Vasile Chis | Babes-Bolyai University (original) (raw)
Papers by Vasile Chis
Croatica Chemica Acta, 2015
Chemical Papers, 2013
Three new compounds based on carbazole planar skeleton were synthesised. Among them there is a ne... more Three new compounds based on carbazole planar skeleton were synthesised. Among them there is a new ligand and a potential DNA intercalator which contains a benzothiazolium moiety connected to the carbazole ring by a vinyl bridge. The absorption and emission spectral properties of this new ligand have been studied by spectroscopic methods.
International Journal of Molecular Sciences, Oct 21, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
RSC Advances, 2016
SERS spectroscopy provided structural data on binding of a dye as monomer and dimer within minor ... more SERS spectroscopy provided structural data on binding of a dye as monomer and dimer within minor groove of adenine–thymine polynucleotides.
International Journal of Molecular Sciences
Nodularin (NOD) is a potent toxin produced by Nodularia spumigena cyanobacteria. Usually, NOD co-... more Nodularin (NOD) is a potent toxin produced by Nodularia spumigena cyanobacteria. Usually, NOD co-exists with other microcystins in environmental waters, a class of cyanotoxins secreted by certain cyanobacteria species, which makes identification difficult in the case of mixed toxins. Herein we report a complete theoretical DFT-vibrational Raman characterization of NOD along with the experimental drop-coating deposition Raman (DCDR) technique. In addition, we used the vibrational characterization to probe SERS analysis of NOD using colloidal silver nanoparticles (AgNPs), commercial nanopatterned substrates with periodic inverted pyramids (KlariteTM substrate), hydrophobic Tienta® SpecTrimTM slides, and in-house fabricated periodic nanotrenches by nanoimprint lithography (NIL). The 532 nm excitation source provided more well-defined bands even at LOD levels, as well as the best performance in terms of SERS intensity. This was reflected by the results obtained with the KlariteTM substr...
Journal of Spectroscopy, 2016
We report results of a systematic Raman, SERS, and DFT study on four beta blocking molecules: Ate... more We report results of a systematic Raman, SERS, and DFT study on four beta blocking molecules: Atenolol, Metoprolol, Propranolol, and, for the first time reported in the literature, Bisoprolol. The choice of these molecules was motivated by the structural similarities between Atenolol, Bisoprolol, and Metoprolol on one hand and by their differences relative to Propranolol. The density functional theory (DFT) approach, using the B3LYP method at the 6-311+G(d,p) level of theory, has been employed for geometry optimization and vibration bands assignments. The obtained results highlight the major role played by the central aromatic ring whose vibrations dominate the Raman spectra in all compounds. While the phenyl group vibrations dominate the Raman spectrum in the case of Atenolol, Bisoprolol, and Metoprolol, the spectrum of Propranolol presents high intensity vibrations of the naphthyl group. SERS performed on gold and silver colloids, at various pH conditions, revealed a higher sensit...
Molecules
The neodymium(III) complex of orotic acid (HOA) was synthesized and its structure determined by m... more The neodymium(III) complex of orotic acid (HOA) was synthesized and its structure determined by means of analytical and spectral analyses. Detailed vibrational analysis of HOA, sodium salt of HOA, and Nd(III)–OA systems based on both the calculated and experimental spectra confirmed the suggested metal–ligand binding mode. Significant differences in the IR and Raman spectra of the complex were observed as compared to the spectra of the ligand. The calculated vibrational wavenumbers, including IR intensities and Raman scattering activities, for the ligand and its Nd(III) complex were in good agreement with the experimental data. The vibrational analysis performed for the studied species, orotic acid, sodium salt of orotic acid, and its Nd(III) complex helped to explain the vibrational behaviour of the ligand’s vibrational modes, sensitive to interaction with Nd(III). In this paper we also report preliminary results about the cytotoxicity of the investigated compounds. The cytotoxic e...
International Journal of Molecular Sciences
Positron emission tomography (PET) uses radioactive tracers and enables the functional imaging of... more Positron emission tomography (PET) uses radioactive tracers and enables the functional imaging of several metabolic processes, blood flow measurements, regional chemical composition, and/or chemical absorption. Depending on the targeted processes within the living organism, different tracers are used for various medical conditions, such as cancer, particular brain pathologies, cardiac events, and bone lesions, where the most commonly used tracers are radiolabeled with 18F (e.g., [18F]-FDG and NA [18F]). Oxygen-15 isotope is mostly involved in blood flow measurements, whereas a wide array of 11C-based compounds have also been developed for neuronal disorders according to the affected neuroreceptors, prostate cancer, and lung carcinomas. In contrast, the single-photon emission computed tomography (SPECT) technique uses gamma-emitting radioisotopes and can be used to diagnose strokes, seizures, bone illnesses, and infections by gauging the blood flow and radio distribution within tissu...
