Synthesis, Crystal structure and Luminescent Property of a New 3D Supramolecular Compound (C6H6NO2)3(C6H5NO2)(PW12O40)•2H2O

A supramolecular compound (C6H6NO2)(3)(C6H5NO2)(PW12O40)center dot 2H(2)O including the Keggin-type [PW12O40](3-) polyanion, [HC6H5NO2] (protonated pyridine-4-carboxylic acid molecule), C6H5NO2(pyridine-4-carboxylic acid molecule) and two free H2O molecules has been synthesized by the hydrothermal method and characterized by elemental analysis, IR spectra, single-crystal X-ray diffraction and powder X-ray diffraction. The crystal belongs to orthorhombic, space group Pnnm with a = 1.0483(3), b = 1.4368(6), c = 2.0526(7) nm, V = 3.0918(18) nm(3), Z = 2, F(000) = 3004, M-r = 3406.07, D-c = 1.757 g-m(-3), mu = 41.241 mm(-1), the final R = 0.0387 and wR = 0.1089 for 2091 observed reflections with I> 2 sigma(I) A total of 30431 reflections were collected, of which 3083 were independent (R-int = 0.0605). 5 is 1.182. The title compound presents a 3-D structure via intermolecular hydrogen bonds among [PW12O40](3-) polyanions and pyridine-4-carboxylic acid ligands. The ultraviolet and luminescence spectra have been studied at room temperature, of which the purple fluorescent emission is located at 363 nm when excited at 264 nm. Fluorescent emission of the compound derives from the pi-pi transitions in the pyridine-4-carboxylic acid ligands.