Influence of the Crystal Structure on the Luminescence Properties of Mixed Eu,La–(1,10‐Phenanthroline) Complexes

A series of europium Eu‐ and La‐doped complexes with two different crystal structures, namely, Eu x La 1– x (phen) 2 (NO 3 ) 3 [phen = 1,10‐phenanthroline, x = 1.0 ( 1 ), 0.88 ( 2 ), 0.73 ( 3 ), and 0.52 ( 4 )] and {[Eu x La 1– x (phen) 2 (H 2 O) 2 (NO 3 ) 2 ](NO 3 ) · 2(phen)(H 2 O)} [ x = 0.28 ( 5 ) and 0.0 ( 6 )], were synthesized in aqueous solution by using different Eu/La ratios.The complexes were characterized by single‐crystal and powder X‐ray diffraction, Fourier transform infrared spectroscopy, elemental analysis, thermogravimetry, and scanning electron microscopy. Compounds 1 – 4 and 5 , 6 were obtained for Eu/La molar ratios higher than 5:5 and smaller than 3:7, respectively. The photoluminescence properties of these compounds depend on the crystal structure, which is determined by the Eu/La reactant ratio. Complexes 1 – 4 exhibit a quantum efficiency ( η = 55 %) and quantum yield ( q = 31 %) higher than 5 ( η = 23 % and q = 6 %). The photophysical properties assessed by using the LUMPAC software are in good accord with the experimental values, particularly, the calculated (26 %) and measured emission quantum yields (31 %; excitation at the ligands at 255 nm).