'Conformational'Solvatochromism:Spatial Discrimination of Nonpolar Solvents by Using a Supramolecular Box of a pi-Conjugated Zinc Bisporphyrin Rotamer

摘要

"Solvatochromism"is the ability of chromophoric molecules to change their absorption and/or luminescence colors as a result of a change in solvent polarity.In principle,solvatochromic shifts are caused by a change in the energy gap between a ground state and excited state of different polarities,since a change in the solvent polarity leads to differential stabilization of these electronic states.Therefore,specific interactions between chromophore and solvent molecules result in variations in the wavelength,intensity,and shape of the absorption and/or luminescence spectra.Recent examples of particular interest include conjugated polymers that change their conformation and give rise to a solvatochromic response.From this general understanding of solvatochromism,one may simply assume that the color of a chromophoric molecule hardly depends on the chemical structures of solvents when their polarities are,for example,equally very low.Here we report the interesting phenomenon that a dialkynylene-bridged zinc bisporphyrin rotamer([ZnP(=)2])shows an explicit solvatochromic response to nonpolar solvents with low dielectric constants(2.23-2.57).To our surprise,it can discriminate the regioisomers of xylene.