The Experts below are selected from a list of 24153 Experts worldwide ranked by ideXlab platform
Rui Fausto - One of the best experts on this subject based on the ideXlab platform.
-
identification of serine conformers by Matrix Isolation ir spectroscopy aided by near infrared laser induced conformational change 2d correlation analysis and quantum mechanical anharmonic computations
Journal of Physical Chemistry B, 2015Co-Authors: Eszter E Najbauer, Gabor Bazso, Rui Fausto, Rui F G Apostolo, Malgorzata Biczysko, Vincenzo Barone, Gyorgy TarczayAbstract:The conformers of α-serine were investigated by Matrix-Isolation IR spectroscopy combined with NIR laser irradiation. This method, aided by 2D correlation analysis, enabled unambiguously grouping the spectral lines to individual conformers. On the basis of comparison of at least nine experimentally observed vibrational transitions of each conformer with empirically scaled (SQM) and anharmonic (GVPT2) computed IR spectra, six conformers were identified. In addition, the presence of at least one more conformer in Ar Matrix was proved, and a short-lived conformer with a half-life of (3.7 ± 0.5) × 103 s in N2 Matrix was generated by NIR irradiation. The analysis of the NIR laser-induced conversions revealed that the excitation of the stretching overtone of both the side chain and the carboxylic OH groups can effectively promote conformational changes, but remarkably different paths were observed for the two kinds of excitations.
-
structure of isolated 1 4 butanediol combination of mp2 calculations nbo analysis and Matrix Isolation infrared spectroscopy
Journal of Physical Chemistry A, 2008Co-Authors: A Lopes J Jesus, Igor Reva, Rui Fausto, Mario T S Rosado, Ermelinda M S Eusebio, J S RedinhaAbstract:Theoretical calculations at the MP2 level, NBO and AIM analysis, and Matrix-Isolation infrared spectroscopy have been used to investigate the structure of the isolated molecule of 1,4-butanediol (1,4-BDO). Sixty-five structures were found to be minima on the potential energy surface, and the three most stable forms are characterized by a folded backbone conformation leading to the formation of an intramolecular H-bond. To better characterize the intramolecular interactions and particularly the hydrogen bonds, natural bond orbital analysis (NBO) was performed for the four most stable conformers, and was further complemented with an atoms-in-molecules (AIM) topological analysis. Infrared spectra of 1,4-BDO isolated in low-temperature argon and xenon Matrixes show a good agreement with a population-weighted mean theoretical spectrum, and the spectral features of the conformers expected to be trapped in the Matrixes were observed experimentally. Annealing the xenon Matrix from 20 to 60 K resulted in significant spectral changes, which were interpreted based on the barriers to intramolecular rotation. An estimation of the intramolecular hydrogen bond energy was carried out following three different methodologies.
-
importance of entropy in the conformational equilibrium of phenylalanine a Matrix Isolation infrared spectroscopy and density functional theory study
Journal of Physical Chemistry A, 2006Co-Authors: Agnieszka Kaczor, Igor Reva, Leonard M Proniewicz, Rui FaustoAbstract:The conformational behavior and infrared spectrum of l-phenylalanine were studied by Matrix-Isolation infrared spectroscopy and DFT [B3LYP/6-311++G(d,p)] calculations. The fourteen most stable structures were predicted to differ in energy by less than 10 kJ mol(-1), eight of them with abundances higher than 5% at the temperature of evaporation of the compound (423 K). Experimental results suggest that six conformers contribute to the spectrum of the isolated compound, whereas two conformers (IIb(3) and IIIb(3)) relax in Matrix to a more stable form (IIb(2)) due to low energy barriers for conformational isomerization (conformational cooling). The two lowest-energy conformers (Ib(1), Ia) differ only in the arrangement of the amino acid group relative to the phenyl ring; they exhibit a relatively strong stabilizing intramolecular hydrogen bond of the O-H...N type and the carboxylic group in the trans configuration (O=C-O-H dihedral angle ca. 180 degrees ). Type II conformers have a weaker H-bond of the N-H...O=C type, but they bear the more favorable cis arrangement of the carboxylic group. Being considerably more flexible, type II conformers are stabilized by entropy and the relative abundances of two conformers of this type (IIb(2) and IIc(1)) are shown to significantly increase with temperature due to entropic stabilization. At 423 K, these conformers are found to be the first and third most abundant species present in the conformational equilibrium, with relative populations of ca. 15% each, whereas their populations could be expected to be only ca. 5% if entropy effects were not taken into consideration. Indeed, phenylalanine can be considered a notable example of a molecule where entropy plays an essential role in determining the relative abundance of the possible low-energy conformational states and then, the thermodynamics of the compound, even at moderate temperatures. Upon UV irradiation (lambda > 235 nm) of the Matrix-isolated compound, unimolecular photodecomposition of phenylalanine is observed with production of CO(2) and phenethylamine.
