Lanthanide(III) coordination polymers from the exo-coordination of Na +: Syntheses, structures, luminescence, and decay dynamics

Abstract

[Na 2[Ln 2( sal) 4(CF 3SO 3) 2(H 2O) 4](CF 3SO 3) 2] n Ln = Nd ( 1) and Eu ( 2) were synthesized from the reaction of salicylaldehyde, lanthanide(III) triflates, and sodium hydroxide. The compounds are iso-structural and possess a 2-D supramolecular network built up from discrete dinuclear Ln(III) units [Ln 2( sal) 4(CF 3SO 3) 2(H 2O) 4] via exo-coordination of Na(CF 3SO 3). The sal ligands display μ 2-O coordination modes involving both the phenolic and carbonyl oxygen atoms while the triflates function as both μ 2 and μ 3 bridges. Each Ln(III) in the network is eight coordinate and in bicapped trigonal prism coordination geometry. Luminescence from [Na 2[Eu 2( sal) 4(CF 3SO 3) 2(H 2O) 4](CF 3SO 3) 2] n showed temperature dependent sensitized emission with significant quadrupolar contribution and decay dynamical studies followed single exponential kinetics. Together these results indicate that in the presence of Na + ions, sal, and triflate are useful ligands in the construction of Ln(III) coordination polymers with unusual luminescence and structures.