Push-pull isomers of indolizino[6,5,4,3-def]phenanthridine decorated with a triarylboron moiety.

1,3-Dipolar cycloaddition reactions between a new azomethine ylide and three BPhMes2-functionalized internal alkynes produced three pairs of fluorescent push-pull regioisomers, which show distinct electronic and photophysical properties. All the six compounds are found to exhibit charge-transfer (CT) fluorescence, and some of which show rare and interesting temperature "turn-on" fluorescence.