Hydrothermal synthesis and structural characterization of three new transition-metal coordination polymers with 2-carboxycinnamic acid

Three new coordination polymers, [Zn2(CCA)2(bpy)]n·0.5nbpy (1), [Zn(CCA)(bpe)(H2O)]n·0.5nH2O (2) and [Mn(CCA)(bpe)]n·2nH2O (3) (H2CCA = 2-carboxycinnamic acid; bpy = 4,4′-bipyridine; bpe = 1,2-bis(4-pyridyl)ethane) have been synthesized by the hydrothermal reactions and characterized by single crystal X-ray diffraction, elemental analysis and IR spectrum. Although both complexes 1 and 2 possess 3D metal-organic frameworks, CCA ligands adopt different coordination modes in them. This can be attributed to the introduction of different auxiliary ligands bpy and bpe. In complex 3, CCA ligands link Mn(II) ions into 1D infinite double-strand helical chains and these chains are bridged by bpe to 2D layers. There are hydrogen bonds among the free water molecules, leading to the formation of 1D infinite water chains, which play an important role in the construction of the 3D microporous network. The fluorescent properties of complexes 1 and 2 have also been investigated.