Auxiliary aromatic-acid effect on the structures of a series of Zn coordination polymers: Syntheses, crystal structures, and photoluminescence properties

Five novel Zn^II-(pyridyl)imidazole derivative coordination polymers, [Zn(L)₂] (1), [Zn₂(μ₃-OH)L(m-BDC)] (2), [Zn₂(μ₃-OH)L(p-BDC)]·H₂O (3), [Zn₂L(BTC)(H₂O)]·2.5H₂O (4) and [Zn_3.5(μ₃-OH)L₂(BTEC)(H₂O)]·H₂O (5) (L=4-((2-(pyridine-2-yl)-1H-imidazol-1-yl)methyl)benzoic acid, p-H₂BDC=1,4-benzenedicarboxylic acid, m-H₂BDC=1,3-benzenedicarboxylic acid, H₃BTC=1,3,5-benzenetricarboxylic acid, H₄BTEC=1,2,4,5-benzenetetracarboxylic acid), were successfully synthesized under hydrothermal conditions through varying auxiliary aromatic-acid ligands and structurally characterized by X-ray crystallography. Compound 1 exhibits a 1D chain linked via double L bridges. Compound 2 features a well-known pcu topology with bent dicarboxylate ligand (m-H₂BDC) as an auxiliary ligand, while 3 displays a bcu network with linear dicarboxylate ligand (p-H₂BDC) as an auxiliary ligand. The structure of compound 4 is a novel 3D (3,5)-connected network with (4·6²)(4·6⁴·8²·10·12²) topology. It is interesting that compound 5 shows an intricate (3,4,8)-connected framework with (4·6²)(4²·6³·8)(4²·6⁴)(4²·6¹⁸·7·8⁶·10) topology. In addition, their infrared spectra (IR), X-ray powder diffraction (XPRD) and photoluminescent properties were also investigated in detail.