Water-mediated through-space-conjugation of aromatic groups for stimuli-responsive photoluminescence

Abstract

Aqueous media acts as a functional component for the metal carbonyl vesicles (MCsome) assembled from FpC3Bithiophene (Fp: (Cp)Fe(CO)2(PPh3), C3: propyl) molecules. The MCsome in THF/water (with the ratio up to 0.30) have an aqueous vesicular membrane, which integrates the assembling blocks and restricts the intramolecular rotation of bithiophene groups. The restriction fixed the relative position of the aromatic groups giving rise to a through-space conjugation (TSC), which is responsible for the fluorescence with the wavelengths and intensities depending on the twisting angle of bithiophene groups. A dialysis process to remove THF trigged a torsional-to-planar rotation switching off the fluorescence, while the irradiation of UV light (wavelength 365 nm) stimulated a planar-to-torsional rotation for the solutions in THF/water mixed solvents, which turned on the fluorescence. This aqueous-mediated TSC-caused fluorescence signifies that water, as in natural systems, can act as a structural and functional component for material innovation.