-
Matrix Isolation ft ir spectra and molecular orbital calculations on neutral n n dimethylglycine
Physical Chemistry Chemical Physics, 2003Co-Authors: Igor Reva, Andrea Gomezzavaglia, Rui FaustoAbstract:The structures and vibrational spectra of the preferred conformers of the neutral form of N,N-dimethylglycine (DMG) were studied by a combined approach, using DFT(B3LYP)/6-311++G** and MP2/6-31++G** calculations and low temperature Matrix Isolation IR spectroscopy. The conformational ground state was found to be the intramolecularly O–H⋯N hydrogen-bonded GAT form, where the (lone pair)-N–C–C and N–C–CO dihedral angles are 30° (gauche; G) and ca. 180° (anti; A), respectively, and the carboxylic group assumes the trans (T) configuration (OC–O–H dihedral angle equal to 180°). The presence in the matrices of two additional conformers, where the carboxylic moiety assumes the most commonly found cis (C) conformation and the N–C–CO axis adopts the syn arrangement (the two conformers differ only in the positions of the methyl groups), could also be established. Observation of these conformers is in consonance with the theoretical predictions, which indicate that the observed conformers should differ in energy by less than 7 kJ mol−1. Full assignment of the observed infrared spectra of both DMG and its -OD isotopomer in Ar and Xe matrices was carried out on the basis of comparison with the theoretically predicted spectra and temperature variation experiments.
-
combined ftir Matrix Isolation and ab initio studies of pyruvic acid proof for existence of the second conformer
Journal of Physical Chemistry A, 2001Co-Authors: Igor Reva, Ludwik Adamowicz, S G Stepanian, Rui FaustoAbstract:The molecular structure of pyruvic acid was investigated by Matrix Isolation FTIR spectroscopy, density functional theory (DFT), and ab initio calculations performed at the RHF, MP2, MP4(SDQ), and CCSD(T) levels of theory with the aug-cc-pVDZ basis set. In these calculations, the geometries of the three lowest energy conformers of pyruvic acid were fully optimized at the DFT/B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ levels. Additionally, the relative energies of the conformers were calculated at the MP4, CCSD, and CCSD(T) levels. Harmonic frequencies and IR intensities were then calculated for these three conformers and were used to account for the zero point vibrational energy corrections and to assist the assignment of the observed bands to the different forms. We found that two conformers are present in the Ar Matrix, and both forms exhibit a planar framework with the carbonyl bonds in a trans arrangement but differ in the orientation of the hydroxyl hydrogen. By varying the temperature of the pyruvic acid...
Keiichi Ohno - One of the best experts on this subject based on the ideXlab platform.
-
absolute configuration and conformation analysis of 1 phenylethanol by Matrix Isolation infrared and vibrational circular dichroism spectroscopy combined with density functional theory calculation
Journal of Physical Chemistry A, 2007Co-Authors: Kei Shinya, Yukiteru Katsumoto, Hiromu Sugeta, Saeko Shin, Yoshiaki Hamada, Keiichi OhnoAbstract:The absolute configuration and conformation of 1-phenylethanol (1-PhEtOH) have been determined by Matrix-Isolation infrared (IR) and vibrational circular dichroism (VCD) spectroscopy combined with quantum chemical calculations. Quantum chemical calculations have identified that there are three conformers, namely, I, II, and III, in which characteristic intramolecular interactions are found. The IR spectrum−conformation correlation for 1-PhEtOH has been developed by the Ar Matrix-Isolation IR measurement and used for the assignments of the observed IR bands. In a dilute CCl4 solution, 1-PhEtOH exists predominantly as conformer I along with a trace amount of conformer II. By considering conformations and intermolecular hydrogen-bonding in the spectral simulation for (S)-1-PhEtOH, we have successfully reproduced the VCD spectrum of (−)-1-PhEtOH observed in a dilute CS2 solution. Thus, (−)-1-PhEtOH is of S-configuration and conformer I in the dilute solution. The same method has been applied to analyze the VC...
