Azulen-1-yl diazenes substituted at C-3 with phenyl-chalcogene moieties: dye synthesis, product characterization and properties

Abstract  

Two synthesis strategies were used for the generation of azulene-1-yl diazenes substituted at C-3 with a phenyl-chalcogenyl moiety, the synthesis of azulenes substituted at C-3 followed by azo-coupling and azulene substitution at C-3 in azulene-azo dyes. The last synthetic route seems to give more satisfactory results for the synthesis of the desired chalcogenic derivatives. Another target of this study was to investigate the changes induced by the phenyl-chalcogenic substitution on the NMR and UV-vis spectra, and also to compare this effect with the one exerted by halogen atoms and by strongly electron donating groups such as AcNH or PhCOO. Whereas the latter groups exhibit a strong influence on the NMR and UV-vis spectra, PhS, PhSe, or PhTe groups as well as halogen atoms produce only a small effect because of the moderate change in electron distribution over the entire molecule.     

On the electrochemical behavior of selanyl azulenes

Journal of Solid State Electrochemistry - The electrochemical behavior of substituted 1-phenylselanyl azulenes has been established by cyclic, differential pulse, and rotating disk electrode...     

Thermodynamics of interactions between lead(II) and cadmium(II) ions and azulene-based complexing polymer films

In order to understand the essential processes/interactions between the metal ions and modified electrodes which are based on complexing polymeric films, access to thermodynamic characteristics is compulsory. The paper enlarges the information concerning the sorption of metal ions within complexing polymer films, particularly based on azulene, which can be involved in metal detection sensors. Interactions between lead(II) or cadmium(II) ions and complexing polymer films have been studied using chemical preconcentration–anodic stripping method. The films have been obtained by controlled potential electrolysis in millimolar solutions of 4-azulen-1-yl-2,6-bis(2-thienyl)pyridine (L) in acetonitrile. PolyL films affinities towards these metal ions have been quantified at different temperatures by means of sorption isotherms. Parameters for sorption of lead(II) and cadmium(II) ions within polyL films have been calculated for Freundlich, Langmuir and Redlich–Peterson isotherms. The best fit was obtained when using Langmuir isotherm. The results evidence that lead ions are better sorbed than cadmium within polyL film. Thermodynamic parameters for the chemical sorption of lead(II) and cadmium(II) ions within polyL films have been calculated.     

4-(Azulen-1-yl) six-membered heteroaromatics substituted in 2- and 6- positions with 2-(2-furyl)vinyl, 2-(2-thienyl)vinyl or 2-(3-thienyl)vinyl moieties

The synthesis of pyrylium and pyridinium salts and pyridines with azulene-1-yl moieties in position 4 and two 2-heteroarylvinyl groups in positions 2 and 6 was accomplished. The pyrylium salts were obtained starting from pyranones and pyridines could be prepared from these salts by treating them with ammonium acetate. The general procedures for the synthesis of pyridinium salts, which occur with good results in less delocalized electronic systems, do not take place when applied to the above obtained pyrylium salts. Therefore, as starting material 4-(azulen-1-yl)-1-(n-butyl)-2,6-dimethylpyridinium perchlorate was used, which was condensed with heteroarylcarboxaldehydes. These compounds were completely characterized and some of their spectra were discussed. Their interaction with some metal ions was revealed, observing an affinity better than in the case of simple azulenepyridines. In the last part of the paper are presented redox potentials for several pyrylium salts and pyridines in comparison with those of the nonvinylogated derivatives.     

Azulene‐1‐azo‐2′‐thiazoles. Synthesis and properties

Several derivatives belonging to a new compound class, namely azulene‐1‐azo‐2′‐thiazoles, were prepared by the diazotization of 2‐aminothiazoles in the presence of HNO₃/H₃PO₄ followed by the coupling of diazonium salts with azulenes in buffered medium. The reactions proved to be general for this class, the yields are, however, considerably influenced by the substituents at thiazole moiety. For the first time a N‐oxide provided from an amino substituted five‐member nitrogenous heterocycle was diazotized and coupled. The structure of the obtained compounds was assigned and their physico‐chemical properties were discussed. The new azulene azo derivatives exhibit a strong bathochromic shift in UV‐Vis due to the intense push‐pull effect of aromatic system and to the intrinsic properties of thiazole moiety.     

2‐(Azulen‐1‐yl)‐4,6‐diphenyl substituted six‐membered heteroaromatics

2‐(Azulen‐1‐yl)‐4,6‐diphenyl substituted pyranylium salts, pyridinium salts and pyridines were efficiently synthesized and the new obtained compounds were completely characterized. Comparative structural analysis between these compounds and their corresponding isomers that contain the azulen‐1‐yl moiety in the 4‐position of the heterocycle, were carried out. These studies are based on calculated dihedral angles formed between central heterocycle and the aromatic substituents and on the obtained electronic and NMR spectra. Due to the restriction in the rotation around azulenyl‐pyridinium bond produced by the quaternary nitrogen substituent, in the herein reported pyridinium salts, the substitution groups of the quaternary nitrogen atom are prochiral. This property leads to the non‐equivalence of gem‐protons or gem‐methyl groups of N‐substituents in the ¹H nmr spectra of the synthesized pyridinium salts.     

Azulene‐substituted pyranylium salts. Syntheses and products characterization

The synthesis of 4‐azulene‐substituted 2,6‐diphenyl‐ and 2,6‐dimethyl‐pyranylium salts and 2‐azulenesubstituted 4,6‐dimethyl‐pyranylium salts by nucleophilic substitution at pyranylium moiety with various azulenes was studied. The starting materials for 2,6‐diphenyl derivatives were 4 chlorinated pyranylium salts. They were obtained by the halogenation with PCl₅ of corresponding pyranones and were used either in situ or after separation. For the synthesis of dimethyl derivatives the corresponding pyranones were treated with POCl₃ and the resulted intermediate was reacted in situ with azulene. In the aim to study the influence of dihedral angle between azulene and pyranylium planes on the recorded spectra, both moieties were adequately substituted. The obtained results were in accord with the calculated values.     

Azulene‐substituted pyridines and pyridinium salts. Synthesis and structure. 1. Azulene‐substituted pyridines

4‐Azulen‐1‐yl substituted 2,6‐dimethyl‐and 2,6‐diphenyl‐pyridines are obtained in good yields from the reaction of corresponding 4‐azulen‐1‐yl‐pyranylium salts and ammonium acetate in ethanol or starting from 4‐chloro‐2,6‐diphenyl‐pyranylium salts in two steps: reaction with azulenes followed by in situ treatment with ammonium acetate. The effect of substitution at the 3‐position of the heterocycle was taken into account. The structure assignment was accomplished with NMR and uv‐vis spectra.