International Journal of Molecular Sciences, 2021
Mutant huntingtin (m-HTT) proteins and calmodulin (CaM) co-localize in the cerebral cortex with s... more Mutant huntingtin (m-HTT) proteins and calmodulin (CaM) co-localize in the cerebral cortex with significant effects on the intracellular calcium levels by altering the specific calcium-mediated signals. Furthermore, the mutant huntingtin proteins show great affinity for CaM that can lead to a further stabilization of the mutant huntingtin aggregates. In this context, the present study focuses on describing the interactions between CaM and two huntingtin mutants from a biophysical point of view, by using classical Molecular Dynamics techniques. The huntingtin models consist of a wild-type structure, one mutant with 45 glutamine residues and the second mutant with nine additional key-point mutations from glutamine residues into proline residues (9P(EM) model). Our docking scores and binding free energy calculations show higher binding affinities of all HTT models for the C-lobe end of the CaM protein. In terms of dynamic evolution, the 9P(EM) model triggered great structural changes i...
Pharmaceutics, 2021
Chiral separation is an important issue for the pharmaceutical industry. Over the years, several ... more Chiral separation is an important issue for the pharmaceutical industry. Over the years, several separation methods have been developed, mainly based on chromatography. Their working principle is based on the formation of transient diastereoisomers, but the very subtle nanoscale interactions responsible for separation are not always understood. Recently, Raman and surface-enhanced Raman (SERS) spectroscopy have provided promising results in this field. Here we present Raman/SERS experimental data that provide useful information concerning the nanoscale interactions between propranolol enantiomers and α, β, and γ cyclodextrins. Raman spectroscopy was used to prove the formation of host–guest intermolecular complexes having different geometries of interaction. The occurrence of new vibrational bands and a change in the intensities of others are direct proofs of complexes’ formation. These observations were confirmed by DFT calculations. By performing SERS measurements on a new type of...
Food Chemistry, 2018
The freshness of citrus fruits commonly available in the market was non-destructively assessed by... more The freshness of citrus fruits commonly available in the market was non-destructively assessed by Raman spectroscopy. Intact clementine, mandarin and tangerine species were characterised concerning their carotenoids skin Raman signalling in a time course from the moment they were acquired as fresh stock, supplying the market, to the physical degradation, when they were no longer attractive to consumers. The freshness was found to strongly correlate to the peel Raman signal collected from the same area of the intact fruits in a time course of a maximum of 20 days. We have shown that the intensity of the carotenoid Raman signal is indeed a good indicator of fruit freshness and introduced a Raman coefficient of freshness (C Fresh), whose time course is linearly decreasing, with different slope for different citrus groups. Additionally, we demonstrated that the freshness assessment could be achieved using a portable Raman instrument. The results could have a strong impact for consumer satisfaction and the food industry.
The Journal of Physical Chemistry A, 1997
Single crystals of room temperature γ-irradiated glycine have been studied with electron nuclear ... more Single crystals of room temperature γ-irradiated glycine have been studied with electron nuclear double resonance (ENDOR) and X-band and high-frequency continuous wave electron paramagnetic resonance (EPR) spectroscopies and electron spin echo spectroscopy. EchoEPR spectroscopy was used to distinguish the radicals with different phase memory relaxation times. Three radicals have been detected, which have been identified as NH 3 +-CH-COO-(radical A), CH 2-COO-(radical B), and CH 2-NH 2 (radical C). Whereas radicals A and B had been observed by other authors in the past, radical C was not detected previously. The hyperfine tensors of the two CH 2 protons and of one of the NH 2 protons were determined by ENDOR. ESEEM (electron spin echo envelope modulation) and HYSCORE (hyperfine sublevel correlation spectroscopy) experiments were performed in order to obtain the relative signs of the hyperfine coupling constants of the three protons. The principal values and the principal directions of the hyperfine tensors are in agreement with the hypothesis of a nonplanar structure of the radical. Unrestricted Hartree-Fock calculations have been carried out for different conformations of radical C. The calculated hyperfine coupling constants are compared with the experimental results.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2012
Absorption spectra of PTCDI (3,4,9,10-perylene-tetracarboxylic-diimide) have been investigated in... more Absorption spectra of PTCDI (3,4,9,10-perylene-tetracarboxylic-diimide) have been investigated in chloroform, N,N'-dimethylformamide (DMF) and dimethylsulfoxide (DMSO). While no signature of assembled PTCDI molecules is observed in chloroform solution, distinct bands assigned to their aggregation have been identified in DMF and DMSO solutions. PTCDI monomers show very similar absorption patterns in chloroform and DMSO solutions. Experimental data, including the vibronic structure of the absorption spectra were explained based on the Franck-Condon approximation and quantum chemical results obtained at PBE0-DCP/6-31+G(d,p) level of theory. Geometry optimization of the first excited state leads to a nice agreement between the calculated adiabatic transition energies and experimental data.
