Photodynamics and Luminescence of Mono‐ and Tri‐Nuclear Lanthanide Complexes in the Gas Phase and in Solution

• Published in: Chemphyschem 2018-11, Vol.19 (22), p.3050-3060
• Main Authors: Liedy, Florian, Bäppler, Florian, Waldt, Eugen, Nosenko, Yevgeniy, Imanbaew, Dimitri, Bhunia, Asamanjoy, Yadav, Munendra, Diller, Rolf, Kappes, Manfred M., Roesky, Peter W., Schooss, Detlef, Riehn, Christoph
• Format: Article
• Language: English
• Subjects: Absorption spectra; Benzoic acid; Coordination compounds; Dysprosium; Emission; gas-phase luminescence; Imines; lanthanides; Ligands; Luminescence; multimetallic complexes; Photoexcitation; photofragmentation; Sensors; Strong interactions (field theory); transient absorption; Vapor phases
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201800599

Lanthanide ions (DyIII, EuIII) are stabilized by coordination with two Schiff base ligands in compounds [Dy{H3L}2](NO3)(EtOH)(H2O)8 (1) and [Eu{H3L}2](NO3)(H2O)8 (3) (H4L, 2,2′‐{[(2‐aminoethyl)imino]bis[2,1‐ethanediyl‐nitriloethylidyne]}bis‐2‐hydroxy‐benzoic acid). The latter is reported here for the first time. Both luminescence and ultrafast photodynamics after photoexcitation via a ligand absorption band (∼400 nm) have been studied. In solution, only the [Eu{H3L}2]+ ([3]+) complex displays the typical lanthanide emission lines, whereas in gas phase both, [Dy{H3L}2]+ ([1]+) and [3]+, show their corresponding transitions depending on excitation energy. The ultrafast excited state dynamics, obtained in gas phase and in solution, are assigned to excited state intramolecular proton transfer processes in the ligands. The antenna ligand moiety of these complexes provides pockets for stabilization of two MnII ions so that we additionally investigated the photophysical behavior of the corresponding tri‐nuclear (NHEt3)2[Ln{MnL}2](ClO4)(H2O)2 (Ln=DyIII, EuIII) compounds (2, 4). Interestingly, the related complexes do not show lanthanide emission, neither in solution nor in gas phase. Transient data in solution and gas phase suggests an efficient quenching of the ligand's electronically excited state by strong interaction with the MnII ions. This effect could possibly be developed further into a design principle for luminescence‐based sensing devices for metal cations. Lanthanide emission quenching: The luminescence and ultrafast electronic dynamics of new DyIII and EuIII Schiff‐base‐analogue complexes are recorded in solution and in the gas phase. Upon incorporation of MnII into the complexes, an excited‐state lifetime shortening as well as efficient quenching of the lanthanide luminescence are observed.