Acid–base controllable singlet oxygen generation in supramolecular porphyrin–gold nanoparticle composites tethered by rotaxane linkers

Abstract

Mechanically-interlocked photosensitizer–quencher systems based on free-base tetraphenylporphyrin (H2TPP)–gold nanoparticle (AuNP) composites has been designed and synthesized by utilizing a rotaxane architecture comprised of secondary ammonium and crown ether subunit. The H2TPP-substituted 24-crown-8 was able to shuttle along the alkanethiolate axle, triggered by deprotonation/protonation at the ammonium station, altering the H2TPP–AuNP distance and the photoexcitation energy transfer efficiency. Upon switching, quantum yields for photosensitized singlet oxygen (1O[Formula: see text] generation and fluorescence after deprotonation were quenched by 46% and 42%, respectively. External environment-responsive1O2generation based on such a protonation/deprotonation-driven molecular switch is potentially advantageous for a variety of applications including photodynamic therapies.