Synthesis and photophysical properties of isocoumarin-based D-π-A systems

We prepared a small library of polarity-sensitive fluorescent dyes characterized by an isocoumarin core properly functionalized with a conjugated push-pull system. The key step of the synthesis is based on a regio-selective silver(I)/p-TSA co-catalyzed cyclization of 2-alkynylbenzoates recently optimized in our laboratory. The photophysical properties of isocoumarin-based D-pi-A systems have been investigated and a rationale was proposed based on their dipole moments and Hammett constants of the ED and EW groups involved.