy of the aerial oxidation of 3,5-DTBCH2 to 3,5-DTBQ. The kinetic parameters have been determined using Michaelis-Menten approach. The K-cat values for 1 in MeCN and 2 in DMF are 10.0 h (1) and 11.2 h (1), respectively. ESI-MS (positive) of 1 and the mixture of 1 and 3,5-DTBCH2 have been recorded and the positive ions have been well assigned. Interestingly, a 1:2 adduct of composition [(CoLOEt-en)-L-II(3,5-DTBQ)(2)+H+](+) has been identified from the spectrum of the mixture of 1 and 3,5-DTBCH2. Unique features of 1 and 2 in terms of showing catechol oxidase activity and, more importantly, unique structural features of compound 1 have been discussed. (C) 2015 Elsevier B.V. All rights reserved. 

Oxonium ion; Catecholase activity; Cobalt(III); Hydrogen bonds; ESI-MS