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Insights into the Tautomerism in meso ‐Substituted Corroles: A Variable‐Temperature 1 H, 13 C, 15 N, and 19 F NMR Spectroscopy Study
Author(s) -
Szymański Sławomir,
Paluch Piotr,
Gryko Daniel T.,
NowakKról Agnieszka,
Bocian Wojciech,
Sitkowski Jerzy,
Koszarna Beata,
Śniechowska Justyna,
Potrzebowski Marek J.,
Kozerski Lech
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201303406
Subject(s) - tautomer , corrole , intramolecular force , chemistry , intermolecular force , proton , nuclear magnetic resonance spectroscopy , density functional theory , spectroscopy , toluene , pyrrole , crystallography , computational chemistry , photochemistry , stereochemistry , molecule , organic chemistry , physics , quantum mechanics
Tris(pentafluorophenyl)corrole and its 15 N‐enriched isotopomer were studied in [D 8 ]toluene solution by 1D and 2D variable‐temperature NMR techniques to establish the mechanisms of tautomerization of the NH protons inside the interior of the corrole macrocycle. Three such rate processes could be identified of which two modulate the spectral line shapes at temperatures above 205 K and the third is NMR‐inaccessible as it is very fast. The latter involves the proton engaged in an unsymmetrical proton sponge unit formed by two pyrrole nitrogen atoms. Temperature and concentration dependences of the two remaining processes were determined. One of them is purely intramolecular and the other is intermolecular at low temperatures, with growing contribution of an intramolecular mechanism at elevated temperatures. The proposed microscopic mechanisms of all these processes are semi‐quantitatively confirmed by quantum chemical calculations using density functional theory.