Picosecond Spectroscopic Studies of Tautomers of a Bisazo Compound in Solutions

Abstract

Spectroscopic properties of a fluorenone-based bisazo compound in different organic solvents have been investigated by means of the steady -state absorption and fluorescence spectroscopy and picosecond timeresolved absorption pump-probe spectroscopy. The spectra of the molecules have been shown to be mainly determined by the excitations localized on individual chromophores -azo fragments. Spectra of the azo-enol and hydrazone-quinone tautomeric forms were distinguished. Excited states of the two forms were found to relax in different ways. The hydrazone-quinone form relaxes predominantly nonradiatively with the 400 ps time constant in rx-chloronaphthalene, resulting in the fluorescence quantum yield of the order of 10-2. The azo-enol form relaxes via two competing ways, directly to the ground state with the time constant of the order of tens of picoseconds, or via the long-lived intermediate state.

Spectroscopic studies of Solophenyl red 3BL polyazo dye tautomerism in different solvents using UV–visible, 1H NMR and steady-state fluorescence techniques

“…The shift of tautomeric equilibrium was observed in different azo compounds by adding acids or alkalis into solvents, or by changing temperature. Moreover, in some cases, the changes caused by heating remained even for several months [4]. It was also found that the type of solvent exerts a profound influence on the tautomerism.…”

“…These classes of organic compounds have extensively been used in both industry for applications such as textiles, papers, leathers, gasoline, additives, foodstuffs, cosmetics and theoretical point of view [1e3]. In addition to other applications, azo compounds are used as photosensitive species in photographic or electrophotographic systems and are the dominant organic photoconductive materials in commercial copiers [4]. Photodynamic therapy (PDT) is a new type of treatment for tumors and certain diseases.…”

“…Proton tautomerism plays an important role in many fields of chemistry and especially biochemistry [6e16]. The hydrazone form that absorbs light at longer wavelengths was found to render higher photoconductivity to duallayered photoreceptors [4]. It is well known that the proton transfer can occur in ground and/or excited state, but only during the last decade the excited state proton transfer has been the subject of substantial interest.…”

The triazine-based azo-azomethine dyes; synthesis, characterization, spectroscopy, solvatochromism and biological properties of 2,2′-(((6-methoxy-1,3,5-triazine-2,4-diyl)bis(sulfanediyl)bis(2,1-phenylene))bis(azanylylidene)bis(methanylylidene))bis(4-(phenyldiazenyl)phenol)

“…They are used in various fields such as paper printing, electronic photography, color formers, dyeing, bleaching, polymers, liquid crystal displays, laser technology, data storage and solar energy conversion [1][2][3][4][5][6][7][8][9][10]. Recently, there is a rapidly growing interest in the potential of their biological-medical applications.…”

Synthesis and Tautomeric Structure of the Azo-Coupling Products of 2-Methyl-7-Phenylpyrimido[1,2-b][1,2,4]triazepine-4,9(3H,5H)-dione

“…[1][2][3][4][5][6][7] In addition to these applications, azo compounds are used as photosensitive species in photographic or electrophotographic systems and are the dominant organic photoconductive materials in commercial copiers. 8 To the best of our knowledge 2-methyl-7-phenylpyrimido [1,2-b] [1,2,4]triazepine-4,9(3H,5H)-dione (3) has not been reported hitherto. In continuation of our previous studies, we report here on the coupling of the novel ring system 3 with diazonium salts in an attempt to synthesise the respective azo derivatives 4 (Scheme 1) and the elucidation of their tautomeric structures.…”