Excited state modifications of copper luminophores
Abstract
This work encompasses three chapters investigating the excited states of copper luminophores. The main body of work focuses on the synthesis and characterization of both copper(II) and copper(I) complexes, namely copper(II) porphyrins and copper(I) phenanthroline derivatives, in order to gain a deeper understanding into the various photochemical processes involved with each derivative. A side project is summarized as an appendix describing the synthesis of various heteroaromatic ligands with potential use in platinum photochemistry. The copper(II) porphyrin derivatives in Chapter 1 offer insight into the emitting and deactivating state associated with these complexes. The data show that the variation in the lifetime of the emitting $\pi$-$\pi\sp\*$ state is not due to thermal population of another excited state of charge-transfer parentage as was previously thought to be the case. Based on the findings herein, we favor the model supporting a vibronic distortion to explain the decrease in lifetime over the series. Previous researchers have noted that sterics play an important role for copper(I) phenanthroline photochemistry. Currently, we have been focusing on the steric effects of remote methyl group both on the R-group in the 2 and 9 positions of phenanthroline as well as on the phenanthroline ligand itself. Through these preliminary studies, a new type of copper(I) phenanthroline has been developed to have a longer excited state lifetime and higher quantum yield. The metal-to-ligand charge-transfer excited states of copper(I) phenanthroline systems tend to be good reducing agents but poor oxidants for kinetic and thermodynamic reasons. However, we demonstrate that reductive electron-transfer quenching is an important pathway for ferrocenes that react with the photoexcited states of $\rm Cu(dpp)\sb2\sp+,\ Cu(dipp)\sb2\sp+$ and $\rm Cu(tptap)\sb2\sp+$ in methylene chloride. This is the first evidence of reductive quenching using copper(I) phenanthroline derivatives.
Degree
Ph.D.
Advisors
McMillin, Purdue University.
Subject Area
Chemistry
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