The Design,Synthesis,and Applications Of Two-Photon Fluorescent Probes Based On Novel Quinolone Fluorophores

In the past two decades,two-photon techniques have been paid more attentions,especially in the field of optical limiting,3D microfabrication,and multiphoton microscopy.Two-photon fluorescence is a kind of anti-Stokes luminescence,often being excited by near infrared light and produce emission in visible region.In biological sample analysis,the NIR excitation light can improve penetration,reduce photodamage and photobleaching,avoid interference from autofluorescence and scattered light,and acquire high temporal/spatial resolution.Hence,two-photon fluorescence has attractive advantages in biomedical research,and possesses promising applications.By using two-photon fluorescent probes,the disadvantages of one-photon probes for bioanalysis and bioimaging can be overcome.As a result,it will be more feasible to achieve dynamic,real-time,and in situ detection.Nowadays,various two-photon materials have been developed with favorable two-photon absorption cross sections.However,many of them are not appropriate for bioanalysis and bioimaging.The main reason is that the rigid and big “?-?” structures made them exhibit poor solubility and low quantum yield in aqueous solution.Therefore,it is more important to design novel two-photon fluorophores to improve their two-photon photophysical properties.Quinoline is a heterocyclic aromatic organic compound.It is an important intermediate in the chemical industry of metallurgy,dyes,polymer,and agriculture.8-hydroxyquinoline,for instance,is widely used in measurement and separation of metal ions.Recent studies also demonstrated that quinoline-based derivatives have good two-photon absorption properties.In this dissertation,6-hydroxyl-quinonline-2-benzothiazole,a good two-photon fluorophore with D-?-A dipole scaffold(D: electron donor;?: conjugated chain;A: electron acceptor),was used to design and synthesize a series of two-photon fluorescent probes.The main contents are presented as following:1)By using tert-butyldiphenylsiyl(TBDPS)as a recognition group,a two-photon fluorine ion probe,QF,was synthesized.Intramolecular charge transfer(ICT)is attributed to the two-photon response of fluorine ions.Upon the addition of fluoride ions,the Si-O bond in QF will be cleaved and initiate an ICT process,resulting a red-shift in fluorescence emission.Moreover,the probe also shows high affinity and good selectivity toward fluoride ions.2)Bis(pinacolato)-diboron was employed as the recognition domain,a two-photon fluorescent probe for specific recognition of H2O2 based on photon-induced energy transfer(PET)mechanism.H2O2 can release the hydroxyl group of the flurophore,thus inhibiting PET process and recovering the fluorescence intensity of probes.3)Based on 2,4-dinitrobenzosulfonate ester,a well-known receptor for thiols,a two-photon fluorescent probe,QCys,for cysteine was synthesized.A PET process is contributed to the two-photon response of cysteine.With a similar hydroxyl protect-release mechanism,the probe gives a specific response to cysteine.