Fluorescent Probes For Small Molecule Based On Coumarin And Quinoline

Fluorescent chemical probes are important tools for the detecting the concentration of molecules and ions in vivo. In recent years, fluorescent probe has obtained more and more attention because of it has high sensitivity and good selectivity, real-time detection, good prospects in biological simple and cheap, and many other advantages, fluorescent probe is widely used in Biological Sciences, Materials Science and Environmental Sciences, used as an effective detection tool. Nowadays, with the widespread used of two-photon microscopy (TPM) in biomedical fields, two-photon fluorescent probes have obtained more and more good graces. Compared to the traditional single photon fluorescence probe, two-photon fluorescence probes not only has good spatial orientation ability, lower toxicity and light bleaching, and greater penetrating power, can be applied to the deep tissue imaging.Hydrogen sulfide is an important signal of small molecules, and it’s also the world-recognized toxic gases. Hydrogen sulfide is typically produced in cytoplasmic matrix and mitochondrial of mammalian in biology, H2S showed a significant impact to cardiovascular and nervous systems, it is involved in a wide variety of physiological processes of life. Therefore, detection of H2S in biological systems has considerable significance for understanding the physiological and pathological functions of hydrogen sulfide.Hydrazine hydrate is a highly reactive base and good reductant, and it’s also often used as an important kind of reactants in pharmaceutical, pesticide, photographic chemicals, emulsifier and fuel in many of the chemical production, it is also used as chemical foaming agent and preservative for heating system in industry. However, the toxic effects of hydrazine hydrate is quite big, it can cause serious damage to the liver, lung, kidney, central nervous system, and may even cause to gene mutation and cancer. Although there is no endogenous hydrazine in live cells, it is readily absorbed by oral, dermal or inhalation routes of exposure thus causing harm to live cells. As a result, hydrazine has been classified as possible cancer-causing environmental contaminants. Therefore, selective and sensitive real-time detection methods of hydrazine in environmental and biological system are highly needed.Based on the research foundation of a large number of documents and the work of our group, we have designed two fluorescent probes CNHS and TNQ to selectively recognise H2S and N2H4 respectively based on coumarin and quinoline precursor, and the structure of CNHS and TNQ was characterized by NMR and ESI-mass spectra. In which, the two-photon fluorescence probe TNQ was based on the mechanism of intramolecular charge transfer (ICT). It can not only detect liquid hydrazine hydrate in vitro, but also can be applied to detect hydrazine hydrate steam of environment and used for biological imaging. TNQ was based on 6-instead of quinolone, which was well applied in Two-photon cell imaging developed by our group. Based on ICT mechanism, we connected the quinoline 6 position with 4-hydroxy phenyl acetylene, this not only increases the size of the probe molecules conjugated system, increase the two-photon absorption ability of the probe, also realize the ICT process of probe, due to the electronic ability of hydroxyl groups. In order to further increase the two-photon absorption cross section of the structure, we increased the 6- instead of quinoline conjugated system, the molecular aldehyde groups was reacted with neighboring amino thiophenol, form a larger rigid conjugate, surface to at the same time to guard the aldehyde group and improve the specificity of the probe. Use to take off the protective reaction of hydrazine hydrate, the corresponding compounds containing hydroxyl De-TNQ as able to esterification reaction with levulinic acid, generate product ester bond was selectively cutted by hydrazine hydrate. We think this to take off the protection process of hydrazine hydrate can increase intramolecular charge transfer (ICT) of probe, it will cause the red shift of the fluorescence spectrum, and this hypothesis is verified by theoretical calculation. Hence, we have designed the ratiometric fluorescent probe TNQ with enlarged two-photon absorption cross-section, and have studied the physical properties of light and recognition mechanism of probe TNQ, and the probe has preliminary success applied in detecting of hydrazine hydrate in the environment and biological cell imaging.