A General Strategy for Through-Bond Energy Transfer Fluorescence Probes Combining Intramolecular Charge Transfer: A...

A general strategy is reported for developing through-bond energy transfer (TBET) fluorescence probes by combining intramolecular charge transfer (ICT). The strategy uses a coplanar donor-π-bridge-acceptor system (SiOPh-PyOH) without spirolactam. The off-on switch of TBET and ICT is controlled by coplanar structure changes in the sensing process instead of spirolactam ring-opening in traditional TBET probes. DFT calculations showed that the energy and charge transfers from SiOPh to PyOH are prohibited. Since the SiOPh has no fluorescence, the probe SiOPh-PyOH shows fluorescence properties similar to that of pyrene. After sensing ONOO^- , the silyl ether is removed and the probe changes into ^- OPh-PyO^- . Electron-donating ICT from OPh to PyO^- induces a large redshift of emission to 594 nm (179 nm shift). TBET from OPh to PyO^- ensures the probe exhibits a large pseudo-Stokes shift of 213 nm. Furthermore, the probe was successfully used in endogenous ONOO^- detection. This study offers a new strategy for the construction of TBET probes emitting in the red region without spirolactam ring-opening, a new ONOO^- sensing system using silyl ether as a reaction site, and a method for the deprotection of silyl ethers with ONOOH under mild conditions.