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Lantanide(III) ions sensitized by crown ethers as precursors of heteroleptic bimetallic luminescent complexes with metals in block d: synthesis, characterization and evaluation of optical properties

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Author(s):
Rodolpho Alessandro Nesta Silva
Total Authors: 1
Document type: Master's Dissertation
Press: Araraquara. 2020-02-27.
Institution: Universidade Estadual Paulista (Unesp). Instituto de Química. Araraquara
Defense date:
Advisor: Ana Maria Pires; Marian Rosaly Davolos; Sergio Antonio Marques de Lima
Abstract

In this study, the synthesis, step by step, and structural and optical characterization of a heterobimetallic system containing Eu3+ coordinated to the ether crown 18crown-6 (18C6) in association with Ni2+ coordinated to deprotonated dibenzoylmethane (dbm) were developed, to evaluate their applicability in light converting optical devices. The bridged 2,2'-bipyrimidine (bpm) ligand was used to join the two complexes and bimetallic formation. The crown ether and the donor N-N ligands had the function of decreasing the probability of coordination of water molecules (luminescent quenchers) to the emitting center and acting as sensitizers, respectively. Isostructural complexes containing Gd3+ were also synthesized for the determination of ligand triplet states in all systems. At the same time, a synthetic route for a new crown ether ligand, dibenzo-18crown-4, DB18C4, was developed which, due to the delay in the improvement of the involved steps, could not be tested in the production of the complexes. All synthesized complexes containing 18C6 crown ether were characterized via FTIR, UV-Vis, complexometric titration, thermal analysis, mass spectrometry and luminescence spectroscopy. The new synthesized ligand, DB18C4, was characterized by FTIR, UV-Vis, mass spectrometry, 1H, 13C NMR, and HH COSY, elemental analysis and its structure was determined by single crystal X-ray diffraction. FTIR data confirmed the formation of the compounds and from thermal analysis and mass spectrometry it was possible to propose the most probable stoichiometry, as follows: [EuCl3(18C6)(H2O)3], [EuCl(18C6)(bpm)2(H2O)]Cl2◦H2O, and [Eu(18C6)(EtOH)(-bpm)2(Ni(dbm)2)2]Cl3. All synthesized complexes emit from orange to red with high color purity. This emission, characteristic of Eu3+, was only possible due to the sensitization of the emitting ion by the donor N-N ligands, since the precursor europium(III) complex exhibited very low luminescent response when compared to the others. And in the bimetallic complex there was a slight lowering of the triplet state of the ligands attributed to the spin-orbit coupling caused by nickel(II). Due to the high color purity, the complexes were considered promising for applications in molecular light-converting devices. The new ligand, which was successfully synthesized and its structure elucidated by the set of techniques used, opens future perspectives in the production of new more efficient complexes, since it will probably also act as a sensitizer in the Eu3+ coordination sphere. (AU)

FAPESP's process: 18/08978-3 - Lantanoid(III) ions sensitized by crown ethers as precursors of bimetallic luminescent heteroleptic complexes with block metals d: synthesis, characterization and evaluation of optical properties
Grantee:Rodolpho Alessandro Nesta Silva
Support type: Scholarships in Brazil - Master