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Dive into the research topics where Fabiano da Silveira Santos is active.

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Featured researches published by Fabiano da Silveira Santos.


Journal of Physical Chemistry A | 2011

Synthesis, Characterization, and Spectroscopic Investigation of Benzoxazole Conjugated Schiff Bases

Fabiano da Silveira Santos; Tania Maria Haas Costa; Valter Stefani; Paulo Fernando Bruno Gonçalves; Rodrigo Roceti Descalzo; Edilson Valmir Benvenutti; Fabiano Severo Rodembusch

Two Schiff bases were synthesized by reaction of 2-(4-aminophenyl)benzoxazole derivatives with 4-N,N-diethylaminobenzaldehyde. UV-visible (UV-vis) and steady-state fluorescence in solution were applied in order to characterize its photophysical behavior. The Schiff bases present absorption in the UV region with fluorescence emission in the blue-green region, with a large Stokes shift. The UV-vis data indicates that each dye behaves as two different chromophores in solution in the ground state. The fluorescence emission spectra of the dye 5a show that an intramolecular proton transfer (ESIPT) mechanism takes place in the excited state, whereas a twisted internal charge transfer (TICT) state is observed for the dye 5b. Theoretical calculations were performed in order to study the conformation and polarity of the molecules at their ground and excited electronic states. Using density functional theory (DFT) methods at theoretical levels BLYP/Aug-SV(P) for geometry optimizations and B3LYP/6-311++G(2d,p) for single-point energy evaluations, the calculations indicate that the lowest energy conformations are in all cases nonplanar and that the dipole moments of the excited state relaxed structures are much larger than those of the ground state structures, which corroborates the experimental UV-vis absorption results.


New Journal of Chemistry | 2012

Bis-silylated terephthalate as a building block precursor for highly fluorescent organic–inorganic hybrid materials

Daniela Pletsch; Fabiano da Silveira Santos; Fabiano Severo Rodembusch; Valter Stefani; Leandra Franciscato Campo

A bis-silylated diethyl 2,5-bis[N,N-(3-triethoxysilyl)propylurea]terephthalate precursor (5) was synthesized from a terephthalate derivative (3) and successfully used to prepare highly fluorescent organosilicas by hydrolytic self-condensation (DPM1) and co-condensation (DPM2) with tetraethoxysilane. The dyes 3 and 5 present absorption in the UV-Vis region and fluorescence emission in the yellow and blue regions, respectively. The red-shifted bands in the absorption spectra of dye 3 with respect to dye 5 can be related to the formation of intramolecular charge transfer (ICT) state even in the ground-state due to the strong electron-donor amino groups and moderate electron-withdrawing carbonyl groups present in the benzenic ring. The small Stokes shift, as well as the high fluorescence quantum yield values discards the intramolecular proton transfer mechanism in the excited state. The fluorescence emission dependence on the solvent polarity indicates that an intramolecular charge transfer (ICT) or a locally excited (LE) state is taking place in the excited state to the dyes 3 and 5, respectively. The new fluorescent hybrid materials (DPM1 and DPM2) show absorption maxima in the solid state located at around 390 nm, indicating that the electronic structure of the fluorescent precursor was not significantly perturbed in the ground state after its self-condensation or co-condensation with TEOS. The fluorescent material DPM2 presents a photophysical behavior quite similar to the precursor in solution. On the other hand, the self-condensed material DPM1 presents a fluorescence emission maximum red-shifted by 33 nm, which can be probably attributed to π–π stacking between the terephthalate cores. Any evidence of auto-organization could be observed in these materials.


