A borindolizine platform for the design of fluorophores with tunable emissions

Here we describe the design and applications of borindolizine, a novel scaffold with broadly tunable fluorescence and a high Stokes shift. Two classes of emitters were synthesized through rational scaffold modification, resulting in blue-emitting carboxyborindolizines (<i>λ</i> _max,em = 431-459 nm) and green-emitting aryl borindolizines (<i>λ</i> _max,em = 489-519 nm). Experimental structure-emission trends were used to validate a computational spectral prediction model and to subsequently design a red-emissive borindolizine scaffold. The red-emissive isoquinolyl borinidolizine was prepared, and the experimental emission (<i>λ</i> _max,abs = 370 nm, <i>λ</i> _max,em = 635 nm) was in excellent agreement with the theoretical emission (<i>λ</i> _max,em = 646 nm). These results show how the application of data science can produce fluorophores with desirable spectroscopic properties through the borindolizine scaffold.