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Complete 1 H and 119 Sn NMR spectral assignment for an asymmetric di[dihydroxotin(IV)] bis‐porphyrin supramolecular host and its corresponding tetraacetato complex
Author(s) -
Brotherhood Peter R.,
Luck Ian J.,
Crossley Maxwell J.
Publication year - 2009
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.2356
Subject(s) - porphyrin , chemistry , supramolecular chemistry , crystallography , proton nmr , two dimensional nuclear magnetic resonance spectroscopy , ligand (biochemistry) , stereochemistry , nmr spectra database , molecule , nuclear magnetic resonance spectroscopy , spectral line , photochemistry , crystal structure , organic chemistry , biochemistry , receptor , physics , astronomy
The full 1 H and 119 Sn NMR spectral assignments for a di[dihydroxotin(IV)] bis‐porphyrin supramolecular host I and for the di[diacetatotin(IV)] complex II are presented. Despite the lack of varied chemical functionality in these molecules, all of their 64 proton environments are non‐equivalent. This is due to the asymmetry afforded by the Tröger's base (methanodiazocine) bridge between the porphyrin and quinoxalinoporphyrin macrocycles. The methanodiazocine bridge imparts chirality and concavity on the host framework and the quinoxalino link to one porphyrin macrocycle results in a negation of C 2 symmetry. The anisotropy of the aromatic porphyrin and quinoxalinoporphyrin macrocycles results in good dispersion for all 60 signals of the host framework and for the four ligands bound in the axial positions of the tin(IV) centres. The full assignment of the 1 H NMR spectra for these systems was achieved using dqf‐COSY, NOESY, ROESY, 1 H‐ 119 Sn HMQC, 1 H‐ 13 C HSQC and 1 H‐ 13 C HMBC spectroscopy at temperatures that optimised dispersion. The 1 H‐ 119 Sn HMQC was particularly useful in this assignment. The 119 Sn chemical shift is sensitive to the functionality of the porphyrin and to the nature of the axial ligation, and the 119 Sn centre couples to both the ligand protons and the β‐pyrrolic protons. This allows unequivocal identification of the spin systems associated with each metal centre. Copyright © 2008 John Wiley & Sons, Ltd.