Interpretation of the temperature dependent g values of the Cu(H2O)2+6 ion in several host lattices using a dynamic vibronic coupling model

Abstract

State selected ion-molecule reactions by a TESICO technique. VI. Vibronic-state dependence of the cross sections in the reactions O+ 2(X 2Π g , v; a 4Π u , v)+H2→ O2H++H, H+ 2+O2 J. Chem. Phys. 77, 4441 (1982) The causes of the previously reported temperature dependence of the g values of the CU(H20)~ + ions in Cu 2 + doped Zn(H 2 0)6(GeF 6 ) and the Tutton's salts M 2 Zn(H 2 0)6(S04)2' where M = K+, Rb+, NH 4 +, and Cs+, supplemented by new experimental measurements on the K + salt, have been investigated. The ground state dynamics of the complexes have been modeled on the cubic E X E J ahn-Teller Hamiltonian perturbed by an orthorhombic lattice strain. For each compound, the vibronic energy levels and associated wave functions were calculated numerically, the overall g values at any temperature being given by a thermal average of the g values of the individual vibronic energy levels, because of rapid exchange between the levels. For the Tutton's salts it was found that the low temperature g values are strongly influenced by the tetragonal component of the lattice strain, with this corresponding to an axial compression of the ligand field. The temperature dependence of the g tensors, on the other hand, was found to depend largely on the orthorhombic component of the lattice strain. For the K + and NH4+ salts, where structural data are available, the strain parameters derived using the model are in good agreement with the geometries reported for the Zn (H 2 0) ~ + host complexes. For Cu2+ doped Zn(H 2 0)6(GeF 6 ) the model implies a lattice strain of tetragonal symmetry corresponding to a slight elongation of the axial metal-ligand bonds. The results are compared with those reported previously by Silver and Getz, and other workers, who used a simple model involving temperature dependent equilibria between energy levels corresponding to different orientations of the Cu (H 2 0) ~ + ions in the host lattices to interpret the temperature dependence of the g tensors.

Structure, Disorder, and Molecular Dynamics in Zn(d,l-histidine)2: EPR of Copper Ion Dopants, X-ray Diffraction, and Calorimetric Studies

“…The height of the barrier ∆E* (defined in Figure 13a) may be estimated proposing for ν h an activated process. Assuming that the tunneling splitting between the energies of states I and II is smaller than the barrier height ∆E*, we use the prediction of transition state theory: 10,[50][51][52] with T ) T c , to obtain from ν h an activation energy ∆E* ≈ 1600 cm -1 . The change of ν h with temperature (eq 8) produces at T c the collapse of the resonances (Figure 11).…”

“…The investigation of vibronic couplings in copper ions started with the early study of a highly symmetric system by Bleaney and Ingram, 4 and was followed by studies of systems with lower symmetries performed by several authors. 3,[5][6][7][8][9][10][11][12] Metal amino acid complexes are useful to model the bonding and properties of metal ions in metaloproteins. 13 An important ligand to metal ions is the amino acid histidine, and many investigations dealing with complexes of histidine with metal ions have been reported.…”

DFT-Based Studies on the Jahn−Teller Effect in 3d Hexacyanometalates with Orbitally Degenerate Ground States

“…33 (7) Dynamic JT coupling in addition to the structural strain is found in solids and produces interesting effects on the g tensor values and to a lesser extent on the magnetic susceptibilities with JT active E g or T g ground states. [56][57][58][59][60][61][62][63][64][65] These deserve further experimental studies.…”

Effects of Vibronic Dynamics of Cu(H2O)6Complexes and Electron Spin Relaxation in Temperature Dependence of EPR Linewidth in Diamagnetic Tutton Salt Single Crystals

“…At low temperatures the complexes are localized in the deepest well but an increase in temperature produces reorientations (jumps) between the wells observed as progressive g-factor averaging [11]. The increase in the linewidth appears at these temperatures where an onset of the g-factors averaging can be seen.…”