Communication: A hydrogen-bonded difluorocarbene complex: <i>Ab initio</i> and matrix isolation study

Sosulin, Ilya S.; Shiryaeva, Ekaterina S.; Tyurin, Daniil A.; Feldman, Vladimir I.

doi:10.1063/1.4999772

Cited by 18 publications

(8 citation statements)

References 26 publications

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“…The atomic basis sets are now made available 93 that allow quantitative calculations of the structure and energetics of typical molecular systems. We are somewhat sorry for our belated report, for they have already been, and are being, used by our colleagues in their studies of unusual molecules under the unusual conditions of lowtemperature high-energy chemistry [94][95][96][97][98][99][100] .…”

Section: Discussionmentioning

confidence: 99%

Atomic basis functions for molecular electronic structure calculations

Laikov

2019

Theor Chem Acc

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Electronic structure methods for accurate calculation of molecular properties have a high cost that grows steeply with the problem size, therefore, it is helpful to have the underlying atomic basis functions that are less in number but of higher quality. Following our earlier work [Chem. Phys. Lett. 416, 116 (2005)] where general correlation-consistent basis sets are defined, for any atom, as solutions of purely atomic functional minimization problems, and which are shown to work well for chemical bonding in molecules, we take a further step here and define a new kind of atomic polarization functionals, the minimization of which yields additional sets of diffuse functions that help to calculate better molecular electron affinities, polarizabilities, and intermolecular dispersion interactions. Analytical representations by generally-contracted Gaussian functions of up to microhartree numerical accuracy grades are developed for atoms Hydrogen through Nobelium within the four-component Dirac-Coulomb theory and its scalar-relativistic approximation, and also for Hydrogen through Krypton in the two-component nonrelativistic case. The convergence of correlation energy with the basis set size is studied, and complete-basis-set extrapolation formulas are developed.

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Section: Discussionmentioning

confidence: 99%

Atomic basis functions for molecular electronic structure calculations

Laikov

2019

Theor Chem Acc

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“…The D 0 of 6.4 and 9.3 kcal mol −1 for the HCl and HF adducts, respectively, are much larger than the classical hydrogen-bond dissociation energies 27 of 3.0 kcal mol −1 for (H 2 O) 2 or (HF) 2 ; however, the dissociation energy of the H 2 O:HF adduct is 6.3 kcal mol −1 . Sosulin et al 13 showed that a weak H-bonded complex existed from the interaction of a F atom of :CF 2 and HF as well as the much stronger bond from the interaction with the electron pair of :CF 2 . We confirmed Sosulin's result with a M06-2X calculation.…”

Section: Discussionmentioning

confidence: 99%

“…Gas-phase, unimolecular, 1,1-HX (X = F, Cl) elimination reactions of 1,1-dihaloalkanes give singlet-state halocarbenes + HX as products. − The halogen atom stabilizes the singlet halocarbene, which is the ground state, and the enthalpy of these reactions is typically about 70 kcal mol –1 . In addition to interest in kinetics of these reactions, − adducts between carbenes and HX molecules provide examples of hydrogen bonding to a carbon atom, and such adducts are beginning to receive attention − in the hydrogen-bond literature. The current study of C 2 D 5 CHFCl provides additional examples of carbene:HX adducts.…”

Section: Introductionmentioning

confidence: 99%

“…For some reactions, energies of certain fixed points on the potential surface were improved by CCSD(T) calculations. Dissociation energies of RC(X)C:HX adducts are of importance for understanding the role of potential wells in exit channels of 1,1-HX reactions, or conversely entrance channels for reactions of carbenes with HX or other electron-pair acceptors. − The effect of substituents on the calculated dissociation energy of carbene:HCl adducts also was monitored. Vibrational frequencies and moments of inertia of the molecule and transition states are used to calculate statistical rate constants, which are compared to experimental rate constants to assign experimental threshold energies, E 0 , to the four unimolecular reactions of C 2 D 5 CHFCl.…”

Section: Introductionmentioning

confidence: 99%

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Experimental and Computational Studies of Unimolecular 1,1-HX (X = F, Cl) Elimination Reactions of C₂D₅CHFCl: Role of Carbene:HF and HCl Adducts in the Exit Channel of RCHFCl and RCHCl₂ Reactions

