Novel efficient and stable heteroaromatic two-photon absorbing dyes

The synthesis and characterization of novel heteroaromatic-based two-photon absorption (TPA) dyes for bio-conjugation is described; the new isothiocyanate and maleimide derive from a class of novel efficient quadrupolar and octupolar/branched chromophores relying on the electronic effects of electron-poor and electron-rich simple heteroaromatic rings; the new systems exhibit very large TPA cross-sections, high chemical stability, and very low photobleaching.