Premium
NMR spectra of the porphyrins. 38 —Conformational analysis of azacycloheptane and azacyclooctane using a novel cobalt(III) porphyrin shift reagent
Author(s) -
Abraham Raymond J.,
Medforth Craig J.
Publication year - 1990
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260280412
Subject(s) - chemistry , porphyrin , tetraphenylporphyrin , ring (chemistry) , cobalt , reagent , proton nmr , nmr spectra database , nuclear magnetic resonance spectroscopy , crystallography , spectral line , stereochemistry , computational chemistry , photochemistry , organic chemistry , physics , astronomy
Abstract A novel NMR shift reagent, cobalt(III) meso ‐tetraphenylporphyrin (CoTPP) was used to determine the conformations of azacycloheptane and azacyclooctane ligands complexed to the metalloporphyrin. Using the observed ring current shifts and a previously calibrated ring current model, the best agreement between the observed and calculated ring current shifts for azacycloheptane was obtained for a chair conformation, in agreement with previous theoretical and experimental studies on the conformational stability of seven‐membered rings. The ring current shifts for azacyclooctane are best interpreted in terms of a mixture of many conformations. These results suggest that CoTPP may be useful as a probe of other conformationally mobile ligands.