Synthesis and physical properties of various organic dyes derived from a single core skeleton, 1,2-dihydroindol-3-one

Various organic dyes were synthesized from 1,2-dihydroindol-3-one analogue via Robinson ring annulation, which proceeded efficiently using DBU as a base to give the π-expanded compounds. These compounds exhibited longer Stokes shifts (over 100 nm) than the 1,2-dihydroindol-3-ones (50–80 nm). Emission peaks of the obtained materials covered the 440–640 nm range.