Untersuchungen zum UV/Vis‐Spektralverhalten von Azofarbstoffen. IV. Zum Einfluß von Lösungsmitteln auf die Farbbande von Azobenzenen

Abstract

Studies on UV/VIS Absorption Spectra of Azo Dyes. IV. Solvent Effects on the Visible Absorption Band of Azobenzenes Solvent effects on \documentclass{article}\pagestyle{empty}\begin{document}$ \begin{array}{*{20}c} \sim \\ {\nu _{\max } } \\ \end{array} $\end{document} values of substituted azobenzenes are studied and correlated with solvent polarity parameters. Poor correlations of \documentclass{article}\pagestyle{empty}\begin{document}$ \begin{array}{*{20}c} \sim \\ {\nu _{\max } } \\ \end{array} $\end{document} values with functions of ϵ and n of solvents are found. A comparison of spectral data with the ET scale shows a much poorer correlation. The correlation with the ET values are significantly better if the protic solvents are excluded. The best of the tested relationships was found with the empirical solvent parameters π*. Values of S in the equation \documentclass{article}\pagestyle{empty}\begin{document}$\begin{array}{*{20}c} \sim \\ {\nu _{\max } } \\\end{array} = {\rm S}\pi ^{\rm *} {\rm + }\begin{array}{*{20}c} \sim \\ {\nu 0} \\\end{array}, $\end{document} depend on the dye structure. It is found a relationship between S and the difference of quantum chemical calculated dipol moments in the first exited singlet (μ(S1)) and in the ground state (μ(S0)) of the dyes.

Synthese, Charakterisierung und UV-VIS-spektroskopisches Verhalten von 4-benzhydrylamino-substituierten Azobenzolen

“…Mit Hilfe dieser lnkrementwerte E~ sind fur die verschiedenen N-Benzhydrylaminogruppen nach einer empirischen Beziehung [4] die HAMMETT-0,-Konstanten zuganglich (2). al, = 0,008 -0,124 E D (2) Die Absorptionsmaxima der Azobenzole 1 , 6 und 11 rnit den daraus erhaltenen E~ und HAMMETT-a,-Konstanten fur die drei neuen Substituenten sind in Tabelle 1 aufgefuhrt: Vergleicht man die gegenuber dem unsubstituierten Azobenzol eintretenden bathochromen Verschiebungen der N-benzhydrylaminosubstituierten Azobenzole mit jenen von Arylazoarenen des Substituententyps -NH-n-Alkyl, so stellt man fest, dal3 die Donatorstarke von -NHCHPh?…”

Solvent Effects on the Electronic Spectra of Some Heterocyclic Azo Dyes

“…[15][16][17][18][19][20][21][22] The first examples of negative solvatochromism in neutral azo dyes containing both strongly electron-donating and -withdrawing moieties were reported by Kim et al. 23 temperature.…”

Negative solvatochromism of azo dyes derived from (dialkylamino)thiazole dimers

“…Neutral azo dyes have been reported to show a positive solvatochromism [5][6][7][8][9][10][11][12] while two types of ionic azo dyes, 4-[2-(triphenylphosphonio)phenylazo]phenolates and 2-(1-methylpyridiniumazo)-and 2-(1-methylqunoliniumazo)tetracyanocyclopentadienides, have been reported to reveal negative solvatochromic behavior. 13,14 Interestingly, the azo dyes 1 showed either positive and negative solvatochromism depending on the diazo components.…”