Metallophorphyrins and their structural analogs (phthalocyanines and porphyrazines are widely used today as organic dyes [1], materials for nonlinear optics and thin-film electronics [2,3], catalysts in redox reactions [4]. Since metallophorphyrins are structurally similar to the important natural metal-containing compounds (hemoglobin, chlorophylls A and B), they can be used as objects for modeling processes occurring in living nature [5,6].Of special importance in chemistry of porphyrins and phthalocyanines are their complexes with iron. Their catalytic activity, coordination and other properties are extensively studied [7,8]. In this connection, it was interesting to establish the effect of the electronic structure of a macrocyclic ligand on the properties of its iron complexes. Variation in the ligand nature makes it possible to change in the wide limits the redox potentials of a central metal cation, to stabilize different oxidation states of iron, and to change its spin state. It should be noted that iron(II) porphyrinate and phthalocyaninate are unstable compounds that are readily oxidized by the oxidizing agents such as the air oxygen, hydrohalic acids, etc. The Fe(III) complexes, in turn, easily undergo dimerization in the alkaline media and form µ -oxodimers [9].This work was undertaken with the aim to synthesize iron complexes with octaphenyltetrapyrazinopor-, and to study their spectral properties. EXPERIMENTAL 5,6-Diphenyl-2,3-dicyanopyrazine ( III ) was obtained and purified following the procedure described in [10]. The electronic absorption spectra were measured on the Cary 1G and Hitachi UV 2000 instruments; IR spectra were recorded on a Avatar FT-IR instrument (with KBr pellets). The 1 H NMR spectra were taken on a Bruker Avance DPX 300 NB instrument (300.13 MHz), the 17 O NMR spectra were measured on a Bruker Avance DRX 400 WB instrument (54.245 MHz) in water enriched with 17 O (8%) in the presence of K 17 OH, obtained by the addition of potassium to water containing 17 O. The concentration of a complex was 1.2 × 10 -3 mol/l. The EPR spectra were recorded on a Bruker ESR 300 E instrument (9.96 GHz) in DMSO or H 2 O at room temperature.The spectral measurements were performed in the Institute of Inorganic Chemistry, Erlangen-Nürnberg University (Germany).
Synthesis of iron(II) octaphenyltetrapyrazinoporphyrazinate (I).(a) Solution of Fe ( CO ) 5 (4.0 ml) was added dropwise over 30 min to a solution of compound III (2.0 g, 0.071 mol) in 20 ml of boiling 1-bromonaphthalene, and the mixture was stirred for 1 h. After cooling, the mixture was diluted with 100 ml of diethyl ether. The obtained green precipitate was filtered off, washed with ether, and dried at room temperature. Complex I was purified in a Sohxlet apparatus by extraction of soluble admixtures with acetone. The yield of complex I was 1.76 g (95.1%).(b) A finely ground mixture of compound III (2 g, 0.071 mol) and iron(III) acetate tetrahydrate (1.2 g, 0.045 mol) was placed in a quartz tube and fused at 250°ë for 30 min. The melt was the...
