On the basis of the density-functional theory, the properties of the reaction product [Fe(H 2 O) 5 (NO)] 2+ of the classical "brown-ring" reaction are studied via the B3LYP hybrid method. Here we have found that the Fe-N-O bond in the optimized structure of [Fe(H 2 O) 5 (NO)] 2+ is linear. In addition, the vibrational frequency, atomic net charges, and spin density are analyzed and then the solvent effects are incorporated via the polarized continuum model self-consistent reaction field. Furthermore, the excitation energies are evaluated using the CIS method. Results when compared with experimental data indicate that the spin-quartet ground state of [Fe(H 2 O) 5 (NO)] 2+ is best described by the presence of Fe II (S ) 2) antiferromagnetically coupled to NO (S ) 1 / 2 ), yielding [Fe II (H 2 O) 5 (NO)] 2+ . This is clearly different from either [Fe III (H 2 O) 5 (NO -)] 2+ or conventional textbook [Fe I (H 2 O) 5 (NO + )] 2+ assignment.

To investigate the temporary anion states of uracil, density functional theory with asymptotically corrected potentials is adopted. The stabilized Koopmans' theorem and stabilized Koopmans-based approximation are used in conjunction with an analytic continuation procedure to calculate its resonance energies and lifetimes. Results indicate the presence of several low-lying π* and σ* temporary anion states of uracil. The characteristics of these resonance orbitals are also analyzed. By comparing them with the experimental values and theoretical calculations, it is believed that the stabilization approach can provide more information on the resonance states.

The studies of shape and core-excited resonances are essential in the bonding and electronic processes of quinones. So far, the experimental results of temporary anion states for p-benzoquinone cannot be fully ascertained computationally. In this paper, both resonances of p-benzoquinone are investigated via the stabilization method (SM). For shape resonances, the stabilized Koopmans theorem is adopted in the framework of long range corrected density functional theory (LC-DFT). As for core-excited resonances, the SM coupled with long range corrected time-dependent density functional theory (LC-TDDFT) is employed. The resonance energies and lifetimes are then estimated via an analytic continuation procedure in conjunction with the stabilization plots. Using this novel combination, previous experimental results of temporary anion states can be successfully identified. It is believed that this novel approach can be an accurate and efficient methodology in the study of temporary anion states of quinones.

No abstract