Nanosized rigid pi-conjugated molecular heterojunctions with multi[60]fullerenes: facile synthesis and photophysical properties.

A series of large, rigid, new, well-defined, D-pi-B-A compounds with three chromophores (truxene moieties at the core, conjugated oligothiophenes as the branch bridges, and [60]pyrrolidinofullerene (C60) segments as the end-capped groups) have been facilely developed in this contribution. Oligothiophene-functionalized truxene derivatives 1-29 are prepared by the Suzuki, the Sonogashira, and the Negishi cross-coupling reactions catalyzed by Pd(PPh3)4 as well as the McMurry reaction, respectively. The 1,3-dipolar cycloaddition of the oligomers with C60 and N-methylglycine yields a new family of star-shaped D-pi-B-A derivatives end-capped with pyrrolidinofullerene moieties as the active materials for photovoltaic devices in which one, two, three, or four C60 moieties are allocated at the peripheral position of well-defined compounds, respectively. We also investigate the UV-vis and photoluminescence behaviors of these pyrrolidinofullerene-functionalized derivatives. The emission is obviously quenched after the inducement of the C60 moieties. We also observe that the emission intensity is decreased with the increase in the number of C60 moieties.