Preparation of a new poly( p-phenylene) type polymer, poly(pyrazine-2,5-diyl), with a coplanar structure Takakazu Yamamoto a, * , Yoshiki Fujiwara a , Hiroki Fukumoto a , Yoshiyuki Nakamura a , Shin-ya Koshihara b , Tadahiko Ishikawa b a Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan b Department of Chemistry and Materials Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan Received 10 March 2003; received in revised form 26 May 2003; accepted 26 May 2003 Abstract Poly(pyrazine-2,5-diyl), PPyrz, was prepared by organometallic dehalogenative polycondensation of 2,5-dibromopyrazine. PPyrz was soluble in conc. H 2 SO 4 and showed an h=c value of 0.45 dl g 21 . PPyrz exhibited the UV – vis peak at the longest wavelength ðl max ¼ 439 nmÞ among the poly( p-phenylene) type polymers. The polymer afforded a simple CP-MAS solid 13 C NMR pattern with peaks at d 143.3 and 148.5. Microwave-assisted synthesis was effective. q 2003 Elsevier Science Ltd. All rights reserved. Keywords: Poly(pyrazine-2,5-diyl); Poly( p-phenylene) type polymer; Coplanar structure 1. Introduction Poly( p-phenylene), PPP, is one of the most fundamental p-conjugated polymers [1–4], and modification of PPP by replacing the CH group of PPP by nitrogen(s) has been carried out to produce, e.g. poly(pyridine-2,5-diyl), PPy [5], and poly(pyrimidine-2,5-diyl), PPyrim [6]. According to the CH-to-N replacement, the polymers attain interesting chemical properties such as metal complex forming reactivity and higher chemical and electrochemical reducibility. Preparation and revealing chemical properties of poly- (pyrazine-2,5-diyl), PPyrz, have also attracted attention [7,8], however, successful preparation of PPyrz has not been reported. The CPK molecular model of PPyrz indicates that this polymer forms a planar main chain which is advantageous for formation of highly p-conjugated main chain. On the other hand, the previously prepared polymer such as PPy and PPyrim are considered to receive o-hydrogen repulsion to cause twisting of the bond in the main chain; if synthesis of head-to-tail type PPyrim is possible, the polymer is also considered to have a coplanar structure. Herein we report synthesis of PPyrz via an organome- tallic polycondensation using a zerovalent nickel complex. Microwave-assisted organic synthesis including polymer synthesis [9] is currently attracting interest and applicability of this method for the present polymer synthesis has also been tested. 0032-3861/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0032-3861(03)00442-7 Polymer 44 (2003) 4487–4490 www.elsevier.com/locate/polymer * Corresponding author. Tel.: þ 81-45-924-5220; fax: þ81-45-924-5276. E-mail address: tyamamot@res.titech.ac.jp (T. Yamamoto).