Perumareddi, Jayarama R.

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.

Electronic-structure studies of Tetrakis(imidazole)sulphatocopper(II) - Cu(C3H4N2)4SO4 and Tetrakis(imidazole)diperchloratocopper(II) - Cu(C3H4N 2)4(ClO4)2 have been carried out by analysis of electronic spectra, magnetic properties and ESR spectra. Solution spectra of both systems in the visible and UV range as well as unpolarised single-crystal spectrum of Cu(Im)4SO4 in the visible have been recorded. Both ligand-field (LF) and charge-transfer (L --> M) bands have been identified and assigned, with the exception of the lowest energy LF band. The Angular Overlap Model has been used to calculate the LF band-maxima and compare with the observed band-maxima The ground-state energy-term for both Cu(Im)4SO4 and Cu(Im)4(ClO4)2 has been established with the use of ESR data to be 2B1g. Magnetic moment for the complexes have been obtained from precise magnetic susceptibility measurements with temperature variation and satisfactorily compared with the calculated values.

The electronic spectrum of Cu(II)(L-His)2 has been measured in the visible-near IR and UV regions. By assigning ligand field bands and by fitting the band maxima with calculated energies using angular overlap model, the structure of the complex has been deduced to be five-coordinate C4v1 The observed bands in the UV spectrum have been assigned as due to ligand-to-metal charge transfer transitions. Electronic spectra of Cu(II)(diphenylcarbazide)2 and Cr(II)(diphenylcarbazone)(H2O)4 complexes have also been measured. By interpretation of the ligand field bands in these spectra, tentative structures of these complexes in solution have been proposed.

The complexes of iodine with linear alkyl (C1, C8, C10 , C12 , C14 and C16) dimethylamine oxides have been studied in the solvents heptane,
dichloromethane, and water. In the solvents heptane and dichloromethane and in aqueous surfactant
micelles, alkyldimethylamine oxides react with iodine to form donor-acceptor
complexes. Trimethylamine oxide is not soluble in heptane and
does not form micelles in water so no complexes were fanned in these
systems. In heptane and in dichloromethane the molecular complex ionizes
to an "inner" complex in the presence of unassociated amine oxide. The
effect of the surface activity is to reduce the concentration of free
amine oxide and suppress this ionization. In the case of trimethylamine
oxide in dichloromethane forming the dihydrate suppresses inner complex
formation. In aqueous micelles the inner complex hydrolyzes to the protonated
amine oxide, iodide ion, and hypoiodous acid which appears to oxidize
water to molecular oxygen in the presence of the amine oxide micelles.
Excess iodine complexes with iodide ion yielding triiodide ion which
forms an undissociated ion pair with the micellar protonated amine oxide.

The polarized crystal spectra of a series of tetragonal
trans- diacidobis (ethylenediamine) chromium (III) complexes, trans-[Cr(en)2XY], where X= Y = Br-, H2O, F-, Cl- and X= H2O, Y = OH-, F-, have been measured at liquid nitrogen temperature,
achieving better resolution of the split components of the cubic spin-allowed
bands, and also definite energy level assignments. The
observed band positions have been fitted with the predicted transition
energies by the use of the appropriate energy equations for d^3 configuration
immersed in tetragonal fields with full configuration interaction.
The ligand field parameters, which include the cubic and axial, and the
electron correlation parameter B have been evaluated by such a fitting.
The derived parameters have been analyzed and their significance discussed.
Using thick crystals, we have uncovered a rich doublet
structure in some of the complexes and tentative values of the electron
correlation parameter C have been obtained for all the complexes.

The ligand field theory of complexes has been completely developed and the energy matrix elements for complexes in various geometries in different coupling schemes have been worked in considerable detail. However for many coupling schemes the computing of energy matrix elements is a tedious and laborious process. In the first part of my thesis we present a solution to the Weak-Field II problem using ladder operators and tensor operators. We used the Weak-Field II as an example to stress the complexity of computing energy matrix elements using ladder operators versus the simplicity of calculating matrix elements with tensor operators. Also the Weak-Field II was used as a model example hoping to be able to accomplish the same with the jj-II coupling scheme. In the last part of my thesis we present a derivation of simplifying expressions for the energy matrix elements for the d 2 complex in the jj-II coupling scheme. It is worth mentioning that the expressions derived can be applied to complexes other than octahedral and further they can be generalized for complexes with n-electrons in the valence shell. Finally, we present a thorough analysis of the electronic spectra of some Nickel(II) complexes.

We have studied the electronic spectra of tetragonal chromium (III) complexes namely trans-[Cr(NH3)4(CN)2]ClO4, trans-[Cr(en)2(CN)2]ClO4, and trans-[Cr(cyclam)(CN) 2]ClO4. These spectra have been analyzed by Gaussian analysis to locate the band maxima of the tetragonal components. The band maxima are then fitted with the tetragonal energy matrices of d3 configuration with full configuration interaction, neglecting spin-orbit interaction. The Dq, Dt, and Ds ligand field and the B and C electron correlation parameters have been extracted from the fitting procedure. The parameters have been analyzed to understand the bonding of these complexes. We have also uncovered the low intensity absorption doublet bands and a high intensity charge transfer band of trans-[Cr(en)2(CN)2]ClO4 which occur around 15,000cm-1 and 49,000cm-1, respectively.