74141-84-7Relevant academic research and scientific papers
Photochromic Properties of Unsymmetric Mono- and Bis(phenylazo)naphthalenes
Yoshida, Katsuhira,Koujiri, Tetsunao,Horii, Taeko,Kubo, Yuji
, p. 1658 - 1664 (2007/10/02)
To utilize the reversible photochromic system of phenylazonaphthalenes in a design of functional molecule, the photochromic behaviors of various substituted phenylazonaphthalenes have been investigated.Introduction of substituents onto ortho positions with respect to the azo group retarded the rate of thermal cis-to-trans isomerization.The retardation effects were greatly dependent on both the number and position of the ortho substituents.To investigate the retardation effects of ortho substituents, the activation parameters were determined; the results suggest that the steric hindrance among the ortho substituents and the two nitrogen lone pairs of the azo group becomes far more severe in an inversional transition-state than in the ground cis-state, which leads to the remarkable slow cis-to-trans isomerization.On the basis of the kinetic data of various phenylazonaphthalenes, the complicated isomerization behaviors of unsymmetric bis(phenylazo)naphthalenes have been elucidated.
Protonation Equilibria of 1-Arylazo-4-naphthols and 1-Arylazo-4-Methoxynaphthalenes
Abate, Lorenzo,Longo, Maria Luisa,Maccarone, Emanuele,Torre, Michele
, p. 628 - 631 (2007/10/02)
The spectroscopic behaviour of substituted 1-arylazo-4-naphthols and 1-arylazo-4-methoxynaphthalenes has been investigated in a solvent system consisting of 20percent v/v ethanol and 80percent v/v sulphuric acid-water in order to measure the protonation equilibrium constants.Some naphthols (I; X=H, o-OCH3, p-OCH3, o-CH3, p-Cl) and all the methoxynaphthalenes (II) show two absorption bands due to the free base and the conjugate acid, with a characteristic isosbestic point.For these compounds, pKBH(1+) values have been calculated using Jaffe's acidity function.Other naphthols (I; X=m-OCH3, m-CH3, p-CH3, o-Cl, m-Cl) show a single absorption band which shifts on changing the acidity of the medium.The lack of an isosbestic point has been ascribed to the overlap of the azo-hydrazone equilibrium with the protonation equilibrium of the azo-group.For methoxynaphthalenes, separate correlations of pKBH(1+) values with ?m and ?p of the substituents are found, owing to the presence in the molecules of two distinct basic centres.
