Syntheses, structures and photoluminescence of a series of metal-organic complexes with 1,3,5-benzenetricarboxylate and pyrazino[2,3-f][1,10]-phenanthroline ligands

A series of new metal-organic coordination complexes, [Co-2(HBTC)(2)(Pyphen)(2)(H2O)(4)]center dot 4H(2)O (1), [Mn(HBTC)(Pyphen)(H2O)] (2), [Cd-2(OH)(BTC)(Pyphen)(2)]center dot H2O (3), [Cu-2(OH)(BTC)(Pyphen)] (4), and [Zn-2(OH)(BTC)(Pyphen)] (5) were prepared through hydrothermal reactions of pyrazino[2,3-f][1,10]-phenanthroline (Pyphen) and 1,3,5-benzenetricarboxylic acid (H3BTC) with different metal salts. All these compounds were structurally determined by X-ray single-crystal diffraction. In the dinuclear Co(II) compound (1) pi-pi interactions exist between Pyphen and HBTC2- ligands, resulting in interesting 2D supramolecular layers. For complex (2), the Mn(II) centers are linked by HBTC2- ligands to form a 2D (4,4) coordination layer, and these layers are interdigitated in pairs. Polymer (3) also possesses a 2D network structure composed of the tetrametallic clusters [Cd-4(mu(2)-OH)(2)], which is extended to 3D arrays through the pi-pi interactions between Pyphen ligands. The isostructural coordination polymers (4) and (5) show the same 3D framework structure. Solid-state luminescent spectra of the Cd(II) and Zn(II) complexes indicate intense fluorescent emissions.