From two-dimensional trapezoid-like layer to three-dimensional porous indium-4,4′-biphenyldicarboxylate MOFs

Three new indium coordination polymers formulated as In(phen)(BPDA)(1.5) (1), In(OH)(H2O)(BPDA) (2), and In(BPDA)(2)center dot Me2NH2 center dot H2O (3) (phen = 1,10-phenanthroline, C12N2H8; H(2)BPDA = 4,4'-biphenyldicarboxylic acid, C14O4H10; Me2NH = dimethylamine, C2H7N), have been synthesized under hydro(solvo)thermal conditions and characterized by infrared (IR), thermal gravimetric analysis (TGA) and luminescence studies. In the two-dimensional (2D) trapezoid-like layer of 1, three BPDA2(-) anions and one phen group bind to a seven-coordinated In3+ ion with the distorted pentagonal bipyramid geometry. In 2, the extended -In-OH-In-chains are connected through BPDA(2-) to form a 3D framework. Complex 3 possesses a two-fold interpenetrating structure, which consists of two independent infinite diamond-like frameworks with point symbol 6(6). All three samples exhibit varied solid-state fluorescence: emissions at 468 nm (intense blue), 559 nm (greenish-yellow), and 577-645 nm (broad intense orange band with a maximum at 611 nm, lambda(ex) = 257 nm) for 1, 567 nm (weak greenish-yellow, lambda(ex) = 344 nm) for 2, and 480 nm (intense greenish-blue, lambda(ex) = 385 nm) for 3.