Dicyanostilbene‐Derived Highly Sensitive Two‐Photon Fluorescence Temperature Probe for Live Cell Imaging

Abstract A novel two‐photon fluorescence temperature‐sensitive probe ( SP ) with the push‐pull electronic architecture (Donor‐ π ‐Acceptor, D‐ π ‐A) derived from dicyanostilbene was developed. Its linearly dependent coefficients ( R 2 ) between the emission intensity of SP and temperature reached 0.998 and 0.999 in one‐ and two‐photon fluorescence (OPF and TPF), respectively, and corresponding function expressions were I F =−0.0144 T +1.2751 (OPF) and I F =−0.0152 T +1.2970 (TPF). Its maximum two‐photon excitation wavelength ( λ max2 ) is 750 nm, and the corresponding maximum two‐photon absorption cross‐section ( δ max ) is 1550 GM. DFT (Density Functional Theory) Calculation demonstrated that the electron cloud densities of two nitrogen atoms (N29 and N31) on two cyano groups are 15.9 and 16.0 times higher than that of nitrogen atom on 9‐carbazolyl group (N13), respectively. This fully indicates that the electron cloud of nitrogen atom on 9‐carbazolyl group is highly delocalized to the fluorophore matrix. SP can be used for live cell imaging and detect cell temperature to diagnose disease within physiological temperature range with excellent photostability and without cytotoxicity.