Spectrochemical Series of Cobalt(III). An Experiment for High School through College

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 10 Issue 2 (2005) pp 115-119

Spectrochemical Series of Cobalt(III). An Experiment for High School through College

Adam R. Riordan, Ariane Jansma, Sarah Fleischman, David B. Green, and Douglas R. Mulford*

Department of Chemistry, Pepperdine University, Malibu, CA 90263, Douglas.Mulford@pepperdine.edu (* Current address Emory University, Douglas.Mulford@emory.edu)
Received July 7, 2004. Accepted September 2, 2004.

Published online: 3 February 2005

Abstract. We present a laboratory project suitable for high school though upper-division college courses that has been designed to allow students to qualitatively investigate or quantitatively generate the spectrochemical series for octahedral cobalt(III) complexes. This experiment is useful for concrete, visual demonstration of the structural and electronic properties of ligand-to-metal bonding. Water, ammonia, nitrite, oxalate, glycinate, ethylenediamine, 1,10-phenanthroline, carbonate, and cyanide are used as ligands to form the cobalt complexes. Each complex has a different color and l_max. This allows students to derive the spectrochemical series by visual inspection or UV–visible spectroscopy. At the high school level, the series can be generated from visual inspection of the colored compounds by use of the transmission color wheel. At the general chemistry level, the series can be generated from spectroscopic data using the l_max of lowest energy. In advanced courses students can calculate crystal field splitting values, D₀, and the ordering of the spectrochemical series can be justified from a metal–ligand interaction point of view.

Key Words: Laboratories and Demonstrations; general chemistry; high school chemistry; bonding; spectrochemical series; crystal field theory; coordination compounds; coordination chemistry; synthesis; spectroscopy

(*) Corresponding author. (E-mail: Douglas.Mulford@emory.edu)

Article in PDF format new file 2/2/2008 (237 KB) HTML format Mulford - erratum 2/2/2008

Supporting Materials:

An introduction to coordination compounds and crystal field theory and raw data for the octahedral d⁶ Tanabe–Sugano diagram are included as supporting material in a Zip file (258 KB).