Journal of Molecular Structure, 2005
In this work, we will report a combined experimental and theoretical study on molecular and vibra... more In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 2,4dinitrophenylhydrazine. FT-IR, FT-IR/ATR and Raman spectra of normal and deuterated DNPH have been recorded and analyzed in order to get new insights into molecular structure and properties of this molecule, with particular emphasize on its intra-and intermolecular hydrogen bonds (HB's). For computational purposes we used density functional theory (DFT) methods, with B3LYP and BLYP exchange-correlation functionals, in conjunction with 6-31G(d) basis set. All experimental vibrational bands have been discussed and assigned to normal modes on the basis of DFT calculations and isotopic shifts and by comparison to other dinitro-substituted compounds [V. Chiş, Chem. Phys., 300 (2004) 1]. To aid in mode assignments, we based on the direct comparison between experimental and calculated spectra by considering both the frequency sequence and the intensity pattern of the experimental and computed vibrational bands. It is also shown that semiempirical AM1 method predicts geometrical parameters and vibrational frequencies related to the HB in a pleasant agreement with experiment, being surprisingly accurate from this perspective.
Journal of Molecular Structure, 2006
IR, Raman and surface-enhanced Raman scattering (SERS) spectroscopies were employed for the struc... more IR, Raman and surface-enhanced Raman scattering (SERS) spectroscopies were employed for the structural investigation of the chelator desferrioxamine B and its Fe(III) complex, ferrioxamine B. Comparing the FT-IR absorptions of desferrioxamine B and ferrioxamine B, the structural changes due to the Fe(III) chelation were clearly evidenced by spectral analysis. Despite the intense C]O stretching vibration in the FT-Raman spectrum of desferrioxamine B, the FT-SERS spectrum is dominated by a strong C]N stretching vibration, indicating a delocalization of the N lone pair of electrons and the formation of the C]N bond in the hydroxamate groups. The desferrioxamine B and ferrioxamine B molecules are adsorbed to the silver colloidal particles through the O atoms of the hydroxamate functional groups, with similar orientation with respect to silver surface.
Journal of Molecular Structure, 2009
In this work, a joint experimental (FT-IR, FT-Raman, NMR) and theoretical DFT study on 3-ethyl-5m... more In this work, a joint experimental (FT-IR, FT-Raman, NMR) and theoretical DFT study on 3-ethyl-5methyl-2-(2-aminoethoxymethyl)-4-(2-chlorophenyl)-1,4-dihydro-6-methyl-3,5-pyridinedicarboxylate benzenesulphonate (amlodipine besylate) compound is reported. The experimental vibrational spectra have been assigned based on DFT calculations performed at B3LYP level of theory using the standard 6-31G(d) basis set and a uniform scaling of the calculated wave numbers. The mean deviation in reproducing the whole Raman and FT-IR spectra by B3LYP/6-31G(d) calculations is 7.7 and 6.0 cm À1 , respectively. The experimental 1 H NMR spectrum of amlodipine besylate was successfully reproduced by theoretical DFT calculations of the nuclear magnetic shielding tensors, using the GIAO method. The molecular electrostatic potential of the molecule has been calculated and used for predicting site candidates for electrophilic attack.