-
absolute configuration and conformation analysis of 1 phenylethanol by Matrix Isolation infrared and vibrational circular dichroism spectroscopy combined with density functional theory calculation
Journal of Physical Chemistry A, 2007Co-Authors: Kei Shinya, Yukiteru Katsumoto, Hiromu Sugeta, Saeko Shin, Yoshiaki Hamada, Keiichi OhnoAbstract:The absolute configuration and conformation of 1-phenylethanol (1-PhEtOH) have been determined by Matrix-Isolation infrared (IR) and vibrational circular dichroism (VCD) spectroscopy combined with quantum chemical calculations. Quantum chemical calculations have identified that there are three conformers, namely, I, II, and III, in which characteristic intramolecular interactions are found. The IR spectrum-conformation correlation for 1-PhEtOH has been developed by the Ar Matrix-Isolation IR measurement and used for the assignments of the observed IR bands. In a dilute CCl(4) solution, 1-PhEtOH exists predominantly as conformer I along with a trace amount of conformer II. By considering conformations and intermolecular hydrogen-bonding in the spectral simulation for (S)-1-PhEtOH, we have successfully reproduced the VCD spectrum of (-)-1-PhEtOH observed in a dilute CS(2) solution. Thus, (-)-1-PhEtOH is of S-configuration and conformer I in the dilute solution. The same method has been applied to analyze the VCD spectra measured in the liquid state of (-)-1-PhEtOH. The absolute configuration of 1-PhEtOH in the condensed phase is enabled by identifying VCD bands that are insensitive to conformational changes and intermolecular interactions. The present work provides a combinatorial procedure for determination of both the absolute configuration and the conformation of chiral molecules in a dilute solution and condensed phase.
-
experimental evidence for intramolecular blue shifting c h o hydrogen bonding by Matrix Isolation infrared spectroscopy
Journal of the American Chemical Society, 2003Co-Authors: Hiroatsu Matsuura, Kei Shinya, Hiroshi Yoshida, Munenori Hieda, Shinya Yamanaka, Takanori Harada, Keiichi OhnoAbstract:Experimental evidence for intramolecular blue-shifting C-H...O hydrogen bonding is presented. Argon Matrix-Isolation infrared spectra of 1-methoxy-2-(dimethylamino)ethane exhibit a band at 3016.5 cm-1. Spectral behavior with annealing indicates that this band is assigned to the most stable conformer, trans-gauche-(trans|gauche'), with an intramolecular C-H...O hydrogen bond. Density functional calculations show that this band arises from the stretching vibration of the C-H bond participating in the formation of the C-H...O hydrogen bond. The C-H bond is shortened by 0.004 A, and the C-H stretching band is blue-shifted by at least 35 cm-1 on the formation of the hydrogen bond. The (C)H...O distance is calculated as 2.38 A, which is shorter than the corresponding van der Waals separation by 0.3 A.
K Sundararajan - One of the best experts on this subject based on the ideXlab platform.
-
effect of methyl substitution on the n h o interaction in complexes of pyrrole with water methanol and dimethyl ether Matrix Isolation infrared spectroscopy and ab initio computational studies
Journal of Physical Chemistry A, 2018Co-Authors: Shubhra Sarkar, N Ramanathan, K SundararajanAbstract:Hydrogen-bonded interactions of pyrrole with water and methanol have been studied using Matrix Isolation infrared spectroscopy and compared with the calculation performed on dimethyl ether. Computations carried out at MP2/aug-cc-pVDZ level of theory yielded two minima for the pyrrole–water and pyrrole–methanol complexes. The global and local minima correspond to the N–H···O and O–H···π complexes, respectively, where the N–H group of pyrrole interacts with oxygen of water/methanol and O–H of water and methanol interacts with the π cloud of pyrrole. Computations performed on the pyrrole–dimethyl ether gave only N–H···O type complex. From the experimental vibrational wavenumber shifts in the N–H stretching and N–H bending modes of pyrrole, as well as in the O–H stretching modes of water and methanol, the 1:1 N–H···O complexes were discerned. The strength of the N–H···O hydrogen bond and the corresponding shift in the N–H stretching vibrational wavenumbers increases in the order pyrrole–water < pyrrole–methan...
