Determining the excited‐state substituent constants of meta‐substituent from 3,4'‐disubstituted stilbenes

Abstract

In this paper, 61 samples of 3,4'-disubstituted stilbenes and 18 samples of 3,3'-disubstituted stilbenes were synthesized, and their UV data were measured in anhydrous ethanol. Based on the UV absorption energy (wavenumber) of 3,4'-disubstituted stilbenes, the excited-state substituent constants s ex CC m ð Þ of metasubstituent were determined by means of curve-fitting. The availability of s ex CC m ð Þ was confirmed by the good correlation with the UV absorption energy of 3,4'-disubstituted stilbenes and 4,4'-disubstituted stilbenes. Further, using the obtained constants s ex CC m ð Þ and the correlation equation, we calculated the UV wavenumbers of 3,3'-disubstituted stilbenes, and the calculated wavenumbers are in good agreement with the experimental values. These results verified that the excited-state substituent constants s ex CC m ð Þ of meta-substituent are reliable parameter to scale the effect of meta-substituent on the UV absorption energy.

An attempt of molecular design and synthesis of 3,4′/4,3′-disubstituted benzylideneanilines with specified UV-Vis absorption maximum wavelength

“…At that time, there were no values of meta‐substituent so that the prediction of UV–Vis absorption ν max values of the meta‐substituted benzylideneanilines couldn't be carried out. Recently, Cao et al proposed excited‐state substituent constants values for several meta‐substituents, which makes it possible to calculate the UV–Vis absorption ν max values of 3,4′/4,3′‐disubstituted benzylideneanilines by using Eqn . Compared with the molecular structure of 4,4′‐disubstituted benzylideneanilines, we think, the 3,4′/4,3′‐disubstituted benzylideneanilines should have different UV–Vis absorption ν max values.…”

“…It can be seen that the UV–Vis absorption ν max values of compounds XBAY can be calculated only known of the σ and constants . Therefore, we try to employ Eqn to design benzylideneanilines with the given UV–Vis absorption ν max values.…”

“…In our previous research, [15][16][17][18][19][20] the excited-state substituent constants have been proposed to quantify the influence of substituent on the UV-Vis absorption ν max values and were applied successfully in quantifying the UV-Vis absorption ν max values of compounds, such as XPh, XPhY, XPh(CH = CH) n PhY (n = 0, 1, 2), XPhCH = NPhY and XPh(CH = CHPh) n Y (n = 0, 1, 2). Moreover, a general equation of quantifying the UV-Vis absorption ν max values of 4,4′-disubstituted benzylideneanilines (XBAY) has been proposed, [15] which is rewritten as shown in Eqn (1).…”

Determining the excited‐state substituent constants of furyl and thienyl groups

“…In 2008, Cao et al [19] proposed an excited-state substituent constant σ ex CC to express the effect of substituents on the properties of compounds at excited state, and then we used the σ ex CC to correlate quantitatively the UV absorption spectra and reduction potential of substituted benzene, substituted stilbene, and Schiff bases. [20][21][22][23][24][25][26] We observed that the UV absorption spectra were mainly affected by the σ ex CC for the substituted benzene and substituted stilbene compounds, while the UV absorption spectra of Schiff bases were affected by both substituents σ ex CC and σ. The constant σ ex CC , proposed by Cao, [19] provides a convenience for investigating quantitatively optical properties of organic compounds, but, up to now, there are only a few number of substituents being determined the σ ex CC values, which cannot far meet the needs of investigation and application.…”

“…Therefore, if we want to increase σ ex CC values of certain groups, we have to do more experiments. [21,27,28] As we know, furyl and thienyl are common optically active groups and appear more frequently in organic compounds, and the extraction of their σ ex CC is an important work for the study of optical materials. Because there is difficult to synthesize compounds with the molecular skeleton of XArCH═CHArY (X = 2furyl, 3-furyl, 2′-methyl-2-furyl, 2-thienyl, 3-thienyl, and 2′-methyl-2-thienyl), we design and synthesize the series of target compounds (XCH═CHArY) and measure their longest wavelength maximum λ max (nm) of UV absorption spectra and try to determine the σ ex CC p ð Þ of furyl and thienyl by means of curve-fitting method.…”