Journal of Molecular Structure, 2011
Structural investigations by different vibrational spectroscopic methods (FTIR, Raman and SERS), ... more Structural investigations by different vibrational spectroscopic methods (FTIR, Raman and SERS), as well as density functional theory (DFT) calculations were performed on paroxetine (IUPAC name: (3S,4R)-3-[(1,3-benzodioxol-5-yloxy)methyl]-4-(4-fluorophenyl)piperidine. After the identification of the lowest energy conformer of the investigated molecule, the FTIR, FT-Raman and SERS spectra were assigned on the basis of DFT calculations at B3LYP/6-31G(d) level of theory. The very good correlation found between experimental and theoretical data is a clear evidence for a reliable assignment of the vibrational bands. The molecular electrostatic potential was calculated and used for the prediction of preferred adsorption sites of the paroxetine molecule on the silver nanoparticles surface. Based on SERS spectra analysis it is shown that the molecule is adsorbed on the silver surface through the benzodioxol ring, in a tilted orientation.
Food Chemistry, 2014
Thiabendazole (TBZ) is a chemical fungicide and parasiticide largely used in food industry agains... more Thiabendazole (TBZ) is a chemical fungicide and parasiticide largely used in food industry against mold and blight in vegetables and fruits during transportation and long term deposit. We investigated the possibility to detect and monitor the TBZ from the chemically treated bananas and citrus fruits available on Romanian market, using surface enhanced Raman spectroscopy (SERS) with a compact, portable, mini-Raman spectrometer. To assess the potential of the technique for fast, cheap and sensitive detection, we report the first complete vibrational characterization of the TBZ in a large pH and concentration range in conjunction with the density functional theory (DFT) calculations. From the relative intensity of the specific SERS bands as a function of concentration, we estimated a total amount of TZB as 78 mg/kg in citrus fruits, 13 times higher than the maximum allowed by current regulations, whereas in banana fruit the value was in the allowed limit.
Chemical Physics, 2005
In this work, we report a combined experimental and theoretical study on molecular structure and ... more In this work, we report a combined experimental and theoretical study on molecular structure and vibrational properties of pyrazinamide (PZA) molecule, with particular emphasize on its intermolecular hydrogen bonds (HBs). FT-IR/ATR, Raman and NMR spectroscopic techniques were coupled with theoretical calculations performed at B3LYP and BLYP levels of theory, in conjunction with 6-31G(d) and cc-pVDZ basis sets. The influence of
Croatica Chemica Acta, 2015
Chemical Papers, 2013
Three new compounds based on carbazole planar skeleton were synthesised. Among them there is a ne... more Three new compounds based on carbazole planar skeleton were synthesised. Among them there is a new ligand and a potential DNA intercalator which contains a benzothiazolium moiety connected to the carbazole ring by a vinyl bridge. The absorption and emission spectral properties of this new ligand have been studied by spectroscopic methods.
International Journal of Molecular Sciences, Oct 21, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
RSC Advances, 2016
SERS spectroscopy provided structural data on binding of a dye as monomer and dimer within minor ... more SERS spectroscopy provided structural data on binding of a dye as monomer and dimer within minor groove of adenine–thymine polynucleotides.
International Journal of Molecular Sciences
Nodularin (NOD) is a potent toxin produced by Nodularia spumigena cyanobacteria. Usually, NOD co-... more Nodularin (NOD) is a potent toxin produced by Nodularia spumigena cyanobacteria. Usually, NOD co-exists with other microcystins in environmental waters, a class of cyanotoxins secreted by certain cyanobacteria species, which makes identification difficult in the case of mixed toxins. Herein we report a complete theoretical DFT-vibrational Raman characterization of NOD along with the experimental drop-coating deposition Raman (DCDR) technique. In addition, we used the vibrational characterization to probe SERS analysis of NOD using colloidal silver nanoparticles (AgNPs), commercial nanopatterned substrates with periodic inverted pyramids (KlariteTM substrate), hydrophobic Tienta® SpecTrimTM slides, and in-house fabricated periodic nanotrenches by nanoimprint lithography (NIL). The 532 nm excitation source provided more well-defined bands even at LOD levels, as well as the best performance in terms of SERS intensity. This was reflected by the results obtained with the KlariteTM substr...
