Photoinduced electron transfer in host-guest interactions of a viologen derivative with a didansyl-pillar[5]arene

Abstract

With the goal of understanding the electron transfer mechanism of fluorophore-functionalized pillararenes, a pillar[5]arene bearing two dansyl fluorophore moieties at the opposite rims of its cavity has been synthesized, and the behavior of such a new host molecule has been thoroughly investigated in the presence of an N,N′-di-(6-bromohexyl)-viologen derivative. 1H NMR, NOESY and DOSY experiments demonstrated that the pillar[5]arene recognizes the viologen derivative, forming a 1:1 host-guest complex by including one of the two bromoalkyl chains within its π-rich cavity. Photophysical and electrochemical studies revealed that, upon guest addition to the host, the fluorescence intensity of the complex is progressively quenched by a photoinduced electron transfer process (PET) from one of the dansyl groups of the host to the viologen moiety of the guest.