Diarylphosphate as a New Route for Design of Highly Luminescent Ln Complexes

Organophosphate-chloride complexes [{(2,6-(i)Pr(2)C(6)H(3)-O)(2)POO}(2)LnCl(CH(3)OH)(4)]·2CH(3)OH, Ln = Nd (1), Eu (2), Gd (3), and Tb (4) have been obtained and structurally characterized. Their reaction with 2,2′:6′,2″-terpyridine leads to the formation of 1:1 adducts ([{(2,6-(i)Pr(2)C(6)H(3)-O)(2)POO}(2)LnCl(terpy)(H(2)O)(2)(CH(3)OH)], Ln = Eu (5), Gd (6), Tb (7) with exception of Nd, where tris-diisopropylphenylphosphate complex [{(2,6-(i)Pr(2)C(6)H(3)-O)(2)POO}(3)Nd) (terpy)(H(2)O)(CH(3)OH)] (8) was obtained due to the ligand metathesis. A bright luminescence observed for the Eu and Tb organophosphate complexes is the first example of an application of organophosphate ligands for 4f-ions luminescence sensitization. Photophysical properties of all complexes were analyzed by optical spectroscopy and an energy transfer scheme was discussed. A combination of two types of ligands into the coordination sphere (phosphate and phenanthroline) allows designing the Eu surrounding with very high intrinsic quantum yield [Formula: see text] (0.92) and highly luminescent Ln complexes for both visible and near-infrared (NIR) regions.