Temperature Dependence of the Crystal Structure and g-Values of [(HC(Ph2PO)3)2Cu](ClO4)2·2H2O: Influence of Dynamic Jahn-Teller Coupling and Lattice Strain Interactions

The temperature dependence of the X-ray crystal structure and powder EPR spectrum of [(HC(Ph2PO)3)2Cu]-(ClO 4)2·2H2O is reported, and the structure at room temperature confirms that reported previously. Below ∼100 K, the data imply a geometry with near elongated tetragonal symmetry for the [(HC(Ph2PO)3)2Cu]2+ complex, but on warming the two higher Cu-O bond lengths and g-values progressively converge, and by 340 K the bond lengths correspond to a compressed tetragonal geometry. The data may be interpreted satisfactorily assuming an equilibrium among the energy levels of a Cu-O6 polyhedron subjected to Jahn-Teller vibronic coupling and a lattice strain. However, agreement with the experiment is obtained only if the orthorhombic component of the lattice strain decreases to a negligible value as the temperature approaches 340 K. © 2005 American Chemical Society.