Highly emissive π-conjugated alkynylpyrene oligomers: Their synthesis and photophysical properties

(Chemical Equation Presented) We newly prepared para- and meta-linked alkynylpyrene oligomers and examined their photophysical properties. Oligomerization of monomeric building blocks was performed by Cu ^I-promoted oxidative coupling reaction. The resulting oligomers mainly consist of 2-mer to 6-mer that were assigned on the basis of MALDI-TOF mass spectra, and the 2-mer, 3-mer, and 4-mer were isolated and fully characterized. From their absorption and fluorescence spectra, the para-linked oligomers were found to be somewhat π-conjugated compared with meta-linked ones, and the fluorescence quantum yields decreased with increasing oligomer length (Φ_f = 0.79-0.55).