Evaporable luminescent lanthanide complexes based on novel tridentate ligand

Abstract

A novel tridentate ligand N-(6-(diphenylphosphoryl)pyridin-2-yl)-2,2,2-trifluoroacetamide (DPPOPFA) was designed and synthesized. Crystal structure of the ligand revealed the “keto” form of ligand in solid state other than the “enol” one, and it was also found that two kinds of molecules with different conformations were connected by hydrogen bonding between amide N–H and phosphoryl P=O. This ionic ligand was used to coordinate a variety of lanthanide ions, forming neutral 3:1 complexes. Absolute overall quantum yields of these complexes in solid states were 36% for Eu(III), 29% for Tb(III) and 3% for Dy(III) with lifetimes of 1.1, 1.1 and 0.087 ms, respectively. The complexes had excellent thermal stability and did not decompose till 370 °C. And they could sublimate in vacuum (1×10−4 Pa) at 330 °C due to the weak molecular interaction.