Density functional study of isomerization of fluoro- and chloroformaldehyde radical cations

Ventura, Oscar N.; Kieninger, Martina; Coitiño, Elena L.

doi:10.1002/(sici)1096-987x(199608)17:11<1309::aid-jcc3>3.0.co;2-q

Cited by 10 publications

(8 citation statements)

References 56 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Increasing the basis set decreases slightly the interaction energy at the CCSD(T). Thus, as shown in previous studies, B3LYP seems to perform much better than UMP2 for radical cation systems. As found for the model system, the B3LYP calculations for the base pair radical cations present values of S 2 between 0.76 and 0.78, while the UHF values lie within 0.92 and 1.3.…”

Section: Model System: Formamidine−formamide Dimersupporting

confidence: 80%

“…B3LYP calculations always collapsed to the single proton transferred complex. As it was found for the phenol-ammonia cation,23f the nonproton transferred minimum at the MP2 level is probably an artifact produced by the spin contamination of the reference wave function ( S 2 = 1.0). Note that the projected MP2 energies as well as the values obtained with the more extensive electron correlation CCSD(T) method increase the stability of the FI • (−H + )−FA(+H + ) isomer compared to that of FI •+ −FA.…”

Section: Model System: Formamidine−formamide Dimermentioning

confidence: 56%

“…These studies have shown that the nonlocal methods that include gradient corrections, in particular the B3LYP one, provide results comparable to MP2 when similar basis sets are used. Moreover, for different radical cations, the B3LYP method has been shown to perform much better than the more computationally demanding UMP2 one, due to the fact that the perturbation expansion converges slowly when the UHF reference wave function has large spin contamination . In contrast, B3LYP does not overestimate spin polarization, which has been related to spin contamination …”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Single versus Double Proton-Transfer Reactions in Watson−Crick Base Pair Radical Cations. A Theoretical Study

et al. 1998

View full text Add to dashboard Cite

Single and double proton-transfer reactions in Watson−Crick Guanine−Cytosine (GC) and Adenine−Thymine (AT) radical cations have been studied using the hybrid density functional B3LYP method. Calibration calculations for the formamidine−formamide dimer, a model system of AT, have shown that B3LYP compares well to the high level ab initio correlated method CCSD(T), both for the neutral and cationic systems. The single proton-transfer reaction is favorable in both the GC and AT radical cations; it takes place from the ionized monomer (guanine and adenine, respectively), which increases its acidity, to the neutral fragment. For the two systems, GC and AT, the nonproton transferred and single proton transferred structures are almost degenerate (ΔE = 1.2 kcal/mol), and the process presents low energy barriers (4.3 kcal/mol for GC and 1.6 kcal/mol for AT). The double proton-transfer reaction is less favorable than the single one, in contrast to what is observed for the neutral systems. The relative stability of the different structures can be understood considering two factors: the relative stability of the asymptotes from which they derive and the number and sequence of the strong and weak hydrogen bonds formed. For the same number of strong short hydrogen bonds, the most stable structures are those in which the strong H-bonds are neighbors. Based on these considerations, a prediction for other pairings is reported.

show abstract

Section: Model System: Formamidine−formamide Dimersupporting

confidence: 80%

Section: Model System: Formamidine−formamide Dimermentioning

confidence: 56%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Single versus Double Proton-Transfer Reactions in Watson−Crick Base Pair Radical Cations. A Theoretical Study

et al. 1998

View full text Add to dashboard Cite

show abstract

“…In particular, for the methanol radical cation, Radom et al 42 have shown that the MP2 method gives an artificially short C-O bond length due to an overestimation of the effects of hyperconjugation, while at the B3LYP level this effect is only slightly overestimated leading to results in much better agreement with high level CCSD(T) 42 and G2 methods. 43 Ventura et al 44 have shown that the bad description of the XHCO + radical cations at the Hartree-Fock level leads to an oscillatory behavior of the MPn series. There are other examples in the literature in which the B3LYP method is shown to provide better results than MP2.…”

Section: Methodsmentioning

confidence: 99%

“…In particular, for the methanol radical cation, Radom et al have shown that the MP2 method gives an artificially short C−O bond length due to an overestimation of the effects of hyperconjugation, while at the B3LYP level this effect is only slightly overestimated leading to results in much better agreement with high level CCSD(T) 42 and G2 methods . Ventura et al have shown that the bad description of the XHCO + radical cations at the Hartree−Fock level leads to an oscillatory behavior of the MP n series. There are other examples in the literature in which the B3LYP method is shown to provide better results than MP2. − The failure of the MP2 method for these systems has mainly been attributed to the spin contamination of the UHF wave function, since it is well-known that the Møller−Plesset perturbation expansion converges slowly when the UHF reference wave function has large spin contamination. , Improved energies can be obtained by employing a projector formalism which annihilates the contamination of higher spins .…”

Section: Methodsmentioning

confidence: 99%

Theoretical Study of the Ionization of Phenol−Water and Phenol−Ammonia Hydrogen-Bonded Complexes

1997

View full text Add to dashboard Cite

The ionization of phenol−water and phenol−ammonia complexes have been determined both using ab initio methods that include electron correlation and the hybrid three-parameter B3LYP density functional method. The most stable structure of phenol−water cation corresponds to the C6H5OH+−H2O non-proton-transferred complex. However, for the phenol−ammonia cation the calculations indicate that the only minimum on the potential energy surface corresponds to the C6H5O−NH4 + proton transferred form. The computed B3LYP adiabatic ionization potentials for C6H5OH−H2O and C6H5OH−NH3 have been determined to be 7.65 and 7.33 eV, respectively. The results obtained indicate that, for the neutral H-bonded systems, the B3LYP density functional method yields very similar results to those obtained with the ab initio MP2 or MCPF methods. However, for the ionized radical cations, B3LYP results compare much better with experiment and to the MCPF method than UMP2. The unscaled B3LYP vibrational frequencies are in very good agreement with the known experimental data.

show abstract

Theoretical study of reaction of trifluoromethyl radical with hydroxyl and hydrogen radicals

1998

View full text Add to dashboard Cite

Ab initio molecular orbital theory and density functional theory calculations have been carried out on the reactions of the trifluoromethyl radical with the hydroxyl and the hydrogen radicals. These reactions are key reactions that underlie a new fire extinguishing mechanism of non‐bromine‐containing halon replacements. The activation energies calculated by the MP2 and QCISD methods are in good agreement with the experimental values. The B3LYP, as well as MP2 and QCISD, give good results for the calculations of the heats of reactions. The GAUSSIAN‐1 and GAUSSIAN‐2 theory calculations present the most acxcurate results on both the activation energies and the heats of reactions. The effects of the scaling factors on the activation energies and the heats of reactions are also evaluated. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 277–289, 1998

show abstract

Density functional study of isomerization of fluoro- and chloroformaldehyde radical cations

Cited by 10 publications

References 56 publications

Single versus Double Proton-Transfer Reactions in Watson−Crick Base Pair Radical Cations. A Theoretical Study

Single versus Double Proton-Transfer Reactions in Watson−Crick Base Pair Radical Cations. A Theoretical Study

Theoretical Study of the Ionization of Phenol−Water and Phenol−Ammonia Hydrogen-Bonded Complexes

Theoretical study of reaction of trifluoromethyl radical with hydroxyl and hydrogen radicals

Contact Info

Product

Resources

About