An assessment of theoretical procedures for the calculation of reliable radical stabilization energies †‡

Abstract

The performance of a variety of theoretical methods in computing stabilization energies of the substituted methyl and vinyl radicalsThe influence of electron correlation (UHF, UMP2, PMP2, RMP2, UB3-LYP, UQCISD, UQCISD(T), UCCSD(T), URCCSD(T) and RRCCSD(T)) and basis set size (from 6-31G(d) to 6-311ϩϩG(3df,3pd)) on stabilization energies is evaluated, as well as the performance of compound methods such as G2, G3, CBS-Q and CBS-APNO and their variants. The results indicate that generally reliable radical stabilization energies can be obtained at modest cost using RMP2/6-311ϩG(2df,p)//RMP2/6-31G(d) energies. A slightly less accurate but more economical procedure is RMP2/ 6-311ϩG(d)//B3-LYP/6-31G(d). UMP2 and PMP2 are unsuitable for obtaining radical stabilization energies for spincontaminated radicals, while UB3-LYP appears generally to overestimate stabilization energies. Computational methodsAb initio molecular orbital calculations 11 were performed using the GAUSSIAN94, 12 GAUSSIAN98, 13 ACESII 14 and MOLPRO96 15 computer programs. The effect of the level of theory on geometries, zero-point vibrational energies, heats of formation and radical stabilization energies has been examined. The theoretical methods include HF, MP2, B3-LYP, QCISD, QCISD(T) and CCSD(T), with basis sets ranging from 6-31G(d) to 6-311ϩϩG(3df,3pd

Molecular Modeling Study of Quercetin and their Metal Complexes

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Antioxidant behavior of mearnsetin and myricetin flavonoid compounds — A DFT study

“…The more delocalized spin density in the radical, the easier is the radical formed and thus the lower is the BDE [47]. In order to explain the variation in the reactivity of the OH groups and the differences in BDE, we have made an attempt to analyze the spin density on the radical species of mearnsetin and myricetin flavonoid compounds.…”

An experimental and computational study on the dissociation behavior of hydroxypyridine N‐oxides in atmospheric pressure ionization mass spectrometry

“…Furthermore, in order to confirm that the relative energies obtained draw the correct trend, single-point restricted open-shell (ROMP2) calculations [16] were carried out for the entire set of previously optimized structures to deal with spin contamination. [17] Calculations were performed in the Centro de Cómputos de Alto Rendimiento, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires.…”