et al. 2019

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The gas-phase unimolecular reactions of C 2 D 5 CHFCl molecules with 94 kcal mol −1 of vibrational energy have been studied by the chemical-activation experimental technique and by electronic-structure computations. Products from the reaction of C 2 D 5 CHFCl molecules, formed by the recombination of C 2 D 5 and CHFCl radicals in a room temperature bath gas, were measured by gas chromatography− mass spectrometry. The 2,1-DCl (81%) and 1,1-HCl (17%) elimination reactions are the principal processes, but 2,1-DF and 1,1-HF elimination reactions also are observed. Comparison of experimental rate constants to calculated statistical rate constants provides threshold energies. The potential surfaces associated with C 2 D 5 (F)C: + HCl and C 2 D 5 (Cl)C: + HF reactions are of special interest because hydrogen-bonded adducts with HCl and HF with dissociation energies of 6.4 and 9.3 kcal mol −1 , respectively, are predicted by calculations. The relationship between the geometries and threshold energies of transition states for 1,1-HCl elimination and carbene:HCl adducts is complex, and previous studies of related molecules, such as CD 3 CHFCl, CD 2 ClCHFCl, C 2 D 5 CHCl 2 , and halogenated methanes are included in the computational analysis. Extensive calculations for CH 3 CHFCl as a model for 1,1-HCl reactions illustrate properties of the exit-channel potential energy surface. Since the 1,1-HCl transition state is submerged relative to dissociation of the adduct, inner and outer transition states should be considered for analysis of rate constants describing 1,1-HCl elimination and addition reactions of carbenes to HCl.

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“…Fluorocarbons, such as CH 2 F 2 and CHF 3 , are considered as ecologically acceptable alternative to conventional chlorofluorocarbons, which are supposed to be responsible for ozone layer depletion . The radiation-induced generation of radicals and other reactive intermediates from fluoroform (CHF 3 ) was recently investigated in our laboratory using matrix isolation FTIR spectroscopy. , …”

Section: Introductionmentioning

confidence: 99%

Radiation-Induced Transformation of CHF₃···CO to the CF₃···CO Complex: Matrix Isolation and Ab Initio Study

2020

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The X-ray-induced transformations of CHF3/CO/Ar and CHF3/CO/Kr systems were investigated by Fourier transform infrared (FTIR) matrix isolation spectroscopy at 6 K. It was found that addition of CO suppressed decomposition of fluoroform in an Ar matrix, probably because of trapping of matrix holes by CO and CHF3···CO complexes. Considerable increase of the CF3/CF2 ratio with increasing CO content in the matrix was attributed to stabilization of the CF3 radical with respect to further radiation-induced fragmentation because of its complexation with the CO molecule. The CF3···CO complex generated from the CHF3···CO precursor complex was characterized by FTIR spectroscopy and ab initio calculations at the CCSD(T) and MP2 levels of theory. To the best of our knowledge, it is the first experimentally observed complex of the CF3 radical. The computed interaction energy was found to be 0.35 kcal/mol at the CCSD(T)/L2a_3 level (0.36 kcal/mol at the MP2/L2a_3 level), taking into account zero-point energy and basis set superposition error corrections. Despite the very weak intermolecular bonding, the complex is characterized by distinct features in the regions of C–F symmetric and antisymmetric stretching (CF3) and CO stretching (the latter one was observed only in a krypton matrix). The geometrical structure of the radical–molecule complex is close to that of its molecular precursor.

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Communication: A hydrogen-bonded difluorocarbene complex: Ab initio and matrix isolation study

Cited by 18 publications

References 26 publications

Atomic basis functions for molecular electronic structure calculations

Atomic basis functions for molecular electronic structure calculations

Experimental and Computational Studies of Unimolecular 1,1-HX (X = F, Cl) Elimination Reactions of C₂D₅CHFCl: Role of Carbene:HF and HCl Adducts in the Exit Channel of RCHFCl and RCHCl₂ Reactions

Radiation-Induced Transformation of CHF₃···CO to the CF₃···CO Complex: Matrix Isolation and Ab Initio Study

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Communication: A hydrogen-bonded difluorocarbene complex: Ab initio and matrix isolation study

Cited by 18 publications

References 26 publications

Atomic basis functions for molecular electronic structure calculations

Atomic basis functions for molecular electronic structure calculations

Experimental and Computational Studies of Unimolecular 1,1-HX (X = F, Cl) Elimination Reactions of C2D5CHFCl: Role of Carbene:HF and HCl Adducts in the Exit Channel of RCHFCl and RCHCl2 Reactions

Radiation-Induced Transformation of CHF3···CO to the CF3···CO Complex: Matrix Isolation and Ab Initio Study

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Experimental and Computational Studies of Unimolecular 1,1-HX (X = F, Cl) Elimination Reactions of C₂D₅CHFCl: Role of Carbene:HF and HCl Adducts in the Exit Channel of RCHFCl and RCHCl₂ Reactions

Radiation-Induced Transformation of CHF₃···CO to the CF₃···CO Complex: Matrix Isolation and Ab Initio Study