Coumarin-lanthanide based compounds with SMM behavior and high quantum yield luminescence

Coumarin-based lanthanide complexes of general formula [Ln(coum) 3 (phen)(H 2 O) x ]· y H 2 O ( Ln-phen , x = 0,1, 0 ≤ y ≤ 1.5; phen = 1,10-phenanthroline; coum = 3-acetyl-4-hydroxylato-coumarin; Ln = Eu, Tb, Dy, Tm) and [Ln(coum) 3 (batho)]·0.7EtOH ( Ln-batho , batho = 4,7-diphenyl-1,10-phenanthroline; Ln = Eu, Tb, Dy, Tm) were synthesized. The magnetic relaxation and photoluminescence behavior of these complexes was compared with that of the related compounds [Ln(coum) 3 (EtOH)(H 2 O)]·EtOH ( Ln-coum ), so as to investigate the effects of incorporating a second chromophore, either the phen or batho ligand, to the original coordination scaffold, provided with three coumarin (coum) ligands. Slow relaxation of the magnetization under H = 0 with moderate activation energies was observed for the Dy-phen ( U / k B = 99.1 K) and Dy-batho ( U / k B = 67.1 K) compounds, whereas Tb analogues presented field-induced single molecule magnet (SMM) behavior, with U / k B = 11.7 K (16.6 K@3 kOe) for Tb-phen ( Tb-batho ), respectively. Luminescent emission in the visible range was observed for all the Ln-coumarin based compounds upon ligand sensitization, with high quantum yields of 45 (40%) for Eu-phen ( Eu-batho ) compounds and 65-76-58% for Tb-coum , phen , batho analogues. Sensitization is mainly provided by the coumarin ligand having the energy difference Δ E between its triplet state T 1 and the lanthanide emitting level closest to the optimum, while the second ligand can play either a synergistic or competing sensitizing role. The Tb-phen/batho compounds presented simultaneously SMM and luminescent behavior, with excellent values of the bifunctional figure of merit ( η SMM-QY ∼ 1000% K). The reported compounds represent a new class of bifunctional materials with potential interesting application in various fields. The new synthesized complexes [Ln(coum) 3 (phen)(H 2 O) x ]· y H 2 O and [Ln(coum) 3 (batho)]·0.7EtOH are interesting bifunctional materials combining high quantum yield luminescence and SMM behavior.