Long-Range LMCT Coupling in Eu Coordination Polymers for an Effective Molecular Luminescent Thermometer*.

A design for an effective molecular luminescent thermometer based on long-range electronic coupling in lanthanide coordination polymers is proposed. The coordination polymers are composed of lanthanide ions Eu and Gd , three anionic ligands (hexafluoroacetylacetonate), and a chrysene-based phosphine oxide bridges (6,12-bis(diphenylphosphoryl)chrysene). The zig-zag orientation of the single polymer chains induces the formation of packed coordination structures containing multiple sites for CH-F intermolecular interactions, resulting in thermal stability above 350 °C. The electronic coupling is controlled by changing the concentration of the Gd ion in the Eu -Gd polymer. The emission quantum yield and the maximum relative temperature sensitivity (S ) of emission lifetimes for the Eu -Gd polymer (Eu:Gd=1:1, Φ =52 %, S =3.73 % K ) were higher than those for the pure Eu coordination polymer (Φ =36 %, S =2.70 % K ), respectively. Enhanced temperature sensing properties are caused by control of long-range electronic coupling based on phosphine oxide with chrysene framework.