DENSITY FUNCTIONAL THEORY BASED MOLECULAR MODELLING OF INORGANIC REACTIONS: MECHANISTIC STUDIES AND ELECTRONIC STRUCTURE CALCULATIONS

Abstract

Density functional theory (DFT) plays a significant role in finding insights of inorganic reactions. In this thesis, DFT is utilized to understand copper- and ruthenium-based inorganic reactions. The thesis is divided into the following seven chapters. Chapter 1 provides an introduction to copper-based enzymes including Particulate methane monooxygenase (pMMO), Tyrosinase, and Copper-nitrite reductase. Furthermore, the problem statements carried out in the next chapters are shown. Chapter 2 discusses DFT-derived studies for the formation of a mixed-valent CuIII−O−CuII species from a P complex via the transfer of 2H+ and 2e− from phenolic groups of ligands to the Cu2O2 core in P. Chapter 3 shows how a mixed-valent CuIII−O−CuII activates a C−H bond of a nitrogen-based ligand and an O−H bond of a water molecule. The mechanisms followed by a mixed-valent CuIII−O−CuII core for C−H and O−H activation are unveiled. Furthermore, the role of a water molecule in C−H hydroxylation via a mixed-valent CuIII−O−CuII core is explained. To assess the relevance of a mixedvalent CuIII−O−CuII core, an aliphatic C−H activation by a symmetrical CuII−O−CuII core is discussed. Chapter 4 discusses modeling a biomimetic [Cu−O−Cu]2+-based model for methane activation by changing one of the copper atoms of Cu−O−Cu with other transition metals such as Fe, Co, and Ag. Variation in transition metal changes the activation barriers for the C−H bond activation of methane. The change in activation barriers is explained based on the distortion-interaction, orbital, spin, and quantum theory of atoms in molecule analysis. Chapter 5 is related to the effect of counter-anions (PhCO2 −, CF3SO3 −, TsO−, and SbF6 −) on the stability of P. Based on DFT-computed indicators such as geometrical, IGMH, relative Gibbs energies, bending angles, orbitals overlap, and distortion-interaction analysis, the bonding and nonbonding interactions between P and counter-anions are shown. These computational indicators present an invaluable tool for precisely evaluating the stability of P cores. Chapter 6 shows interactions between CuII-nitrite complex and a protonated amine in the second coordination sphere. The structural aspect of the complex is explained using computational analysis in the absence of its crystal structure. The H-bonding interaction between the nitrite anion and the outer coordination sphere ammonium moiety is discussed. Chapter 7 is related to RuII-catalyzed C−H bond activation of 2-phenyl pyridine using 2- hydroxypyridine-based ligands. The crucial role of pyridone ligand in enhancing the C−H bond activation of 2-phenyl pyridine using DFT is discussed.