The dependence of the spin-Hamiltonian parameters of the [Ti(OH2)6]3+ cation on the mode of water co-ordination
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Single crystal X-band EPR spectra of Ti(III) doped C(NH2)3MIII(SO4)2 ·6H2O Gu[MIII:Ti]SH, MIII = GaIII, A1III) collected at ∼1.9 K, are presented. Principal g values for Gu[Ga:Ti]SH and Gu[A1:Ti]SH of g∥ ∼ 0.965, g⊥ ∼ 0, and g∥ ∼ 0.984, g⊥ ∼ 0, respectively, are derived. The values of g∥are significantly less than that previously reported for Cs[Ga:Ti]SH (g∥∼ 1.161) and this work is principally concerned with accounting for the difference. Analytical expressions are derived for the first-order Jahn-Teller coupling coefficients between the states comprising the 2Tg (Th) ground term and the twisting librations of the coordinating water molecules, in the framework of the Angular Overlap Model (AOM); and, values of g∥ computed by numerical diagonalisation of the vibronic Hamiltonian. On the basis of differences in the mode of water co-ordination alone, g∥is calculated to increase from 0.965 (Gu[Ga:Ti]SH) to ∼1.10 (Cs[Ga:Ti]SH), in fair agreement with experiment. The EPR spectra of Gu[Ga:Ti]SH contain well-resolved proton superhyperfine structure. The magnitude of the superhyperfine coupling constant far exceeds that inferred from the EPR spectrum of Cs[Ga:Ti]SH, and this too is rationalised in terms of the different stereochemistries of the [Ti(OH2)6]3+ cation in the two crystal systems.
Original language | English |
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Journal | Chemical Physics |
Volume | 282 |
Issue number | 2 |
Pages (from-to) | 245-263 |
Number of pages | 19 |
ISSN | 0301-0104 |
DOIs | |
Publication status | Published - 1 Sep 2002 |
ID: 240003257