Research On The Influence Factors Of Spectroscopy Performance For Diphenylfulvens And Aromatic Schiff Base

Substituent polar constants (Hammett electronic effects constant σ, conjugative effectσ R,inductive effect F) have important effect on the13C NMR chemical shift value δc(C=N)of C=N bond in di-benzyl schiff bases. However, whether substituent excited state constantex CChas influence on the δc(C=N) or not it was not studied. In this work, depth analysis onthe δc(C=N) of di-benzyl schiff bases shows that the exCChas important effect on theδc(C=N) indeed, andσ R, Fand exCCcan be employed to quantify the change rule ofδc(C=N), in which the error is within the experimental uncertaninty. In order to make acomparision, a set of nomo-benzyl schiff base GPhCH=NC6were synthesized, theirexperimental δc(C=N) were measured, and also the correlation between the δc(C=N) valuesand the parametersσ R, Fand exCCwas carried out. It was found that the δc(C=N) ofnomo-benzyl schiff bases it similar with that of di-benzyl schiff bases, they all can bequantitatively expressed byσ R, Fand exCC, but there is a difference between theδc(C=N) values of two set of compounds, that isσ R, Fand exCChave stronger influenceon the δc(C=N) of di-benzyl schiff bases.The study result shows that the substituent influence on the UV absorption spectrum ofDiphenylfulvens can be expressed by excited state substituent parameters exCCand polarityparameters p,which is more accurate than parameter p. The change rule of UVabsorption spectrum of Diphenylfulvens in more than10kinds of different solvents can beexpressed by using three parameters, exCC, pand the solvatochromic dye ET(30), and theET(30) is better than the n-octanol/water partition coefficient logP in scaling the solvent effect.Research shows that carbon disulfide may be an unsuitable solvent for determining the UVabsorption spectrum of Diphenylfulvens.The UV absorption energy(υmax) of prepared nomo-benzyl Schiff bases GPhCH=NC6weremeasurated in ethanol, the inverstigated result show that the ultraviolet absorption energy ofthese compounds can not described by substituent polarity paramenters p, and can be expressed very well by substituent excited state parameters exCCand ground state polarity parameters pFurther research showed that the UV absorption energy between Diphenylfulvens and stilbenes containing nonpolar bond C=C have good linear relationship,but the UV absorption energy between nomo-benzyl schiff bases and di-benzyl schiff basescontaining polar bond C=N have not good linear relationship, perhaps it is due to the dihedralangle of groups attached at the end of C=N deviating from the plane in containing C=Ncompounds, which makes a larger difference of conjugate condition between nomo-benzylschiff bases and di-benzyl schiff bases.