Photolytic Properties of Ortho-Substituted 4-[N,N-Bis(β- Hydroxyethyl)amino]azobenzenes in Polymer Substrates

Abstract

The synthesis of some novel derivatives of 4-[ N,N -bis(β-hydroxyethyl)-amino]azobenzene is reported, and the effects of ortho -substituents on photoinduced trans → cis isomerism about the azo group, mass spectral behavior, and the photostability of these dyes are described. An ortho-nitro group inhibits trans → cis photoisomerism about the azo group and affords poor photostability. Those ortho-substituted dyes showing a greater tendency to undergo photoinduced trans → cis isomerism and recover quickly are also more photostable and less subject to rupture at the β-nitrogencarbon bond in the mass spectrometer. The photolysis experiments were done using acetate and triacetate film and fiber, and the mass spectrometric analyses were done by direct probe using the electron-impact technique.The effects of various electron-donating and electron-attracting groups on the color and fastness properties of azo dyes have been described in a number of papers during the past four decades [2-5, 7, 10, 12-17, 19 J. Perhaps the more interesting of these studies are those describing the anomalous effects of an orthonitro group on the photostability of such dyes [ t 0, 12-14, 17 ] . Although as a general rule, electron-withdrawing groups increase the photostability of 4-N,N dialkylaminoazobenzenes (1) when placed ortho or para to the azo linkage, an ortho-nitro group decreases photostability significantly. To explain these results, Mehta and Peters [ 12 proposed that the negatively charged oxygen atoms of an ortho-nitro group inhibit delocalization of the electrons between the azo nitrogen atoms, and this renders the ~ -N bond on the coupler side more susceptible to photolytic cleavage. On the other hand, not only does the photostability of these dyes improve when the nitro group is moved to the para-position, but workers have also found ( for a review see reference 21) that the thermal cis -trans isomerization of azobenzenes occurs by a rotational mechanism resulting from the delocalization of the electrons at the azo group to form a nitrogen-nitrogen single bond (see dye 2).Little has been reported, however, about the effects of ortho substituents on the trans -cis photoisomerism of aminoazobenzenes and the possible relationship

Unexpected photochemical debenzylation of 2,5-bis(dibenzylamino)-3,6-dichloro-p-benzoquinone

“…The light fading phenomena of dyes and dyed substrates have been studied focusing on the fading mechanisms of dyes [8e10]. There are several reports on photochemical dealkylation of amino groups of dyes [11,12], although an example with a benzyl group is still unknown. A benzyl group is also well-known as a protecting group for amino moieties in addition to that for alcoholic hydroxy groups [13].…”

Fusarium oxysporum degradation and detoxification of a new textile-glycoconjugate azo dye (GAD)

“…The synthesis of the model yellow GAD (4) has been accomplished according to the previously described (Bianchini et al 2008) procedure showed in Fig 1, starting from known compounds 1 ( Bartalucci et al 2007) and 2 (Freeman & McIntosh 1989). A solution of compound 1 (0.97 g, 3.40 mmol) (Fig 1) and compound 2 (2.40 g, 6.66 mmol) in dry tetrahydrofuran (THF) (20 mL) was treated at room temperature with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC, 1.28 g, 6.68 mmol) and 4-dimethylaminopyridine (DAMP, 244 mg, 2.00 mmol) and the solution was stirred at room temperature until the starting material completely disappeared (thin layer chromatography e TLC, 12 h).…”

Photoinduced debenzylation of 2,5-bis(dibenzylamino)-3,6-dichloro- p -benzoquinone

“…To our knowledge, it was the first report on the debenzylation of amino groups in organic dyes, whereas there are several reports on the corresponding N-dealkylation reaction [25][26][27].…”