Copper(I) complexes have been studied through both experimental and computational means in the presented work. Overall, the work focuses on photophysical and photochemical properties of copper(I) complexes. Photophysical and photochemical properties are found to be dependent on the geometries of the copper(I) complexes. One of the geometric properties that are important for both photochemical and photophysical properties is coordination number. Coordination numbers have been observed to be dependent on both ligand size and recrystallization conditions. The complexes geometric structure, as well as the electronic effects of the coordination ligands, is shown both computationally as well as experimentally to affect the emission energies. Two-coordinate complexes are seen to have only weak emission at liquid nitrogen temperature (77 K), while at room temperature (298 K) the two-coordinate complexes are not observed to be luminescent. Three-coordinate complexes are observed to be luminescent at liquid nitrogen temperature as well as at room temperature. The three-coordinate complexes have a Y-shaped ground (S0) state that distorts towards a T-shape upon photoexcitation to the lowest lying phosphorescent state (T1). The geometric distortion is tunable by size of the coordinating ligand. Luminescence is controllable by limiting the amount of non-radiative emission. One manner by which non-radiative emission is …

The multi-reference correlation consistent composite approach (MR-ccCA) was designed to reproduce the accuracy of more computationally intensive ab initio quantum mechanical methods like MR-ACPF-DK/aug-cc-pCV?Z-DK, albeit at a significantly reduced cost. In this dissertation, the development and applications of the MR-ccCA method and a variant of its single reference equivalent (the relativistic pseudopotential ccCA method) are reported. MR-ccCA is shown to predict the energetic properties of reactive intermediates, excited states species and transition states to within chemical accuracy (i.e. ±1.0 kcal mol 1) of reliable experimental values. The accuracy and versatility of MR-ccCA are also demonstrated in the prediction of the thermochemical and spectroscopic properties (such as atomization energies, enthalpies of formation and adiabatic transition energies of spin-forbidden excited states) of a series of silicon-containing compounds. The thermodynamic and kinetic feasibilities of the oxidative addition of an archetypal arylglycerol ?-aryl ether (?-O-4 linkage) substructure of lignin to Ni, Cu, Pd and Pt transition metal atoms using the efficient relativistic pseudopotential correlation consistent composite approach within an ONIOM framework (rp-ccCA-ONIOM), a multi-level multi-layer QM/QM method formulated to enhance the quantitative predictions of the chemical properties of heavy element-containing systems larger than hitherto attainable, are also reported.