The Chemical Educator
ISSN: 1430-4171 (electronic version)
Abstract Volume 8
Issue 4 (2003) pp 248-250
Models of Coenzyme B12. An Undergraduate Chemistry Experiment Combining Synthesis of Cob(III)aloxime Complexes and Their Characterization by 1H NMR and Cyclic Voltammetry
Elizabeth A. Landis, Steven T. Scroggins, Mark H. Schofield*, Lee Y. Park*
Department of Chemistry, Williams College, Williamstown, MA 01267,
Published online: 8 July 2003
Abstract. An upper level undergraduate inorganic chemistry experiment in which students synthesize a series of octahedral cobalt(III) complexes of the type Co(dmgH)2Br(L) and Co(dmgH)2Me(L) where L can be a variety of substituted pyridines or imidazoles is described. The electronic structure of the series of complexes can be examined using 1H NMR spectroscopy and cyclic voltammetry. Shifts in the 1H NMR methyl resonance can be directly correlated with the electron-donating ability of the base and, therefore, the electron density at the metal center. Similarly, cyclic voltammetric studies reveal a significant shift in the reduction potentials, consistent with changes in the electron-donating ability of the axial base, while the oxidation potentials are largely unaffected by the identity of the axial ligand.
Key Words: Laboratories and Demonstrations; inorganic; bioinorganic; synthesis; 1H NMR; cyclic voltammetry
Supporting Materials:Supporting material for this article includes information on reagents, representative NMR and cyclic voltammetric results, full NMR data for all of the methylcobaloxime complexes reported, and a handout with details provided to students in our upper-level inorganic laboratory. Materials are available in a single Zip file (138 KB) 10.1333/s00897030698a.
Issue date: August