Linear Conjugated Systems Bearing Aromatic Terminal Groups. VIII. Syntheses and Electronic Spectra of Bis(4-biphenylyl)- and 2,2′-Difluorenylpoly-ynes

In order to get further information on the effect of terminal groups on the spectral regularity of diarylpoly-ynes, we carried out the syntheses of bis(4-biphenylyl)poly-ynes (In, n=1–6) and 2,2′-difluorenylpoly-ynes (IIn, n=1–4 and 6). The bathochromic shift of the longest-wavelength absorption maxima (λL) along with the increase in n was found to be expressed by the following empirical formulas: In:λL=24.0n1.1+304 (nm in tetrahydrofuran) IIn:λL=9.0n1.5+350 (nm in tetrahydrofuran) The spectral behavior of bis(4-biphenylyl)poly-ynes (In) strongly supported the relationship λL∝n in diphenylpoly-ynes.