Alexander, Bruce, Crayston, Joe A. and Dines, Trevor J. (2007) Cyclic voltammetry and spectroelectrochemical study of nickel and cobalt diphenyltetraazaannulene complexes. Journal of Electroanalytical Chemistry, 605 (2). pp. 109-117. ISSN 0022-0728 (doi:https://doi.org/10.1016/j.jelechem.2007.03.026)

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Abstract

The absorption spectra. cyclic voltammetry and spectroelectrochemistry of [Ni(II)DPTAA] and [Co(II)DPTAA] (DPTAA = 6,13-diphenyldibenzo[b,i][1,4,8,11] tetraaza[14]annulene) complexes in DMF are reported in detail. The ligand oxidation is observed for [Ni(II)DPTAA] at +0.70 V vs. SCE whereas Ni2(+/+) occurs at - 1.60 V. For [Co(II)DPTAA], a ligand oxidation redox couple is seen at +0.56 V while the Co2+/+ and Co2+/3+ redox couples appear at -1.21 and +0.24 V, respectively. All observed redox couples are assigned to reversible one-electron processes on account of peak separations and scan-rate dependency. These processes were further investigated by spectroelectrochemistry for [Co(II)DPTAA]. For [Co(II)DPTAA], axial ligation of pyridine was found to shift the Co2+/3+ redox couple more negative. while the ligand oxidation was shifted to more positive potentials. From a spectrophotometric titration of [Co(II)DPTAA] with pyridine an equilibrium constant, K-f, was determined for the binding of pyridine to [Co(II)DPTAA]. This was found to be 10.2 dm(3) mol(-1), slightly lower than that of [Co(II)TAA], indicating the influence of the phenyl groups. From this value and shifts in the Co2+/3+ redox couple upon ligation, an equilibrium constant for the binding of pyridine to [Co(III)DPTAA], K'(f), was found to be 5.06 x 10(6) dm(3) mol(-1). (c) 2007 Elsevier B.V. All rights reserved.

Item Type:	Article
Additional Information:	[1] First published online: 19 April 2007. [2] Published in print: 15 July 2007. [3] Further discussion of the absorption spectra, cyclic voltammetry of the two complexes recorded at different scan rates. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/ j.jelechem.2007.03.026.
Uncontrolled Keywords:	tetraazaannulenes, marcocycles, spectroelectrochemistry, cyclic voltammetry, electrocatalysis
Subjects:	Q Science > QD Chemistry T Technology > TP Chemical technology
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science > School of Science (SCI)
Related URLs:	Publisher Organisation
Last Modified:	13 Feb 2020 10:41
URI:	http://gala.gre.ac.uk/id/eprint/2467

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