Design of donor-acceptor geometry for tuning excited-state polarization: fluorescence solvatochromism of push-pull biphenyls with various torsional restrictions on their aryl-aryl bonds

In this work, push pull biphenyl analogs (4-(N,N-dimethylamino)-4'-formylbiphenyl) with a modulated dihedral angle of the aryl aryl bond, using a bridged structure or methyl groups, were synthesized. Photophysical measurements of the synthesized compounds revealed the effect of the torsion between N,N-dimethylaniline (donor) and benzaldehyde moieties (acceptor) on their solvatochromic properties. Our data showed that the sensitivity of the fluorescence maxima to solvent polarity gradually increases as the biphenyl chromophore was restricted to a twisted conformation. This finding indicates that changing the torsional restrictions on the donor acceptor system can be a factor to take into account for the development of novel solvatochromic dyes. (C) 2014 Elsevier Ltd. All rights reserved.