Helcio Batista - Academia.edu (original) (raw)

Papers by Helcio Batista

Journal of Luminescence, Feb 1, 2016

Using as precursor the mononuclear lanthanide (Ln) macrocyclic complex, based on the 15-crown-5 e... more Using as precursor the mononuclear lanthanide (Ln) macrocyclic complex, based on the 15-crown-5 ether (C) ligand and coordinated water (W) molecules, [LnCW 4 ] 3 þ , four novel analogous complexes for each of the three Ln(III) ions (Ln¼Eu, Tb and Gd) were synthesized through systematic substitution of water molecules by the antenna-type ligands: 2,2′-dipyridyl (D), 1,10-phenanthroline (P) and 2,2′;6',2′′-terpyridine (T). The corresponding formulae of the complexes, obtained in a trichloride salt form, were the following: [LnCW 4 ] 3 þ , [LnCP 2 ] 3 þ , [LnCDW] 3 þ , [LnCDP] 3 þ , and [LnCT] 3 þ. The compounds were characterized by elemental analysis, UV and infrared spectroscopy and investigated through luminescence spectroscopy. For the Eu(III) and Tb(III) complex series, the most luminescent ones were [EuCDP] 3 þ and [TbCT] 3 þ , respectively. Motivated by this fact, two dinuclear analogous Eu(III) and Tb(III) complexes, based on the two-site coordinating macrocyclic ligand lariat-silacrown ether (S), as well as analogous Gd(III) complexes, were obtained as hexachloride salts with the following formulae: [Eu 2 SD 2 P 2 ] 6 þ , [Gd 2 SD 2 P 2 ] 6 þ , [Tb 2 ST 2 ] 6 þ and [Gd 2 ST 2 ] 6 þ. Also, [Eu 2 SW 8 ] 6 þ , [Tb 2 SW 8 ] 6 þ and [Gd 2 SW 8 ] 6 þ complexes were prepared and used as reference non-antenna type dinuclear compounds. Comparing the luminescence between the antenna mononuclear complexes with the analogous dinuclear ones, for Eu(III) and Tb(III) ions, almost no change was observed. On the other hand, in the particular case of Eu (III), comparing the mono-and dinuclear non-antenna reference complexes [EuCW 4 ] 3 þ and [Eu 2 SW 8 ] 6 þ , a surprisingly much higher luminescence intensity was observed for the dinuclear complex ($ one order of magnitude). The proposed cause for this behavior is the peculiar electronic properties of the siloxane group, which has a partial character of (p-d)π hyperconjugation. Results of quantum chemical theoretical calculations of molecular and electronic structures, using DFT methods, reinforce such special properties of the siloxane and also show that its presence is responsible for considerable differences in the coordination sphere between the mono-and dinuclear species, such as in the coordination number, which decreases from nine to seven. Furthermore, particularly in the dinuclear [Eu 2 SW 8 ] 6 þ complex, one water molecule per coordination center suffers a hydrolysis, donating a proton to the near NH 2 of an amino-propyl function, present in the siloxane group bridging the two mononuclear moieties, and this event could also be related with the observed enhanced luminescence.

Journal of Luminescence, Jun 1, 1997

The adduct Eu(btfa)3bipy (btfa = 4,4,4-trifluoro-1-phenyl-2,4-butanedione, bipy = 2,2&amp... more The adduct Eu(btfa)3bipy (btfa = 4,4,4-trifluoro-1-phenyl-2,4-butanedione, bipy = 2,2'-bipyridine) was synthesized and its X-ray structure was determined. The UV absorption spectra of the ligands and complex were obtained in ethanolic solution. The luminescence spectrum of the solid complex at 77 K suggests the existence of a single emitting site, in agreement to the X-ray structure. The electronic spectrum of the

RSC Advances, 2021

So far, no conclusive evidence of a ground-state contact ion-pair containing a hydrocarbon carboc... more So far, no conclusive evidence of a ground-state contact ion-pair containing a hydrocarbon carbocation has been given in the gas phase.

