Applications of Alkynyl-linked Transition Metal Compounds on Chemically Modified Electrodes

University Of Vermont & State Agricultural College, Burlington VT

Investigators

Abstract

In this project funded by the Chemical Structure, Dynamics and Mechanisms B Program in the Division of Chemistry, Professor William E. Geiger of the University of Vermont is studying electrochemistry in addressing chemical, biochemical, and environmental problems. The most common type of electrochemical cell is one in which two metal electrodes communicate through an electrolyte solution, with chemical reactions taking place at each electrode. Traditionally, the electrodes have been composed of expensive and rare metals such as platinum and gold. In the interest of both cost and sustainability, these traditional metals need to be replaced by cheaper and more common, preferably carbon-based, materials. However, carbon surfaces themselves lack the chemical structure needed to carry out many important reactions, such as those required in efficient fuel cells. The project is designed to molecularly alter the surface structure of carbon, thereby increasing the efficiency of these reactions. These studies provide training in electrochemistry and transition-metal chemistry for undergraduate and graduate students, in addition to high school students. The students are also experiencing other research groups through a number of collaborating arrangements. Professor Geiger is developing a new chemical electrode modification method based on electrochemical oxidation of either an ethynyl-containing molecule or a metal-activated ethynyl molecule. An ethynyl group provides a nearly ideal linkage between a molecular substrate and a carbon surface owing to its ability to offer facile electronic communication between those moieties, its very strong bonding to the surface, and its structural integrity. Both organometallic molecules and porphyrin complexes containing transition metals are being attached to the electrode surfaces. Routes to electrode modification by porphyrins containing a number of different transition metals are being be explored, and one or more electrocatalytic reactions, such as the oxygen reduction reaction, are being probed. Electrodes also are being modified with ethynyl-linked metal photosensitizers and ethynyl-linked multi-electron transfer agents, with the goal of providing new electrode surfaces for efficient biosensors and neural sensors. A new approach to analysis of chemically modified electrodes by magnetic circular dichroism is being studied.