EPR spectroscopy and hybrid density functional studies of dialkoxyphosphinyl-phenyl iminoxy radicals

Density functional theory and ab initio studies on hyperfine coupling constants of phosphinyl radicals

“…The fourth rung of the ladder consists of the hybrid functionals, that is, those that include a mixture of HF exchange with DFT exchange‐correlation functionals. A prominent member of this group is the functional B3LYP, which is the “workhorse” of applied quantum chemistry, and its successful applications to A iso of 2p radicals have been reported . Although the A ii dip values predicted in this study with B3LYP correspond well with experiments, the A iso values appear inferior to their counterparts at the TPSS level.…”

Toward an Understanding of the Ambiguous Electron Paramagnetic Resonance Spectra of the Iminoxy Radical from o-Fluorobenzaldehyde Oxime: Density Functional Theory and ab Initio Studies

“…Owing to the unpaired electron density -3 -on both the O and N atoms, these iminoxyls were utilized in double-heteroatom-containing cyclizations leading to differently functionalized isoxazolines and cyclic nitrones regarded as important reagents for pharmacology. 8,9 The angular structure of the C=N-O• moiety, theoretically confirmed for various R 1 R 2 C=N-O• radicals by our DFT calculations [10][11][12][13][14][15] , provides an exceptional ability of the iminoxyls with two different substituents at azomethine carbon (R 1 ≠ R 2 ) to exist as two isomers, E and Z, with the possibility of interconversion. It is characteristic that when one of the substituents is a phenyl ring its rotation is manifested in the EPR spectrum.…”

Revisiting the electrochemical formation, stability and structure of radical and biradical anionic structures in dinitrobenzenes

“…Ab initio and density functional theory (DFT) electronic structure methods have been extensively employed in the interpretation, assignment and explanation of reduction potentials and ESR spectra [49][50][51][52][53]. For instance, these methods can yield ESR parameters such as the hyperfine coupling constants as well as the g-tensor with high accuracy [49].…”

“…For instance, these methods can yield ESR parameters such as the hyperfine coupling constants as well as the g-tensor with high accuracy [49]. However, these calculated ESR parameters are quite dependent upon the theoretical level employed, namely, electronic correlation, DFT functional and basis sets [51]. Usually, pure generalized gradient approximation (GGA) functionals such as BLYP are known to underestimate the calculated ESR parameters, due to underestimation of the spin polarization effects, whereas the unrestricted Hartree-Fock (UHF) method overestimates these properties.…”

“…These considerations can partially explain (error cancellation) the success of hybrid functionals, that combine GGA and UHF contributions for the exchange functional, such as B3LYP, and allow the determination of ESR parameters more accurately [49]. Also, a correct selection of basis sets is very important since a large contribution for the isotropic HFCC is related to the spin density at the nuclei, thus requiring specialized (EPR-II, EPR-III) or very large Gaussian basis sets (triple and quadruple zeta with polarization functions) or large STO basis sets [51,52]. In addition, solvent effects are quite important for correlating the calculated ESR parameters with the experimental spectra.…”