Synthesis and characterization of the photochromic properties of new pyrrolidene dyes bearing benzothiazole or benzothiazolium acceptor groups

Schiff bases are an important class of compounds with a variety of applications in medicinal, materials and supramolecular chemistry due to their biological (anticancer, antimalaria, antivirus, antimicrobial, etc.) and optical properties (chemosensors, photochromic, nonlinear optical). UV irradiation of these compounds leads to the trans-cis isomerization of the C=N bond with formation of an unstable species that returns thermally with variable speed to the initial form. Recently, we have showed that the kinetic rate of the thermal cis-trans re-isomerization of pyrrolidene Schiff bases, at room temperature, can be controlled through proper substitution at the aniline ring of the molecule.1a As part of an on-going research to develop efficient heterocyclic systems for photochromic applications1a-e we decided to explore the potential of a new series of heterocyclic imines 1 and the corresponding vinyl derivatives 2 functionalized with benzothiazole or benzothiazolium acceptors groups linked to the pyrrole ring through position 2 or 6 of the benzothiazole ring.