New Journal of Chemistry | 2017

Synthesis and photophysical study of new fluorescent proton transfer dihydropyrimidinone hybrids as potential candidates for molecular probes

Vanessa Pereira de Souza; Vinícius Vendrúsculo; Ana Moira Morás; Luiza Steffens; Fabiano da Silveira Santos; Dinara Jaqueline Moura; Fabiano Severo Rodembusch; Dennis Russowsky

A series of fluorescent aldehydes were synthesized and used in a conventional Biginelli multicomponent reaction under Lewis acid CeCl3·7H2O catalysis. The photoactive hybrid dihydropyrimidin-2-ones (Flu-DHPM) were isolated in reasonable to good yields. The compounds presented emission in the visible region with a large Stokes’ shift and low quantum yield of fluorescence as expected, ascribed to the phototautomerism in the excited state (ESIPT). Moreover, the ESIPT process allowed for Flu-DHPM with intense emission in the solid state compared to the dihydropyrimidin-2-ones (DHPMs) without the benzazolic core. The observed photophysical features were successfully used to explore these compounds as fluorescent probes in biological media. In addition, cell imaging experiments demonstrated that these photoactive hybrids have potential for use as cellular markers.


New Journal of Chemistry | 2016

Small heterocycles as highly luminescent building blocks in the solid state for organic synthesis

Fabiano da Silveira Santos; Natália Goedtel Medeiros; Ricardo F. Affeldt; Rodrigo da Costa Duarte; Sidnei Moura; Fabiano Severo Rodembusch

New photoactive mono-formylated benzoxazole derivatives were obtained as stable solids with excellent yields through a Duff functionalization protocol using a simple synthetic methodology. Despite several attempts to obtain the desired formyl compounds through the Duff reaction, which allows different acidic conditions to the studied compounds the key step was to use urotropine and trifluoroacetic acid as reagents. Additionally, the present protocol also allowed us to simplify the purification methodology in spite of the previously reported literature. The compounds present absorption in the UV region (ca. 340 nm) and fluorescence emission with a large Stokes shift in the blue-yellow regions, related to a phototautomerism in the excited state (ESIPT). In the solid state, main emission bands located in the cyan-green to green regions were observed with higher fluorescence quantum yields. Compound 20 was successfully applied as an optical sensor for amines in solution.


Journal of Sol-Gel Science and Technology | 2012

Photophysics of aminobenzazole dyes in silica-based hybrid materials

Silvia Regina Grando; Fabiano da Silveira Santos; Marcia Russman Gallas; Tania Maria Haas Costa; Edilson Valmir Benvenutti; Fabiano Severo Rodembusch

In this work two aminobenzazole derivatives (5-AHBT and 5-AHBI) were dispersed in silica-based hybrid materials with different surface hydrophobicity, which were obtained by the sol–gel process using tetraethylorthosilicate as inorganic precursor and dimethyldimethoxysilane as organic precursor, with a molar percent of organic precursor changing from 0 to 50%. The photophysics of the obtained doped silica hybrid materials was investigated by means ultraviolet–visible diffuse reflectance and steady-state fluorescence emission spectroscopy in the solid state. The materials present absorption maxima located around 353 and 318xa0nm when doped with 5-AHBT and 5-AHBI, respectively. The red shifted absorption maxima of the 5-AHBT can be explained by the better electron delocalization allowed by the sulfur atom in relation to the nitrogen. The fluorescence emission spectra are located in the blue-green regions and the high Stokes shift indicates that the ESIPT mechanism occurs in the excited state for both dyes. The photophysical behavior of 5-AHBT shows that this dye is more affected by the matrix polarity due to specific interactions that take place in the ground state.


New Journal of Chemistry | 2018

Lophine and pyrimidine based photoactive molecular hybrids. Synthesis, photophysics, BSA interaction and DFT study

João Paulo Bizarro Lopes; Viktor Saraiva Câmara; Dennis Russowsky; Fabiano da Silveira Santos; Roiney Beal; Pablo A. Nogara; João Batista Teixeira da Rocha; Paulo Fernando Bruno Gonçalves; Fabiano Severo Rodembusch; Marco Antonio Ceschi

Two photoactive molecular hybrids containing both lophine and pyrimidine moieties were synthesized by multicomponent reaction. The compounds present absorption in the UV-region (below 300 nm) and fluorescence emission in the violet region due to the lophine moiety. Experimental evidence indicates that photoinduced electron transfer (PET) occurs in the excited state of the hybrids. The observed photophysical features were successfully used to explore the interaction of the compounds with bovine serum albumin (BSA) in phosphate buffer solution (PBS) where a significant suppression mechanism was observed for both molecular hybrids. The DFT and TD-DFT calculations were performed at the ωB97XD level of theory. The results show low influence of the solvent on the wavelengths. However, the dipole moment undergoes a significant modification when the solvent is changed, showing a high polar behavior towards the excited state. Calculations also show us that the excitation is local, and that there is no charge transfer.


