Infrared and EPR Spectra of the Difluoronitroxide Radical

Misochko, Eugenii Ya.; Акимов, А. В.; Goldschleger, Ilya U.; Wight, Charles A.

doi:10.1021/ja9821450

Cited by 18 publications

(15 citation statements)

References 15 publications

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“…However, annealing for 100 min at 26 K results in the formation of several product bands (trace b) that were identified as FO 2 , F 3 NO, and F 2 NO. The last of these is a new species whose infrared bands were identified for the first time in a preliminary report of this work . A key piece of evidence for identifying the F 2 NO radical was the observation of its EPR spectrum in experiments carried out under similar conditions (vide infra).…”

Section: Resultsmentioning

confidence: 71%

“…We recently reported that F 2 NO and F−FNO are formed in an argon matrix containing NO and F 2 when samples are photolyzed at 355 nm and subsequently annealed at 24 K for 100 min. The method takes advantage of the ability of F atoms to diffuse long distances through solid argon at temperatures above 20 K (i.e., well below its melting point), , thereby forming unstable radicals and reaction intermediates that are isolated from photolytic precursor molecules. − A propitious combination of EPR and FTIR spectroscopic detection (carried out in separate experiments under similar conditions) allowed us to unambiguously identify the F 2 NO radical and to report its fundamental vibrational frequencies for the first time.…”

Section: Introductionmentioning

confidence: 99%

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Endothermic Formation of a Chemical Bond by Entropic Stabilization: Difluoronitroxide Radical in Solid Argon

et al. 1998

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Difluoronitroxide radical (F2NO) has been formed in solid argon matrices by successive addition of two diffusing F atoms to NO. This radical exists in dynamic equilibrium with a van der Waals complex (F−FNO). Measurements of the equilibrium concentrations as a function of temperature show that the changes in enthalpy and the entropy associated with formation of the F2NO radical are ΔH = 1240 ± 180 J/mol and ΔS = 62 ± 10 J/(mol K). Because both these quantities are positive, the equilibrium favors F2NO only at elevated temperatures. This situation is a rare case in which formation of a chemical bond is stabilized only by an increase in the entropy of the system.

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Section: Resultsmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Endothermic Formation of a Chemical Bond by Entropic Stabilization: Difluoronitroxide Radical in Solid Argon

et al. 1998

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“…Hence, we compare our results whenever possible with data obtained from microwave spectroscopy in the gas phase. However, in the case of BO, CO + , FCO, NO 2 , and SiF 3 , gas phase values are available only for B, C, N, and F and in the case of HCO only for H. For other cases, we resort to a comparison with the available EPR data recorded in rare gas matrices (O in BO, C in HCO and FCO, O in CO + , N, F in F 2 NO), in a methane matrix (O in HCO), in a SF 6 matrix (N, F in F 2 NO, Si in SiF 3 ), in solid solution of SF 6 (O in NO 2 ), or in single crystals (CH 3 SO). These results differ from the gas phase values, and in some cases the differences are substantial, e.g., the fluorine iHFCCs in FCO measured in the gas phase and in solid carbon monoxide differ by 80 MHz (see Table ).…”

Section: Resultsmentioning

confidence: 99%

Accurate Prediction of Hyperfine Coupling Tensors for Main Group Elements Using a Unitary Group Based Rigorously Spin-Adapted Coupled-Cluster Theory

Datta

Gauß

2019

J. Chem. Theory Comput.

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We present the development of a perturbative triples correction scheme for the previously reported unitary group based spin-adapted combinatoric open-shell coupled-cluster (CC) singles and doubles (COS-CCSD) approach and report on the applications of the newly developed method, termed “COS-CCSD(T)”, to the calculation of hyperfine coupling (HFC) tensors for radicals consisting of hydrogen, second- and third-row elements. The COS-CCSD(T) method involves a single noniterative step with scaling of the computational cost for the calculation of triples corrections to the energy. The key feature of this development is the use of spatial semicanonical orbitals generated from standard restricted open-shell Hartree–Fock (ROHF) orbitals, which allows the unperturbed Hamiltonian operator to be defined in terms of a diagonal spin-free Fock operator. The HFC tensors are computed as a first-order property via implementation of an analytic derivative scheme. The required one-particle spin density matrix is computed by using one- and two-particle spin-free density matrices that are obtained from the analytic derivative implementation, in this way avoiding the use of any spin-dependent operator and maintaining spin adaptation of the CC wavefunction. Benchmark calculations of HFC tensors for a set of 21 radicals indicate reasonably good agreement of the COS-CCSD(T) results with experiment and a consistent improvement over the COS-CCSD method. We demonstrate that the accuracies of the isotropic hyperfine coupling constants obtained in unrestricted HF (UHF) reference based spin–orbital CCSD(T) calculations deteriorate when spin contamination in the UHF wavefunction is large, and the results may even become qualitatively incorrect when spin polarization is the driving mechanism. Within a similar noniterative perturbative treatment of triple excitations, the spin-adapted COS-CCSD(T) approach produces accurate results, thus ensuring cost-effectiveness together with reliability.

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“…151 This species was stabilised in solid argon (radical was generated in successive reactions of diffusing fluorine atoms with isolated NO molecule). 152,153 IR and EPR spectroscopic studies revealed that in the temperature range 17 ± 35 K the radical F 2 NO . exists in dynamic equilibrium with the pre-reaction com-…”

Section: F2nomentioning

confidence: 99%

Modern applications of matrix isolation technique to investigation of radical species generated in atom–molecular chemical reactions

Misochko¹,

Акимов²,

Goldschleger³

2003

Russ. Chem. Rev.

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Infrared and EPR Spectra of the Difluoronitroxide Radical

Cited by 18 publications

References 15 publications

Endothermic Formation of a Chemical Bond by Entropic Stabilization: Difluoronitroxide Radical in Solid Argon

Endothermic Formation of a Chemical Bond by Entropic Stabilization: Difluoronitroxide Radical in Solid Argon

Accurate Prediction of Hyperfine Coupling Tensors for Main Group Elements Using a Unitary Group Based Rigorously Spin-Adapted Coupled-Cluster Theory

Modern applications of matrix isolation technique to investigation of radical species generated in atom–molecular chemical reactions

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