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

Abstract

In this work, we present the synthesis of three novel 3D Cd(ii) coordination polymers, {[Cd(IN) 2 ]·H 2 O} n (1), [Cd 2 (IN) 2 (SO 4)(DMF) 2 ] n (2) and {[Cd 3 (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 (4·6 2) 2 (4 2 ·6 10 ·8 3) constructed from mononuclear [CdO 4 N 2 ] clusters with the help of HIN. 2 is defined as a 6-connected pcu net with the Schläfli symbol {4 12 ·6 3 } which is built from binuclear [Cd 2 (SO 2) 2 ] clusters and HIN linkers. 3 can be regarded as a 9-connected ncd net with the Schläfli symbol {3 6 ·4 22 ·5 8 }, which consists of paddlewheel trinuclear [Cd 3 (O 2 C) 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 > CH 3 OH > CH 2 Cl 2) and in the solid state. The lifetime of all the molecules is in microsecond scale. © The Royal Society of Chemistry.