Synthesis and properties of novel aziridinyl azo dyes from 2-aminothiophenes—Part 2: Application of some disperse dyes to polyester fibres

A series of yellow to greenish-blue aziridinyl azo dyes and their azo precursors containing a thienyl coupling moiety has been applied to conventional polyester fibre as well as microdenier polyester by high temperature exhaust dyeing. Heat transferability of these dyes onto polyester fibre has also been examined, using conventional heat-transfer printing techniques. The relevant dyeing characteristics, heat transferability, build-up, dyeability on microfibre polyester, washfastness and lightfastness are given. These aziridinyl dyes are reactive to polyester fibres under HT dyeing conditions. Fabrics dyed with aziridinyl dyes are more resistant to solvent extraction than those dyed with conventional dyes. Residual liquors showed only a pale colour when fabric dyed with aziridinyl dyes was dissolved and then precipitated, whereas a coloured polyester precipitate was obtained.     

Novel azo dyes derived from phthalimide. Part 1: Synthesis and spectroscopic properties

A series of azo dyes has been synthesised based on N -alkylphthalimide diazo components featuring one of three different alkyl groups. An analogous set of dyes was prepared in which the N -alkylphthalimidylazo systems bore an o,o -dibromo-substitution pattern. In these cases, cyanodebromination was performed to give the corresponding dicyano analogues. All the synthesised intermediates and dyes were characterised by mass spectrometry, proton nuclear magnetic resonance spectroscopy and elemental analysis. The absorption maxima of the dyes in dimethylformamide (N,N-dimethyl ∼) were observed to be in the range 435–608 nm and found to be consistent with results seen in previous studies of conventional monoazo disperse dyes. Replacement of both halogens in the dibromo-substituted dyes with cyano groups led to large bathochromic shifts (128–141 nm) in absorption maxima. Bathochromism was also observed when acetylamino groups were present on the coupler ring ortho to the azo link. However, variation of the N -alkyl function on the imido ring from n -butyl to sec -butyl and iso -propyl had little effect on absorption maxima, values being similar to that reported for the parent N -unsubstituted analogue.     

Synthesis and spectroscopic properties of novel azo dyes derived from phthalimide

A set of azo dyes has been synthesised using N -substituted phthalimides as diazo components. 3,5-Dibromo- N -substituted-phthalimidylazo derivatives were cyanated by cyanodehalogenation to give dicyano analogues. All of the synthesised intermediates and dyes have been characterised by mass spectrometry, ¹H-NMR or elemental analyses. The gamut of colour of the prepared dyes spanned much of the visible spectrum: absorption maxima of the dyes in formamide were observed in the range 436 to 609 nm. Consistent with results seen in previous studies of non-phthalimido monoazo disperse dyes, replacement of dibromo groups with dicyano functions in the phthalimide-based set led to large bathochromic shifts in absorption maxima, as did the introduction of acetylamino groups onto the coupler ring ortho to the azo link. However, switching an N -propyl function on the imido ring for a benzyl or 3-cyanopropyl substituent had little effect on absorption maxima. Good correlations between the observed absorption maxima of certain dyes and those of model analogues predicted by Pariser–Parr–Pople molecular orbital calculations were observed when steric effects were absent.     

Studies of novel monomeric and polymeric azo disperse dyes

A series of polymeric dyes were synthesized by free‐radical addition polymerization of monomeric dyes that were derived from diazotized 2‐amino‐3,5‐bis‐(ethoxycarbonyl)‐4‐methylthiophene by coupling with various N‐arylmaleimides. All the polymeric dyes were characterized by elemental analysis, IR and visible spectroscopy, viscometry, and TGA. Color and dyeability of the polymeric dyes are discussed by comparing them with those of the corresponding monomeric dyes. All the dyes have been found to give various color shades with good to very good depth and levelness on the fiber. The dyeing of the monomeric dyes shows good fastness to light and very good to excellent fastness to washing, perspiration, sublimation, and solvents. The corresponding polymeric dyes show excellent fastness properties. The percentage dyebath exhaustion and fixation on the fiber have been found to be good to very good (60–90%). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1380–1389, 2002; DOI 10.1002/app.10276     

Synthesis, properties and application of four new 1;2 aluminium-complexed azo dyes

In view of the well-known environmental concerns associated with the synthesis and application of certain metal-complexed acid dyes, potentially less toxic analogues of four chromium and cobalt 1;2-complexed azo dyes were synthesised by employing aluminium in lieu of chromium or cobalt. The aluminium-complexed dyes produced brighter shades on nylon 6.6 and wool than the corresponding 1;2-complexed dyes based on chromium, cobalt and iron. The lightfastness results of nylon 6.6 and wool dyed with the 1;2 aluminium-complexed dyes were, in general, better than the unmetallised precursors, but inferior to the corresponding chromium, cobalt and iron dyes.     

