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Synthesis, structural studies, and oxidation catalysis of the late-first-row-transition-metal complexes of a 2-pyridylmethyl pendant-armed ethylene cross-bridged cyclam

Chen, Z.; Zhang, Z.; Yin, G.; Jones, Donald G.; Wilson, Kevin R.; Cannon-Smith, Desiray J.; Shircliff, Anthony D.; Zhang, Zhan; Chen, Zhuqi; Prior, Timothy J.; Yin, Guochuan; Hubin, Timothy J.

Authors

Z. Chen

Z. Zhang

G. Yin

Donald G. Jones

Kevin R. Wilson

Desiray J. Cannon-Smith

Anthony D. Shircliff

Zhan Zhang

Zhuqi Chen

Guochuan Yin

Timothy J. Hubin

Abstract

The first 2-pyridylmethyl pendant-armed ethylene cross-bridged cyclam ligand has been synthesized and successfully complexed to Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ cations. X-ray crystal structures were obtained for all six complexes and demonstrate pentadentate binding of the ligand with the requisite cis-V configuration of the cross-bridged cyclam ring in all cases, leaving a potential labile binding site cis to the pyridine donor for interaction of the complex with oxidants and/or substrates. The electronic properties of the complexes were evaluated using solid-state magnetic moment determination and acetonitrile solution electronic spectroscopy, which both agree with the crystal structure determination of high-spin divalent metal complexes in all cases. Cyclic voltammetry in acetonitrile revealed reversible redox processes in all but the Ni²⁺ complex, suggesting that catalytic reactivity involving electron-transfer processes is possible for complexes of this ligand. Kinetic studies of the dissociation of the ligand from the copper(II) complex under strongly acidic conditions and elevated temperatures revealed that the pyridine pendant arm actually destabilizes the complex compared to the parent cross-bridged cyclam complex. Screening for oxidation catalysis using hydrogen peroxide as the terminal oxidant for the most biologically relevant Mn²⁺, Fe²⁺, and Cu²⁺ complexes identified the Mn²⁺ complex as a potential mild oxidation catalyst worthy of continued development.

Journal Article Type Article
Publication Date Mar 2, 2015
Journal Inorganic chemistry
Print ISSN 0020-1669
Electronic ISSN 1520-510X
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 54
Issue 5
Pages 2221-2234
Institution Citation Jones, D. G., Wilson, K. R., Cannon-Smith, D. J., Shircliff, A. D., Zhang, Z., Chen, Z., …Hubin, T. J. (2015). Synthesis, structural studies, and oxidation catalysis of the late-first-row-transition-metal complexes of a 2-pyridylmethyl pendant-armed ethylene cross-bridged cyclam. Inorganic chemistry, 54(5), 2221-2234. https://doi.org/10.1021/ic502699m
DOI https://doi.org/10.1021/ic502699m
Keywords Cross-bridged cyclam; Pendant-arm macrocycle; Oxidation catalysis
Publisher URL http://pubs.acs.org/doi/abs/10.1021/ic502699m
Copyright Statement ©2016 University of Hull
Additional Information This document is the Accepted Manuscript version of a Published Work that appeared in final form in Inorganic chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/ic502699m

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