-
blue shift of the c h stretching vibration in chf3 h2o complex Matrix Isolation infrared spectroscopy and ab initio computations
Chemical Physics, 2016Co-Authors: R Gopi, N Ramanathan, K SundararajanAbstract:Abstract As a result of hydrogen bonding in CHF 3 -H 2 O complex, ab initio computations exhibited a blue shift in the C-H stretching region of CHF 3 sub-molecule. In this work, we have investigated whether the blue-shifting in CHF 3 -H 2 O complex can be experimentally discerned using Matrix Isolation infrared spectroscopy. The 1:1 CHF 3 -H 2 O complex was therefore trapped and studied in argon and neon matrices. Experimentally a blue shift of 20.3 and 32.3 cm −1 in the C-H stretching region of CHF 3 sub-molecule for the CHF 3 -H 2 O complex was observed in argon and neon matrices. The structure of the complex and the energies were computed at MP2 level of theory using a 6-311++G(d,p) and aug-cc-pVDZ basis sets. Computations indicated only one minimum corresponded to a C-H⋯O interaction between the hydrogen of fluoroform and oxygen of water. AIM and NBO analyses were performed to understand the reasons for blue-shifting of the C-H stretching wavenumber in the complex.
-
evidence for phosphorus bonding in phosphorus trichloride methanol adduct a Matrix Isolation infrared and ab initio computational study
Journal of Physical Chemistry A, 2015Co-Authors: Prasad Ramesh Joshi, K Sundararajan, N Ramanathan, K SankaranAbstract:The weak interaction between PCl3 and CH3OH was investigated using Matrix Isolation infrared spectroscopy and ab initio computations. In a nitrogen Matrix at low temperature, the noncovalent adduct was generated and characterized using Fourier transform infrared spectroscopy. Computations were performed at B3LYP/6-311++G(d,p), B3LYP/aug-cc-pVDZ, and MP2/6-311++G(d,p) levels of theory to optimize the possible geometries of PCl3–CH3OH adducts. Computations revealed two minima on the potential energy surface, of which, the global minimum is stabilized by a noncovalent P···O interaction, known as a pnictogen bonding (phosphorus bonding or P-bonding). The local minimum corresponded to a cyclic adduct, stabilized by the conventional hydrogen bonding (Cl···H–O and Cl···H–C interactions). Experimentally, 1:1 P-bonded PCl3–CH3OH adduct in nitrogen Matrix was identified, where shifts in the P–Cl modes of PCl3, O–C, and O–H modes of CH3OH submolecules were observed. The observed vibrational frequencies of the P-bond...
-
experimental evidence for blue shifted hydrogen bonding in the fluoroform hydrogen chloride complex a Matrix Isolation infrared and ab initio study
Journal of Physical Chemistry A, 2014Co-Authors: R Gopi, N Ramanathan, K SundararajanAbstract:The 1:1 hydrogen-bonded complex of fluoroform and hydrogen chloride was studied using Matrix-Isolation infrared spectroscopy and ab initio computations. Using B3LYP and MP2 levels of theory with 6-...
-
experimental evidence for blue shifted hydrogen bonding in the fluoroform hydrogen chloride complex a Matrix Isolation infrared and ab initio study
Journal of Physical Chemistry A, 2014Co-Authors: R Gopi, N Ramanathan, K SundararajanAbstract:The 1:1 hydrogen-bonded complex of fluoroform and hydrogen chloride was studied using Matrix-Isolation infrared spectroscopy and ab initio computations. Using B3LYP and MP2 levels of theory with 6-311++G(d,p) and aug-cc-pVDZ basis sets, the structures of the complexes and their energies were computed. For the 1:1 CHF3–HCl complexes, ab initio computations showed two minima, one cyclic and the other acyclic. The cyclic complex was found to have C–H···Cl and C–F···H interactions, where CHF3 and HCl sub-molecules act as proton donor and proton acceptor, respectively. The second minimum corresponded to an acyclic complex stabilized only by the C–F···H interaction, in which CHF3 is the proton acceptor. Experimentally, we could trap the 1:1 CHF3–HCl cyclic complex in an argon Matrix, where a blue-shift in the C–H stretching mode of the CHF3 sub-molecule was observed. To understand the nature of the interactions, Atoms in Molecules and Natural Bond Orbital analyses were carried out to unravel the reasons for blu...
