Negative Halochromism Research Articles

Identification of azaphilone derivatives of Monascus colorants from Talaromyces amestolkiae and their halochromic properties

Currently, the ability to produce several kinds of water-soluble red natural colorants makes the genus Talaromyces particularly important to the dye industry, which can be an alternative to the use of harmful synthetic colorants. In this study, colored compounds produced by Talaromyces amestolkiae were extracted, characterized chemically and the color stability of the fermented broth without any extraction procedure was further evaluated over pH variation. Five azaphilones compounds were detected by Ultrahigh Performance Liquid Chromatography-Mass Spectrometry system, all being complexes of the fatty acid amino-hexanedioic acid and azaphilone Monascus colorants. The color of the fermented broth was stable at a wide range of pH (3–9). Furthermore, T. amestolkiae colorants precipitated through hydrolysis of key chemical groups at extremely acidic (pH 1) and lose red color in extremely basic (pH 13) medium, showing negative halochromism. Nevertheless, these findings enhance the industrial relevance of azaphilone colorants produced by biotechnological process.

Push-pull azobenzene chromophores with negative halochromism

This work describes the synthesis and properties of monoazobenzene compounds carrying multiple electron-donating and electron-withdrawing substituents. The donors are methoxy and dialkylamine groups. The acceptors are cyano and nitro groups. The position of these groups has a strong influence on the absorption spectrum. When the nitro and cyano groups are located at the ortho and para positions to the azo bond, respectively, then the absorption maximum (λmax) can be found at 484 nm. However, switching this arrangement leads to a 57 nm red-shift (λmax = 541 nm). This shift can be enhanced further (λmax = 584 and 604 nm) by moving one of the methoxy groups from the ortho to the meta position and by encompassing the nitrogen atom in a five-membered ring. Interestingly, under acidic conditions, a reversible blue-shift (negative halochromism) is observed.

Synthesis and Application of Direct Dyes Derived From Terephthalic and Isophthalic Acids on Cotton Fabrics

The synthesis of direct dyes derived from terephthalic and isophthalic acid using J and H- acids was undertaken with the view of replacing benzidine moiety in the production of direct dyes. The amide derivatives of isophthalic and terephthalic acids were used as the coupling components while aniline and its derivatives were used as the source of diazo components. The amide derivatives were characterized by Gas Chromatography/Mass Spectrometry and Infra-red analysis. The spectroscopic properties of the dyes in various solvents were also examined and most of the dyes showed bathochromic shifts when the solvent was changed to more polar solvents. The dyes also showed positive and negative halochromism with the addition of few drops of hydrochloric acid (HCl). The synthesized dyes were applied to cotton fabrics and their performance properties evaluated. They have good exhaustion in the presence of electrolyte and have good wash fastness properties upon application of after-treating agents of values of 3-4, 4 and 4-5. They also had good fastness properties to light of values between 4-7. Their resistance to rubbing and perspiration had values between 3 and 4-5. The toxicity of the synthesized coupling components was studied using the Dietrich Lorke (LD50) method on Albino miceand they were found to be non-toxic.

Colour and halochromic properties of azo dyes derived from 10-methyl-9-methylene-9,10-dihydroacridine as coupling component

10-Methyl-9-methylene-9,10-dihydroacridine, in the form of its methylsulfate salt, couples to arenediazonium ions to give highly bathochromic azo dyes. These are typical donor–acceptor chromophoric systems, exhibiting a progressive bathochromic shift as the electron withdrawing strength of the diazonium component increases. Thus λ max values range in ethanol from 561 nm for the 4- N,N-dimethylaminophenylazo derivative to 650 nm for the 2-cyano-4-nitrophenylazo dye. Further increases in the electron withdrawing effect of the arylazo substituent lead to a hypsochromic shift, as evidenced by the 3,5-dinitro-2-thienylazo derivative, with a λ max value of 610 nm in ethanol. The arylazo derivatives are strongly basic, with p K b values in the range 4.6–8.2, and show negative halochromism. Thus protonation gives azonium cations which absorb at shorter wavelengths than the parent dyes, and in some cases the pH-induced visual colour change is sufficiently pronounced to render the dyes of value as indicators.

Electron Acceptors of the Fluorene Series. 9.1 Derivatives of 9-(1,2-Dithiol-3-ylidene)-, 9-(1,3-Dithiol-2-ylidene)-, and 9-(1,3-Selenathiol-2-ylidene)fluorenes: Synthesis, Intramolecular Charge Transfer, and Redox Properties

The synthesis and physical properties of four series of novel fluorene push−pull compounds (4−7) of the D−π−A type with intramolecular charge transfer (from 1,3- and 1,2-dithiole and 1,3-selenathiole donor (D) moieties) are described. The nature of the heteroatom (S or Se) in the donor fragment has no effect on the maxima of intramolecular absorption bands (λICT), whereas a change of position of the heteroatoms in the dithiole moiety from 1,3 to 1,2 leads to a substantial bathochromic shift in λICT. Solvatochromism, thermochromism, and negative halochromism in these compounds are demonstrated. Cyclic voltammograms of 4−7 exhibit two, separate, single-electron reversible redox waves, the potentials of which (as well as the ICT energies in the molecules) are quantitatively described by σp- constants of the substituents in the fluorene ring. Compounds 4−7 exhibit reversible salt formation in sulfuric acid, and for compound 5g in diluted sulfuric acid an additional absorption in the near-IR region has been observed that we attribute to radical species formation from the equilibrium [5g-H]+ + 5g ⇄ 5g•+ + [5g-H]•.