Spectrophotometric investigations and computational calculations of prototropic tautomerism and acid-base properties of some new azo dyes

The prototropic tautomerism in four novel azo compounds derived from pyrazolo[1,5-a]pyrimidin-7(4H)-one was intensively examined. Tautomeric structures which result from annular and azo-hydrazone tautomerism were exposed to semiempirical and density functional theory (DFT) calculations, allowing the recording of structural parameters, physicochemical properties and equilibrium constants to be recorded. The values of the equilibrium constants determined among the most stable forms clearly showed that compounds 1 and 2 co-exist in the NH and hydrazone forms. However, NH tautomers were strongly preferred to other forms in compounds 3 and 4. The observed electronic absorption bands were assigned and compared with the predicted transitions using a time-dependent DFT method (TDDFT). In all solvents employed, except for DMF and acetonitrile, compounds 1 and 2 exhibited azo-hydrazone tautomerism. However, the ionized species were predominant in highly polar solvents for compounds 3 and 4. In DMF, all the investigated dyes exist either in acid-base equilibrium or in the ionized form depending on the molecular structure. Hence, the values of the ionization constant (K_ion) and Gibbs free energy (ΔG) of the equilibrium existing in solution were calculated. In addition, the pK_a values of the investigated dyes were determined spectrophotometrically.     

The synthesis and structural study of two benzothiazolyl azo dyes: X-ray crystallographic and computational study of azo–hydrazone tautomerism

The synthesis, FT-IR, ¹H and ¹³C NMR characterisation, as well as crystal and molecular structure determined by single-crystal X-ray diffraction data, of two azo dyes derived from 6-aminobenzothiazole: 6-[(4-N,N-dimethylaminophenyl)diazenyl]benzothiazole and 6-[(2-hydroxy-1-naphthyl)diazenyl]benzothiazole are reported. Both dyes are essentially planar with the exclusion of methyl groups in 6-[(4-N,N-dimethylaminophenyl)diazenyl]benzothiazole, which exibits 100% E-configuration in terms of orientation of the substituents about the central azo linkage. Single-crystal X-ray study of 6-[(2-hydroxy-1-naphthyl)diazenyl]benzothiazole was undertaken to established whether the hydrazone or azo tautomer was present in the solid state as well as any potential shift in tautomeric equilibrium imparted by temperature variation (296 and 100 K). Density functional theory calculations revealed that the hydrazone tautomer was more stable than the azo tautomer and that the tautomeric equilibrium was shifted towards the hydrazone form at lower temperature.     

Dyeing and fastness properties of polyamide fabrics using some acid‐based monoazo disperse dyes

A series of monoazo disperse dyes derived from naphthalimide containing butyric acid has been applied on polyamide fabrics. The build up and dyeing properties of these dyes such as leveling property, wash, light, perspiration for alkaline and acidic conditions, and rubbing fastnesses on polyamide fabrics have been investigated. The results showed that the applied dyes are capable of producing red to bluish red hues on polyamide fabrics. Because of the presence of both carboxylic acid and hydroxyl groups on the molecular structure of Dye 3, it showed desired and more strength in respect to other used dyes. Comparing the build up of these dyes to commercial dyes such as disperse red 60 and disperse red 73 revealed that most of the used dyes have higher build up in comparison to the commercial ones. Measurement of fastness properties of dyed samples indicated that they have good wash (4–5), rubbing (4), perspiration (4–5), and heat fastnesses (4–5) and they possess less than moderate light fastness (3–4) on polyamide fabrics. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Novel azo dyes derived from phthalimide. Part 2: Dyeing properties and colour fastness on polyester fibres†

The coloration and fastness properties of 18 carbocyclic monoazo disperse dyes bearing a phthalimide ring fused to the aromatic ring of their diazo components have been investigated. In each case, the phthalimidyl nitrogen atom was substituted with either a butyl, sec‐butyl or isopropyl group, while the adjoined phenyl ring bore a substitution pattern typical of commercial colorants. Dye uptake and build‐up onto both conventional and microfibre polyester through exhaustion dyeing were examined: while the expected tendency of greater exhaustion on microfibre was noted, there were few clear trends with respect to dye structure. The nature of the N‐alkyl group made no consistent difference to dye uptake. Attempts to explain the observed percentage exhaustion values by mapping them to calculated partition coefficient or solubility parameter values were unsuccessful. Wash fastness tended to be best for blue dicyano‐substituted derivatives, which may be as a result in part of these substituents promoting hydrolysis of the adjacent phthalimide ring to give more soluble phthalate species. In contrast, the dicyano dyes had relatively poor photostability compared with their unsubstituted analogues.     

Synthesis and dyeing properties of novel disperse dyes. Part 2: Pyrazole disperse dye derivatives

Several new disperse dyes derived from thiosemicarbazides and acetoacetanilide have been synthesised. The dye structures were ascertained by chemical analysis and infrared measurements. Prepared dyes were used for dyeing nylon fabric by the exhaustion method. The colour strengths and dye fixation on the fabric were also determined. The results suggest a practical significance.     