Revista processos químicos, Jul 1, 2015

Chemical Physics, 2002

We introduce the concept of overlap polarizability of a single directional chemical bond and prop... more We introduce the concept of overlap polarizability of a single directional chemical bond and propose an expression for this quantity. The concept of ionic specific valence is also introduced, as a consequence of a relation, involving the bond force constant, between the overlap ...

Chemical Physics, 2011

In this work, it were performed computational design and synthesis of a new luminescent Eu(III) c... more In this work, it were performed computational design and synthesis of a new luminescent Eu(III) complex with the usual 1,10-phenanthroline ligand substituted in the 4 and 7 positions by chlorine atoms, which one has shown a higher luminescent output than that of the non-substituted analogous complex. The molecular structures for all complexes using the Sparkle and DFT methods were obtained, such as their coordination bond distances with values in a typical range. Analyzing the direct Eu(III) ion excitation for the phenCl complex, all of them are red shifted in comparison to the one of the phen complex suggesting that the ion environment is more polarizable in the first case, this corroborate with results obtained for intensities and R02 parameters.

... Israel, Ivani, Ivoneide, Jailson, Jayme, Juca, Juliana de Wagner, Júnior, Kátia, Leda, Letíci... more ... Israel, Ivani, Ivoneide, Jailson, Jayme, Juca, Juliana de Wagner, Júnior, Kátia, Leda, Letícia, Lucila, Mozart, Marcelo Leão, Marcelo Zaldini, Nivan, Otávio, Paulo gaúcho, Paulo Neilson, ... Aos cafezinhos, às leituras do Dalai Lama, do Chico Xavier, do Brás Cubas do Machado, ...

Inorganic Chemistry, Aug 1, 1998

The 2,2&a... more 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.

Journal of Luminescence, 2006

The complexes tris(4,4,4-Trifluoro-1-(1-naphthyl)-1,3-butanedionate) (2,2 0-bipiridyl) Ln(III), L... more The complexes tris(4,4,4-Trifluoro-1-(1-naphthyl)-1,3-butanedionate) (2,2 0-bipiridyl) Ln(III), Ln(tan) 3 bipy, where Ln(III) ¼ Eu 3+ and Gd 3+ have been synthesized, characterized and their photophysical properties (absorption, excitation and luminescence spectra and emission quantum yield) investigated down to 4.2 K. The Eu(tan) 3 bipy complex has its molecular structure experimentally determined using X-ray crystallography and theoretically using the SMLC/AM1 method as well as their electronic singlet and triplet states were calculated, using the INDO/S-CI method with a point charge model to represent the Eu 3+ ion, where two values were adopted, +3.0e and +3.5e, to investigate the imperfect shielding of the 4f shells. The so calculated +3.5e model electronic absorption spectrum and low lying triplet state energies agreed very well with the experimental ones. The emission quantum yield of the Eu 3+ complex is quite low at room temperature, namely 7%, probably due to the too low lying triplet state, 19,050 cm-1 , and increases by a factor of three when the temperature is lowered to 4.2 K. This strong thermal effect indicates the presence of a channel deactivating the main emitting state, what can be due to a LMCT state possibly lying in the same spectral region, as usually found in Eu 3+ compounds.

International Journal of Quantum Chemistry, 2002

ABSTRACT Due to the spatial extent of the 5s and 5p filled orbitals of lanthanide ions, the shiel... more ABSTRACT Due to the spatial extent of the 5s and 5p filled orbitals of lanthanide ions, the shielding of the nuclear charge is not perfect at close distances to the ion. Thus, ligand atoms should experience different effective charge depending upon their distance to the central ion. Using electrostatic arguments and ab initio calculations for Eu3+, we have proposed an improved model that describes the ion as an effective charge, q(r), whose value has the following radial dependence, q(r)=3+14e. This functional form of the point charge has been implemented into the ZINDO program and INDO/S-CI calculations have been performed for the Eu(btfa)3bipy, Eu(btfa)3⋅2H2O, Eu(bzac)3bipy, and Eu(bzac)3⋅2H2O compounds. The comparison with the experimental absorption spectrum was used to optimize the exponent A parameter. Application of this model to several other Eu3+ coordination compounds yielded better results for the calculated absorption spectra than the fixed 3+ point-charge model. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001

