Synthesis, X-ray Structure, Spectroscopic Characterization, and Theoretical Prediction of the Structure and Electronic Spectrum of Eu(btfa)₃·bipy and an Assessment of the Effect of Fluorine as a β-Diketone Substituent on the Ligand−Metal Energy Transfer Process

Abstract

The 2,2'-dipyridyl adducts of two europium beta-diketonate complexes, Eu(btfa)(3).bipy [btfa = 4,4,4-trifluoro-1-phenyl-2,4-butanedione, bipy = 2,2'-dipyridyl] and Eu(bzac)(3).bipy [bzac = 1-phenyl-2,4-butanedione], have been prepared. The crystal structure of the former with chemical formula EuC(40)H(26)O(6)N(2)F(9) has been solved by single-crystal X-ray diffraction methods. The complex crystallizes in the monoclinic space group P2(1)/n with a = 11.122(5) Å, b = 22.860(8) Å, c = 15.870(6) Å, beta = 102.62(3)(o), V = 3937(5) Å(3), and Z = 4. A single, eight-coordinate environment, which approximates a square antiprism, is found for the europium(III). The UV absorption spectra of both complexes were obtained from ethanol solutions and, in the case of Eu(btfa)(3).bipy, from a thin film. In both cases the absorption spectra are reasonably well predicted by the INDO/S-CI method using, for Eu(btfa)(3).bipy, both the X-ray data and that obtained through the SMLC/AM1 method as input geometry and, for Eu(bzac)(3).bipy, that obtained through the SMLC/AM1 method. There is a blue shift of the calculated spectra relative to the solution spectra and a slightly larger blue shift compared to the spectrum of the thin film. Both complexes are luminescent under near-UV excitation, and the spectra are in accord with the existence of a single emitting site in each. The increased quantum yield in the fluorinated complex is correlated with a decrease in the bipy-europium(III) distance, a closer match of the lowest ligand-centered triplet state (that level which is primarily responsible for the energy transfer from the ligands to the europium(III)), and the lower vibrational energy of the C-F bonds relative to the C-H bonds. In the fluorinated complex the calculations show that the lowest triplet level is primarily localized on the 2,2'-dipyridyl whereas in the nonfluorinated complex this is the second lowest triplet level.

Kinetic study of thermal decomposition of new Eu(III), Tb(III) and Gd(III) complexes with beta-diketone ligands and 4,4-diphenyl-2,2-dipyridyl, chloride of 1,10-phenantrolinium

“…More recently, extensive works have been carried out to comprehend the kinetic and thermochemical behaviors of β-diketone complexes and metallic β-diketone containing Ln 3+ ions [24,25]. Conventional isothermal experiments have appeared to be more commonly employed for those complexes because they are straightforward in opposition to nonisothermal procedures.…”

“…Recently, it has been found out that distinct luminescent properties of Ln 3+ ions could also be used for applications in biomedical [10,19], sensing [19,20] and optical imaging [14,21] due to their long-lived (milliseconds timescale) excited states. This had led to the most interesting developments in the coordination chemistry of Ln 3+ , and interests in its new applications are still emerging nowadays [22,23].More recently, extensive works have been carried out to comprehend the kinetic and thermochemical behaviors of β-diketone complexes and metallic β-diketone containing Ln 3+ ions [24,25]. Conventional isothermal experiments have appeared to be more commonly employed for those complexes because they are straightforward in opposition to nonisothermal procedures.…”

Theoretical and experimental photophysical studies of the tris(4,4,4-trifluoro-1-(1-naphthyl)-1,3-butanedionate) (2,2′-bipiridyl)-europium(III)

“…In order to gain insight into the factors that determine the quantum yield and other relevant properties of lanthanide complexes our group has been investigating the photophysical properties of a number of new lanthanide complexes, using an approach based upon both theoretical and experimental work [8][9][10][11][12][13][14][15][16][17]. The results have shown that the quantum yield of a lanthanide complex arises from a balance among the rates of several processes, e.g., ligand to Ln 3+ energy transfer, multiphonon relaxation, energy back-transfer, crossover to charge-transfer states, etc.…”

“…The results have shown that the quantum yield of a lanthanide complex arises from a balance among the rates of several processes, e.g., ligand to Ln 3+ energy transfer, multiphonon relaxation, energy back-transfer, crossover to charge-transfer states, etc. The control of these rates, as well as of other relevant physical properties, has been accomplished by a thorough selection of ligands, allowing us to develop some promising LCMDs [8,[11][12][13][14][15], with high quantum yields at room temperature, leading to new applications [6,7]. We are now reporting the synthesis, spectroscopic, X-ray characterization, and photophysical investigation, as well as the molecular and electronic structure prediction with emphasis on the ligand-centered triplet energy level of the lanthanide complexes Ln(tan) 3 …”

Synthesis, crystal structures and photoluminescence properties of Sm-based enantiomeric pair

“…Usually, there are two types of lanthanide b-diketonates depending on whether the ratio of b-diketonate anion to lanthanide cation in the adducts is 3:1 (tris complexes) or 4:1 (tetrakis complexes) [3]. In particular, the tris complexes are most useful and extensively studied [4]. When three b-diketonates ''antenna" ligands chelated a trivalent lanthanide cation, the resultant complex is electrically neutral.…”