Tuning the Optical and Electrochemical Properties of M(CO)4(phenanthroline) Compounds via Substituents on the Phenanthroline Ligand: An Upper-Division Inorganic Laboratory

This experiment involves the preparation and characterization of M(CO) 4(L^L) compounds, where L^L is 1,10-phenanthroline or a related derivative and M is Cr or Mo. The purpose of the experiment is to study the effects of electron-withdrawing or electron-donating phenanthroline substituents on the resulting properties of the metal compound, analogous to current research being done on materials for dye-sensitized solar cells. The degree of electron donation is controlled via 3,4,7,8-tetramethyl (electron donating) or 5-chloro (electron withdrawing) substitution of phenanthroline. The compounds are studied using IR, UV-vis, and cyclic voltammetry. Trends are observed in these data as a function of the relative electrondonating character of the ligand. The effects of changing the central metal atom are also examined. This experiment follows a research-based model, which can be completed in a single six-hour session. © 2010 American Chemical Society and Division of Chemical Education, Inc.