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The NMR spectra of the porphyrins. 17—Metalloporphyrins as diamagnetic shift reagents, structural and specificity studies

✍ Scribed by Raymond J. Abraham; Geoffrey R. Bedford; Brian Wright

Publisher
John Wiley and Sons
Year
1982
Tongue
English
Weight
770 KB
Volume
18
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

The nature of the metalloporphyrin‐ligand complexes produced by zinc, magnesium and cobalt porphyrins with basic ligands has been investigated using the diamagnetic ring current shifts of the porphyrin on the ligand protons. The metal to nitrogen bond lengths in some metallo‐meso‐tetraphenylporphyrin (pyridine) complexes have been determined and compared with the data of the crystalline complexes. The geometry of the Zn meso‐tetraphenylporphyrin complexes with 2‐picoline, quinoline and isoquinoline has been investigated. Steric interactions between the ligand and the porphyrin in 2‐picoline and quinoline produce a dramatic increase in the ZnN bond length when compared to the unstrained analogues pyridine and isoquinoline. This large increase is associated with comparatively minor angle distortions in the complex. The specificity of the Zn meso‐tetraphenylporphyrin complexation shifts has been determined for a range of benzyl and butyl compounds. The complexation shift is linearly related to the basicity of the ligand for a wide range of basicities.

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