Graduate Program

Chemistry

Degree Name

Master of Science (MS)

Semester of Degree Completion

Spring 2018

Thesis Director

Radu F. Semeniuc

Thesis Committee Member

Rebecca A. Peebles

Thesis Committee Member

Zhiqing Yan

Thesis Committee Member

Daniel J. Sheeran

Abstract

Seven new copper(II) complexes were prepared from the condensation reaction of 4-tert-butyl-2,6-diformylphenol with two equivalents of bis(pyrazolyl)ethanamine or 3,5-dimethyl-bis(pyrazolyl)ethanamine moieties in the presence of two equivalents of various copper(II) starting materials having different counter ions (i.e. acetate - AcO-, perchlorate - CIO4-, tetrafluoroborate - BF4-, nitrate - NO3-, and chloride - Cl-). The resulting copper(II) complexes were characterized in solid state by single crystal X-ray crystallography, and in solution by UV-Vis and ESI/MS spectroscopies.

X-ray crystallographic studies showed that in solid state two types of complexes are obtained. In one case, a tetranuclear complex was obtained: {Bu1-C6H2(O)[CH=N-CH2-CH(pz)2]2}2Cu4(μ4-O)(OAc)4(L2Cu4(μ4-O)(OAc)4, pz = pyrazolyl ring). All other complexes were found to be dinuclear, with a general formula of LCu2(OR)(X)2, where R = H and CH3, and X = ClO4-, BF4-, Cl-, and AcO-). In all complexes, the coordination geometry around the copper ions was found to be a distorted square pyramid. The bond lengths and angles lie in the normal range found in these types of bonds, and the copper-copper distances vary from 2.962 Å to 3.086 Å.

UV-Vis and ESI/MS studies demonstrated that in solution all complexes are dinuclear, including the tetranuclear complex (L2Cu4(μ4-O)(OAc)4), which transforms into a dinuclear complex of the formula LCu2(OH)(OAc)2.

The L2Cu4(μ4-O)(OAc)4 complex has the ability to mimic two different processes: catecholase activity (oxidizing catechols to their respective quinones) and phenoxazinone synthase activity (oxidizing o-aminophenol to phenoxazinone). The catalytic mechanism for the first process was investigated, and it was found that the oxidation reaction occurs simultaneously via two different pathways, one involving molecular oxygen and the other hydrogen peroxide as oxidants. The LCu2(OH)(ClO4)2, LCu2(OH)(BF4)2 and LCu2(OH)(NO3)2 complexes are also catalytically active, but the nature of the product of the catechol - to - quinone oxidation reaction remains unknown at this time.

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