Dyes derived from aminothiophenes. Part 5: Spectral properties of some nitro-substituted thiophene-based azo disperse dyes

The spectroscopic properties of a series of nitro-substituted thienyl-2- and thienyl-3-azo dyes in neutral and acidic solution were examined. In agreement with resonance theory and PPP-MO calculations, nitrothienyl-2-azo derivatives were found to be more bathochromic than analogues lacking nitro groups. Absorption intensities, half-band widths and positive solvatochromic shifts were also greater; additionally, the nitrothienyl-2-azo dyes exhibited negative halochromism. The nitrothienyl-3-azo dyes were hypso- and hypochromic relative to their thienyl-2-azo isomers. The spectra and halochromism of the 2,4-disubstituted dyes indicated the presence of steric hindrance.

Pyridinium N‐Phenolate Betaine Dyes and Their Application to the Characterization of the Polarity of Solvents, XXII. Syntheses and UV/Vis Spectroscopic Properties of Solvatochromic, Halochromic, and Chiro‐Solvatochromic Pyridinium N‐Phenolate Betaine Dyes with Four Stereogenic Centers

AbstractSyntheses (Schemes 1–3), negative solvatochromism (Table 1), cation‐induced negative halochromism (Table 2), and chiro‐solvatochromism (Tables 3 and 4) of the new crown ether‐substituted chiral pyridinium N‐phenolate betaine dyes 18a, b and 28a, b, each posessing four stereogenic centers, are described. The absolute configuration at the four stereogenic centers of the chiral betaine dyes has been confirmed by X‐ray crystal structure analysis of the intermediate phenol 14a (Figure 1). Solutions of the chiral betaine dyes 18a, b and 28a, b, prepared by addition of monochiral amines and amino alcohols to solutions of the salts 17a, b and 27a, b in ethanol, exhibit in some cases small but significant chirosolvatochromic band shifts of up to Δλ = 10–12 nm (Tables 3 and 4), caused by chiral recognition of the monochiral guest molecules.

Pyridinium N‐Phenoxide Betaines and Their Application to the Characterization of Solvent Polarities, XX. – Synthesis, Solvatochromism, and Halochromism of Chromoionophoric Crown Ether‐substituted Pyridinium N‐Phenolate Betaine Dyes

AbstractSynthesis, negative solvatochromism (Table 1, Figure 1), and negative halochromism (Tables 2–3, Figures 2–3) of the new crown ether‐substituted pyridinium N‐phenolate betaine dyes 3–6 are described. In contrast to other known chromoionophores, 3–5 exhibit a cation‐selective negative halochromism, which manifests itself as a hypsochromic shift of the longwavelength intramolecular charge‐transfer (CT) absorption band of the betaine chromophore on addition of salts. As this CT absorption band lies within the visible spectral region, the cation‐induced colour change can be followed easily by eye, which suggests an application of these new chromoionophoric betaine dyes as cation indicators. The halochromism of 3–6 constitutes a new type of true halochromism, in contrast to the trivial halochromism first defined by Baeyer and Villiger in 1902.

Pyridinium N‐Phenoxide Betaines and Their Application to the Characterization of Solvent Polarities, XIX. The Halochromism of Pyridinium N‐Phenoxide Betaine Dyes in Acetonitrile Solution

AbstractThe halochromism of the negatively solvatochromic pyridinium N‐phenoxide betaine dye 1 has been measured in acetonitrile solution and linearly correlated with the effective charge of the cations of the added alkaline and alkaline earth salts. The observed negative halochromism of betaine dye 1 constitutes a new type of true halochromism, in contrast to the trivial halochromism found for the first time by Baeyer and Villiger in 1902.

An Exceptionally-Large Negative Halochromism in 2-(4-Ethoxycarbonylphenyl)2,3-dihydro-3,3-dimethyl-5,6-cycloheptapyrazoledione, a Hinopurpurin Derivative

Abstract 2-Aryl-2,3-dihydro-3,3-dimethyl-5,6-cycloheptapyrazolediones with an electron-releasing group at C-4 on the benzene ring showed a bathochromic shift in acid solution, whereas the 4-ethoxycarbonylphenyl derivative showed a negative halochromism; 484 nm in ethyl acetate, 517, 566, and 600(sh) nm in trifluoroacetic acid, and 455 nm in coned sulfuric acid.

Untersuchungen zum UV/Vis‐Spektralverhalten von Azofarbstoffen. XI. Allgemeine Zusammenhänge zwischen Struktur und Farbe protonierter Azofarbstoffe

Studies on U.V./Vis Absorption Spectra of Azo Dyes. XI. General Relationships between Structure and Colour of Protonated Azo DyesThe U.V.‐VIS spectra of a wide range of azo dyes having structural variations in both diazo and coupling components in acidic solution are discussed.The azonium cation can be regarded as a donor‐acceptor chromophore. Thus, structural variations which give a bathochromic shift in λmax, are explained. The negative halochromism is also discussed with reference to this model.

Synthesis and Electronic Spectra of Some Disperse Dyes Derived from 9‐Phenylazo‐1‐ketojulolidine

Several monoazo dyes have been prepared from 1‐ketojulolidine and compared with their julolidine counterparts. The presence of a carbonyl group in the terminal bridging system leads to improved light fastness properties on synthetic‐polymer fibres, but also to an essentially constant hypsochromic shift (70 nm) of the first absorption band. The azojulolidine dyes exhibit a marked negative halochromism. Unlike the parent julolidine dyes, the ketofulolidine disperse dyes are not suitable for transfer printing.