Luminescent Europium(III) Coordination Zippers Linked with Thiophene-Based Bridges

Abstract

Novel Eu(III) coordination polymers [Eu(hfa)3 (dpt)]n (dpt: 2,5-bis(diphenylphosphoryl)thiophene) and [Eu(hfa)3 (dpedot)]n (dpedot: 2,5-bis(diphenylphosphoryl)ethylenedioxythiophene) with hydrogen-bonded zipper structures are reported. The coordination polymers are composed of Eu(III) ions, hexafluoroacetylacetonato ligands, and thiophene-based phosphine oxide bridges. The zig-zag orientation of single polymer chains induced the formation of densely packed coordination structures with multiple intermolecular interactions, resulting in thermal stability above 300 °C. They exhibit a high intrinsic emission quantum yield (ca. 80 %) due to their asymmetrical and low-vibrational coordination structures around Eu(III) ions. Furthermore, the characteristic alternative orientation of substituents also contributes to the dramatically high ligand-to-metal energy transfer efficiencies of up to 80 % in the solid state.

Keywords: coordination polymers; energy transfer; europium; luminescence; thermal stability.