Synthesis, spectral features and biological activity of some novel hetarylazo dyes derived from 6-amino-1,3-dimethyluracil Hessamoddin Yousefi a , Asieh Yahyazadeh a,⇑ , Mohammad Reza Yazdanbakhsh a , Mehdi Rassa b , Enayat O’llah Moradi-e-Rufchahi c a Department of Chemistry, Faculty of Sciences, University of Guilan, Rasht, Iran b Department of Biology, Faculty of Sciences, University of Guilan, Rasht, Iran c Department of Chemistry, Faculty of Sciences, Lahijan Branch, Islamic Azad University, Lahijan, Iran article info Article history: Received 8 January 2012 Received in revised form 8 February 2012 Accepted 8 February 2012 Available online 16 February 2012 Keywords: Azo dyes Hetarylazo Uracil Solvent effect Substituent effect Antimicrobial activity abstract A series of hetarylazoaminouracil dyes were prepared by coupling of 6-amino-1,3-dimethyluracil with eight diazotized heterocyclic amines in nitrosyl sulphuric acid. The prepared azo dyes were characterized by UV–Vis, FT-IR, 13 C NMR, 1 H NMR spectroscopic techniques and elemental analysis. The solvatochro- mism of dyes was evaluated with respect to wavelength of maximum absorption (k max ) in seven solvents with different polarities: acetic acid, methanol, water, chloroform, acetonitrile, dimethyl sulfoxide and dimethyl formamide. The effects of acid, base and concentration of the dye on the visible absorption spec- tra were also reported. In addition, the antimicrobial activity of the synthesized dyes was evaluated on Escherichia coli, Bacillus subtilis, Micrococcus leuteus and Pseudomonas aeruginosa. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Azo dyes constitute the largest class of dyes with the greatest variety of colors, having wide applications in textile, food, paper printing and cosmetic industries [1–4]. Among the azo dyes, het- erocyclic azo compounds are very important due to their bril- liant color, excellent light, washing and sublimation fastness, and chromophoric strength; which are the cause of their wide application as high level-dying agents in the dyestuff industry [5,6]. Recently, the increasing usage of these dyes in electronic industry, such as colorimetric sensors, nonlinear optical (NLO) devices and liquid crystalline displays (LCDs) has attracted much attention [7–14]. Furthermore, some heterocyclic azo compounds have also found use as ligands to generate a special category of metal azo complexes which are exploited enormously in the manufacture of colorimetric sensors-which lend themselves to cations and anions [15–20]. In this regard, a number of studies have been devoted to the characterization, purification and application of natural and synthetic dyes and azo dyes as anti- bacterial [21–29]. With respect to the importance of these com- pounds, the present paper has focused on the synthesis of some new hetarylazo disperse dyes 1–8 derived from 6-amino-1,3- dimethyluracil as coupling component, and the examination of their antimicrobial activities in detail. The visible absorption spectroscopic properties at different concentrations in acidic, ba- sic and neutral media are also reported. The compounds’ struc- tures are shown in Scheme 1. 2. Experimental 2.1. Materials and methods All starting materials were obtained from Merck and were used without further purification. IR spectra were recorded on a Shima- dzu-8400 FT-IR spectrometer (in KBr pellets). 1 H and 13 C NMR spectra were obtained on a Bruker DRX-500 Avanced spectrometer. Chemical shifts of spectra were expressed in ppm downfield from tetramethylsilane. Melting points were measured on a Büchi Melting Point B-540 instrument and are uncorrected. The absorp- tion spectra of the compounds were run on a Cary UV–Vis double-beam spectrophotometer (Model 100). Elemental analyses were made by a Carlo-Erba EA1110 CNNO-S analyzer and agreed with the calculated values. The antimicrobial activity of the syn- thesized dyes was evaluated on Escherichia coli, Bacillus subtilis, Micrococcus leuteus and Pseudomonas aeruginosa. 0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2012.02.017 ⇑ Corresponding author. Tel./fax: +98 1313233262. E-mail address: ayahyazadeh53@yahoo.com (A. Yahyazadeh). Journal of Molecular Structure 1015 (2012) 27–32 Contents lists available at SciVerse ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc