The Spectroscopic and Electrochemiluminescence (Ecl) Properties of Dipicolinc Acid (Dpa), (Bpy)2Ru2+ (Bpy = 2,2'- Bipyridine) and Electrogenerated Chemiluminescence Quenching of Ru(Bpy)32+ in the Presence of Phenolic Estrogens

Jessica Byrd

Date of Graduation

Spring 2005

Degree

Master of Science in Chemistry

Department

Chemistry and Biochemistry

Committee Chair

Mark Richter

Abstract

The spectroscopic and electrochemiluminescence (ECL) properties of dipicolinic acid (DPA), (bpy)2Ru2+ (bpy=2,2̀-bipyridine) and the species formed when DPA and (bpy)2Ru2+ are allowed to react (abbreviated (bpy)2Ru(DPA)+) are reported. UV-Vis absorption maxima for (bpy)2Ru2+, and (bpy)2Ru(DPA)+ are 493 and 475 nm, respectively, indicating the in situ formation of a complex between DPA and (bpy)2Ru2+. DPA, (bpy)2Ru2+, and (bpy)2Ru(DPA)+ display ECl upon oxidation nin the presence of the oxidative-reductive coreactant tri-n-propylamine (TPA). The ECl of (bpy)2Ru(DPA)+ is at least 2-fold higher than either of the parent species. An ECL spectrum of (bpy)2Ru(DPA)+ displays a peak maximum 40 nm red-shifted from the photoluminescence peak maximum suggesting that the excited state formed electrochemically is different than that formed spectroscopically. In a separate project, quenching of Ru(bpy)3,2+ (bpy = 2,2̀-bipyridine) electrogenerated chemiluminescence (ECL) has been observed in the presence of a series of phenolic estrogens. More specifically, bisphenol A (BPA), nonylphenol (NP), diethylstilbestrol (DES), quercetin dehydrate (QD) were tested for their ability to quench the ECL of Ru(bpy)3,2+ using phenol (PH) and benzoquinone (BQ) as standards. In all instances, quenching is observed with 100-fold excess of phenolic estrogen (as compared to ECL lumiophore) with complete quenching observed for BPA, DES and QD between 8.000 and 10,000 fold excess. Photoluminescence and UV-Vis experiments coupled with bulk electrolysis support the formation of benzoquinone products upon electrochemical oxidation. The mechanism of quenching is believed to involve energy transfer from the excited state luminophore to benzoquinone species formed upon oxidation at the electrode surface.

Subject Categories

Chemistry

Copyright

© Jessica Byrd

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