Synthesis Of New AIE Molecules And Their Application In Detection Of Metal Ions,Cancer Diagnosis And Phototherapy

Traditional organic fluorescent materials are majorly hydrophobic compounds with planar and large?-conjugation system.They were usually highly emissive in solution but showed weak or quenched emission in the aggregate or solid state.This phenomenon was called aggregation-caused quenching(ACQ).Fluorescent materials with ACQ effect always display small Stokes shift and poor photostability.In 2001,Tang et al.proposed the concept of aggregation-induced emission(AIE)which is completely contrary to ACQ phenomenon.Fluorophores with AIE feature are non-emissive or faintly emissive in solution but highly emissive in the aggregation and solid state,thus usually show large Stokes shift and superior resistance against photobleaching.AIE molecules are attracting wide attention in the field of bioimaging,chemo/biosensors and photodynamic diagnosis and therapy of diseases and so on.O-phenanthroline has a large conjugation plane and strong electron-absorbing ability,so it can be used as a good acceptor unit.D-A-D type molecule is constructed by introducing donor unit to promote the red shift of molecular absorption spectrum,and its coordination ability can ndow the molecule with ion recognition function.The nitrogen atom in o-phenanthroline can enhance its electron-withdrawing ability by forming a salt,thereby further red-shifting the absorption and emission wavelength of the molecule,and constructing a near-infrared I/II region photodiagnosis reagents.Thereafter,here in this dissertation,a series of AIE active molecules were designed and synthesized based on the o-phenanthroline derivatives.Their applications in chemo-sensing,photodynamic antibacterial and photothermal cancer therapy were also studied.The main results are shown as follows:By using o-phenanthroline as the electron acceptor(A)unit,triphenyl amine or tetraphenylethylene derivatives as the electron donor(D)moiety,two molecules DTPAP and DTPEP with D-A-D structure were designed and synthesized.Photophysical assays displayed that the increase of rotors in the acceptor moiety are favorable for their AIE characteristics.DTPAP displayed ACQ feature,while DTPEP is AIE active.Comparing to DTPAP,DTPEP exhibited redshifted absorption and emission spectra,with a 90 nm redshift in the emission maxima.DTPAP can act as a fluorescent probe for Hg²⁺and Cu²⁺with a turn-off mode on different emission wavelength.DTPEP can be used for selective sensing of Hg²⁺in aqueous solution with high sensitivity ranging from acidic to alkaline p H.This provides a facile method for the detection of Hg²⁺and Cu²⁺,which are useful and meaningful for environmental protection and human health.Two ionic compounds DTPAP-Br and DTPAP-2Br were synthesized by ionic reaction of compound DTPAP.The ionic characteristics renders DTPAP-Br and DTPAP-2Br water solubility and enhanced intramolecular push-pull effect.Thus,their absorption and emission spectra gradually redshifted as the numbers of ions increases.Theoretical calculations demonstrated that the formation of ionic salts make efficient separation of their HOMO and LUMO electron orbital distributions,and as a consequence,the energy gap for DTPAP-2Br is smaller than that of DTPAP-Br.Moreover,the reactive oxygen species(ROS)generation capability can be enhanced after the ionic reaction.As the increase of positive charges,the binding of molecules with bacteria was also enhanced.Thus,DTPAP-2Br exhibited efficient photodynamic antibacterial effect against staphylococcus aureus.Even when the concentration was lowered to 0.6?M,the killing efficiency of DTPAP-2Br against staphylococcus aureus remained as high as 100%.Additionally,DTPAP-2Br showed little cytotoxicity toward normal cells,which provides a great promise for its application in photodynamic antibacterial therapy.Further,the bromide anion in DTPAP-2Br was change to pentacyanyl cyclopentadiene anion to obtain DTPAP-5CN.Experimental results showed that both DTPAP-2Br and DTPAP-5CN exhibited similar absorption and weak emission spectra in solution.While in aggregate and in nanoparticles(NPs),DTPAP-5CN NPs exhibited redshifted absorption and emission spectra extended to NIR II region,in comparison to DTPAP-2Br NPs.The ROS generation and photothermal conversion efficiency(PCE)of DTPAP-5CN NPs were also much higher than DTPAP-2Br NPs.PCE of DTPAP-5CN NPs reached 72%.By varying the excitation wavelength,DTPAP-5CN NPs can be used for fluorescence imaging targeting mitochondria and lipid droplet respectively,and displayed efficient ROS generation in live He La cells.Notably,DTPAP-5CN NPs can be successfully applied for synergistic photodynamic and photothermal cancer therapy in tumor bearing live mice.