Complexes of Counterion-Trapped Molecules: Extreme Polarity, Rich IR-Activity, and Internal-Field Moderated Transformations

Highly polar molecular systems are needed for many practical applications based on light-matter and intermolecular interactions, from solar-energy utilization to self-assembly. Novel insertion complexesInsertion complexes of non- and polar molecules non-covalently trapped between M–X counter-ions are designed, and their properties predicted. The M-molecule-X systems can be meta- or stable by up to 1 eV relative to molecule + MX. Such polar-molecule complexes can be lowest-energy conformers with significant stabilizing energy barriers (by up to ~ 1 eV), thus being thermodynamically stable species with huge dipoles of up to above 25 D. Interesting features include the nonobvious contributions of the molecule’s dipole moment to the system stability and polarityPolarity, the cooperativity of pair interactions, the inversion of ionic-neutral dissociation channels, the reshaping up to isomerizationIsomerization of the molecule due to framing ion-pairsIon-pairs. The IR spectraIR spectroscopy are predicted to considerably vary and sensitively indicate the formation of both the M-molecule-X and MX-molecule conformers, with intensities up to an order of magnitude higher in the complexes, facilitating their reliable detection and differentiation in experiments. The above suggests a way of adding polarityPolarity to nonpolar molecules, thus enhancing their experimental detection and characterization. The resulting increased attraction could promote molecular self-assembly and chemical reactions as well. The latter is exemplified by isomerizationsIsomerization of trapped molecules, with the related barriers significantly altered due to internal electric field. The process IR signatures are also predicted.