Various crystal structures based on 4,4′-(diethynylanthracene-9,10-diyl) dibenzoic acid: from 0D dimer to 3D net framework

Abstract

Three coordination polymers, {[Co₂(L)₂(H₂O)₈]·(H₂O)₂·(DMF)₂}_n (1), {[Cd₂(L)₂(H₂O)₅]·(H₂O)₂·(DMF)₂}_n (2), and {[Eu(L)_1.5(H₂O)₃]·(H₂O)·(DMF)₂}_n (3) (H₂L = 4,4′-(diethynylanthracene-9,10-diyl) dibenzoic acid) based on a new dicarboxylate ligand have been synthesized and structurally characterized, in which the di-carboxylate ligand could act as multi-dentate bridging linker with different connection modes to connect various metal ions. Complex 1 exhibits an oligomer structure containing a mono-dentate dicarboxylate ligand and di-nuclear cobalt joint. Complex 2 is a double-chained 1D wire based on a bidentate-chelating/bridging ligand and mono-Cd ion. In contrast, complex 3 possesses a 3D open framework based on an infinite Eu-(μ₂-OOC) chain and bridging ligands. In terms of the distinction between the three crystal structures, it is concluded that the coordination number and mode of metal ions and ligands play important roles in constructing the final crystal structure. In addition, the thermal stabilities and photoluminescence behavior of 1–3 and the gas sorption of 3 are further discussed in relative detail.