Synthesis, structural studies, kinetic stability, and oxidation catalysis of the late first row transition metal complexes of 4,10-dimethyl-1,4,7,10-tetraazabicyclo[6.5.2]pentadecane

Authors

Donald G. Jones, Southwestern Oklahoma State University
Kevin R. Wilson, Southwestern Oklahoma State University
Desiray J. Cannon-Smith, Southwestern Oklahoma State University
Anthony D. Shircliff, Southwestern Oklahoma State University
Zhan Zhang, Huazhong University of Science and Technology
Zhuqi Chen, Huazhong University of Science and Technology
Timothy J. Prior, University of Hull
Guochuan Yin, Huazhong University of Science and Technology
Timothy J. Hubin, Southwestern Oklahoma State UniversityFollow

Document Type

Article

Publication Date

2-11-2015

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.

Publication Title

INORGANIC CHEMISTRY

Volume

54

Issue

5

First Page

2221

Last Page

2234

Recommended Citation

Jones, Donald G.; Wilson, Kevin R.; Cannon-Smith, Desiray J.; Shircliff, Anthony D.; Zhang, Zhan; Chen, Zhuqi; Prior, Timothy J.; Yin, Guochuan; and Hubin, Timothy J., "Synthesis, structural studies, kinetic stability, and oxidation catalysis of the late first row transition metal complexes of 4,10-dimethyl-1,4,7,10-tetraazabicyclo[6.5.2]pentadecane" (2015). Faculty Articles & Research. 4.
https://dc.swosu.edu/cas_cp_articles/4