Photo-Click Chemistry to Design Highly Efficient Lanthanide beta-Diketonate Complexes Stable under UV Irradiation
authors Lima, PP; Nolasco, MM; Paz, FAA; Ferreira, RAS; Longo, RL; Malta, OL; Carlos, LD
nationality International
journal CHEMISTRY OF MATERIALS
author keywords Eu3+ and Gd3+ complexes; trans-to-cis photoisomerization; trans-1,2-bis(4-pyridyl)ethylene; luminescence intensity and quantum yield enhancement; photostability mechanism; degradation under UV irradiation
keywords ORGANIC-INORGANIC HYBRIDS; TRANSFER EXCITED-STATES; TO-CIS ISOMERIZATION; LUMINESCENT MATERIALS; CONICAL INTERSECTIONS; ENERGY-TRANSFER; EUROPIUM; LIGAND; PHOTOISOMERIZATION; EU(III)
abstract Europium (t-Eu) and gadolinium (t-Gd) beta-diketonate complexes with photoactive t-bpete ligand, [Ln-(btfa)(3)(t-bpete)(MeOH)] (Ln = Eu, Gd), where btfa(-) and t-bpete are 4,4,4-trifluoro-1-phenyl-1,3-butanedionate and trans-1,2bis(4-pyridyl)ethylene, respectively, were synthesized, characterized by vibrational, absorption (reflectance) and photoluminescence spectroscopies and their crystal structure was determined using single-crystal X-ray diffraction. B3LYP calculations were performed to support the interpretation and rationalization of the experimental results. The complexes, under UV irradiation, do not display the typical photodegradation of the beta-diketonate ligands exhibiting, in turn, an unprecedented photostability during, at least, 10 h. During UV-A exposure (>330 nm), the emission intensities of both complexes increase drastically (similar to 20 times), whereas for t-Eu the emission quantum yield is enhanced at least 30 fold A mechanism based on a photoclick trans-to-cis isomerization of both t- and c-bpete moieties was proposed to explain the abnormal photostability of these compounds, either in solid state or in solution. The experimental and computational results are consistent with a photostationary state involving the trans-to-cis isomerization of the bpete ligand under continuous UV -A exposure, which thus diverts the incident radiation from other deleterious photochemical or photophysical processes that cause the typical photobleaching behavior of chelate lanthanide complexes. This shielding mechanism could be extended to other ligands permitting the design of new lanthanide-based photostable systems under UV exposure for applications in lighting, sensing, and displays.
publisher AMER CHEMICAL SOC
issn 0897-4756
year published 2013
volume 25
issue 4
beginning page 586
ending page 598
digital object identifier (doi) 10.1021/cm303776x
web of science category Chemistry, Physical; Materials Science, Multidisciplinary
subject category Chemistry; Materials Science
unique article identifier WOS:000315618500010
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