Journal of the Korean Chemical Society 2012, Vol. 56, No. 3 Printed in the Republic of Korea http://dx.doi.org/10.5012/jkcs.2012.56.3.348 -348- Synthesis, Structure Investigation and Dyeing Assessment of Novel Bisazo Disperse Dyes Derived from 3-(2'-Hydroxyphenyl)-1-phenyl-2-pyrazolin-5-ones M. A. Metwally*, S. Bondock, S. I. El-Desouky, and M. M. Abdou † Department of Chemistry, Faculty of Science, Mansoura University, ET-35516 Mansoura, Egypt. * E-mail: mamegs@mans.edu.eg † Scholarship of Academy of Scientific Research and Technology, ASRT, Egypt. (Received February 14, 2012; Accepted May 7, 2012) ABSTRACT. In an attempt to find a new class of bisazo disperse dyes with better dyeing properties, a series of novel bisazo dyestuffs based on 4-arylhydrazono-3-(2'-hydroxyphenyl)-1-phenyl-2-pyrazolin-5-ones 3a-f were prepared by diazocoupling of p-nitrophenyl diazonium chloride with 4-arylhydrazono-3-(2'-hydroxyphenyl)-1-phenyl-2-pyrazolin-5-ones 2a-f. Com- pounds 3a-f were subsequently reacted with acetic anhydride in the presence of p-toluenesulfonic acid afford the cor- responding O-acetyl derivatives 4a-f. The latter products as well as spectral data indicated that compounds 3a-f exist predominantly in the azo-hydrazone tautomeric form (H) as the ZE-configuration. Additionally, two series of the synthesized dyes 3a-f and 4a-f were applied as disperse dyes for dyeing polyester fabrics and their fastness properties were evaluated. Also the position of color in CIELAB coordinates (L*, a*, b*, H*, C*) was assessed. Key words: Bisazo pyrazolin-5-ones, Azo-hydrazone tautomerism, Fastness properties, CIELAB coordinates INTRODUCTION It has been known for many years that polyester fibre are the most important synthetic fibre and reached the sta- tus of the highest volume of production among the other synthetic fibres. Disperse dyes are a major class of dyes used nowadays for dyeing polyester fibre owing to their brilliancy, wide range of hue, excellent fastness proper- ties, in addition to the environmental and economic rea- sons. 1 A large fraction of such dyes are basically derivatives of pyrazolone, possessing the azo chromophore. They have attracted strong interest due to their widespread in a large number of azodisperses dyes, 2-4 as well as for their useful biological and pharmacological properties. 5-7 These compounds exist almost exclusively in the hydrazo tauto- meric form both in solutions and in the crystalline state. 8-13 In addition to, azophenols and their derivatives have aroused much interesting owing to their potential appli- cation in dyes chemistry. Due to their auxochromic nature, the resultant dyes have many advantages including bright hues and their useful for dyeing of almost all kind of fab- rics, whether natural or synthetic. Another interesting fea- ture of azophenols lies on its possibility to form an equilibrium mixture of two tautomeric form, azophenol or hydrazoquinone. 14-20 Therefore, the aforesaid findings stimulated us to com- bine two of the above-mentioned azo dyes together in a single molecular framework, hoping to discover a new lead structure that would have a significant interesting tautomeric structures and dyeing characteristics, mainly strong ability of these dyes on fabrics. In the light of these applications, and in continuation of our recent work aim- ing at the synthesis and elucidation of the tautomeric struc- tures of 4-arylhydrazono-3-(2-hydroxyphenyl)-2-pyrazolin- 5-ones, 21,22 this paper is concerned with the synthesis and investigate the actual structure(s) of bisazo disperse dyes based on 3-(2-hydroxyphenyl)-1-phenyl-2-pyrazolin-5-ones. In addition to synthesizing these proposed candidates, their spectroscopic properties and their application in dye- ing polyester fabrics were studied. EXPERIMENTAL SECTION Materials and Instrumentation All the chemicals used were of commercial grade. They were further purified by standard procedures prior to use. 23 2,3,4-Chromantrione-3-arylhydrazones 1a-f were prepared by the process reported in the literature. 24 The various 4-arylhydrazono-3-(2' -hydroxyphenyl)-1-phenyl-2- pyrazolin-5-ones 2a-f were prepared as previously we described. 21 Elemental analyses were performed at the Microanalytical Center, Cairo University, using CHNS- 932 (LECO) Vario Elemental Analyzers and the results were within the accepted range (±0.40) of the calculated