Optical Properties of Iridium(III) Cyclometalates: Excited State Interaction with Small Molecules and Dynamics of Light-Harvesting Materials

The research presented in this thesis concerns the use and understanding of luminescent Ir(III) cyclometalates. Areas of research involve the design, synthesis, and characterization of novel luminescent Ir(III) cyclometalates, including photophysical investigation of their phosphorescent excited states using steady-state and time resolved absorption/luminescence spectroscopies. This broad research description may be further separated into two subareas: study of excited state interaction with small molecules and excited-state dynamics of metal-organic light harvesting dyads.;Interaction of Ir(III) cyclometalates with the small molecule carbon dioxide (CO2) is the subject of Chapter One. Most optical detection schemes previously developed for CO2 use indirect detection methods, which rely upon measuring changes in pH brought about by hydrolysis of CO 2 on of CO2 were accomplished through development of a system where hydrazine, a simple amino ligand, when coupled into the coordination sphere of an Ir(III) cyclometalate reacts with CO2. The result of this reaction provides a shift in the luminescence wavelength, a previously unobserved optical response for CO2 detection.;Chapter Two investigates phosphorescent excited states and their ability to function as triplet sensitizers for the generation of singlet oxygen ( 1O2) and luminescent probes for molecular oxygen (O 2) concentration. Interaction of phosphorescent excited states with O2 results in energy transfer from the luminescent probe to O 2, quenching the phosphorescent excited state. Energy transfer also generates the reactive oxygen species (ROS) 1O2. We have used this duality to develop an analytical methodology to follow the serendipitously discovered photoreactivity of 1O2 with common organic solvent dimethyl sulfoxide (DMSO) using the luminescence profile of Ir(III) and Ru(II) phosphors.;In Chapter Three a detailed study involving the design, synthesis, and characterization of the electrochemical and phototophysical properties of Ir(III) cyclometalates with pendant terthiophenes as secondary organic chromophores is presented. The interplay of the excited states between each chromophore represents an interesting photoredox active system for energy-to-light or light-to-energy devices. Greater knowledge of the primary photophysical events within these complexes will provide a better understanding of how energy moves in these hybrid systems after light absorption, leading to increased device efficiency.