Theoretical study on the gas and solution phase enthalpies, free energies and equilibrium constants for the isomerisation of [1.1]paracyclophane derivatives as potential molecular switches

Theoretical studies were conducted on the predicted gas and solution phase thermodynamic properties for isomerisation of various [1.1]paracyclophane derivatives to their corresponding transannular[4 + 4] adducts at representative levels of density functional and composite method theories. Calculations suggest that the [1.1] paracyclophane to transannular[4 + 4] adduct isomerisations are not likely amenable to thermodynamic solvent tuning for the methylene, ether and thioether-bridged derivatives using a broad range of nonpolar and polar aprotic and polar protic implicit solvation models, but may be receptive towards solvent tuning for the amine-bridged analogues. Varying the nature of the cyclophanic bridging atoms and the electron-withdrawing/releasing character of photochemically/thermally stable substituents on the pi-systems is predicted to facilitate substantial variation of the isomerisation equilibria to a much greater degree than changing the solvent environment.