83AzaPcs, the aza-analogues of phthalocyanines, are presently receiving considerable attention, and have been explored for applications, e.g. as traditional industrial dyes and pigments [1], as advanced materials in high technology applications [2], and in photodynamic cancer therapy [3]. An important quality of the AzaPcs, compared to the Pcs, is the enhanced solublility caused by the additional nitrogen atoms in the macrocycle. Substituents in the periphery of the AzaPcs may further enhance their solubility, and also influence the electronic excitation energies of these compounds.Previously, we have reported [4 -6] octasubstituted AzaPcs where heteroatoms, i.e. sulfur, oxygen or nitrogen link the substituents to the macrocycle. Some of the sulfur-, and all of the oxygen-bound substituents were exchangeable during the cyclotetramerization reactions, due to the electronwithdrawing pyrazine-dicarbonitrile system.Octasubstituted AzaPcs with carbon linked substituents are better known, and in addition to those mentioned in a recent review [7], there are other examples, e.g. [8 -11]. Condensation reactions of diaminomaleonitrile and α-diketones give pyrazine-dicarbonitriles, which are cyclized to this type of substituted AzaPcs.Presently our aim was to synthesize octasubstituted AzaPcs with heteroaromatic side chains bound to the macrocycle through carbon-carbon bonds, thus providing stable substituents. The heteroaromatic substituents are expected to influence both polarity and the electronic spectra of the macrocycles.
Results and DiscussionDiaminomaleonitrile (DAMN) and the α-diketones 2,2'-thenil (1a), 2,2'-furil (1b) and 2,2'-pyridil (1c) gave the corresponding pyrazines 2a-c. Compounds 2a and 2b were obtained in good yields from reactions in acetic acid solutions, whereas no reaction was observed between 1a or 1b with DAMN in refluxing acetonitrile. However, 2c was obtained Abstract. Magnesium, copper(II) and nickel(II) complexes of octasubstituted azaphthalocyanines 3 -5 have been prepared from di-fur-2-yl, di-thien-2-yl and di-pyrid-2-yl pyrazine-2,3-dicarbonitriles 2. Compounds 2 were prepared in good yields from condensations of diaminomaleonitrile and the diketones 2,2'-furil, 2,2'-thenil and 2,2'-pyridil. AzaPcs 3 -5 give green pyridine solutions with Q-bands at 650 -670 nm and ε-values of 60 000 -190 000.