Synthesis, characterization, crystal structures and photophysical properties of pillar-layer nickel metal-organic frameworks based on 2-aminoterepthalic acid and 5-aminoisopthalic acid

Five new compounds, [Ni2(2-NH2BDC)2(bipy)2(H2O)4](1), [Ni(5-aip)(phen)(H2O)3].2H2O (2), [Ni4(5-aip)3(bipy)3(H2O)7]. 19H2O (3), [Ni(5-aip)(bipy)(H2O)]n·2H2ODMF (4), and [Ni2(2-NH2BDC)2(phen)2(H2O)4](5) based on 5-aminoisophthalic acid and 2-aminoterepthalic acid, have been synthesized at room temperature using methanol and water solvent mixture and structurally determined using single crystal X-ray diffraction.Compounds 1–3 are discret complex while compound 4 shows two-dimensional (2D) pillar-layer architecture. In all these compounds, channels are observed through CH···O interactions between adjacent molecules. Compounds 1–5 displayed one broad emission band with a center at 384 nm when excited 294 nm in their solid state at room temperature, attributed to ligand-to-metal charge transfer. In comparison with emission peaks of 5-aminoisophthalic acid and 2-aminoterepthalic acid, the luminescent emissions of these compounds are blue-shifted due to a decrease of the energy gap between the ground and excited states in the ligand upon complexation with Ni(II).