Synthesis of hydroxyoligophenylenes containing electron‐donating, electron‐accepting groups, or π‐deficient aromatic ring and their solvatochromic behavior

We have reported oligo( p‐ phenylene)s (OPPs) with an OH group located at one end, namely, OPP( n )‐OHs (where n is the number of benzene rings). The OPPs exhibited significant solvatochromism; the deprotonation of the OH groups of OPP( n )‐OHs , when treated with NaH, caused a bathochromic shift of absorption maxima (λ max ) that increased with the donor numbers (DNs) of the solvents. We assumed that the solvatochromism exhibited by OPP( n )‐ONa was attributed to an intramolecular charge shift from the sodium phenoxy group(s) to the adjacent rings. In this study, to investigate the assumption, hydroxyoligophenylenes ( R‐OPP( n )‐OH ) with an electron‐donating dimethylamino group ( n  = 3, R = NMe 2 ), an electron‐accepting nitro group ( n  = 3, R = NO 2 ), and a π‐deficient pyridine ring ( n  = 2, R = Py) were synthesized by the Suzuki coupling reaction. The deprotonation of the OH group of by treatment with NaH caused a bathochromic shift (Δλ) of λ max of R‐OPP( m )‐ONa . The Δ λ of the deprotonated species increased with the DNs of the solvents. The emission peak positions of R‐OPP( m )‐ONa depended on the DNs of the solvents; therefore, the emission color could be tuned by changing the solvent. R‐OPP( m )‐OH received an electrochemical oxidation of the OH group and OPP unit. The data related to the remarkable solvatochromic behavior of R‐OPP( n )‐ONa will be useful information for the development of new luminescent materials.