Synthesis and Spectral Properties of meso -Nitro-Substituted Octaethylporphyrins and Their Co(II) Complexes
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hesis and Spectral Properties of meso-Nitro-Substituted Octaethylporphyrins and Their Co(II) Complexes N. V. Chizhovaa,*, A. I. Rusanova, and N. Zh. Mamardashvilia a G.A.
Krestov Institute of Chemistry of Solutions of the Russian Academy of Sciences, Ivanovo, 153040 Russia *e-mail: [email protected] Received April 28, 2020; revised April 28, 2020; accepted May 12, 2020
Abstract—The reaction of 2,3,7,8,12,13,17,18-octaethylporphyrin with sodium nitrite in trifluoroacetic acid produced 5-nitro-2,3,7,8,12,13,17,18-octaethylporphyrin, 5,15-dinitro-2,3,7,8,12,13,17,18-octaethylporphyrin, and 5,10,15-trinitro-2,3,7,8,12,13,17,18-octaethylporphyrin. Reactions of octaethylporphyrin, mono-, di-, tri-, and tetranitro-substituted porphyrins coordination to cobalt(II) acetate in a chloroform–methanol mixture were studied. The corresponding Co(II) porphyrinates were obtained and identified. It was shown that, upon dissolution of Co(II) octaethylporphyrinates in dimethylformamide in the presence of NaOH, the Co(II)→Co(III) oxidation occurs in the coordination site of the macrocycle. Keywords: octaethylporphyrin, meso-nitro-substituted porphyrins, cobalt complexes, nitration reactions, complexation
DOI: 10.1134/S1070363220100102 Porphyrins and their metal complexes are used as components of solar cells, agents for photodynamic therapy of cancer diseases, and sensors for detecting ions and gaseous substrates of different nature [1]. Selective introducing electron-donor and electronacceptor substituents into a porphyrin molecule makes it possible to create systems with an uneven distribution of electron density within the tetrapyrrole macrocycle, which is of interest for creating materials with nonlinear optical properties or enhanced n-conductivity [2, 3]. The introduction of nitro groups into porphyrin molecules
makes it possible to obtain compounds with new properties which are useful from a practical point of view (for example, good solubility in organic solvents and high stability of metal complexes in aggressive media). Nitrosubstituted porphyrins may be of interest as objects for further chemical transformations [4–5]. The nitration of Zn(II) octaethylporphyrinate using N2O4 in dichloromethane was described earlier [6]. When treating zinc complexes of nitro-substituted porphyrins with glacial acetic acid, the corresponding porphyrin ligands were obtained. para-Nitro-substituted
Scheme 1.
1878
SYNTHESIS AND SPECTRAL PROPERTIES OF meso-NITRO-SUBSTITUTED OCTAETHYLPORPHYRINS 1879 Scheme 2.
DMF
tetraphenylporphyrins were synthesized under the action of NaNO2 in trifluoroacetic acid [5]. I n t h i s p a p e r, t h e n i t r a t i o n r e a c t i o n s o f 2,3,7,8,12,13,17,18-octaethylporphyrin 1 at mesopositions by the action of NaNO2 in trifluoroacetic acid (Scheme 1) were studied. It was shown that when porphyrin 1 is treated with sodium nitrite in trifluoroacetic acid at room temperature, 5-nitro-2,3,7,8,12,13,17,18-octaethylporphyrin 2 and a mixture of 5,10- and 5,15-dinitrooctaethylporphyrins are formed depending on the
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