Theoretical Characterisation of Phosphinyl Radicals and Their Magnetic Properties: g Matrix

Abstract

The g matrices (g tensors) of various phosphinyl radicals (R2 P(.) ) were calculated using the DFT and multireference configuration interaction (MRCI) methods. The g matrices were distinctly dependent on the molecular structure of the radical. To thoroughly examine this dependence, the contributions from individual atoms and excited states were calculated. The former revealed the gain from the phosphorus atom to be preeminent unless PO or PS bonds are present in the radical molecule. The contributions owing to excited states arising from electronic transitions between doubly occupied molecular orbitals and the SOMO were clearly positive, as in the case of semiquinone and niroxide radicals. The transitions from the phosphorus lone pair were of paramount importance. Surprisingly, unlike for semiquinones and nitroxides, a significant negative contribution was observed from excitations from the SOMO to unoccupied molecular orbitals. For radicals with PO bonds, this contribution to the g2 component was dominant.

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

“…It is important to note that our recent multireference configuration interaction (MRCI) calculations on •PR 2 corroborate this conclusion reached on the FOD basis . The MRCI computations showed that the predominant configuration of the total ground state wave function is that predicted by the DFT methods with a weight of 86.57, 86.08, and 83.36% for PMe 2 , P(OMe) 2 , and P(SMe) 2 , respectively, and the admixtures from other configurations were each less than 0.5%.…”

“…Since the solvent effect was found to be unimportant, and its available implementation in ORCA allows only for its inclusion in the reference wave function of the post‐SCF calculations, the solvent effects will not be further pursued for the sake of discussion clarity. Previously, we demonstrated that the solvent effect on the g tensor of •PR 2 is also insignificant …”

“…As the resolution of the identity approximation in the Split‐RI‐J variant was used in the geometry optimizations, an appropriate auxiliary basis set was employed . It was previously demonstrated that this theory level for phosphinyl radicals can predict the molecular structure that is in excellent agreement with the results of X‐Ray diffraction experiment . In addition, the molecular structures for PMe 2 , P(OMe) 2 , and P(SMe) 2 were optimized at the computationally more expensive MP2/def2‐TZVP level.…”

“…The structural diversity among •PR 2 radicals brings rich variety to their electronic and magnetic properties. Recently, we have reported the correlation of the molecular and electronic structure of •PR 2 radicals with their g matrix …”

Synthesis, characterization, single crystal X-ray structure, EPR and theoretical studies of a new hybrid inorganic-organic compound [Cu(Hdien)2(H2O)2](pnb)4·4H2O and its structural comparison with related [Cu(en)2(H2O)2](pnb)2

“…A critical aspect in the MRCI/SORCI method is the choice of reasonable active space[27,29]. The present case demands inclusion of the five copper d orbitals in the active space.…”