Hydroxylated Fluorescent Dyes for Live‐Cell Labeling: Synthesis, Spectra and Super‐Resolution STED

Hydroxylated rhodamines, carbopyronines, silico‐ and germanorhodamines with absorption maxima in the range of 530–640 nm were prepared and applied in specific labeling of living cells. The direct and high‐yielding entry to germa‐ and silaxanthones tolerates the presence of protected heteroatoms and may be considered for the syntheses of various sila‐ and germafluoresceins, as well as ‐rhodols. Application in stimulated emission depletion (STED) fluorescence microscopy revealed a resolution of 50–75 nm in one‐ and two‐color imaging of vimentin‐HaloTag fused protein and native tubulin. The established structure–property relationships allow for prediction of the spectral properties and the positions of spirolactone/zwitterion equilibria for the new analogues of rhodamines, carbo‐, silico‐, and germanorhodamines using simple additive schemes. Modular design for portable dyes: Hydroxylated rhodamines, carbopyronines, and Si‐ and Ge‐rhodamines absorbing at 530–640 nm showed specific labeling of living cells and provided optical resolution of 50–75 nm in one‐ and two‐color STED microscopy. The established structure–property relationships allow property predictions of the new dye analogues.