Rigid rod-like molecular wires of nanometric dimension. Electronic energy transfer from a naphthyl to an anthracenyl unit connected by a 1,4-pentaphenylene spacer

We have synthesized the multicomponent species N-(ph)5-A, where a 1-naphthyl (N-) and a 9-anthryl (-A) units are connected by a 1,4-pentaphenylene rod-like spacer (-(ph)5-). The overall length of the compound is 3.1 nm and the center-to-center distance between the naphthyl and anthryl units is 2.6 nm. The absorption and emission spectra of N-(ph)5-A have been investigated in cyclohexane solution at 293 K and compared with those of model compounds of the component units. Emission spectra, fluorescence quantum yields and excited state lifetimes show that in N-(ph)5-A the fluorescence of the naphtyl and oligophenyl units is completely quenched by energy transfer to the fluorescent excited state of the anthryl unit. The mechanism of the energy transfer process is discussed.