A self-recovering mechanochromic chiral π-gelator

Mechanochromism is a stress induced perturbation of electronic property in molecular materials. It is shown here that the presence of a branched chiral chain facilitates mechanochromic response in a molecular assembly as illustrated with a chiral oligo(p-phenylenevinylene) derived -gelator (OPVC). OPVC exhibits a reversible mechanochromism while the analogous achiral derivative (OPVA) having a linear side chain does not, as established from the fluorescence and circular dichroism (CD) studies. The helically twisted chromophore packing in OPVC allows mechanical reorganization of the self-assembly and the associated fluorescence intensity variation at different wavelength positions in the broad emission spectrum, resulting in a perturbation in the colour ratio leading to the observed mechanochromic emission color change. This exciting new finding may have wide ranging implications in the design of stimuli responsive molecular materials with reversible optical properties.