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Acid–base behavior of triazoleporphyrazines in proton‐donating media
Author(s) -
Khelevina O. G.,
Ferro V. R.,
Islyaikin M. K.,
Veselkova E. A.,
Stryapan M. G.,
de la Vega J. M. García
Publication year - 2005
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.848
Subject(s) - chemistry , protonation , moiety , hypsochromic shift , ring (chemistry) , intramolecular force , pyrrole , conjugated system , aromaticity , base (topology) , photochemistry , free base , stereochemistry , crystallography , molecule , organic chemistry , ion , mathematical analysis , physics , mathematics , quantum mechanics , fluorescence , polymer , salt (chemistry)
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.