Abnormal effect of hydroxyl on the longest wavelength maximum in ultraviolet absorption spectra for bis-aryl Schiff bases

Abstract

Two sets of bis-aryl Schiff bases that contain 4(or 4′)-OH and 2(or 2′)-OH were synthesized. The first set consists of 4-HOArCH=NArY and XArCH=NArOH-4′, and the second set consists of 2-HOArCH=NArY and XArCH=NArOH-2′. Their ultraviolet absorption spectra were measured and investigated. A very interesting phenomenon was observed by analyzing their wave number ν max (cm −1 ) of longest wavelength maximum λ max (nm) of ultraviolet. Compared with the change regularity of the ν max of XArCH=NArY (where the X and Y excluded OH), the 4′-position hydroxyl (4′-OH) and 2′-position hydroxyl (2′-OH) have abnormal performance. The details are the following: the 4′-OH contributes an additional red shift to the ν max of XArCH=NArOH-4′ (λ max increase), whereas the 2′-OH contributes an additional blue shift to the ν max of XArCH=NArOH-2′ (λ max decrease). In addition, there are ortho steric effects of all 2-OH and 2′-OH on the ν max for 2-HOArCH=NArY and XArCH=NArOH-2′, and the ortho steric effect contributes a red shift to their ν max . These experimental facts can provide an important theoretical reference for us using aryl Schiff base compounds as optical materials and performing the molecular design. KEYWORDS hydroxyl, ortho steric effect, Schiff base, substituent effect, ultraviolet absorption spectra

Effect of substituents on the UV spectra of supermolecular system: Silver nanoparticles with bi‐aryl Schiff bases containing hydroxyl

“…Compound b The values were taken from Hansh et al [27] c The values were taken from previous studies. [28][29][30][31][32][33] d Indicator variable of 4′-OH.…”

“…To quantify the effect of substituent on the UV spectra of organic compounds, author's group [28][29][30][31][32][33] proposed excited-state substituent constant σ ex CC . Using the σ ex CC constant together with Hammett electronic effect constant σ, [27] the wavenumbers ν max of the λ max were well correlated for these conjugated compounds involving substituted stilbenes and benzenes, [25,[30][31][32][33][35][36][37][38] styrene TABLE 2 The λ′ max (nm) of MC, λ WSL (nm) of MC-AgNPs, Δν WSL (cm −1 ), and substituent effect constants of groups X and Y for XBAYs (2 and 4) No.…”

Synthesis of new cyclotriphosphazene derivatives bearing Schiff bases and their thermal and absorbance properties

“…Schiff bases (imines) are among the most popular classes of organic compounds due to their excellent kinetic and thermodynamic stabilities and potential photoelectric properties [16][17][18][19][20][21]. Aryl Schiff bases, which contain a classical π -conjugated system, have potential optoelectronic properties [16,17,22,23]. There are important influences on the molecular properties due to the substituents on the aromatic rings of an aryl Schiff base [16,24,25].…”

“…Aryl Schiff bases, which contain a classical π -conjugated system, have potential optoelectronic properties [16,17,22,23]. There are important influences on the molecular properties due to the substituents on the aromatic rings of an aryl Schiff base [16,24,25].…”

“…Schiff base ligands (2a-2d) bearing four different side groups at the para position on the terminal phenyl ring were prepared from the condensation reaction of 4-aminophenol with benzaldehyde, p -fluoro-, chloro-, and bromobenzaldehyde in ethanol[16,39]. Full substituted cyclotriphosphazene products (3a-3d) were synthesized from the nucleophilic substitution reactions of chlorocyclotriphosphazene (1) with Schiff bases including hydroxyl groups in high yields.…”