Pseudo-Jahn-Teller Effect in Natural Compounds and Its Possible Role in Straintronics I: Hypericin and Its Analogs.

The distortions and instability of high-symmetry configurations of polyatomic systems in nondegenerate states are usually ascribed to the pseudo-Jahn-Teller effect (PJTE). The geometries of hypericin, isohypericin, and fringelite D were optimized within various symmetry groups. Group-theoretical treatment and (TD-)DFT calculations were used to identify the corresponding electronic states during the symmetry descent.

Keto-enol Tautomerism of hydroxy-substituted arenes: Theoretical study and experimental consequences.

In this work, the chemical equilibrium between enol and keto tautomers occurring in phenol, naphthols and selected 29 hydroxy substituted polycyclic aromatic hydrocarbons classified into 4 structural types was investigated. The reaction Gibbs energies were computed using the density functional theory combined with the solvent continuum model. We have demonstrated how the consecutive condensation of benzene rings together with two-dimensional molecular arrangement and the position of the hydroxyl group modifies this equilibrium.

On the Potential Role of the (Pseudo-) Jahn-Teller Effect in the Membrane Transport Processes: Enniatin B and Beauvericin.

The molecular structure of mycotoxins enniatin B and beauvericin, which are used as ionophores, was studied using density functional theory in various symmetry groups and singly charged states. We have shown that the charge addition or removal causes significant structural changes. Unlike the neutral C molecules, the stability of the charged C structures was explained by the Jahn-Teller or Pseudo-Jahn-Teller effect.

Spectroscopic behavior differences between lumazine and alloxazine in the DMSO-water mixture.

The absorption and emission spectra were investigated for lumazine, alloxazine and their cyanated or fluorinated derivatives, respectively. The spectroscopic properties were modulated by varying water concentration in dimethyl sulfoxide (DMSO). Some intriguing experimental results were found for the samples containing 65 % of water and 35% of DMSO.