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

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

Electronic structure and fluorescence of the Mg(II) complex of 1,4-diazepinotribenzoporphyrazine

“…The difficulty with isolating pure products was due mainly to their tendency to aggregate. The PMR spectrum of the monosubstituted Mg complex also was consistent with the existence of the diazepine ring in the 6H-tautomeric form [4] over a broad temperature range (190-390 K). Evidence of the isomeric 1H-form was observed at low temperatures (190-230 K).…”

“…We use for these the abbreviations MPADz 4 The stability of these is determined mainly by the electron-donor properties of the substituents, in particular, the macrocycle, to which the diazepine is bonded. (Dashed lines show C-C bonds formed upon annelation to the macrocycle.…”

“…Thus, mono-, di-, and tridiazepine derivatives of Mg-porphyrazine in which benzene rings were annelated to the other pyrrole rings were synthesized [4]. A mixture of the desired products was obtained according to mass spectrometry.…”

Stability of Magnesium(II) Azaporphyrins and Porphyrazines

“…[21] Диссоциация комплекса в этой среде тоже является ацидопротолитической и протекает с выделением лиганда в непротонированной форме (Рисунок 4). зависимости lnk эф от lna CH 3 COOH имеют тангенс угла наклона ~2 (Рисунок 5).…”

“…= 74.8 0 С). MgТАР был получен по методу, [36] MgТАР(С 6 Н 5 ) 8 ) получали по методу Линстеда, [37] MgТТМТАР был получен по методу, [35] MgDzB 3 Pz был получен согласно методике, [21] MgMAТВР был получен по методу, [38] ТАТВР получен по методу. [38] Бензоаннелированные трифторметилфенилпорфиразины получали по методу.…”