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

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.

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.

Citation

Jones, D. G., Wilson, K. R., Cannon-Smith, D. J., Shircliff, A. D., Zhang, Z., Chen, Z., Prior, T. J., Yin, G., & 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

• Journal Article Type: Article
• Acceptance Date: Nov 13, 2014
• Online Publication Date: Feb 11, 2015
• Publication Date: Mar 2, 2015
• Deposit Date: Aug 24, 2015
• Publicly Available Date: Nov 23, 2017
• Journal: Inorganic chemistry
• Print ISSN: 0020-1669
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 54
• Issue: 5
• Pages: 2221-2234
• DOI: https://doi.org/10.1021/ic502699m
• Keywords: Cross-bridged cyclam; Pendant-arm macrocycle; Oxidation catalysis
• Public URL: https://hull-repository.worktribe.com/output/377855
• Publisher URL: http://pubs.acs.org/doi/abs/10.1021/ic502699m
• 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
• Contract Date: Nov 23, 2017