Acid–base behavior of triazoleporphyrazines in proton‐donating media

Abstract

The acid–base properties of some peripheral substituted triazoleporphyrazines in proton‐donating media with poor‐donating character were experimentally studied. The substitution of one pyrrole moiety in the porphyrazine‐like compounds by one triazole ring in the triazoleporphyrazines leads to an increase in the basicity. The protonation of the triazoleporphyrazines results in a hypsochromic shift of the Q‐bands in the UV–visible spectra. A DFT study of some selected structural models of the unsubstituted triazoleporphyrazine shows that the protonation strongly influences on the molecular electron structure of this compound and that it occurs preferentially through the nitrogen atom located at position 4 of triazole ring. The protonation through the other basic centers (the triazoleporphyrazine is a multicenter conjugated base) leads to different protonated forms which differ notably in their aromatic character. Therefore, this compound could be considered an intramolecular switch of aromaticity. Copyright © 2004 John Wiley & Sons, Ltd.

Lewis Acid Modulation in a Amido‐functional Diarylethene and Its Hypsochromism Effect

“…[12][13][14][15][16][17][18][19][20] The π-conjugation in molecular systems underwent important factors in all photophysical properties. The idea to prepare molecular photoswitches by controlling π-conjugation using photochromic compounds was first illustrated by Lehn and Irie [21][22][23][24][25] and enhanced by Tian group [26][27][28] to exploit molecular properties and create molecular switches.…”

Thiadiazole-containing expanded heteroazaporphyrinoids: a gas-phase electron diffraction and computational structural study

“…Previously it was found that the introduction of two 1,2,4triazole rings to the phthalocyanine molecule, replacing two opposite isoindole rings, resulted in an ABAB-type system with little conjugation in the macroring, 5,6 but replacement of only one isoindole subunit by a triazole ring leads to the formation of an aromatically conjugated macrosystem similar to that of phthalocyanine. Thus, aromatic triazolephthalocyanines [7][8][9] and triazoleporphyrazines [10][11][12] have been synthesised.…”