Abstract
Deactivation of an excited species to the ground state in a photochemical process can occur via non-radiative decay or via photon emission. Quenching is the process in which photochemical reactions can be slowed by the addition of a "quencher". Reductive quenching provides additional routes for the excited species to return to the ground state by means of electron transfer or energy transfer. Three series of reductive quenchers were synthesized from Ruthenium (II) complexes and characterized: Cyclopentadienyl ruthenium tris-pyrazole borate (CpRuHBpz3), Cyclopentadienyl ruthenium tris-(dimethyl)pyrazole borate (CpRuHB(3,5-Me2)pz3), and Pentamethylcyclopentadienyl ruthenium tris-pyrazole borate (Cp*RuHBpz3). The two cyclopentadienyl compounds have similar oxidation potentials, their rates of electron transfer quenching should be comparable, but their rates of energy transfer quenching should differ. However, when comparing CpRuHBpz3 and Cp*RuHBpz3 the major difference in their ability to quench should be electron transfer. Transient laser experiments, electrochemistry, and emission analysis are currently being utilized to investigate the properties of the quenchers.
