Synthesis and spectroscopic structural studies of the adducts formed in the reaction of aminopyridines with TCNQ Siham Y. AlQaradawi * , E.M. Nour Department of Chemistry and Earth Sciences, College of Arts and Sciences, University of Qatar, P.O. Box 2713, Doha, Qatar Received 28 November 2005; received in revised form 14 February 2006; accepted 17 February 2006 Available online 30 March 2006 Abstract The adducts 7,7-dicyano-8,8-di-m-aminopyridilequinodimethane and 7,7-dicyano-8,8-di-p-aminopyridilequinodimethane are formed by the reaction of the electron donors 3-aminopyridine (3APY) and 4-aminopyridine (4APY), respectively, with the p-acceptor 7,7,8,8-tetracyano- quinodimethane (TCNQ). The reactions were studied using electronic, infrared and mass spectral and thermal measurements. The results indicate that the aminopyridines undergo rapid N-substitution by TCNQ forming the reaction products and HCN molecules. A general mechanism for the reactions as well as the structures of the reaction products are proposed. q 2006 Elsevier B.V. All rights reserved. Keywords: Aminopyridines; TCNQ; Spectra; Thermal 1. Introduction In the last decades, the chemical and physical properties of some charge–transfer complexes formed in the reactions of s- and p-electron acceptors with various electron donors such as simple amines, polyaza, polysulfure and crown ethers have been the subject of many investigations [1–7]. 7,7,8, 8-Tetracyanoquinodimethane (TCNQ) is a good p-acceptor able to form with electron donors stable solid products [8–10]. Some of them show interesting electronic properties [11,12]. In previous studies [1,2], we have reported the formation of stable charge transfer complexes formed in the reaction of the donor 2,3-diaminopyridine (DAPY) with p-acceptors teracya- noethylene (TCNE) and chloranil and of phenacetin (phen) with TCNE in chloroform where the obtained CT-complexes were formulated as [(DAPY)(TCNE) 3 ], [(DAPY)(chloranil)] and the novel compound [(phen)(TCNE) 12 ], respectively. In the present investigation, we report the obtained results concerning the complexation of aminopyridines with TCNQ. The aim of the work is to investigate the nature and structure of the new reaction products in both solution and solid state. CN CN CN CN TCNQ N NH 2 4-aminopyridine (4APY) N NH 2 3-aminopyridine (3APY) 2. Experimental All chemicals used were of high grade. 7,7,8,8-Tetracya- noquinodimethane (TCNQ) was obtained from BDH while 2-, 3- and 4-aminopyridines were obtained from Aldrich Chemical Co. The electronic absorption spectra were recorded in the region of 700–250 nm using a Perkin–Elmer double beam spectrometer, model EZ 210, with quartz cell of 1.0 cm path length. The infrared spectra were recorded from KBr discs using a Nicolet FT-IR spectrometer model 670. The solid product formed in the reaction of 3- or 4-aminopyridines with TCNQ was isolated by the addition of an excess saturated solution of aminopyridines (50 ml) to a saturated solution of TCNQ (30 ml) in CHCl 3 . The dark reddish-brown precipitates formed were filtered off and washed several times with amounts of CHCl 3 and dried in vacuo. The products were identified as 7,7-dicyano-8,8-di-m-aminopyr- idilequinodimethane (C 20 H 14 N 6 ), analysis: C, 70.23 (71.01%); H, 3.47 (4.14%) and N, 25.40 (24.85%) and as 7,7-dicyano-8, Journal of Molecular Structure 794 (2006) 251–254 www.elsevier.com/locate/molstruc 0022-2860/$ - see front matter q 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2006.02.031 * Corresponding author. Fax: C974 4830549. E-mail address: siham@qu.edu.qa (S.Y. AlQaradawi).