Synthesis, structure, and physicochernical investigations of the new alpha Cu0.50TiO(PO4) oxyphosphate

摘要

The room-temperature crystal structure of a new Cu(II) oxyphosphate-alpha(Cu0.50TiO)-Ti-II(PO4)-was determined from X-ray single crystals diffraction data, in the monoclinic system, space group P2(1)/c. The refinement from 5561 independent reflections lead to the following parameters: a = 7.5612(4)angstrom, b = 7.0919(4)angstrom, c = 7.4874(4),k, beta = 122.25(1)degrees, Z = 4, with the final R = 0.0198, wR = 0.0510. The structure of a (Cu0.50TiO)-Ti-II(PO4) can be described as a TiOPO4 framework constituted by chains of tilted corner-sharing [TiO6] octahedra running parallel to the c-axis and cross linked by phosphate [PO4] tetrahedra, where one-half of octahedral cavities created are occupied by Cu atoms. Ti atoms are displaced from the center of octahedra units in alternating long (2.308 angstrom) and short (1.722 angstrom) Ti-O(1) bonds along chains. Such O(1) atoms not linked to P atoms justify the oxyphosphate formulation alpha Cu0.50TiO(PO4). The divalent cations Cu2+ occupy a Jahn-Teller distorted octahedron sharing two faces with two [TiO6] octahedra. EPR and optical measurements are in good agreement with structural data. The X-ray diffraction results are supported by Raman and infrared spectroscopy studies that confirmed the existence of the infinite chains -Ti-O-Ti-O Ti-.alpha Cu0.50TiO(PO4) shows a Curie-Weiss paramagnetic behavior in the temperature range 4-80 K. (c) 2006 Published by Elsevier Inc.