Research Computer simulations are extremely useful tools of modern theoretical chemistry that provide fundamental understanding of molecular processes and rigorous interpretations of experiments from first principles. However, a rigorous and general method for describing the influence of quantum effects on equilibrium and dynamical properties of complex systems (e.g., those with many degrees of freedom) has yet to be established. Such an accomplishment would make a major impact in our understanding of a wide range of chemical processes, including reactions in bio-molecules where proton and electron transfer often involve quantum tunneling and coherences. In addition, a broad area of research and technology development would also benefit from these advances in computational methods, since there is currently a real need for truly convenient and powerful techniques capable of describing quantum processes in new materials. Figure 2: Snapshots of the instantaneous electronic iso-density surface at intervals of 2.5 fs during the photo-induced interfatial electron transfer in a functionalized TiO2 semiconductor nanostructure. Our research is concerned with the development of rigorous and practical methods for simulations of quantum processes in complex systems as well as with applications studies of photochemical processes in proteins, semiconductor materials, and systems of environmental interest. We have recently made significant progress toward the establishment of rigorous quantum mechanical approaches for describing equilibrium and dynamical properties of complex quantum systems. We are currently investigating how to extend these calculations to investigate quantum mechanical processes involved in light harvesting mechanisms in semiconductor materials (e.g., functionalized TiO2) and biological molecules (e.g., rhodopsin). These studies aim to unravel the nature of molecular mechanisms responsible for the efficient detection and utilization of photon energy, advance our understanding of the primary photochemical event in the vertebrate vision process, and to examine the potential application of laser coherences to control photo-transduction dynamics. Other studies focus on the equilibrium and dynamical properties of weakly bound hydrated complexes responsible for changes in the global climate, including studies of the electronic structure and photo-reactivity of hydrated ozone complexes.