Highly Polar Insertion Complexes with Focused IR Spectra and Internal Field-Inhibited Isomerization.

Complexes of a polar molecule (benzene trioxide) and alkali halide diatoms are predicted to form stable conformers through not only a common attachment, but also trapping the molecule between the counterions. Two possible low- and no-barrier routes of formation of such an insertion complex are identified, and stability and other properties of this and other conformers are analyzed, including polarity and charge distribution. Calculated IR spectra indicate a bright feature specific for the insertion complex, facilitating its reliable experimental detection. Isomerization of the ion-pair-trapped molecule shows a nonobvious inhibition effect (through an increased potential energy barrier) compared to the free molecule due to the reduction of its polarity in the isomerization. Formation of a flatter isomer, trioxonine, is clearly "reported" by a sharp alteration of the IR spectrum, distinguishable also from its variation for the nonreactive relaxation of the insertion complex into an attached one.