Light Conversion Control in NIR-Emissive Optical Materials Based on Heterolanthanide Er_xYb_3-x Quinolinolato Molecular Components

Homo- and heterobimetallic homoleptic complexes of general formula Er_xYb_3-xQ₉ (Q = 8-quinolinolato; x = 0, 1; x = 1, 2; x = 2, 3) and the corresponding heteroleptic complexes Er_xYb_3-xQ₈NO₃ (x = 0, 1b; x = 1, 2b; x = 2, 3b), where one Q ligand is replaced by a nitrate anion, have been synthesized and fully characterized by means of compositional (energy-dispersive X-ray spectrometry, inductively-coupled plasma-mass spectrometry, and electrospray ionization mass spectrometry) and structural (X-ray diffraction) investigations to study the effects of ligand substitution and variation of metal composition on their chemical and photophysical properties. Advanced spectroscopic and photophysical studies in the visible and near-infrared spectral regions have allowed the achievement of a detailed picture of the photocycle leading to narrow-band lanthanide luminescent emission, providing evidence of highly efficient ligand-to-metal and metal-to-metal (Yb-to-Er) resonance energy transfers thanks to the short intermetallic distances in heterolanthanide molecular species. Highly homogeneous silica thin films doped with 2 have shown to retain the optical properties of the dopant complex in solution, proving the suitability of this class of complexes for preparing Er/Yb codoped optical materials for potential applications as waveguides or amplifiers with controlled composition and distribution of the optically active metals.