STUDIES ON DESIGNED RUTHENIUM COMPLEXES AND THEIR REACTIVITIES

Abstract

The thesis entitled “Studies on Designed Ruthenium Complexes and Their Reactivities” is presented in eight chapters. This thesis outlines the designing and synthesis of new bidentate and tridentate ligand frames with different functional groups, including imine (-CH=N-), diazo (-N=N-), carboxamide (-CONH-), and sulfonamide (-SO2NH-) groups, which were characterized by several spectroscopic techniques. These ligands were utilized for the synthesis of a variety of ruthenium complexes like pincer type, organometallic compounds, and coordination compounds. Ruthenium complexes were characterized by numerous spectroscopic methods, including elemental analysis, FT-IR, UV-Visible, MS, CHNS, and NMR spectroscopy. The molecular structure of the representative metal complexes was determined by X-ray crystallography. These complexes were used as nitric oxide donors in the presence of visible light and utilized for wound healing and antibacterial agents. Another series of the ruthenium complexes including organometallics and coordination compounds were utilized as catalysts for different novel methodology invonving C-N and C-C bond formation using several reactions like N-alkylation reactions, styrene reduction, quinolines synthesis, α‐alkylation reactions, alcohol oxidation, aromatization reaction via HAT pathway, and azine synthesis. These complexes were explored in the deoxyribonucleic acid (DNA) interaction, inhibition of protein aggregation including BSA (bovine serum albumin), amyloid beta peptides, and prion protein) studies. Further, complexes were also explored for their antibacterial, anticancer, and antitubercular study The thesis has been divided into eight chapters of convenience and clarity, and organized as follow: Chapter 1: General Overview of Ruthenium and its Chemistry Ruthenium chemistry is diversified, and its compounds have many unique features, such as changing redox properties and photophysical and photochemical capabilities. These characteristics are of vital importance and have been widely explored due to their usefulness in both chemical and biological research. Ruthenium complexes are also commonly utilized in dye-sensitized photovoltaic cells, synthetic photosynthesis, and chemical transformation processes. As a result, the coordination chemistry of ruthenium complexes with diverse ligands has lately been attracting a lot of attention. Ruthenium is found in many compounds in its stable oxidation states of 2+ and 3+, and the ruthenium complexes are always low-spin octahedral in nature. Ruthenium compounds have distinct properties that make them suitable for application in medicinal chemistry. Several ruthenium compounds containing polydentate ligands have been used as nitric oxide donors, nitric oxide scavengers, antimicrobials, antimalarials, and anticancer medicines. Ruthenium complexes have been shown to have a wide range of applications in organic and organometallic synthesis due to their great tolerance for diverse functional groups. Ruthenium complexes absorb visible light; this characteristic is used in the development of solar cells, which generate solar energy. Chapter 2: Photodissociation of Nitric Oxide from Designed Ruthenium Nitrosyl Complex: Studies on Wound Healing and Antibacterial Activity A photoactivable NO releasing complex [Ru.L(2)] has been synthesized by complex [Ru.L(1)]. Newly synthesized bidentate ligands, i.e., 4-methoxy-N′-phenyl-N'-(pyridin-2-ylmethyl)benzohydrazide La and 4-nitro-N′-phenyl-N'-(pyridin-2-ylmethyl)benzohydrazide Lb were utilized to synthesize complex [Ru.L(1)]. Complex [Ru.L(1)] was characterized by ESI-MS, and the solid structure of the complex [Ru.L(2)] was investigated by X-ray crystallography. Different spectroscopic techniques were employed for the identification of ligands (La and Lb) as well as complexes ([Ru.L(1)] and [Ru.L(2)]). Calculations employing DFT and TD-DFT were made better to understand the electronic properties of [Ru.L(2)]. The photo liberation experiments were screened in the presence of a visible light lamp. The Griess assay experiment was used to quantify the photo-released amount to NO. Then, it (NO) was successfully transferred to the reduced myoglobin (Mb). The complex [Ru.L(2)] at 50 μg/mL concentration was used for wound healing and antimicrobial activity on B16F1 mouse skin cells and Escherichia coli bacteria, respectively. We observed a considerable wound healing activity of [Ru.L(2)] after 36 h of incubation in the light-treated cells compared to the control medium. Also, it shows >99 % inhibition of bacterial cells after 1.5 h of treatment in the presence of light.