| A. In Chapter I a general outline of the conceptual and theoretical background necessary to an understanding of optical and thermal electron-transfer processes is presented. In Chapter II these ideas are applied to an analysis of the experimental results obtained on the mixed-valence ion-pairs {M('II)(CN)(,6),(NH(,3))(,5)Ru('III)(L)}('1-) in solution where M = Fe, Ru, Os and L = substituted pyridines. The effects of the thermodynamic driving force for the thermal reaction and the natures of M and L on the optical interaction are discussed. Good agreement between the kinetically measured (4.3 x 10('6) M('-1) s('-1)) and optically derived theoretical prediction ((TURN)2 x 10('5) M('-1) s('-1)) for the rate constant of the thermal reaction Fe('II)(CN)(,6)('4-) + Ru('III)(NH(,3))(,5)py('3+) (--->) Fe('III)(CN)(,6)('3-) + Ru('II)(NH(,3))(,5)py('2+) is demonstrated. In Chapter III a similar analysis is carried out for the ion-pair {Fe('II)(CN)(,6)('4-),PQ('2+)}('2-) (PQ('2+) = paraquat, methylviologen). In this case the optically derived prediction for the bimolecular, the thermal rate constant is (TURN)2 x 10('-5)M('-1) s('-1) and the kinetically derived result is (TURN)1 x 10('-3)M('-1) s('-1). In Chapter IV the solid-state spectra and electrical conductivities of some mixed-valence solids, {M('II)(CN)(,6)}(,3){(NH(,3))(,5)Ru('III)(L)}(,4), derived from the mixed-valence ion-pairs are discussed.;C. Chapter VI deals with the excited-state behavior in the binuclear complexes {(dpte)(,2)Ru('II)Cl(L)Ru('III/II)Cl(bpy)(,2)}('3+/2+) and {(NH(,3))(,5)Ru('III/II)(L)Ru('II)Cl(bpy)(,2)}('4+/3+) (where dpte = 1,2-bis-diphenylthioethane, bpy = 2,2'-bipyridine, and L = 4,4'-bipyridine; 1,2-bis-bipyridylethylene; and 1,2-bis-bipyridylethane) as studied by luminescence and transient absorbance spectroscopy. The effects of the nature of the bridging ligand and the electron content of the dimers (Ru('II)-L-Ru('II) vs. Ru('III)-L-Ru('II)) are discussed. It is found that both intramolecular energy-transfer and electron-transfer are facile processes in these dimers.;B. In Chapter V the solvatochromism of the charge-transfer transitions in Ru(II) complexes such as {(NH(,3))(,5)Ru('II)(L)}('n+) where L = pyridine, bipyridine, pyridinium and in Ru(III) complexes such as {(NH(,3))(,5)Ru('III)(L)}('3+) where L = oxidizable nitrogen donor is discussed and is shown to arise because of specific solute-solvent interactions of a hydrogen bonding nature. The solvato-chromatic shifts are found to correlate well with a variety of different solvent scales based on hydrogen bonding ability; the donor number scale of Gutmann, the (beta) scale of Kamlet and Taft, the (DELTA)H(,p) scale due to Arnett, and the E(,b) scale of Drago. A modified set of donor numbers which includes steric effects for this type of interaction is proposed. |
