Synthesis And Properties Of Near-Infrared Fluorescent Chemosensors Based On BODIPY And DCM Chromophores

Fluorescent probes are expected to be powerful tools for the analysis of many environmental and biological relevant analytes due to the simplicity, high sensitivity and high spatial resolution of fluorescence. The development in fluorescent probes has become an active research field, such as probes for pH, viscosity, anions, toxic cations in environment and in vivo, DNA etc.. However, the most reported fluorescent probes have poor performance in aqueous solutions, and exhibit short absorption and emission wavelengths in the visible range. Accordingly, it is desirable to develop novel fluorescent probes to overcome these limitations, making them promising probes for analytes in biological system.Among many fluorophores, both boron-dipyrromethene (BODIPY) and dicyanomethylene-4H-pyran chromophores (DCM) have been recognized as promising building blocks for the construction of molecular sensors. BODIPY fluorescent dyes have several advantages, such as high fluorescence quantum yields, sharp absorption and fluorescence emission spectra, and high photophysical stability and chemostability. Based on the typical Intramolecular Charge Transfer (ICT) mechanism, DCM derivatives have high fluorescence quantum yields with a long emission wavelength (>600nm). As suggested, BODIPY and DCM fluorescent dyes might have potential to be applied in bioimaging.In this dissertation, synthesis and systematic study of spectroscopic characteristics of several6-hydroxyindole-based BODIPY and DCM derivatives have been described. All these dyes display distinct spectral response to pH, F-, Zn2+. In these chemsensors, the specific sensitivity and near-infrared (NIR) are focused as follows:In Chapter1The development of supramolecular chemistry and molecular recognition is introduced. The factor of influencing fluorescence and effect of fluorescence spectra to molecular recognition are introduced, especially concentrated on the molecular recognition based on BODIPY molecules. Finally, the major points in this dissertation are proposed;In Chapter2Synthesis and spectroscopic characteristics of BODIPY-OH and BODIPY-O-in various solvents containing an organic base have been described. The straightforward interconversion of phenol/phenolate induces distinct changes in absorption and emission spectra. The spectra of BODIPY-O-are dependent upon the environment polarity, exhibiting a wide wavelength range. Compared with BODIPY-OH (in the range571 to586nm), BODIPY-O-shows a large red-shift, modulated in the range629to681nm by the polarity of solvents. λem values of BODIPY-OH are in the range571to586nm. As demonstrated, the color of the solution can be converted from the phenol form of BODIPY-OH to the phenolate form. The high fluorescence quantum yield of BODIPY-O" shows relatively large Stokes shift in solvent/base combinations through excited state deprotonation from (BODIPY-OH)*to (BODIPY-O-)*, suggesting that BODIPY-OH is suitable for exploration in bioassays.In Chapter3A novel6-hydroxyindole-based boron dipyrromethene based NIR fluorescent chemodosimeter BODIPY-OSi for F-has been developed with high selectivity via specific Si-O cleavage, exhibiting several characteristics:the incorporated larger conjugation of6-hydroxyindole in the BODIPY unit resulting in a NIR fluorescence probe with emission at676nm; a dramatic color change from pink to indigo, allowing the colorimetric detection of F-by the naked eye; turn-on fluorescence to obtain the ideal signal-to-noise ratio, and high ratiometric fluorescent determination with an internal standard using the isosbestic point at567nm as excitation wavelength (71times); fast response within30s.In Chapter4A novel ICT-based fluorescent chemodosimeter DCPOSi for F-is presented. Incorporating one benzene unit into a DCPOSi dye can result in a remarkable red shift of about140nm to700nm of DCPO-in the presence of F-, falling in the near-infrared region:bringing a color change from slight yellow to blue by the naked eyes, realizing a qualitative determination of F-with a colorimetric method; displaying high F-selectivity over various competitive anions, ascribing to the strong affinity of F-toward silicon; exhibiting a NIR turn-on fluorescence intensity to1000times to get the ideal signal-to-noise ratio and high ratiometric fluorescent limit determination (8.5×10-8M) with suitable sensitivity, and fast response within30s.In Chapter5Synthesis and photophysical evaluation of a NIR Zn2+turn-on fluorescent probe1-OH with high selectivity have been reported. The coordination of1-OH to Zn2+induces distinct emission enhancement at NIR region (680nm), resulting in deprotonation of the phenol unit and the rigidification of C=N bond, being attributable to the Zn2+binding to the Schiff-base ligand based on CHEF. No detection disturbance of Zn2+by other cations is successfully realized, especially with little interference from Cd2+. With the particular attractive emission at NIR,1-OH is suitably used for the bioimaging of Zn2+in Breast Cancer MCF-7cells with several advantages such as cell-permeability, and the desirable NIR turn-on emission beneficial to deep light penetration and weak autofluorescence of biological tissues. The CHEF strategy is expected to further help construct turn-on NIR fluorescent probes for metal ions.In chapter6BODIPY-OH is protected by BF2for the second time. Two noval BODIPY derivatives DIBODIPY-1and DIBODIPY-2are synthesized. The ultraviolet spectra and fluorescence spectra and fluorescence quantum efficiency in several solvents are investigated, showing fluorescence quantum yields of DIBODIPY-1is9times higher than fluorescence quantum yields of DIBODIPY-2. The fluorescence lifetime of DIBODIPY-1and DIBODIPY-2are2.74ns and3.55ns by time resolved fluorescence device. The radiation transition constant and non-radiation transition constant are also analyzed. The redox properties of DIBODIPY-1and DIBODIPY-2are investigated by cyclic voltemmetric experiments.In chapter7A conclusion is delivered.