Journal of Luminescence, Feb 1, 2016

Using as precursor the mononuclear lanthanide (Ln) macrocyclic complex, based on the 15-crown-5 e... more Using as precursor the mononuclear lanthanide (Ln) macrocyclic complex, based on the 15-crown-5 ether (C) ligand and coordinated water (W) molecules, [LnCW 4 ] 3 þ , four novel analogous complexes for each of the three Ln(III) ions (Ln¼Eu, Tb and Gd) were synthesized through systematic substitution of water molecules by the antenna-type ligands: 2,2′-dipyridyl (D), 1,10-phenanthroline (P) and 2,2′;6',2′′-terpyridine (T). The corresponding formulae of the complexes, obtained in a trichloride salt form, were the following: [LnCW 4 ] 3 þ , [LnCP 2 ] 3 þ , [LnCDW] 3 þ , [LnCDP] 3 þ , and [LnCT] 3 þ. The compounds were characterized by elemental analysis, UV and infrared spectroscopy and investigated through luminescence spectroscopy. For the Eu(III) and Tb(III) complex series, the most luminescent ones were [EuCDP] 3 þ and [TbCT] 3 þ , respectively. Motivated by this fact, two dinuclear analogous Eu(III) and Tb(III) complexes, based on the two-site coordinating macrocyclic ligand lariat-silacrown ether (S), as well as analogous Gd(III) complexes, were obtained as hexachloride salts with the following formulae: [Eu 2 SD 2 P 2 ] 6 þ , [Gd 2 SD 2 P 2 ] 6 þ , [Tb 2 ST 2 ] 6 þ and [Gd 2 ST 2 ] 6 þ. Also, [Eu 2 SW 8 ] 6 þ , [Tb 2 SW 8 ] 6 þ and [Gd 2 SW 8 ] 6 þ complexes were prepared and used as reference non-antenna type dinuclear compounds. Comparing the luminescence between the antenna mononuclear complexes with the analogous dinuclear ones, for Eu(III) and Tb(III) ions, almost no change was observed. On the other hand, in the particular case of Eu (III), comparing the mono-and dinuclear non-antenna reference complexes [EuCW 4 ] 3 þ and [Eu 2 SW 8 ] 6 þ , a surprisingly much higher luminescence intensity was observed for the dinuclear complex ($ one order of magnitude). The proposed cause for this behavior is the peculiar electronic properties of the siloxane group, which has a partial character of (p-d)π hyperconjugation. Results of quantum chemical theoretical calculations of molecular and electronic structures, using DFT methods, reinforce such special properties of the siloxane and also show that its presence is responsible for considerable differences in the coordination sphere between the mono-and dinuclear species, such as in the coordination number, which decreases from nine to seven. Furthermore, particularly in the dinuclear [Eu 2 SW 8 ] 6 þ complex, one water molecule per coordination center suffers a hydrolysis, donating a proton to the near NH 2 of an amino-propyl function, present in the siloxane group bridging the two mononuclear moieties, and this event could also be related with the observed enhanced luminescence.

Journal of Luminescence, Jun 1, 1997

The adduct Eu(btfa)3bipy (btfa = 4,4,4-trifluoro-1-phenyl-2,4-butanedione, bipy = 2,2&amp... more The adduct Eu(btfa)3bipy (btfa = 4,4,4-trifluoro-1-phenyl-2,4-butanedione, bipy = 2,2'-bipyridine) was synthesized and its X-ray structure was determined. The UV absorption spectra of the ligands and complex were obtained in ethanolic solution. The luminescence spectrum of the solid complex at 77 K suggests the existence of a single emitting site, in agreement to the X-ray structure. The electronic spectrum of the

RSC Advances, 2021

So far, no conclusive evidence of a ground-state contact ion-pair containing a hydrocarbon carboc... more So far, no conclusive evidence of a ground-state contact ion-pair containing a hydrocarbon carbocation has been given in the gas phase.

