Development of a Unique Class of Spiro‐Type Two‐Photon Functional Fluorescent Dyes and Their Applications for Sensing and Bioimaging

Spiro compounds with rigid structures have attracted significant attention in the recent years due to their useful applications in diverse fields such as asymmetric catalysis and organic optoelectronic materials. However, spiro cores have not yet been employed as the spiro‐type two‐photon fluorescent dyes in the aspects of sensing and bioimaging. Therefore, the spiro‐type two‐photon fluorescent dyes with excellent two‐photon properties are highly sought after. Here, a unique class of spiro‐type two‐photon fluorescent dyes (STP) is engineered and applied in sensing and bioimaging. The studies indicate that the novel STP fluorescent dyes have favorable two‐photon properties from the point view of spiro compounds. By exploiting the superior two‐photon optical properties of the STP dyes, the first two‐photon ratiometric HOCl fluorescent probe STP‐HClO for sensing and imaging HOCl in the living cells and living tissues is constructed, demonstrating the profound value of the new STP dyes for the unprecedented development of the sprio‐type fluorescent sensing and imaging agents. It is believed that the innovative STP dyes may pave the way for designing more efficient spiro‐type two‐photon fluorescent probes and organic optoelectronic materials as well.