Long-range LMCT coupling in Eu(III) 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(III) and Gd(III), 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(III) ion in the Eu(III)-Gd(III) polymer. The emission quantum yield and the maximum relative temperature sensitivity ( S m ) of emission lifetimes for the Eu(III)-Gd(III) polymer (Eu:Gd = 1:1, Φ tot = 52%, S m = 3.73% K -1 ) were higher than those for the pure Eu(III) coordination polymer ( Φ tot = 36%, S m = 2.70% K -1 ), respectively. Enhanced temperature sensing properties are caused by control of long-range electronic coupling based on phosphine oxide with chrysene framework.