Syntheses, crystal structures and luminescent properties of three new gallium complexes containing pyridine-2,6-dicarboxylic acid

Three new gallium complexes formulated as [Ga(PDA)₂][Ga(H₂O)(PDA)(phen)]·4H₂O(1), [Ga(PDA)2]· (H₂IN)·2H₂O(2) and [Ga(OH)(PDA)(H₂O)]2(3)(H₂PDA=pyridine-2,6-dicarboxylic acid; phen=1,10-phenanthroline; HIN=isonicotinic acid) have been synthesized under hydrothermal conditions. In the mixed-ligand system of complex 1, PDA^2- and phen are connected to the central Ga³⁺ cation as tri- and bi-dentate ligands, respectively. In complex 2, each Ga³⁺ cation is six-coordinated by two PDA^2- anions octahedrally. Complex 3 shows a binuclear structure, with the bond distance of Ga1-Ga2 being 0.30061(3) nm. The 3D supramolecular structures of the three complexes are constructed via hydrogen bonds and aromatic π-π packing interactions. All the three complexes exhibit intense blue emission at room temperature in the solid state, which are attributed to π^*-π transition centered on the ligands.