Ihor W. Tarnawskyj

Azo pigments and their intermediates. On the anomalous optical absorption of bisazo pigments from 4,4′-diamino-1,1′-dianthrimide and 2-hydroxy-3-naphthanilides

Abstract A number of bisazo pigments ( 2a–2o ), which were designed to extend the optical absorption of azo pigments to longer wavelengths (greater than 650 nm), enabling these pigments to be useful in photoreceptors in light-emitting diode (LED) (680 nm) and diode laser (780 nm) printers, were synthesized by coupling a red-absorbing amine ( 1 , 4,4′-diamino-1,1′-dianthrimide, λ max ≈ 680 nm) and 2-hydroxy-3-naphthanilide couplers using the classic azotization-coupling procedure. All bisazo pigments synthesized are dark blue solids with melting points higher than 300 °C. They absorb at λ max ≈ 610- nm in the visible region in the solid state. Their wavelengths of absorption, which are insensitive to electronic and steric effects exerted by the substituents in the coupler moiety, are unexpectedly at shorter wavelengths than that of 1 (λ max ≈ 680 nm). In order to facilitate our understanding of the hypsochromic shift of absorption from 1 to 2a–2o , the nature of the electronic transition of the long-wavelength absorption band of 1 was studied systematically by absorption spectroscopy. Results from structural effect and solvent effect experiments indicate that the long-wavelength absorption in 1 is a charge-transfer band resulting from an intramolecular charge-transfer interaction between the two aminoanthraquinonyl rings. In the bisazo pigment structure, owing to the steric repulsion between the two coupler moieties, such an intramolecular interaction is prohibited. This changes the conformation of the bisazo pigment and is shown to be responsible for the hypsochromic shift of the optical absorption from 1 to bisazo pigments 2a–2o .

Azo pigments and their intermediates: Effect of substitution on the diazotization and coupling reactions of o-hydroxyanilines

Abstract The effects of substituents on the diazotization and coupling reactions of o-hydroxyanilines have been studied. When the substituent is a strong electronwithdrawing group, e.g. NO 2 , the resulting substituted 2-hydroxy-lbenzenediazonium chloride is highly acidic, even in aqueous hydrochloric acid solution. It deprotonates and forms the corresponding substituted 1,2-benzoquinone-1-diazide. For less electron-withdrawing or even electronreleasing substituents, the so-generated diazonium chlorides are soluble in the aqueous hydrochloric acid solution. These diazotized products are isolated as hexafluorophosphate salts. The coupling reactions between various diazotized products of o-hydroxyanilines and 2-hydroxy-3-naphthanilide are shown to proceed through the 1,2-benzoquinone-1-diazide intermediate, regardless of their original structure. Synthetic results show that the substituted 1,2-benzoquinone-1-diazide intermediate is only reactive when it is activated by a substituent that is more electron-withdrawing than the chloro group.

Azo pigments and their intermediates: A CP MAS 13C-NMR study of the tetrazotized products of 1,5-diamino-4,8-dihydroxyanthraquinone

Abstract An attempt to use 1,5-diamino-4,8-dihydroxyanthraquinone ( 1 ) as a precursor to synthesize bisazo pigments, by an azotization-coupling reaction sequence, is reported. The tetrazotization of 1 , by a slight excess of sodium nitrite, is effective both in concentrated hydrochloric acid and concentrated sulfuric acid. In concentrated hydrochloric acid, the tetrazonium product was isolated as the tetrafluoroborate salt, 3 , by adding fluoroboric acid into the azotized solution. In concentrated sulfuric acid, the tetrazonium product was isolated as the sulfate salt, 4 , by simply diluting the azotized solution with ice-water. The structures of 3 and 4 were characterized by IR and crosspolarization magic angle spinning (CP MAS) 13 C-NMR spectroscopy, as well as solution NMR measurements. Due to their high acidity, 3 and 4 deprotonate to form 5 , an insoluble purple-brown solid in dilute aqueous solution or in organic solvents. Compound 5 only dissolves in acidic solutions and, since this involves a protonation reaction, it can only be characterized by solid-state techniques. In this work, the structure of 5 was established by IR and CP MAS 13 C-NMR spectroscopy. Two characteristic carbonyl stretchings at 1670 and 1655 cm −1 are observed in the IR spectrum and two carbonyl carbons at 176.8 and 178.2 ppm are observed in the solid-state 13 C-NMR spectrum. The protonation-deprotonation relationships between 3 , 4 and 5 were established from their solution and solid-state NMR spectra. The facile deprotonation of 3 and 4 and the insolubility of 5 in any solvents are shown to be a hindered factor for the synthesis of bisazo pigments.

Effect of reaction temperature on the average crystallite size of Se x Te 1− x alloys

Electrophotographic properties of chalcogenide materials are readily influenced by altering their composition and/or structure. Dark decay and cycle down of photoreceptors utilizing small particle generators are both directly proportional to average crystallite size (ACS). This paper describes a novel chemical method to control the ACS of Se, Te, and Se x Te 1− x alloys. These chalcogenide materials are prepared as powders by the reduction or coreduction of Se IV and/or Te IV intermediates with hydrazine, in organic media. To control the ACS of precipitated chalcogens the reaction is carried out at the desired temperature. X-ray diffraction measurements are used to determine the ACS, homogeneity, and phase of these precipitated powders.

Azo pigments and their intermediates. A facile synthesis of photoreceptor grade anilide couplers from 2-hydroxy-11H-benzo(a)carbazole-3-carboxylic acid

Abstract A facile, two-step synthesis for anilide couplers of 2-hydroxy-11H-benzo(a) carbazole-3-carboxylic acid, by first converting the acid to its phenyl ester and then condensing the phenyl ester with an aniline derivative to form an anilide, is reported. The synthesis is very general and a variety of anilides have been synthesized in an overall yield of⩾60%. The synthesized anilides are of high purity and can be used to synthesize photoreceptor-grade (IR-sensitive) azo pigments without further purification. The procedure described in this work is shown to be more efficient than other processes reported in the literature, such as direct condensation of the acid with an aniline or indirect condensation of the acid with an aniline through an acid chloride or methyl ester intermediate. More importantly, we have demonstrated that neither yield-loss nor deterioration in product purity is observed as the scale of the synthesis increases.

Azo pigments and their intermediates. A new class of couplers for red and near-IR sensitive photogenerating azo pigments

Abstract The synthesis of azoic couplers, 2,8-dihydroxy-3-naphthanilide and its derivatives, by first converting 2,8-dihydroxy-3-naphthoic acid into its phenyl ester followed by condensing the phenyl ester with an aniline derivative, is reported. Photogenerating bisazo and trisazo pigments have been prepared by coupling 2,8-dihydroxy-3-naphthanilide with 2,7-diamino fluorenone and tris( p -aminophenyl)amine, respectively. The absorption spectra of these pigments are found to be red-shifted relative to analogous pigments synthesized from 2-hydroxy-3-naphthanilide. The data suggest that 2,8-dihydroxy-3-naphthanilides are new coupler components for red and near-IR absorbing photogenerating azo pigments. Evidence is provided that the red shift is a result of an intramolecular H-bonding between the 8-OH group in the coupler moiety and the nitrogen atom in the hydrazone unit of the pigment. Comparison of the pigments synthesized in this work with those from 2-hydroxy-11 H -benzo(si)carbazole-3-carboxanilides suggests that the wavelength extension achieved by carbazole-couplers may also be a H-bonding effect, between the N-H group in the carbazole ring and the nitrogen in the hydrazone unit. The advantage of using the couplers described in this work for preparing red and near-IR absorbing photogenerating pigments is discussed.