Lowry, Robert K. Jr.

Ligand field theory of d^3 transition metal ions in
cubic and quadrate fields is briefly summarized, along with
the features of the predicted spectra. Diffuse reflectance
spectra of a variety of quadrate chromium(III) complexes are
measured with special emphasis on uncovering the component
structures of the spin-forbidden transitions. Energy level
assignments are made for components of both spin-allowed
and spin-forbidden bands by fitting of the calculated and
observed energy levels. Electron correlation and ligand
field parameters are derived by the fitting procedure, and
the usefulness of the repulsion parameters Band C in bonding
considerations is discussed. Results reveal the need for certain
refinements of the present state of ligand field theory.
The need for improved experimental techniques to provide
more precise and abundant spectral data is evident. When
more data is available it will be possible to continue the extensions
of the theory of ligand fields to s ystems of lower symmetries.