The use of N-bridgehead heterocyclic indolizinium ylide in the synthesis of aza-cyanine dyes A.I.M. Koraiem, R.M. Abd El-Aal * , N.M. Salah El-Deen Chemistry Department, Aswan Faculty of Science, South Valley University, Aswan, Egypt Accepted 6 January 2005 Available online 13 April 2005 Abstract The reaction of 3-methyl-8-oxime-1-phenylpyrazolo [4,5-d]indolizinium (bezoindolizinium) ylide iodide with 2(4)-methyl substituted heterocyclic quaternary salts give 8[2(4)]-aza-monomethine cyanine dyes. Meanwhile, the reaction with carbonyl compounds followed by reaction with 2-methyl quinolinium methiodide salts afforded 5(2)-aza-trimethine cyanine dyes. On the other hand, the reaction of 5-formyl-2-methyl-4-phenylpyrazolo[4,5-d]indolizinium (benzoindolizinium) ylide iodide with hydroxylamine hydrochloride followed by reaction with N-methyl heterocyclic quaternary salts afforded the corresponding 5[4(1)]-aza-dimethine cyanine dyes. These new compounds are characterized with elemental analyses, visible absorption, IR, 13 C NMR, 1 H NMR and mass spectroscopy. The correlations between the structure and spectral properties of these dyes have been studied. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Indolizinium ylide; Aza-cyanine; Aza-monomethine; Aza-trimethine; Aza-dimethine 1. Introduction There is growing interest by our group in the synthesis of N-bridgehead heterocyclic compounds in view of their use in the synthesis of cyanine dyes [1e4]. Aza-cyanine dyes have potential applicability in non- linear optics, as optical sensors, and in physiology/ biochemistry areas [5e7]. Also, they are used as organic photoconductors to their complexation ability and photophysical properties [8e11]. Recently, they are used as a new chromofluoroionophore [12e14]. There is currently much interest in the use of the indolizinium chromophores for non-linear optical ap- plications [15]. This paper will describe the synthesis and spectral behaviour of new indolizinium aza-cyanine dyes having a pyrazolo[4,5-d]indolizinium ring moiety. 2. Experimental All melting points are uncorrected. Elemental anal- yses were carried out at the Microanalytical center (Cairo University). The IR (n KBr ) spectra were de- termined with Perkin Elmer Infrared 127ß spectropho- tometer (Cairo University). 1 H NMR spectra were recorded with a Bruker AMX-250 spectrometer. 1 H NMR and 13 C NMR 2D spectra were measured with a Bruker AMX-400 spectrometer and with TMS as an internal standard. Mass spectra were recorded on an HpMs 6988 spectrometer (Cairo University). The electronic absorption spectra were recorded within the wavelength range (350e700) on 6405 UV/visible re- cording spectrophotometer (Faculty of Science, Aswan). * Corresponding author. Fax: C2097480450. E-mail address: abdelal2001@yahoo.com (R.M. Abd El-Aal). 0143-7208/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.dyepig.2005.01.007 Dyes and Pigments 68 (2006) 235e242 www.elsevier.com/locate/dyepig