Hydrothermal syntheses and structural characterization of two organic-inorganic hybrid compounds based on Lindqvist polyanions

摘要

Two organic-inorganic hybrid polyoxometalates {[V_2W_4O_(19){Cu(2,2'-bipy)_2}_2] centre dot (4,4'-bipy)}_n (1) and [Co(2,2'-bipy)_3][W_6O_(19)] centre dot H_2O (2) (2,2'-bipy = 2,2'-bipyridine, 4,4'-bipy = 4,4'-bipyridine), constructed by Lindqvist polyanions and transition metal coordination cations, have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR, UV spectra, thermogravimetric (TG) analyses, X-ray photoelectron spectroscopy (XPS), and single-crystal X-ray diffraction. Compound 1 is a neutral molecule and consists of a di-V~V substituted Lindqvist-type polyanion [V_2W_4O_(19)]~(4-), two supporting copper cations [Cu(2,2'-bipy)_2]~(2+) and one free 4,4'-bipy. Neutral molecules of 1 are extended to a 2-D grid-like network by pi-pi stacking interactions between pyridine groups. The molecular structure of 2 contains one [W_6O_(19)]~(2-) cluster polyanion and a [Co(2,2'-bipy)_3]~(2+). Inductively coupled plasma (ICP) analysis and XPS spectrum of 1 prove the presence of V~V. TG curves of 1 and 2 indicate two weight loss steps.