Preferred orientation of imidazole ligands in metalloporphyrins

Recent work has suggested that axial ligand orientation can affect the physiocochemical properties of metalloporphyrins. Analysis of crystallographic data indicates that axial imidazole ligands in metalloporphyrins tend to prefer sterically unfavorable orientations that eclipse equatorial M-N/sub p/...

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Veröffentlicht in:J. Am. Chem. Soc.; (United States) 1986-03, Vol.108 (6), p.1163-1167
Hauptverfasser: Scheidt, W. Robert, Chipman, Daniel M
Format: Artikel
Sprache:eng
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Zusammenfassung:Recent work has suggested that axial ligand orientation can affect the physiocochemical properties of metalloporphyrins. Analysis of crystallographic data indicates that axial imidazole ligands in metalloporphyrins tend to prefer sterically unfavorable orientations that eclipse equatorial M-N/sub p/ bonds. Charge iterative extended Hueckel theory calculations on electronic effects for a broad selection of representative systems indicate a previously unrecognized orientational preference in the M-N(imidazole) ..pi.. bond which favors eclipsed orientations. Somewhat surprisingly, this ..pi.. bond is found to be dominated by the metal p..pi..-imidazole p..pi.. interaction. These theoretical results provide an explanation of the mystery of why the orientation effect seems to be insensitive to metal d/sup n/ configuration, spin state, oxidation state, and the presence or absence of a sixth axial ligand. 23 references, 1 figure, 3 tables.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja00266a008