The Study Of Fluorescent Amide Compounds

The traditional organic fluorescent compounds are usually composed of conjugated unsaturated groups or aromatic rings,which have good conjugated systems and rigid structures.In recent years,some researchers found some nontraditional organic fluorescent polymers with only amide,primary amine,secondary amine and tertiary amine and other simple functional groups.Because of their excellent fluorescence properties,good water solubility,low biological toxicity,and easy functionalization,they have draw wide attention.However,their structures are relatively complex,which make it difficult to clarify the luminescent centers.What's more,the fluorescence properties can be influenced by many factors,so that it is relatively difficult to understand the luminescence mechanism.The fluorescent amide compounds have simple structures and can be easilyprepared,which is conductive to systematically study the corresponding relationship between structures and the fluorescence properties and clarify the luminescent centers.What's more,the studies of fluorescence mechanism can be carried out through both the experiments and theoretical calculation.And the understanding of their fluorescence mechanism could provide some enlightenment on the light-emitting mechanism of the non-traditional fluorescent polymers.In this paper,the detailed research contents are as follows:1.A series of fluorescent amide compounds were synthesized through the acyl chloride method with different carboxylic acids and organic amines.The carboxylic acids and organic amines include Acetic acid,propane diacid,tricarballylic acid,citric acid,ethylamine,ethylenediamine,?-aminopropyl trimethoxy silane and(N-??-aminoethyl?-?-aminopropyl methyl dimethoxyl silane.The products prepared by the monoacid have no emission while the others can emit fluorescence and the fluorescent properties of the products synthesized by citric acid are better.The structures were measured by ¹H-NMR and ESI-MS spectra.The results show that the products prepared by triple carboxylic acid and diamine contains different structures and it is hard to purify them because of similar properties.We try various experimental conditions to get only one product instead of mixture.2.A series of monosubstituted fluorescent amide compounds were prepared with citric acid and diamines containing different number of methylenes,including hydrazine hydrate,ethanediamine,1,3-propanediamine?PDA?,1,4-butanediamine.The research results show that the quantum yields?QY?can be influenced by the number of methylenes between amino groups,and the highest product's QY is 29.6%,which ascribed to the product of rection between CA and PDA?CA-PDA?.In addition,it was found that this kind of fluorescent amide compounds have Aggregation-Induced Emission?AIE?.The fluorescence intensity is enhanced with the increasing of the concentration of CA-PDA,and in the solid state,it emits strong fluorescence.In addition,the solvent viscosity effect experiment shows that with the increased viscosity,the fluorescence intensity is enhanced and the peak is blue-shifted,which suggest the AIE is attributed to the restriction of intramolecular motions?RIM?.This kind of fluorescent amide compounds also have twisted intramolecular charge transfer?TICT?effect.The fluorescence intensity decreases and fluorescence peaks red-shift with increasing of solvent polarity which are attributed to TICT effect.3.The optimized molecular structures calculated by time-dependent density functional theory?TD-B3LYP?,the optimal structures show that intramolecular hydrogen bonds were formed in CA-PDA molecule.The hydrogen bonds makes the spatial overlay of the electron clouds of intramolecular amide and carboxyl groups,which may facilitate both intramolecular cluster and through-space conjugation effect.The HOMO and LUMO of CA-PDA show that the electron ortals exactly cover O-C=O and N-C=O double bonds,suggesting O-C=O and N-C=O are closely related to the fluorescence emission.Therefore,this is the reason why this kind of fluorescent amide compounds emit fluorescence.CA-PDA could be used as an ON-OFF-ON fluorescent probes,and further used in biological imaging due to the low cytotoxicity CA-PDA.The ion detection experiments show that with addtion of Hg²⁺in CA-PDA solution,the fluorescence intensity decreased obviously,then after being added sulfhydryl amino acids,it recovered.In this paper,CA-PDA was applied in cell imaging of A549 cells;4.A series of fluorescent amide compounds were prepared with citric acid and poly-amines,including diethylenetriamine?DETA?,triethylenetetramine?TETA?and tetraethylenepentamine?TEPA?.The experiment results show that the QY can be impacted with the number of amino groups.CA-DETA has the highest QY,up to 58.9%,however,QYs of CA-TETA and CA-TEPA decrease successively.5.The resulting compounds prepared from diamine or polyamine have similar fluorescence properties,which suggest similar emitting mechanism.However,the fluorescence intensity of compounds prepared from polyamine rises obviously with the increasing of temperature and storage time.It may be related to a specific interaction between nitrogen in their stuctures and oxygen.The fluorescence intensity of CA-DETA is quenched in the presence of Hg²⁺,Fe³⁺,Cu²⁺and Co³⁺,but the quenching effects of Hg²⁺and Fe³⁺are more obvious.6.Thestructureandfluorescencepropertiesofhydrolyzationproduct?H-CA-AEAPMDS?of CA-AEAPMDS have been explored.CA-AEAPMDS is a resulting product of CA and AEAPMDS studied by our group before.H-CA-AEAPMDS have up-conversion luminescenc,and is applied in cell imaging in Hela cells.Also,H-CA-AEAPMDS can be used as an ON-OFF-ON fluorescent probes to detect Hg²⁺and sulfhydryl amino acids.Furthermore,the fluorescence intensity H-CA-AEAPMDS is also quenched in the presence of Fe³⁺.Through hydrolysis property of CA-AEAPMDS,we prepared fluorescent glass and fluorescent SiO₂ microspheres,explored the feasibility of H-CA-AEAPMDS to build multipurpose composite materials.In conclusion,the fluorescent amide compounds have relative simple structures and excellent fluorescence performance.The emitting mechanism was studied through them also provide effective support to understanding the fluorescence mechanism of the unconventional fluorescent polymers.And they have potential to be applied in fluorescent tracer and cell imaging.