Igor Reva - One of the best experts on this subject based on the ideXlab platform.
-
structure of isolated 1 4 butanediol combination of mp2 calculations nbo analysis and Matrix Isolation infrared spectroscopy
Journal of Physical Chemistry A, 2008Co-Authors: A Lopes J Jesus, Igor Reva, Rui Fausto, Mario T S Rosado, Ermelinda M S Eusebio, J S RedinhaAbstract:Theoretical calculations at the MP2 level, NBO and AIM analysis, and Matrix-Isolation infrared spectroscopy have been used to investigate the structure of the isolated molecule of 1,4-butanediol (1,4-BDO). Sixty-five structures were found to be minima on the potential energy surface, and the three most stable forms are characterized by a folded backbone conformation leading to the formation of an intramolecular H-bond. To better characterize the intramolecular interactions and particularly the hydrogen bonds, natural bond orbital analysis (NBO) was performed for the four most stable conformers, and was further complemented with an atoms-in-molecules (AIM) topological analysis. Infrared spectra of 1,4-BDO isolated in low-temperature argon and xenon Matrixes show a good agreement with a population-weighted mean theoretical spectrum, and the spectral features of the conformers expected to be trapped in the Matrixes were observed experimentally. Annealing the xenon Matrix from 20 to 60 K resulted in significant spectral changes, which were interpreted based on the barriers to intramolecular rotation. An estimation of the intramolecular hydrogen bond energy was carried out following three different methodologies.
-
importance of entropy in the conformational equilibrium of phenylalanine a Matrix Isolation infrared spectroscopy and density functional theory study
Journal of Physical Chemistry A, 2006Co-Authors: Agnieszka Kaczor, Igor Reva, Leonard M Proniewicz, Rui FaustoAbstract:The conformational behavior and infrared spectrum of l-phenylalanine were studied by Matrix-Isolation infrared spectroscopy and DFT [B3LYP/6-311++G(d,p)] calculations. The fourteen most stable structures were predicted to differ in energy by less than 10 kJ mol(-1), eight of them with abundances higher than 5% at the temperature of evaporation of the compound (423 K). Experimental results suggest that six conformers contribute to the spectrum of the isolated compound, whereas two conformers (IIb(3) and IIIb(3)) relax in Matrix to a more stable form (IIb(2)) due to low energy barriers for conformational isomerization (conformational cooling). The two lowest-energy conformers (Ib(1), Ia) differ only in the arrangement of the amino acid group relative to the phenyl ring; they exhibit a relatively strong stabilizing intramolecular hydrogen bond of the O-H...N type and the carboxylic group in the trans configuration (O=C-O-H dihedral angle ca. 180 degrees ). Type II conformers have a weaker H-bond of the N-H...O=C type, but they bear the more favorable cis arrangement of the carboxylic group. Being considerably more flexible, type II conformers are stabilized by entropy and the relative abundances of two conformers of this type (IIb(2) and IIc(1)) are shown to significantly increase with temperature due to entropic stabilization. At 423 K, these conformers are found to be the first and third most abundant species present in the conformational equilibrium, with relative populations of ca. 15% each, whereas their populations could be expected to be only ca. 5% if entropy effects were not taken into consideration. Indeed, phenylalanine can be considered a notable example of a molecule where entropy plays an essential role in determining the relative abundance of the possible low-energy conformational states and then, the thermodynamics of the compound, even at moderate temperatures. Upon UV irradiation (lambda > 235 nm) of the Matrix-isolated compound, unimolecular photodecomposition of phenylalanine is observed with production of CO(2) and phenethylamine.
-
Matrix Isolation ft ir spectra and molecular orbital calculations on neutral n n dimethylglycine
Physical Chemistry Chemical Physics, 2003Co-Authors: Igor Reva, Andrea Gomezzavaglia, Rui FaustoAbstract:The structures and vibrational spectra of the preferred conformers of the neutral form of N,N-dimethylglycine (DMG) were studied by a combined approach, using DFT(B3LYP)/6-311++G** and MP2/6-31++G** calculations and low temperature Matrix Isolation IR spectroscopy. The conformational ground state was found to be the intramolecularly O–H⋯N hydrogen-bonded GAT form, where the (lone pair)-N–C–C and N–C–CO dihedral angles are 30° (gauche; G) and ca. 180° (anti; A), respectively, and the carboxylic group assumes the trans (T) configuration (OC–O–H dihedral angle equal to 180°). The presence in the matrices of two additional conformers, where the carboxylic moiety assumes the most commonly found cis (C) conformation and the N–C–CO axis adopts the syn arrangement (the two conformers differ only in the positions of the methyl groups), could also be established. Observation of these conformers is in consonance with the theoretical predictions, which indicate that the observed conformers should differ in energy by less than 7 kJ mol−1. Full assignment of the observed infrared spectra of both DMG and its -OD isotopomer in Ar and Xe matrices was carried out on the basis of comparison with the theoretically predicted spectra and temperature variation experiments.
