Kinetic and energetic studies of ground and excited state inorganic reactions

Studies of ground and excited state inorganic reactions are important in developing knowledge of electron and energy transfer processes. Chapter one of this thesis will introduce the photophysics of ruthenium(II) polypyridine complexes and their applications in both chemical and biological processes. Chapter two describes the synthesis and study of five novel heteroleptic ruthenium(II) polypyridines complexes, with the general formula [Ru(NNN)(NN)CN]+ , where NNN and NN are tridentate and bidentate polypyridines ligands, respectively. All complexes show a marked improvement in emission quantum yield and lifetime relative to [Ru(trpy)(bpy)CN]PF6, where trpy and bpy are 2,2\u27:6\u27,2\u27\u27-terpyridine and 2,2\u27-bipyridine, respectively. One is the longest lived and brightest emitting dppzp (6\u27-(2\u27\u27-pyridyl)-dipyrido[3,2-a:2\u27,3\u27-c]phenazine) containing Ru(II) complex synthesized to date. The solvent and temperature dependencies of the complexes are examined and show the influence of deactivating 3dd states and the energy gap law. Ru(dppzp)(bpy)CN+ is shown to be a luminescent “light switch” for DNA as the emission is quenched in water but visible when the complex binds to DNA. However, it does not show the same light-switch effect with temperature as seen with Ru(II) complexes of the bidentate ligand dppz (dipyrido[3,2-a;2\u27,3\u27-c]phenazine). In chapter 3, under the guidance of Dr. Dale Margerum, the reactions of aqueous ClO2· and tryptophan are investigated by stopped-flow kinetics, and the products are identified by HPLC coupled with ESI-MS and by ion chromatography. In the proposed mechanism, the initial reaction is a one-electron oxidation to form a tryptophyl radical cation and chlorite ion. The radical cation deprotonates to form a neutral tryptophyl radical that combines rapidly with a second ClO2· to give an observable, short-lived adduct with proposed C(H)-OClO bonding. The overall reaction consumes two ClO2· per tryptophan and forms ClO2− and HOCl. Decay of the tryptophyl-OClO adduct at pH 6.4 gives five initial products that are observed after 2 min and are separated by HPLC with elution times that vary from 4 to 17 min. One initial product with MW = 236 decays within 47 min to yield the most stable product, N-formylkynurenine (NFK) that also has a molecular weight of 236