Synthesis of Solvatochromic Copper(II) Complex and Determination of the Donor Numbers of Polar Solvents

This article describes a simple undergraduate laboratory experiment in which students prepared and analyzed the solvatochromic mixed ligand copper(II) complex of acetylacetonate with 1,10-phenanthroline and tetraphenylborate. The complex was synthesized using low-odor acetylacetonate and odorless 1,10-phenanthroline ligands with equipment typically available in a standard general chemistry laboratory. Depending on the polar organic solvents used, the solutions of the complex exhibited a variety of colors ranging from green via blue to violet. The solutions’ d–d absorption wavelengths correlated well with the donor numbers of the solvents, thus facilitating students’ estimation of the unknown donor numbers of the solvents. Completing this experiment enhanced the students’ understanding of the basic calculations in chemistry.