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Electron spin resonance and optical studies of doped copper (II) Tetrahedral complexes

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Cashion, SP (1989) Electron spin resonance and optical studies of doped copper (II) Tetrahedral complexes. Honours thesis, University of Tasmania.

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Abstract

This report presents an investigation of a pseudotetrahedral bromocuprate
(II) compound. The bromocuprates exhibit a great structural diversity, however,
the comparatively rare compressed tetrahedral compounds have been somewhat
neglected. The determination of the electronic and geometric structure of these
compounds has implications in the analysis of active sites in copper blue proteins.
Electron Spin Resonance (E.S.R.) and optical spectra have been
measured at low temperature, for single crystals of copper (II) doped into bis(
ethylenediammoniummonobromide) tetrabromozincate (II), ( enH.HBr)2 ZnBr4.
The room temperature powder reflectance spectrum has also been measured for this
compound, along with that of the pure zinc analogue.
The transition energies derived from the electronic spectra have been
assigned and compared to the respective transitions based on previous studies.
With the aid of a computer program, a set of theoretical transition energies has been
calculated utilizing the Angular Overlap Model. Adjusting these to fit the observed
values confirms the presence of a distorted tetrahedral geometry for the guest ion.
At 77K, the E.S.R. spectrum of (enH2)2Zn[Cu]Br6 exhibits well
resolved copper hyperfine and bromine superhyperfine couplings. Computer
simulation techniques have produced optimum values for these parameters, which
suggest that the principal z-axis of the superhyperfine tensor does not coincide with
the copper-bromine bond direction. The bonding in the guest [CuBr4]2- ion has
been described in terms of the relative unpaired electron density within the bromine
4s and 4p orbitals, which shows an increased covalency when compared with the
chlorine counterpart. A highly rhombic g tensor results in an unusual groundstate.
The calculated mixing coefficients and corresponding wavefunction parameters
show that the dz2 orbital makes a small but significant contribution by mixing with
the pure dx2-y2 orbital.

Item Type: Thesis (Honours)
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Date Deposited: 27 May 2014 06:05
Last Modified: 15 Sep 2017 01:06
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