Hydrothermal synthesis, crystal structure and luminescence of four novel metal–organic frameworks

Using the principle of crystal engineering, four novel metal–organic coordination polymers, {[Cd1(nic)2(H2O)]2[Cd2(nic)2(H2O)2]}n (1), [Cd2(fma)2(phen)2]n (2), [Cd(fma)(bipy)(H2O)]n (3) and [Zn(mal)(bipy)·3H2O]n (4) (nic=nicotinate, fma=fumarate, mal=malate, phen=phenanthroline, bipy=2,2′-bipyridine) have been synthesized by hydrothermal reaction of M(CH3COO)2·2H2O (M=Zn, Cd) with nicotinic acid, fumaric acid and cooperative L (L=phen, bipy), respectively. X-ray analysis reveals that complex 1 possesses an unprecedented two-dimensional topology structure constructed from three-ply-like layers, complex 2 is an infinite 2D undulating network, complex 3 is a 1D zigzag chain and complex 4 belongs to a 1D chain. The results indicate a transformation of fumarate into malate during the course of hydrothermal treatment of complex 4. The photophysical properties have been investigated with luminescent excitation and emission spectra.