Synthesis and fluorescence of multi-dimensional structures of two cobalt (II) complexes between 2,2′-bipyridine and different chain length of aliphatic dicarboxylic, succinic or glutaric acid

Two coordination polymers [Co(μ-succinato)(H2O)2(2,2′-bipy)] 1 and [Co2(μ-H2O)(μ-glutarato)2(2,2′-bipy)2] 2 have been synthesized and characterized by single crystal X-ray diffraction, IR, thermal analysis (TGA) and fluorescence measurement. The crystallographic analysis reveals that these two compounds exhibit different in structures. Compound 1, cobalt (II) complex with succinic acid shows 1-D helical chain whereas compound 2, cobalt (II) complex with glutaric acid shows 1-D dinuclear polymeric chain. In compound 1, hydrogen bond are formed between water of crystalline, coordination water and uncoordinated carboxyl group of succinate ligand with adjacent chain extended 1-D chain into 2-D layer and also weak π–π interaction extend 2-D layer into 3-D network. Compound 2, π–π interaction between 2,2′-bipyridine in adjacent chain are formed resulting in 2-D layer. Each 2-D layer form Van der Waals interaction to each other building 3-D framework. In addition, these two compounds exhibit strong fluorescence at room temperature in the solid state.