A two-dimensional coordination polymer with Eu(III) luminescence sensitized by an aromatic 4,8-disulfonyl-2,6-naphthalenedicarboxylic acid ligand

A multifunctional ligand of 4,8-disulfonyl-2,6-naphthalenedicarboxylic acid (H4-DSNDA) and its Eu(III) coordination polymer {(H-dpp)[Eu(DSNDA)(H2O)4](H2O)4}n (dpp = 1,3-di(4-pyridyl)propane) (1) have been synthesized. Compound 1 is a 2D anionic network based on the paddle-wheel Eu2(CO2)4 building blocks charge-balanced by the monoprotonated H-dpp molecules. Compound 1 shows intense red characteristic europium(III)-centered emission. The Eu(III) emissive state exhibits a single-exponential decay with a lifetime of 0.212 ms as measured at 613 nm after excitation at 346 nm. No observable emission peak arising from the DSNDA4− ligand (λem = 408 nm) is observed in the emission spectrum of compound 1, indicating an efficient energy transfer occurs from DSNDA4− organic ligand to Eu(III) ions. The results reveal the large π-rich aromatic organic ligand is a suitable chromophoric moiety for sensitization of Eu(III) luminescence.