Design,Synthesis Of Benzotriazole Derivatives As Fluorescent Molecules And Investigation On Their Photoluminescence Properties

Benzotriazole,as a nitrogen-containing organic heterocyclic molecule,has been of great interest in the field of organic chemistry.It has been widely used in many fields,such as biology,medicine,materials,fluorescence,electrochemistry and organic synthesis.Compared with other nitrogen-containing heterocyclic molecules,benzotriazoles have better biological activity and chemical stability.The unique electronic structure of benzotriazole makes it easy to coordinate with metal ions and obtain stable coordination compounds.At the same time,benzotriazoles have a variety of coordination modes for metal cations.The advantages of simple synthesis conditions and many modifiable sites have led to the synthesis of many benzotriazole derivatives and their application in various research directions of organic chemistry.Due to the high conjugation and strong electron-pulling ability of benzotriazole molecules,benzotriazole derivatives have full potential in the field of organic fluorescent molecules.However,unfortunately,there are not many reports on the organic fluorescent molecules of benzotriazoles.Therefore,the work in this paper focuses on the design,synthesis and properties of a series of fluorescent molecules with benzotriazole as the basic backbone.The main research results obtained are as follows.(1)(E)-4-(2-(1H-benzo[d][1,2,3]triazol-1-yl)vinyl)-N,N-dimethylaniline(BTADA),a derivative based on benzotriazole,was designed and synthesized by introducing N,N-dimethylamino groups with strong electron-giving ability to the benzotriazole ring.BTADA has a typical TICT effect,showing different fluorescence wavelengths of 449-570 nm in organic solvents with different polarities,and a linear relationship with the solution polarity.In addition,BTADA exhibits good aggregation-induced luminescence properties.In the crystalline state,BTADA can be excited with intense yellow fluorescence,and after grinding,the fluorescence color will be blue-shifted to some extent.BTADA is one of the few H-aggregates with AIE properties and the first reported AIE molecule based on benzotriazole derivatives,playing a pioneering role in expanding the range of AIE molecules.Since both benzotriazole sites and N,N-dimethylamino groups in the molecule can bind hydrogen ions,BTADA exhibits a unique dual response mechanism of first red shift and then blue shift in response to hydrogen ions,which also makes it applicable to a wider range of hydrogen ion concentrations.Using this feature,we have achieved monitoring of specific organic reaction processes.(2)Seven fluorescent probes with coumarin-benzotriazole as the backbone were designed and synthesized.The fluorescence properties of the compounds were modulated by introducing functional groups with different electronic effects such as methyl,methoxy,halogen,N,N-diethyl and nitro at sites 6 and 7 of coumarin,respectively.Subsequently,we compared the response effects of these seven compounds for different biological sulfhydryl compounds and used(E)-3-(2-(1Hbenzo[d][1,2,3]triazol-l-yl)vinyl)-4-chloro-7-(diethylamino)-2H-chromen-2-on(BTAC(e))as a representative to explore the ability of this class of compounds to detect biological sulfhydryl compounds in living cells.Among them,BTAC(e),a compound with N,N-diethyl attached to the coumarin 7 site,has green fluorescence.Its fluorescence emission wavelength in tetrahydrofuran solution is 507 nm.When it comes in contact with biothiolated compounds,BTAC(e)exhibits specific recognition against homocysteine(Hcy),and its fluorescence intensity can be increased 4-fold in response.The synthesis of this probe greatly fills the gap in the effective identification of cysteine(Cys)and Hcy by fluorescent probes.The probe has the advantages of short response time(<15 min),low detection limit(1.55×108 mol L-1),and low cytotoxicity,realizing rapid,efficient,and specific detection of homocysteine in living tumor cells.(3)A novel fluorescent ligand,(E)-N’-((1H-benzo[d][1,2,3]triazol-6yl)methylene)-7-(diethylamino)-2-oxo-2H-chromene-3-carbohydrazide(BTANC),was designed and synthesized,and its fluorescence emission wavelength was 485 nm in tetrahydrofuran solution by introducing an N,N-diethylamino group with strong electron-giving ability to the coumarin ring,thus constructing an intramolecular charge-transfer channel in the molecule,which gives BTANC a strong photoluminescence ability.Multiple binding sites for liganding with metal cations.The ligand stabilization constant was 3.41 × 106,and the ligand stabilization process was accompanied by the quenching of BTANC fluorescence by Pd2+.On this basis,the BTANC-Pd complex was also used in the catalysis of the Sonogashira coupling reaction for a variety of different substrates,obtaining up to 99%yields.Combined with their fluorescence properties,We proposed a pioneering approach to monitor the reaction progress by the fluorescence intensity changes in the reaction system.For the first time,we translated the changes of the oxidation state of the catalyst metal center at a microscopic scale into the fluorescence intensity changes in the reaction system at a macroscopic level.This is currently the first metal ligand that combines fluorescence activity with catalytic efficiency.Such fluorescent ligands with catalytic ability provide a new powerful tool for monitoring the progress of sensitive organic reaction systems,and at the same time can help us to better observe the metal valence changes in catalytic reactions and thus understand the reaction mechanism.(4)We designed and synthesized a series of novel benzotriazole derivatives.Among them,(E)-1-(2-(pyridin-4-yl)vinyl)-1H-benzo[d][1,2,3]triazole(BTAB(c))with a pyridine ring has strong electron-donating ability and can act as an excellent donor molecule.Based on this,we selected three classic acceptor molecules:tetracyanoethylene(TCNE),2,4,6-tribromophenol(TBP)and 2,4,6tris(p-hydroxyphenyl)-1,3,5-triazine(THPTA),and after screening,a new type of organic co-crystal structure BTAB(c)-TCNB was ultimately prepared.We used theoretical calculation methods such as MESP and DFT to analyze the structure of BTAB(c)-TCNB,and characterized it by PXRD and XRD,and the obtained structure data were consistent with the theoretical calculation results.It was found that the organic co-crystal BTAB(c)-TCNB has AIE activity,and under the excitation of 365 nm ultraviolet light,the crystal exhibits strong yellow fluorescence.This is the first report of an organic co-crystal with optical activity constructed by benzotriazole derivatives,providing a new idea and basis for the composition of organic co-crystals.The hydrogen bonds between the molecules in BTAB(c)-TCNB can be broken by acid vapor,leading to fluorescence quenching.When exposed to air,the fluorescence can be restored.This reversible fluorescence change makes BTAB(c)-TCNB highly potential in multiple application areas such as anti-counterfeiting labels and acid vapor sensors.