Date of Award

8-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Committee Member

Julia L. Brumaghim, Committee Chair

Committee Member

William T Pennington

Committee Member

Joseph S. Thrasher

Committee Member

Daniel C. Whitehead

Abstract

Coordination chemistry of imidazole thione and selone compounds with 2nd and 3rd row d-block metals are of considerable interest due to their wide-ranging applications of reducing heavy metal toxicity, catalysis, and antimicrobial and antitumor activity. Antioxidant behavior of some imidazole thiones and selones is attributed to their ability to scavenge hydrogen peroxide or other reactive oxygen species as well as their coordination of redox-active iron and copper to prevent hydroxyl-radical-mediated DNA damage. Chapter 1 of this dissertation provides an overview of 2nd and 3rd row d-block metal complexes with imidazole thione and selone ligands and their applications.

Ruthenium complexes with labile solvato ligands represent versatile synthons for entry into Ru(II) coordination chemistry. Thus, homoleptic and heteroleptic solvato Ru(II) complexes were synthesized from readily available RuCl3∙xH2O (Chapter 2). An improved synthesis of [Ru(NCCH3)6][BF4]2 affords higher yields with fewer reaction steps, and the [Ru(NCCH3)2(DMSO)3Cl][BF4]1.5[Cl]0.5[Na], [Ru(NCCH3)4(DMSO)2][BF4]2, and [Ru(NCCH3)5(DMSO)][BF4]2, (DMSO = dimethylsulfoxide) mixed-solvato complexes could be useful for synthesizing heteroleptic Ru(II) complexes.

Sulfur and selenium compounds can scavenge reactive oxygen species to prevent oxidative damage, and metal coordination can improve this activity. Therefore, novel homoleptic Ru(III) and Ru(II) complexes with methimazole (MMI), N,N'-dimethylimdiazole thione (dmit) and selone (dmise) ligands of the formula [RuL6]Cl3 and [RuL6][BF4]2 were synthesized (Chapter 3). Heteroleptic complexes RuL4Cl2 were also synthesized with the same three ligands. The [RuL6]Cl3 complexes quickly react with hydrogen peroxide, with the MMI and dmise complexes reacting significantly faster than the dmit complex. [Ru(MMI)6]Cl3 also prevents iron-mediated DNA damage at very low micromolar concentrations.

Ruthenium nitrosyl complexes are some of the most investigated compounds for biological NO delivery. Therefore, Ru(II)-nitrosyl complexes [Ru(NO)(L)4Cl][BF4]2 (L = dmit dmise) were synthesized from RuCl3·xH2O with silver nitrate as a simple and convenient nitrosyl source (Chapter 4). This novel method considerably simplifies synthesis of Ru-nitrosyl complexes with good yields and avoids the use of unstable or toxic starting materials to generate nitrosyl complexes. This work develops Ru(II) and Ru(III) chemistry as starting materials and with thione, selone, and nitrosyl ligands that have promising biological applications as antitumor, antimicrobial, and photodynamic therapy agents as well as catalytic applications.

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