Synthesis and Spectral Properties of Unsymmetrically Substituted Mn(II) and Mn(III) Octaethylporphyrins
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hesis and Spectral Properties of Unsymmetrically Substituted Mn(II) and Mn(III) Octaethylporphyrins S. V. Zvezdinaa,*, N. V. Chizhovaa, and N. Zh. Mamardashvilia a
Krestov Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, 153045 Russia *e-mail: [email protected] Received March 17, 2020; revised April 13, 2020; accepted April 13, 2020
Abstract—5-Mononitro-2,3,7,8,12,13,17,18-octaethylporphyrin, 5,10,15-trinitro-2,3,7,8,12,13,17,18-octaethylporphyrin, and their Cd(II) complexes were synthesized. The coordination reactions of 2,3,7,8,12,13,17,18-octaethylporphyrin and its mono- and trinitro-substituted derivatives and the metal-exchange reactions of the synthesized Cd(II) octaethylporphyrin complexes with Mn(II) chloride in DMF were investigated by spectrophotometry. The corresponding Mn(II) and Mn(III) porphyrins were obtained and identified. The kinetic parameters of the studied reactions were determined. Keywords: octaethylporphyrin, mono-, trinitrosubstituted octaethylporphyrins and their Cd(II), Mn(II), and Mn(III) complexes, nitration, complexation, metal-exchange reactions, spectral properties
DOI: 10.1134/S1070428020080072 Porphyrins and their metal complexes are used as app-efficient emitters, components of solar batteries, agents for photodynamic therapy, and sensor systems for the determi-nation of various metals and gases [1]. The introduction of electron-withdrawing substituents and fragments into porphyrin molecules significantly increases their electron deficiency, which can be especially interesting when creating materials with increased n-conductivity [2]. Nitro-substituted porphyrins are of particular interest because they exhibit increased resistance to oxidation and can be used as objects for further chemical transformations [3–4]. Gong and Dolphin [5] described the nitration of Zn(II) octaethylporphyrin with N2O4 in methylene chloride. Depending on the concentration of the nitrating agent and the reaction time, meso-nitro-substituted derivatives containing one to four nitro groups in the porphyrin molecule. Zinc 5,10,15,20-tetranitrooctaethylporphyrin was synthesized with zinc nitrate in acetic anhydride [6]. The corresponding porphyrin ligands were prepared by treatment of nitro-substituted zinc porphyrinates with glacial acetic acid or hydrochloric acid. In the present work we studied the nitration of 2,3,7,8,12,13,17,18-octaethylporphyrin (1) with a mixture of nitric and sulfuric acids in glacial acetic acid and with
sodium nitrite in trifluoroacetic acid at room temperature (Scheme 1). It was shown that the nitration of porphyrin 1 with a mixture of nitric and sulfuric acids in glacial acetic acid in a 1 : 1 : 3 ratio at room temperature for 5 min gave 5-nitro-2,3,7,8,12,13,17,18-octaethylporphyrin (2). The mass spectrum of the synthesized compound showed a peak at m/z 579.1, corresponding to the molecular ion of compound 2 (calculated for C36H45N5O2 579.8). Treatment of porphyrin 1 with sodium nitrite (molar ratio 1 : 50) in trifluoroacetic acid for 3 days formed 5,10,15-
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