AIE Active Symmetrical and Asymmetrical Quinoxaline Derivatives: Effect of Donor Modulation in D-A-D Framework on...

Organic luminophores demonstrating stimuli-responsive emission have gained significance attention in various optoelectronic applications. We designed a series of donor-acceptor-donor style unsymmetrical and symmetrical quinoxaline derivatives by employing acceptors phenanthrene-quinoxaline (PQ) and acenaphthene-quinoxaline (AQ) with donors phenothiazine (PTZ), tetraphenylethylene (TPE), and N-substituted phenothiazine (N-PTZ). The derivatives PQ1 and AQ1 possess symmetrical substitution of PTZ on both sides and were synthesized by Suzuki cross-coupling reaction of PQ and AQ respectively; whereas the set of derivatives PQ2, AQ2 and PQ3, AQ3 contain PTZ unit on one side and N-PTZ unit and TPE unit on other side, respectively. The quinoxaline derivatives PQ1, AQ1, PQ3, and AQ3 show intense emission in the solid-state with solvatochromism and reversible mechanochromism owing to the twisted donors TPE and PTZ. In contrast, the derivatives PQ2 and AQ2 are nonemissive solids although show unique reversible grinding induced color-switching properties following a blue-shift in griding in the AQ2 derivatives. The effect of choice of various AIE type donors and heterocyclic acceptors which enable easy modulation of photophysical and stimuli-responsive properties were studied. These results provide a rational strategy for design of donor-acceptor organic molecules for achieving solid-state emission and stimuli-responsive properties.