Effects of solvents and temperature on the luminescence properties of Cd-isonicotinic acid frameworks based on mono-, bi-, and trinuclear cluster units.

In this work, we present the synthesis of three novel 3D Cd(II) coordination polymers, {[Cd(IN)2].H2O}n (1), [Cd2(IN)2(SO4)(DMF)2]n (2) and {[Cd3(IN)5.5].0.5OH-}n (3) (HIN = isonicotinic acid). Coordination polymers 1 and 2 were obtained via solvothermal reactions. The synthesis of coordination polymer 3 was realized by a simple temperature induced single crystal to single crystal transition from 1. Single-crystal X-ray diffraction analyses revealed that 1-3 exhibit three different structural types: 1 displays a (6,3)-connected rtl net with the Schläfli symbol (4.62)2 (42.610.83) constructed from mononuclear [CdO4N2] clusters with the help of HIN. 2 is defined as a 6-connected pcu net with the Schläfli symbol {412.63} which is built from binuclear [Cd2(SO2)2] clusters and HIN linkers. 3 can be regarded as a 9-connected ncd net with the Schläfli symbol {36.422.58}, which consists of paddlewheel trinuclear [Cd3(O2C)5] clusters and a bridging HIN. Coordination polymers 1-3 display luminescence with emission maxima containing deep blue, blue, light blue and green at 298 K or 77 K both in solvents (polarity: DMF > CH3OH > CH2Cl2) and in the solid state. The lifetime of all the molecules is in microsecond scale. [ABSTRACT FROM AUTHOR]