| The different performance is a very worthy research topic for the organic compounds containing the intramolecular charge transfer(ICT)and the intramolecular proton transfer(IPT),in which their parent molecular structure is similar.In this work,43 samples of compounds,2-difluoroboroxy-N-(phenyl-ethylene)-aniline 2-OBF2-XAr C(Me)=NAr Y(2-OBF2-XPEAY)with ICT were synthesized to study the above theoretical topic.The molecular structure of the target compounds was characterized by using the nuclear magnetic resonance spectrum,and the chemical shift?C(C(Me)=N)of C atom in the bridge bond was assigned;The fluorescence emission spectra of the compounds in solid-state and in dichloromethane solution were measured respectively,and the fluorescence emission wavelength Em and their wavenumber?em were recorded;The ultraviolet(UV)spectra absorption spectrum of the compounds in dichloromethane solution were measured,and the maximum wavelength of UV absorption?max(nm)and their wavenumber?max(cm-1,?max=1/?max)were recorded;The redox potential of the compounds was measured by cyclic voltammetry(CV),and the oxidation potential Eox of the compounds were obtained.The quantitative structure-performance correlation analysis method was used to study the influence of substituent effects on the solid?em,solution?em,?max,?C(C(Me)=N)and Eox of2-OBF2-XPEAY.There is intramolecular proton transfer in the Schiff base of o-hydroxy-N-(phenylethylene)aniline Schiff base 2-OH-XAr C(Me)=NAr Y(2-OH-XPEAY),and there is no methyl group in the side bond of o-difluoroboroxy disubstituted diaryl Schiff bases 2-OBF2-XAr C=NAr Y(2-OBF2-XBAY).Their spectral properties of two kinds of compounds were compared.The main conclusions are as following:(1)The influence of substituent effect on the fluorescence emission wave number?em of2-OBF2-XPEAY was researched.The two kinds of electronic effects with C-terminal and O-terminal as the location reference group affect the?em simultaneously and compete with each other,that is,there is homoring competition effect.The quantitative equation of2-OBF2-XPEAY was compared with that of both 2-OH-XPEAY and 2-OBF2-XBAY,and it can be seen that the factors affecting the?em of the three kinds of compounds are different.The fluorescence wavelength Em of compounds 2-OBF2-XPEAY containing the same X?Y group pairs were compared with that of 2-OH-XPEAY and 2-OBF2-XBAY,and the result show that when the substituent X=H,the fluorescence emission wavelength Em of most2-OBF2-XPEAY compounds is larger than that of 2-OH-XPEAY compounds,but the difference is not significant;When the substituent X=4-OMe,the fluorescence emission wavelength of 2-OH-XPEAY is generally larger than that of 2-OBF2-XPEAY,and the difference is large;When the substituent X?Y are H(i.e.no substituent),the Em of2-OBF2-XPEAY is red shift 5 nm versus that of 2-OBF2-XBAY.When substituent X=H,the Em change a little for 2-OBF2-XPEAY versus and 2-OBF2-XBAY.When X=4-OMe,the Em change significantly for 2-OBF2-XPEAY versus 2-OBF2-XBAY.The Em of 2-OBF2-XPEAY in a solid state is concentrated in 400 nm to 600 nm,which has no significant quantitative correlation with the electron effect of the substituent group,and there may be other unknown factors to be studied further.(2)The influence of the substituent effect of compounds 2-OBF2-XPEAY on the maximum UV absorption wave number?max was studied,in which the homoring competition effect was observed.That is,the substituent parameters with C-terminal and O-terminal as the localization reference should be used in establishing the quantitative correlation equation.The?max of 2-OBF2-XPEAY was mainly affected by the excited state parameter C C(X)(C)of X substituent with C-terminal as the localization group.In addition,the interaction between methyl group in the bridge bond and Y substituent,?~2,also affects on the?max.Although the contribution of?~2 to the?max is relatively small,it can adjust the?max of 2-OBF2-XPEAY finely.Comparing the?max of those compounds 2-OH-XPEAY and 2-OBF2-XPEAY containing the same X?Y group pairs.It is found that the?max of most 2-OH-XPEAY is greater than that of 2-OBF2-XPEAY.While for?max of 2-OBF2-XPEAY and 2-OBF2-XBAY containing the same X?Y group pairs,the?max of 2-OBF2-XPEAY is smaller than that of2-OBF2-XBAY,and their wavelength difference??max are in the range of 15-25 nm.(3)The chemical shifts of the C atom in the bridge bond of 2-OBF2-XPEAY were quantitatively correlated.The parameters used in the correlation equation all are that of taking the C-terminal as a reference;it shows that the influence of the electronic effect of the C-terminal as the positioning reference is greater than that of the O-terminal in homoring competition effect.The total contribution of conjugation effect?R(X)C and excited state substitution parameter C C(X)C of X substituent is 85.07%.Comparing the chemical shift of C atom in bridge bond of 2-OH-XPEAY and 2-OBF2-XPEAY containing the same X?Y group pairs,the chemical shift?C of C atom in the bridge bond of 2-OBF2-XPEAY is larger than that of 2-OH-XPEAY and 2-OBF2-XBAY.Comparing the chemical shift of C atom in bridge bond of 2-OBF2-XPEAY and 2-OBF2-XBAY containing the same X?Y group pairs,the difference??C of the chemical shift of C atom in bridge bond of 2-OBF2-XPEAY and2-OBF2-XBAY with X=H is in the range of 8-14.However,the difference??C of substituent X=4-OMe is in the range of 4-6.(4)The oxidation-reduction potential of the compound 2-OBF2-XPEAY was measured by the CV method,and only the redox potential of compound Eox was obtained.This may be that the bridge bond C(CH3)=N+is difficult to be oxidized,and the oxidation reaction results from the F in BF2 structure.A 4-parameter equation was obtained by quantitatively correlating the Eox to substituent parameters involving the sum of the ground state parameters of X and Y substituents[?(X)+?(Y)],the excited state parameters of X substituents C C(X),the excited state parameters of Y group C C(Y)and the special cross interaction term??~2 of X and Y groups.Among them,the sum of[?(X)+?(Y)]has the greatest influence on the Eox. |
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