Journal of Spectroscopy, 2016
We report results of a systematic Raman, SERS, and DFT study on four beta blocking molecules: Ate... more We report results of a systematic Raman, SERS, and DFT study on four beta blocking molecules: Atenolol, Metoprolol, Propranolol, and, for the first time reported in the literature, Bisoprolol. The choice of these molecules was motivated by the structural similarities between Atenolol, Bisoprolol, and Metoprolol on one hand and by their differences relative to Propranolol. The density functional theory (DFT) approach, using the B3LYP method at the 6-311+G(d,p) level of theory, has been employed for geometry optimization and vibration bands assignments. The obtained results highlight the major role played by the central aromatic ring whose vibrations dominate the Raman spectra in all compounds. While the phenyl group vibrations dominate the Raman spectrum in the case of Atenolol, Bisoprolol, and Metoprolol, the spectrum of Propranolol presents high intensity vibrations of the naphthyl group. SERS performed on gold and silver colloids, at various pH conditions, revealed a higher sensit...
Molecules
The neodymium(III) complex of orotic acid (HOA) was synthesized and its structure determined by m... more The neodymium(III) complex of orotic acid (HOA) was synthesized and its structure determined by means of analytical and spectral analyses. Detailed vibrational analysis of HOA, sodium salt of HOA, and Nd(III)–OA systems based on both the calculated and experimental spectra confirmed the suggested metal–ligand binding mode. Significant differences in the IR and Raman spectra of the complex were observed as compared to the spectra of the ligand. The calculated vibrational wavenumbers, including IR intensities and Raman scattering activities, for the ligand and its Nd(III) complex were in good agreement with the experimental data. The vibrational analysis performed for the studied species, orotic acid, sodium salt of orotic acid, and its Nd(III) complex helped to explain the vibrational behaviour of the ligand’s vibrational modes, sensitive to interaction with Nd(III). In this paper we also report preliminary results about the cytotoxicity of the investigated compounds. The cytotoxic e...
International Journal of Molecular Sciences
Positron emission tomography (PET) uses radioactive tracers and enables the functional imaging of... more Positron emission tomography (PET) uses radioactive tracers and enables the functional imaging of several metabolic processes, blood flow measurements, regional chemical composition, and/or chemical absorption. Depending on the targeted processes within the living organism, different tracers are used for various medical conditions, such as cancer, particular brain pathologies, cardiac events, and bone lesions, where the most commonly used tracers are radiolabeled with 18F (e.g., [18F]-FDG and NA [18F]). Oxygen-15 isotope is mostly involved in blood flow measurements, whereas a wide array of 11C-based compounds have also been developed for neuronal disorders according to the affected neuroreceptors, prostate cancer, and lung carcinomas. In contrast, the single-photon emission computed tomography (SPECT) technique uses gamma-emitting radioisotopes and can be used to diagnose strokes, seizures, bone illnesses, and infections by gauging the blood flow and radio distribution within tissu...
International Journal of Molecular Sciences, 2021
Mutant huntingtin (m-HTT) proteins and calmodulin (CaM) co-localize in the cerebral cortex with s... more Mutant huntingtin (m-HTT) proteins and calmodulin (CaM) co-localize in the cerebral cortex with significant effects on the intracellular calcium levels by altering the specific calcium-mediated signals. Furthermore, the mutant huntingtin proteins show great affinity for CaM that can lead to a further stabilization of the mutant huntingtin aggregates. In this context, the present study focuses on describing the interactions between CaM and two huntingtin mutants from a biophysical point of view, by using classical Molecular Dynamics techniques. The huntingtin models consist of a wild-type structure, one mutant with 45 glutamine residues and the second mutant with nine additional key-point mutations from glutamine residues into proline residues (9P(EM) model). Our docking scores and binding free energy calculations show higher binding affinities of all HTT models for the C-lobe end of the CaM protein. In terms of dynamic evolution, the 9P(EM) model triggered great structural changes i...
Pharmaceutics, 2021
Chiral separation is an important issue for the pharmaceutical industry. Over the years, several ... more Chiral separation is an important issue for the pharmaceutical industry. Over the years, several separation methods have been developed, mainly based on chromatography. Their working principle is based on the formation of transient diastereoisomers, but the very subtle nanoscale interactions responsible for separation are not always understood. Recently, Raman and surface-enhanced Raman (SERS) spectroscopy have provided promising results in this field. Here we present Raman/SERS experimental data that provide useful information concerning the nanoscale interactions between propranolol enantiomers and α, β, and γ cyclodextrins. Raman spectroscopy was used to prove the formation of host–guest intermolecular complexes having different geometries of interaction. The occurrence of new vibrational bands and a change in the intensities of others are direct proofs of complexes’ formation. These observations were confirmed by DFT calculations. By performing SERS measurements on a new type of...
Food Chemistry, 2018
The freshness of citrus fruits commonly available in the market was non-destructively assessed by... more The freshness of citrus fruits commonly available in the market was non-destructively assessed by Raman spectroscopy. Intact clementine, mandarin and tangerine species were characterised concerning their carotenoids skin Raman signalling in a time course from the moment they were acquired as fresh stock, supplying the market, to the physical degradation, when they were no longer attractive to consumers. The freshness was found to strongly correlate to the peel Raman signal collected from the same area of the intact fruits in a time course of a maximum of 20 days. We have shown that the intensity of the carotenoid Raman signal is indeed a good indicator of fruit freshness and introduced a Raman coefficient of freshness (C Fresh), whose time course is linearly decreasing, with different slope for different citrus groups. Additionally, we demonstrated that the freshness assessment could be achieved using a portable Raman instrument. The results could have a strong impact for consumer satisfaction and the food industry.
The Journal of Physical Chemistry A, 1997
Single crystals of room temperature γ-irradiated glycine have been studied with electron nuclear ... more Single crystals of room temperature γ-irradiated glycine have been studied with electron nuclear double resonance (ENDOR) and X-band and high-frequency continuous wave electron paramagnetic resonance (EPR) spectroscopies and electron spin echo spectroscopy. EchoEPR spectroscopy was used to distinguish the radicals with different phase memory relaxation times. Three radicals have been detected, which have been identified as NH 3 +-CH-COO-(radical A), CH 2-COO-(radical B), and CH 2-NH 2 (radical C). Whereas radicals A and B had been observed by other authors in the past, radical C was not detected previously. The hyperfine tensors of the two CH 2 protons and of one of the NH 2 protons were determined by ENDOR. ESEEM (electron spin echo envelope modulation) and HYSCORE (hyperfine sublevel correlation spectroscopy) experiments were performed in order to obtain the relative signs of the hyperfine coupling constants of the three protons. The principal values and the principal directions of the hyperfine tensors are in agreement with the hypothesis of a nonplanar structure of the radical. Unrestricted Hartree-Fock calculations have been carried out for different conformations of radical C. The calculated hyperfine coupling constants are compared with the experimental results.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2012
Absorption spectra of PTCDI (3,4,9,10-perylene-tetracarboxylic-diimide) have been investigated in... more Absorption spectra of PTCDI (3,4,9,10-perylene-tetracarboxylic-diimide) have been investigated in chloroform, N,N'-dimethylformamide (DMF) and dimethylsulfoxide (DMSO). While no signature of assembled PTCDI molecules is observed in chloroform solution, distinct bands assigned to their aggregation have been identified in DMF and DMSO solutions. PTCDI monomers show very similar absorption patterns in chloroform and DMSO solutions. Experimental data, including the vibronic structure of the absorption spectra were explained based on the Franck-Condon approximation and quantum chemical results obtained at PBE0-DCP/6-31+G(d,p) level of theory. Geometry optimization of the first excited state leads to a nice agreement between the calculated adiabatic transition energies and experimental data.
Journal of Molecular Structure, 2005
In this work, we will report a combined experimental and theoretical study on molecular and vibra... more In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 2,4dinitrophenylhydrazine. FT-IR, FT-IR/ATR and Raman spectra of normal and deuterated DNPH have been recorded and analyzed in order to get new insights into molecular structure and properties of this molecule, with particular emphasize on its intra-and intermolecular hydrogen bonds (HB's). For computational purposes we used density functional theory (DFT) methods, with B3LYP and BLYP exchange-correlation functionals, in conjunction with 6-31G(d) basis set. All experimental vibrational bands have been discussed and assigned to normal modes on the basis of DFT calculations and isotopic shifts and by comparison to other dinitro-substituted compounds [V. Chiş, Chem. Phys., 300 (2004) 1]. To aid in mode assignments, we based on the direct comparison between experimental and calculated spectra by considering both the frequency sequence and the intensity pattern of the experimental and computed vibrational bands. It is also shown that semiempirical AM1 method predicts geometrical parameters and vibrational frequencies related to the HB in a pleasant agreement with experiment, being surprisingly accurate from this perspective.
