Design, Synthesis And Applications Of Fluorescent Sensing Materials And Probes Based On Rhodamine

Organic fluorescent molecules are wildly applied to vital fields,such as anti-counterfeit,photoelectric device,sensing and so on,for their advantages including a great diversity of structures,facile modification,and controllable functions.To date,the patterns of the output signal for most of the fluorescent sensors are based on the turn-on emission of a single range of visible light or the ratiometric change of two bands of visible light.What's more,the function of the sensors is usually limited.In this thesis,organic fluorescent sensors towards acid/base and probes towards reactive oxygen species(ROS)or reactive nitrogen species(RNS)in live cells with multi-function and versatile reporting channels are designed and synthesized by simple but rational modification and grafting of traditional fluorophores.The main strategy designing the sensors and probes relies on connecting different fluorophores to rhodamine leuco form.By introducing energy transfer mechanism,the sensors and probes output multi-channel signals.The details of the studies are presented as follows:(1)By connecting the fluorophore 2-hydroxyl-benzothiazole(HBT)with excited state intramolecular proton transfer(ESIPT)character to the leuco form of rhodamine B through the spiro lactam bond,a new multi-channel fluorescent organic molecule with aggregation induced enhanced emission(AIEE)and reversible ring-opening/ring-closing was developed.The newly synthesized molecule inherited the optical properties perfectly of the matrix structure of the energy donor in the ring-closed form and maintained the ability of opening/closing the spiro lactam ring of rhodamine B.Through analysis of the crystal structure of the molecule,the intrinsic reason for its emission with high quantum yield in the solid state was understood.Red,green and blue(RGB)emission could be obtained and used as different signal channels to sense acid/base.During the tests of the spectra,RGB emission was obtained and the corresponding form of the molecule existed under different condition was confirmed by theoretical calculations,NMR data and comparing with the reference molecule.The possibility of the energy transfer from the AIEE donor to the traditional aggregation-caused quenching(ACQ)acceptor was raised by comparing the excitation spectra with commercial Rhodamine B.The introduction of ESIPT and energy transfer(ET)enabled the molecule emitting blue,green and red light with large Stocks shift efficiently excited with 365 nm light.High intensity of RGB emission in the polymer film was utilized in the fields of sensing acid/base,display and anti-counterfeit due to the restriction of the vibration and rotation by the polymer.(2)By linking the blue light emitting 7-hydroxyl-3-carboxyl coumarin to the green light emitting rhodol through amide bond to form the classic F?rster resonance energy transfer(FRET)system,a single probe towards ROS/nitroxyl with different signal channels was fabricated by introducing the ROS/nitroxyl recognition group to each fluorophore.The reaction of boron ester with different ROS was tested and the ability of the probe to detect ROS and nitroxyl was confirmed.The rare photoinduced electron transfer(PET)phenomenon from the donor luminophore to the acceptor luminophore was found and utilized to give a direct turn-off signal for sequence sensing peroxynitrite and nitroxyl.With the help of cetyl trimethyl ammonium bromide(CTAB),the probe could penetrate into Hela cells and gave real-time signal towards peroxynitrite and nitroxyl.(3)Nitric oxide is an important gaseous signal molecule with the radical nature,one member of RNS.To date,most nitric oxide probes are based on the PET effect of the aniline recognition group towards the fluorophore with single turn-on emission,while a few ratiometric probes lack the ability to target important organelle.Therefore,we choose naphthalimide as the energy donor due to the facile multi-site modification and rhodamine as the acceptor to construct a FRET system.We developed a mitochondria targeted ratiometric probe towards nitric oxide in a relative convenient synthetic route to give a more reliable detection result.Since the overlap of the emission of the donor and the acceptor caused severe interference under the low concentration of nitric oxide,we tried to collect the signal using different excitation light and remarkable ratiometric results could be gained.The probe exhibited good water solubility and cytomembrane permeability.The probe successfully detected exogenous nitric oxide in RAW 264.7 cells with moderate mitochondria-targeting ability.However,the poor sensitivity limited the probe to sense endogenous nitric oxide.