Cyanine dyes of new heterocyclic ring systems: Synthesis and structure-spectra studies H.A. Shindy * , M.A. El-Maghraby, Fayez M. Eissa Department of Chemistry, Aswan Faculty of Science, Aswan 81528, Egypt Received 9 August 2004; received in revised form 5 October 2004; accepted 5 December 2004 Available online 9 March 2005 Abstract New cyanine dyes including monomethine cyanine dyes (simple cyanine dyes) and trimethine cyanine dyes (carbocyanine dyes) incorporating benzo[2,3-b;2#,3#-b#]bispyrazolo[4,5-b]-1,4-(oxa-, thia-, and pyra)-zine-6,12-dione were prepared. Structure-spectra studies were carried out via measuring the electronic visible absorption spectra of these dyes in 95% ethanol. Structural confirmations were determined through elemental analysis, IR, 1 H NMR spectroscopy and MS spectral data at the Micro Analytical Center, Cairo University. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Cyanines; Cyanine dyes; Synthesis; Structure-spectra studies 1. Introduction Cyanine dyes have wide applications in various fields [1e9], such as near infra red laser dyes, fluorescent labeling agents for proteins, fluorescent tags in DNA sequencing, optical information storage devices, histo- logical staining, antimicrobial operations, solar energy conversion systems, cosmetic ingredients, dyes for polymers, as well as sensitizers for various silver halide emulsions. 2. Results and discussion 2.1. Synthesis 1:2 molar ratios of p-chloranil (1) and 4-amino-5- (hydroxy, mercapto and imino)-3-methyl-1-phenyl- pyrazole [10] (2aec) were reacted in ethanol containing pyridine to give 4,10-dimethyl-2,8-diphenyl-5,11-dihy- dro-benzo[2,3-b; 2#,3#-b#]bispyrazolo[4,5-b]-1,4-(oxa-, thia-, and pyra-)-zine-6,12-dione (3aec) (Scheme 1, Table 1). Quternization of (3aec) using equimolar and/or bimolar ratios of iodoethane produced monocationic (4aec) and/or dicationic (5aec) derivatives. Interaction of the monocationic compounds (4aec) with iodoethane quaternary salts of pyridine, quinoline and isoquino- line in equimolar ratios in ethanol containing few drops of piperidine gave 4[4(1)]-monomethine cyanine dyes (6aee). Also interaction of the dicationic compounds (5aec) with equimolar and/or bimolar ratios of iodo- ethane quaternary salts of pyridine, quinoline and isoquinoline in ethanol containing piperidine yielded 4[4(1)]-dicationic monomethine and/or 4,10[4(1)]-dica- tionic bismonomethine cyanine dyes (7aee), (8aee), respectively (Scheme 1, Table 2). Chemical confirmations for compounds (8aee) were obtained through reaction of (7aee) with equimolar ratios of iodoethane quater- nary salts of pyridine, quinoline and isoquinoline in * Corresponding author. Tel.: C20 2 097 232 2725; fax: C20 2 097 348 0450. E-mail address: fayezeissa@hotmail.com (F.M. Eissa). 0143-7208/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.dyepig.2004.12.012 Dyes and Pigments 68 (2006) 11e18 www.elsevier.com/locate/dyepig