Journal of Molecular Structure, 2006
IR, Raman and surface-enhanced Raman scattering (SERS) spectroscopies were employed for the struc... more IR, Raman and surface-enhanced Raman scattering (SERS) spectroscopies were employed for the structural investigation of the chelator desferrioxamine B and its Fe(III) complex, ferrioxamine B. Comparing the FT-IR absorptions of desferrioxamine B and ferrioxamine B, the structural changes due to the Fe(III) chelation were clearly evidenced by spectral analysis. Despite the intense C]O stretching vibration in the FT-Raman spectrum of desferrioxamine B, the FT-SERS spectrum is dominated by a strong C]N stretching vibration, indicating a delocalization of the N lone pair of electrons and the formation of the C]N bond in the hydroxamate groups. The desferrioxamine B and ferrioxamine B molecules are adsorbed to the silver colloidal particles through the O atoms of the hydroxamate functional groups, with similar orientation with respect to silver surface.
Journal of Molecular Structure, 2009
In this work, a joint experimental (FT-IR, FT-Raman, NMR) and theoretical DFT study on 3-ethyl-5m... more In this work, a joint experimental (FT-IR, FT-Raman, NMR) and theoretical DFT study on 3-ethyl-5methyl-2-(2-aminoethoxymethyl)-4-(2-chlorophenyl)-1,4-dihydro-6-methyl-3,5-pyridinedicarboxylate benzenesulphonate (amlodipine besylate) compound is reported. The experimental vibrational spectra have been assigned based on DFT calculations performed at B3LYP level of theory using the standard 6-31G(d) basis set and a uniform scaling of the calculated wave numbers. The mean deviation in reproducing the whole Raman and FT-IR spectra by B3LYP/6-31G(d) calculations is 7.7 and 6.0 cm À1 , respectively. The experimental 1 H NMR spectrum of amlodipine besylate was successfully reproduced by theoretical DFT calculations of the nuclear magnetic shielding tensors, using the GIAO method. The molecular electrostatic potential of the molecule has been calculated and used for predicting site candidates for electrophilic attack.
Journal of Molecular Structure, 2011
Structural investigations by different vibrational spectroscopic methods (FTIR, Raman and SERS), ... more Structural investigations by different vibrational spectroscopic methods (FTIR, Raman and SERS), as well as density functional theory (DFT) calculations were performed on paroxetine (IUPAC name: (3S,4R)-3-[(1,3-benzodioxol-5-yloxy)methyl]-4-(4-fluorophenyl)piperidine. After the identification of the lowest energy conformer of the investigated molecule, the FTIR, FT-Raman and SERS spectra were assigned on the basis of DFT calculations at B3LYP/6-31G(d) level of theory. The very good correlation found between experimental and theoretical data is a clear evidence for a reliable assignment of the vibrational bands. The molecular electrostatic potential was calculated and used for the prediction of preferred adsorption sites of the paroxetine molecule on the silver nanoparticles surface. Based on SERS spectra analysis it is shown that the molecule is adsorbed on the silver surface through the benzodioxol ring, in a tilted orientation.
Food Chemistry, 2014
Thiabendazole (TBZ) is a chemical fungicide and parasiticide largely used in food industry agains... more Thiabendazole (TBZ) is a chemical fungicide and parasiticide largely used in food industry against mold and blight in vegetables and fruits during transportation and long term deposit. We investigated the possibility to detect and monitor the TBZ from the chemically treated bananas and citrus fruits available on Romanian market, using surface enhanced Raman spectroscopy (SERS) with a compact, portable, mini-Raman spectrometer. To assess the potential of the technique for fast, cheap and sensitive detection, we report the first complete vibrational characterization of the TBZ in a large pH and concentration range in conjunction with the density functional theory (DFT) calculations. From the relative intensity of the specific SERS bands as a function of concentration, we estimated a total amount of TZB as 78 mg/kg in citrus fruits, 13 times higher than the maximum allowed by current regulations, whereas in banana fruit the value was in the allowed limit.
Chemical Physics, 2005
In this work, we report a combined experimental and theoretical study on molecular structure and ... more In this work, we report a combined experimental and theoretical study on molecular structure and vibrational properties of pyrazinamide (PZA) molecule, with particular emphasize on its intermolecular hydrogen bonds (HBs). FT-IR/ATR, Raman and NMR spectroscopic techniques were coupled with theoretical calculations performed at B3LYP and BLYP levels of theory, in conjunction with 6-31G(d) and cc-pVDZ basis sets. The influence of