Structural Manipulation of Triboluminescent Lanthanide Coordination Polymers by Side-Group Alteration

Abstract

Novel Eu(III) coordination polymers with furan-based bridging ligands [Eu(hfa)3(Cy)]n and [Eu(hfa)3(Tol)]n (hfa: hexafluoroacetylacetonato, Cy: 2,5-bis(dicyclohexylphosphoryl)furan), Tol: 2,5-bis(di-p-tolylphosphoryl)furan) are reported. The rigidity of assembly steric structures was controlled by intermolecular interactions through the side groups in bridging ligands. They exhibited one of the best performances (thermal stability above 320 °C and external photoluminescence quantum yields of up to 71%) among reported lanthanide(III) compounds. The triboluminescence activity was demonstrated to be dependent on the mechanical stability of the coordination polymers, which was proportional to the number of hydrogen atoms in the side groups. The second example of a large TL/PL spectral difference in [Tb,Eu(hfa)3(Tol)]n also revealed discrete photophysical processes under the conditions of grinding and UV irradiation.