-
conformers of nonionized proline Matrix Isolation infrared and post hartree fock ab initio study
Journal of Physical Chemistry A, 2001Co-Authors: S G Stepanian, Igor Reva, E D Radchenko, Ludwik AdamowiczAbstract:Matrix-Isolation IR spectroscopy and ab initio calculations performed at the DFT, MP2, MP4, and CCSD(T) levels of theory were employed to investigate the conformational topology of the nonionized amino acid proline and its deuterated derivative, N,O-dideuteroproline (proline-d2). In the calculations, equilibrium structures of 15 low-energy proline conformers were obtained using the DFT/B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ methods. The harmonic frequencies and IR intensities of the conformers were calculated for the DFT geometries, and these data was used to account for the zero-point vibration energy correction and to assist the analysis of the experimental Matrix-Isolation IR spectra. Two proline conformers were found to be present in the Ar Matrix. They are the lowest energy conformer with a N···HO H bond (conformer IIa) and the second conformer with a NH···OC H bond (conformer Ia). We found that the DFT/B3LYP and MP2 methods are not capable of predicting the relative energies of the proline conformers...
-
combined ftir Matrix Isolation and ab initio studies of pyruvic acid proof for existence of the second conformer
Journal of Physical Chemistry A, 2001Co-Authors: Igor Reva, Ludwik Adamowicz, S G Stepanian, Rui FaustoAbstract:The molecular structure of pyruvic acid was investigated by Matrix Isolation FTIR spectroscopy, density functional theory (DFT), and ab initio calculations performed at the RHF, MP2, MP4(SDQ), and CCSD(T) levels of theory with the aug-cc-pVDZ basis set. In these calculations, the geometries of the three lowest energy conformers of pyruvic acid were fully optimized at the DFT/B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ levels. Additionally, the relative energies of the conformers were calculated at the MP4, CCSD, and CCSD(T) levels. Harmonic frequencies and IR intensities were then calculated for these three conformers and were used to account for the zero point vibrational energy corrections and to assist the assignment of the observed bands to the different forms. We found that two conformers are present in the Ar Matrix, and both forms exhibit a planar framework with the carbonyl bonds in a trans arrangement but differ in the orientation of the hydroxyl hydrogen. By varying the temperature of the pyruvic acid...
Sebastian Riedel - One of the best experts on this subject based on the ideXlab platform.
-
Matrix Isolation and quantum chemical analysis of the c3v conformer of xef6 xeof4 and their acetonitrile adducts
Journal of Physical Chemistry A, 2018Co-Authors: Maxim Gawrilow, Sebastian Riedel, Helmut Beckers, Lan ChengAbstract:A joint experimental-computational study of the molecular structure and vibrational spectra of the XeF6 molecule is reported. The vibrational frequencies, intensities, and in particular the isotopic frequency shifts of the vibrational spectra for 129XeF6 and 136XeF6 isotopologues recorded in the neon Matrix agree very well with those obtained from relativistic coupled-cluster calculations for XeF6 in the C3v structure, thereby strongly supporting the observation of the C3v conformer of the XeF6 molecule in the neon Matrix. A C3v transition state connecting the C3v and Oh local minima is located computationally. The calculated barrier of 220 cm–1 between the C3v minima and the transition state corroborates the experimental observation of the C3v conformer and the absence of the Oh conformer in solid noble gas matrices. For comparison Matrix-Isolation spectra have also been recorded and analyzed for the 129XeOF4 and the 136XeOF4 isotopologues. The Matrix-Isolation complexation shifts obtained for the XeF6·N...
