High Stability of a Donor–Acceptor Type Oxazepine-Containing Fluorophore and Its Applications in Cellular Imaging and Two-Photon Deep Tissue Imaging

A new donor (D)–acceptor (A) type naphthalene-based oxazepine-containing fluorophore, OXN-1, is reported, which shows unusually high stability in various environments. Its photophysical properties and structural stabilities under harsh conditions are thoroughly examined. The high stability of OXN-1 is explained by quantum chemical calculations. Its exceptional bioimaging capabilities for cells with low cytotoxicity are verified. In addition, its deep tissue imaging ability with two-photon microscopy (TPM) is evaluated.