Journal of the Brazilian Chemical Society | 2017

Synthesis and Photophysical Characterization of Proton Transfer-Based Thiourea Derivatives: Potential Application as Colorimetric Naked-Eye Chemosensor for Fluoride Detection in Solution

Cláudia de Brito da Silva; Thais Kroetz; Fabiano da Silveira Santos; Fabiano Severo Rodembusch

Two new thiourea derivatives were synthesized through the reaction of photoactive aminohydroxybenzazoles and p-isothiocyanate benzoic acid via nucleophilic addition reaction. The compounds were characterized using high resolution mass spectrometry with eletrospray ionization (HRMS-ESI), Fourier transform infrared (FTIR), C and H nuclear magnetic resonance (NMR) spectroscopies. UV-Vis and steady-state fluorescence in solution were also applied to characterize their photophysical behavior. The compounds present absorption in the ultraviolet region (ca. 300 nm) and fluorescence emission with a large Stokes’ shift in the UV-A and green region, with the longer wavelength related to phototautomerism in the excited state (ESIPT). Both compounds were investigated as optical sensors for the detection of anions in solution, presenting a potential application for fluoride ion detection by naked-eye and UV-Vis spectroscopy. The continuous variation method plot gave a 1:1 stoichiometric ratio between the chemosensors and F for the new formed species. The UV-Vis and H NMR titration experiments reflect the establishment of a hydrogen bond interaction between the thiourea moiety of the chemosensors and fluoride. In addition, the presence of fluoride in solution tailored the fluorescence emission of one compound favoring the ESIPT emission.


Physical Chemistry Chemical Physics | 2012

Evidence for excited state intramolecular charge transfer in benzazole-based pseudo-stilbenes

Fabiano da Silveira Santos; Rodrigo Roceti Descalzo; Paulo Fernando Bruno Gonçalves; Edilson Valmir Benvenutti; Fabiano Severo Rodembusch


Sensors and Actuators B-chemical | 2018

Low pH optical sensor based on benzothiazole azo dyes

Felipe Lange Coelho; Cláudia de Ávila Braga; Gabriel Modernell Zanotto; Eduarda Sangiogo Gil; Leandra Franciscato Campo; Paulo Fernando Bruno Gonçalves; Fabiano Severo Rodembusch; Fabiano da Silveira Santos


Photochemical and Photobiological Sciences | 2018

Photoacidity as a tool to rationalize excited state intramolecular proton transfer reactivity in flavonols

Luís Gustavo Teixeira Alves Duarte; José Carlos Germino; Cláudia de Ávila Braga; Cristina Aparecida Barboza; Teresa Dib Zambon Atvars; Fabiano da Silveira Santos; Fabiano Severo Rodembusch

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Dive into the Fabiano da Silveira Santos's collaboration.

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Fabiano Severo Rodembusch

Universidade Federal do Rio Grande do Sul

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Paulo Fernando Bruno Gonçalves

Universidade Federal do Rio Grande do Sul

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Edilson Valmir Benvenutti

Universidade Federal do Rio Grande do Sul

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Natália Goedtel Medeiros

Universidade Federal do Rio Grande do Sul

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Ricardo F. Affeldt

Universidade Federal do Rio Grande do Sul

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Cláudia de Ávila Braga

Universidade Federal do Rio Grande do Sul

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Dennis Russowsky

Universidade Federal do Rio Grande do Sul

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Leandra Franciscato Campo

Universidade Federal do Rio Grande do Sul

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Rodrigo Roceti Descalzo

Universidade Federal do Rio Grande do Sul

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Tania Maria Haas Costa

Universidade Federal do Rio Grande do Sul

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