-
Matrix Isolation and quantum chemical analysis of the c3v conformer of xef6 xeof4 and their acetonitrile adducts
Journal of Physical Chemistry A, 2018Co-Authors: Maxim Gawrilow, Sebastian Riedel, Helmut Beckers, Lan ChengAbstract:A joint experimental-computational study of the molecular structure and vibrational spectra of the XeF6 molecule is reported. The vibrational frequencies, intensities, and in particular the isotopic frequency shifts of the vibrational spectra for 129XeF6 and 136XeF6 isotopologues recorded in the neon Matrix agree very well with those obtained from relativistic coupled-cluster calculations for XeF6 in the C3v structure, thereby strongly supporting the observation of the C3v conformer of the XeF6 molecule in the neon Matrix. A C3v transition state connecting the C3v and Oh local minima is located computationally. The calculated barrier of 220 cm-1 between the C3v minima and the transition state corroborates the experimental observation of the C3v conformer and the absence of the Oh conformer in solid noble gas matrices. For comparison Matrix-Isolation spectra have also been recorded and analyzed for the 129XeOF4 and the 136XeOF4 isotopologues. The Matrix-Isolation complexation shifts obtained for the XeF6·NCCH3 relative to those of free Matrix isolated XeF6 and CH3CN are in good agreement with those reported for crystalline XeF6·NCCH3.
-
a Matrix Isolation and computational study of molecular palladium fluorides does pdf6 exist
ChemInform, 2016Co-Authors: Antony V Wilson, Sebastian Riedel, Lester Andrews, Xuefeng Wang, Felix Brosi, Timothy Nguyen, Adam J Bridgeman, Nigel A YoungAbstract:Binary palladium fluorides from PdF to PdF6 are investigated by Matrix-Isolation methods using thermal evaporation and laser ablation to generate Pd atoms for reaction with F2-doped Ar and Ne matrices as well as neat F2 matrices.
-
extending the row of lanthanide tetrafluorides a combined Matrix Isolation and quantum chemical study
Chemistry: A European Journal, 2016Co-Authors: Thomas Ventschmidt, Zongtang Fang, Zachary Lee, David A Dixon, Sebastian RiedelAbstract:Only the neutral tetrafluorides of Ce, Pr, and Tb as well as the [LnF7 ](3-) anions of Dy and Nd, with the metal in the +IV oxidation state, have been previously reported. We report our attempts to extend the row of neutral lanthanide tetrafluorides through the reaction of laser-ablated metal atoms with fluorine and their stabilization and characterization by Matrix-Isolation IR spectroscopy. In addition to the above three tetrafluorides, we found two new tetrafluorides, (3) NdF4 and (7) DyF4 , both of which are in the +IV oxidation state, which extends this lanthanide oxidation state to two new metals. Our experimental results are supported by quantum-chemical calculations and the role of the lanthanide oxidation state is discussed for both the LnF4 and [LnF4 ](-) species. Most of the LnF4 species are predicted to be in the +IV oxidation state and all of the [LnF4 ](-) anions are predicted to be in the +III oxidation state. The LnF4 species are predicted to be strong oxidizing agents and the LnF3 species are predicted to be moderate to strong Lewis acids.
-
polyfluorides and neat fluorine as host material in Matrix Isolation experiments
Chemistry: A European Journal, 2015Co-Authors: Felix Brosi, Helmut Beckers, Thomas Ventschmidt, Stefanie Kieninger, Tobias Schloder, Sebastian RiedelAbstract:The use of neat fluorine in Matrix Isolation is reported, as well as the formation of polyfluoride monoanions under cryogenic conditions. Purification procedures and spectroscopic data of fluorine are described, and Matrix shifts of selected molecules and impurities in solid fluorine are compared to those of common Matrix gases (Ar, Kr, N2 , Ne). The reaction of neat fluorine and IR-laser ablated metal atoms to yield fluorides of chromium (CrF5 ), palladium (PdF2 ), gold (AuF5 ), and praseodymium (PrF4 ) has been investigated. The fluorides have been characterized in solid fluorine by IR spectroscopy at 5 K. Also the fluorination of Kr and the photo-dismutation of XeO4 have been studied by using IR spectroscopy in neat fluorine. Formation of the [F5 ](-) ion was obtained by IR-laser ablation of platinum in the presence of fluorine and proven in a Ne Matrix at 5 K by two characteristic vibrational bands of [F5 ](-) at $\tilde \nu $=850.7 and 1805.0 cm(-1) and its photo-behavior.