Click Synthesis And Property Invesitagation Of Triazole-bridged D-?-A Structured Triphenylamine Fluorescence Chemical Sensors

Push-pull molecules including some ones with D-?-A structure have been widely applied to some fields such as functional materials due to intramolecular charge transfer property(ICT).In recent years,with the rapid development of functional materials,people pay more attention to explore large conjugated compounds as donor in order to both improve the ICT process and enhance fluorescence emission.Triphenylamine(TPA),which is a star-like structured molecule with a nitrogen atom in center,is a well-known electron donating luminescent molecule based on lone pair electrons of nitrogen atom.What is more,the three benzene rings linked with the nitrogen atom of triphenylamine with its obvious activity,structural diversity and easily modified property,can be connected with different substituents at appropriate position and a series of luminescent materials with certain functions can be produced.We firstly synthesize a triphenylamine-derivative based on triphenylamne and D-?-A structure,which show methanol selectively responsive charactivity.If added different substituents to the para-position of triphenylaminbe,we can get a series of color-adjustable molecules.(1)We report a novel D-?-A structured molecule(TTO),synthesized by coupling triphenylamine(electron-donor)and p-toluenesulfonyl(electron-acceptor)via Cu(I)catalytic 1,3-dipolar cycloaddition(click chemistry)forming a triazole bridge.In general,TTO experiences Intramolecular charge transfer once excited by light,but which is inhibited in methanol due the synergy of H–bonding and solvent polarity,and then TTO exhibits strong fluorescence and can be used as a highly selective fluorescence probe for methanol identification.Notably,TTO is able to excellently probe methanol from its homologue ethanol in water with a high sensitivity,good selectivity and detection limit of below 0.7%(volume concentration),which demonstrates the promise potential of TTO for practical applications.(2)On the basis of our previous work,a series of triphenylamine-derivatives(ATTO,BTTO,CTTO)with D-?-A structure are synthesize by replace para-position of triphenylamine by ethynyl,bromo and methyl aimed to explore the influence of conjugated effect and inductive effect on configuration,ICT process and fluorescencespectra: in terms of ATTO,on the one hand,ethynyl-substitude can increase conjugation system,enhance the ability to provide electron and ICT process,on the contrary,decrease the H-bonding effect,causing more high fluorescence and weak methanol fluorescence selectivity,on the other hand,ethynyl increases steric hindrance and weaken ?-? stacking and then induce blue shift of emission peak in solid state.Then we talk to BTTO,bromo-substitude as an electron-withdrawing group weaken conjugation system and ICT process and conversely strengthen the H-bonding effect,which cause weak fluorescence emission and strong methanol fluorescence selectivity,moreover,it increase ?-? stacking and induce red shift of emission peak in solid state.Finally we analyze other molecule CTTO,the fluorescence of methyl-substitude as an electron-donating group is similar to the ATTO and is different from BTTO based on inductive effect.(3)In order to make clear the mechanism of methanol responsive fluorescence,we simulate the dissolve process of TTO in different ten solvents including methanol,research the configuration under the lowest energy on the ground state and excited state and calculate the absorption and fluorescence spectra with the method of time-dependent density functional theory(TD-DFT)and polarizable continuum fields model(PCM).The results reveal that TTO has a rigid concave shape and twisted conformation.And with the increase of polarity,TTO tend to more stable and has a lower energy.It is interesting that the energy of TTO in methanol is exceptionally higher than one in other solvents,wavelength is shorter and molar absorption coefficient is higher,which can prove that TTO show methanol responsive fluorescence.Meanwhile,the single bond break in excited state,which lay a foundation to synthesize terminal triazole group.In this paper,we have developed a fluorescence probe to detect methanol and especially can recognize methanol from its homologue ethanol.What is more,we illustrate that conjugated effect and inductive effect have a great influence fluorescence intensity and emission peak of D-?-A structured molecule,which lay a foundation on color-adjustable molecule.