Presented at: National Organization for the Professional Advancement of Black Chemists and Chemical Engineers
Date: March 25-30, 2002
Authors: Hershel Jude, Greg T. Carroll, Jeannette Krause Bauer, William B. Connick*
Department of Chemistry, University of Cincinnati
The efficient conversion of solar energy to chemical energy is a critical challenge facing chemists today. A central problem is that absorption of light by a molecule is an intrinsically one-electron process. Consequently, traditional solar-to-chemical energy conversion strategies are limited to one-photon/one-electron chemistry. However, the activation of most important target substrates (e.g., H2O, CO2, N2) requires multiple redox equivalents.
In an effort to overcome this problem, we are designing platinum metal chromophores that will transfer two electrons when excited by a single photon. In this presentation, we will describe our recent efforts to develop two-electron platinum photo-reagents using the cyclometallating pincer ligand pip2NCN- (pip2NCNH = 1,3-bis[(piperdyl)methyl]benzene).
We have synthesized a series of new platinum(II) and platinum(IV) complexes, including dimeric comounds such as [(pip2NCN)Pt(m-bpy)Pt(pip2NCN)]2+. The synthesis and properties of monomeric complexes with two pincer ligands also will be discussed.
The ligands in these systems are able to accommodate both the octahedral geometry of Pt(IV) and the square planar geometry Pt(II). Spectroscopic and electrochemical results suggest that these complexes are capable of undergoing photoinduced outer-sphere two-electron transfer reactions.