Template co-condensation of 2,3-dicyano-5,7-diphenyl-6H-1,4-diazepine 1 with 10-fold molar excess of phthalodinitrile 2 in the presence of MgII propoxide or butoxide in the corresponding alcohol leads to a mixture of Mg(II)-diazepinoporphyrazines 3-6 from which the low symmetry 3: 1 species 3, which contains three annulated benzene and one 1,4-diazepine rings, is separated by column chromatography as the aquo complex, [2,4-diphenyltribenzo [b, g, l][ 1,4] diazepino[2,3-q] porphyrazinato( aquo) magnesium(II)], [Bz(3)DzPzMg(H(2)O)]. The complex 3 can be demetalated in acetic or trifluoroacetic acids under mild conditions with formation of the corresponding free-base [Bz(3)DzPzH(2)] 3a. This latter is also formed by co-cyclotetramerization of the same precursors 1 and 2 in the presence of sodium ethoxide in ethanol or lithium butoxide in butanol followed by demetalation of the intermediate disodium or dilithium salts in acid medium. The constitution and structure of the obtained compounds were established on the basis of elemental analysis, mass spectrometry, and (1)H NMR spectra. The variable temperature 1H NMR measurements provide evidence that in porphyrazines 3 and 3a the 1,4-diazepine ring exists predominantly in the 6H-form over a wide temperature range. The free energy of activation for the inversion of the 1,4-diazepine ring determined for 3 is 45.6 +/- 1.7 kJ mol(-1). Solution UV-visible spectra measurements in acidic media (CH(2)Cl(2)/CF(3)COOH) provide evidence that the MgII complex 3 is easily protonated on the meso-N atom of the porphyrazine macrocycle followed by slow demetallation with formation of the free base 3a in its neutral form or as a species protonated on the diazepine ring.

Synthesis and Spectroscopic Properties of Low-Symmetry Tribenzoporphyrazines with Annulated 6H-1,4-Diazepine Ring / Donzello, Maria Pia; Ercolani, Claudio; Mannina, Luisa; Viola, Elisa; Alena, Bubnova; Ol'ga G., Khelevina; Pavel A., Stuzhin. - In: AUSTRALIAN JOURNAL OF CHEMISTRY. - ISSN 0004-9425. - STAMPA. - 61:4(2008), pp. 262-272. [10.1071/CH08071]

Synthesis and Spectroscopic Properties of Low-Symmetry Tribenzoporphyrazines with Annulated 6H-1,4-Diazepine Ring

DONZELLO, Maria Pia;ERCOLANI, Claudio;MANNINA, LUISA;VIOLA, ELISA;
2008

Abstract

Template co-condensation of 2,3-dicyano-5,7-diphenyl-6H-1,4-diazepine 1 with 10-fold molar excess of phthalodinitrile 2 in the presence of MgII propoxide or butoxide in the corresponding alcohol leads to a mixture of Mg(II)-diazepinoporphyrazines 3-6 from which the low symmetry 3: 1 species 3, which contains three annulated benzene and one 1,4-diazepine rings, is separated by column chromatography as the aquo complex, [2,4-diphenyltribenzo [b, g, l][ 1,4] diazepino[2,3-q] porphyrazinato( aquo) magnesium(II)], [Bz(3)DzPzMg(H(2)O)]. The complex 3 can be demetalated in acetic or trifluoroacetic acids under mild conditions with formation of the corresponding free-base [Bz(3)DzPzH(2)] 3a. This latter is also formed by co-cyclotetramerization of the same precursors 1 and 2 in the presence of sodium ethoxide in ethanol or lithium butoxide in butanol followed by demetalation of the intermediate disodium or dilithium salts in acid medium. The constitution and structure of the obtained compounds were established on the basis of elemental analysis, mass spectrometry, and (1)H NMR spectra. The variable temperature 1H NMR measurements provide evidence that in porphyrazines 3 and 3a the 1,4-diazepine ring exists predominantly in the 6H-form over a wide temperature range. The free energy of activation for the inversion of the 1,4-diazepine ring determined for 3 is 45.6 +/- 1.7 kJ mol(-1). Solution UV-visible spectra measurements in acidic media (CH(2)Cl(2)/CF(3)COOH) provide evidence that the MgII complex 3 is easily protonated on the meso-N atom of the porphyrazine macrocycle followed by slow demetallation with formation of the free base 3a in its neutral form or as a species protonated on the diazepine ring.
2008
tribenzoporphyrazines; Synthesis and Spectroscopic Properties
01 Pubblicazione su rivista::01a Articolo in rivista
Synthesis and Spectroscopic Properties of Low-Symmetry Tribenzoporphyrazines with Annulated 6H-1,4-Diazepine Ring / Donzello, Maria Pia; Ercolani, Claudio; Mannina, Luisa; Viola, Elisa; Alena, Bubnova; Ol'ga G., Khelevina; Pavel A., Stuzhin. - In: AUSTRALIAN JOURNAL OF CHEMISTRY. - ISSN 0004-9425. - STAMPA. - 61:4(2008), pp. 262-272. [10.1071/CH08071]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/229648
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