Revista processos químicos, Jul 1, 2015

Chemical Physics, 2002

We introduce the concept of overlap polarizability of a single directional chemical bond and prop... more We introduce the concept of overlap polarizability of a single directional chemical bond and propose an expression for this quantity. The concept of ionic specific valence is also introduced, as a consequence of a relation, involving the bond force constant, between the overlap ...

Chemical Physics, 2011

In this work, it were performed computational design and synthesis of a new luminescent Eu(III) c... more In this work, it were performed computational design and synthesis of a new luminescent Eu(III) complex with the usual 1,10-phenanthroline ligand substituted in the 4 and 7 positions by chlorine atoms, which one has shown a higher luminescent output than that of the non-substituted analogous complex. The molecular structures for all complexes using the Sparkle and DFT methods were obtained, such as their coordination bond distances with values in a typical range. Analyzing the direct Eu(III) ion excitation for the phenCl complex, all of them are red shifted in comparison to the one of the phen complex suggesting that the ion environment is more polarizable in the first case, this corroborate with results obtained for intensities and R02 parameters.

... Israel, Ivani, Ivoneide, Jailson, Jayme, Juca, Juliana de Wagner, Júnior, Kátia, Leda, Letíci... more ... Israel, Ivani, Ivoneide, Jailson, Jayme, Juca, Juliana de Wagner, Júnior, Kátia, Leda, Letícia, Lucila, Mozart, Marcelo Leão, Marcelo Zaldini, Nivan, Otávio, Paulo gaúcho, Paulo Neilson, ... Aos cafezinhos, às leituras do Dalai Lama, do Chico Xavier, do Brás Cubas do Machado, ...

Inorganic Chemistry, Aug 1, 1998

The 2,2&a... more 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.

Journal of Luminescence, 2006

The complexes tris(4,4,4-Trifluoro-1-(1-naphthyl)-1,3-butanedionate) (2,2 0-bipiridyl) Ln(III), L... more The complexes tris(4,4,4-Trifluoro-1-(1-naphthyl)-1,3-butanedionate) (2,2 0-bipiridyl) Ln(III), Ln(tan) 3 bipy, where Ln(III) ¼ Eu 3+ and Gd 3+ have been synthesized, characterized and their photophysical properties (absorption, excitation and luminescence spectra and emission quantum yield) investigated down to 4.2 K. The Eu(tan) 3 bipy complex has its molecular structure experimentally determined using X-ray crystallography and theoretically using the SMLC/AM1 method as well as their electronic singlet and triplet states were calculated, using the INDO/S-CI method with a point charge model to represent the Eu 3+ ion, where two values were adopted, +3.0e and +3.5e, to investigate the imperfect shielding of the 4f shells. The so calculated +3.5e model electronic absorption spectrum and low lying triplet state energies agreed very well with the experimental ones. The emission quantum yield of the Eu 3+ complex is quite low at room temperature, namely 7%, probably due to the too low lying triplet state, 19,050 cm-1 , and increases by a factor of three when the temperature is lowered to 4.2 K. This strong thermal effect indicates the presence of a channel deactivating the main emitting state, what can be due to a LMCT state possibly lying in the same spectral region, as usually found in Eu 3+ compounds.

International Journal of Quantum Chemistry, 2002

ABSTRACT Due to the spatial extent of the 5s and 5p filled orbitals of lanthanide ions, the shiel... more ABSTRACT Due to the spatial extent of the 5s and 5p filled orbitals of lanthanide ions, the shielding of the nuclear charge is not perfect at close distances to the ion. Thus, ligand atoms should experience different effective charge depending upon their distance to the central ion. Using electrostatic arguments and ab initio calculations for Eu3+, we have proposed an improved model that describes the ion as an effective charge, q(r), whose value has the following radial dependence, q(r)=3+14e. This functional form of the point charge has been implemented into the ZINDO program and INDO/S-CI calculations have been performed for the Eu(btfa)3bipy, Eu(btfa)3⋅2H2O, Eu(bzac)3bipy, and Eu(bzac)3⋅2H2O compounds. The comparison with the experimental absorption spectrum was used to optimize the exponent A parameter. Application of this model to several other Eu3+ coordination compounds yielded better results for the calculated absorption spectra than the fixed 3+ point-charge model. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001