Synthesis,spectral properties and application of novel disazo disperse dyes derived from polyester waste

Terephthalic dihydrazide was obtained through aminolytic depolymerisation of polyester bottle waste by using hydrazine hydrate. It was further reacted with 4‐aminobenzoic acid in the presence of polyphosphoric acid to obtain a cyclic compound, 4,4′‐[5,5′‐(1,4)‐phenylene)bis(1,3,4‐oxadiazole‐5,2‐diyl)dianiline, having a heterocyclic moiety. Diazotisation of this compound followed by coupling with various N,N‐disubstituted anilines afford a series of novel disazo disperse dyes. The structures of these synthesised dyes were confirmed by elemental analysis and Fourier Transform–infrared, proton nuclear magnetic resonance and mass spectroscopy. Ultraviolet–visible spectra of these azo dyes in different polar solvents showed considerable variation in the wavelength of maximum absorbance (λ_max). Application of these dyes on polyester and nylon fabrics using high‐temperature dyeing methods gave brilliant yellowish red hues with fair to moderate light fastness and very good to excellent wash fastness and sublimation fastness.     

Monoazo disperse dyes. Part 3; Synthesis and fastness properties of some novel 4,5-disubstituted thiazolyl-2-azo disperse dyes

Novel blue disperse dyes bearing a 5-nitro substituent on various C-4 substituted thiazolyl-2-azo dyes have been prepared using m -aminoacetanilide derived coupling components. These dyes have been characterised using a range of spectroscopic techniques and exhibit interesting fastness behaviour on dyed polyester. For Parts 1 and 2 in this series, see references 9 and 10, respectively.     

Switching azonaphthols containing a side chain with limited flexibility. Part 1. Synthesis and tautomeric properties

A series of azo dyes, possessing amide fragments with restricted flexibility tethered to 4-(phenyldiazenyl)naphthalen-1-ol, was obtained from 1-hydroxy-2-naphthoic acid by subsequent conversion to amides and diazo coupling. It was shown that the position of the tautomeric equilibrium in solution strongly depends on the solvent in both UV and NMR concentration scale. The compounds exist as pure enol forms in chloroform and hydrocarbons, while in polar solvents (acetone, acetonitrile, alcohols) a tautomeric mixture is observed. According to the quantum-chemical calculations the aggregation of the keto tautomer is the possible reason for this shift in the position of the tautomeric equilibrium. To support the theoretical predictions, it was found that from acetone the keto form crystallizes as a dimer with hydrogen bonding between N₁-H in the one molecule and amide CO in the other forming a three-dimensional structure. The importance of the side-chain nitrogen atom on the dimer formation was confirmed by solution and solid state study of 4-(phenyldiazenyl)-2-acetylnaphthalen-1-ol. The results indicate that the new azo-dyes obtained could be suitable candidates for switching and sensing applications in non-polar solvents.     

Synthesis and characterization of hetarylazo disperse dyes derived from substituted N‐β‐acetoxyethylanilines—Application on cellulose acetate

The heterocyclic amines 2‐amino‐6‐methoxy‐ and 2‐amino‐6‐nitrobenzothiazole, 3‐amino‐5‐nitro‐[2,1]‐benzisothiazole, and 2‐amino‐3,5‐dinitrothiophene were diazotized and coupled to substituted N‐β‐acetoxyethylanilines to give dyes which colored cellulose acetate in red to deep blue hues. The color of the dyes is discussed with respect to the nature of the heterocyclic ring and to the substituents in the diazo and coupling component. Dyeing and fastness properties of the dyes on cellulose acetate are also reported. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3479–3483, 2004     

Synthesis of 6-(4-diethylamino)phenyl-2-oxo-2H-pyran-3-carbonitorile derivatives and their fluorescence in solid state and in solutions

One-pot synthesis of a new 2-pyrone dye (3a) by the reaction of 4-diethylamino-acetophenone (1) with methyl 2-cyano-3,3-bis(methylsulfanyl)acrylate (2) in the presence of sodium hydroxide as the base was carried out in DMSO. Compound 4a was synthesized by the replacement of methylsulfanyl group of 3a with dimethylamine at 4-position of pyrone ring. Similarly, compound 5a was prepared via the reaction of 3a with diethyl malonate. Compounds 3a-5a exhibited the following fluorescence in the solid state: red (3a), green (4a), and orange (5a). In addition, it was revealed that 2-pyrone dyes exhibit fluorescence in various solvents and show positive solvatochromism. Compounds 3a and 5a exhibited intense fluorescence in chloroform and dichloromethane (fluorescence quantum yield Φ: 0.94-0.95). In contrast, compound 4a exhibited intense fluorescence in polar solvents (methanol: Φ = 0.92). These 2-pyrone dyes have the potential for applications in various fields.     

Synthesis,spectral properties and dyeing on polyester of monoazo dyes from indol‐2‐one derivatives

Three series of phenylazo disperse dyes were prepared by coupling diazotised 4‐aniline dyes with 5‐indol‐2‐one dyes. The structures of these dyes were determined by proton nuclear magnetic resonance, Fourier Transform–infrared and elemental analysis. The effects of solvent on the ultraviolet–visible absorption spectra of these dyes were studied. The dyes displayed a λ_max shift of between 399 and 438 nm. The dyes were finally applied in the dyeing of polyester fibres in order to investigate their colour range and dyeing properties. Most of the dyes displayed high rubbing fastness and good washing and sublimation fastnesses on polyester fibres.