Premium
15 N‐CPMAS‐NMR Study of the Problem of NH Tautomerism in Crystalline Porphine and Porphycene
Author(s) -
Wehrle Bernd,
Limbach HansHeinrich,
Köcher Matthias,
Ermer Otto,
Vogel Emanuel
Publication year - 1987
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.198709341
Subject(s) - tautomer , chemistry , proton , structural isomer , proton nmr , spectral line , nmr spectra database , reaction rate constant , computational chemistry , carbon 13 nmr , stereochemistry , kinetics , physics , quantum mechanics , astronomy
Solid state, variable temperature 15 N‐NMR studies make it possible to predict the behavior of the four N atoms and the two internal H atoms in the isomeric porphine and porphycene. The spectra of porphine indicate a statistical disorder of the internal H atoms. In the case of porphycene it can be concluded that there are two non‐equivalent unsymmetric proton transfer systems. Since the NH…N distances are very short, the energy barrier for the rearrangement is very small. Therefore, other than in the case of porphine, in porphycene the interconversion of the tautomers is so rapid that the rate constants for the proton transfer could not be determined by the 15 N‐CPMAS‐NMR method.