Synthesis, structure and luminescence of two europium complexes of diphenylimidazophenanthrolines

Abstract

Two new europium coordination compounds, [Eu₂(papip)₂(PhCOO)₆] and [Eu₂(phpip)₂(PhCOO)₆] (papip is 1-phenyl-2-(4-aminophenyl)imidazo[4,5-f][1,10]phenanthroline and phpip 1-phenyl-2-(4-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline), have been synthesized hydrothermally and structurally characterized, involving the in situ hydrolysis of phenylacetonitrile to phenylacetate. The –NH₂ group in the former complex was unexpectedly generated from the –NO₂ group of free 1-phenyl-2-(4-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline during the reaction process, representing the first such transformation in a hydrothermal reaction. Both complexes exhibit bright red photoemission typical of Eu(III) f–f transition under UV excitation, with long excited state lifetimes and quite high photoluminescence quantum yields.