INFRARED STUDIES OF PORPHYRINS. VALENCE AND LIGAND FIELD EFFECTS IN METAL COMPLEXES
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Date
1963
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Ohio State University
Abstract
‘‘Previous studies of metal-porphyrin $chemistry^{1}$ have demonstrated the manner in which electronic effects of peripheral substituents on the porphyrin ring are transmitted through centrally coordinated divalent iron to cis-coordinated carbon monoxide, and how they affect the strength of pi-bonding to the iron. In the present study, the effects of the centrally coordinated metal on vibrational modes of 2,4-diacetyldeuteroporphyrin IX dimethyl ester have been examined, when the metal is Mn(III), Fe(III),Co(II), Fe(II), Co(II), Ni(II) Cu(U), Zn(II), Pd(II), or Ag(II). All of these compounds except the Co(III) complex have been purified and characterized by ultraviolet, visible, and infrared spectroscopy, and by elemental analyses. The Co(III) complex bus been purified and identified by visible and infrared spectroscopy. The major vibrational bands, for which assignments have been at least partially determined, have been examined in terms of shifts in frequency with each of several types of metal properties. In addition to requiring the separation of these compounds into complexes of trivalent, and first and second row transition metals, the frequencies of several vibrational modes such as the methane CH out-of-place deformation exhibit the non-linearity with number of d electrons which is characteristic of ligand field stabilization effects. Other modes, such as the corresponding in-plane deformation are affected by the metal to a negligible extent. The frequency of the acetyl Co stretching mode of the trivalent metal complexes is about $10\;cm^{-1}$ higher than that of the divalent metal complexes, but is otherwise negligibly affected by the metal. However, the relative intensities of these vibrations vary in a manner which is consistent with ligand field stabilization.’‘
Description
$^{\dag}$Present address: Department of Physiological Chemistry, Ohio State Univeristy, College of Medicine, Columbus, Ohio. $^{1}$Fed. Proc., 21, 46 (1962).
Author Institution: Department of Physiological chemistry, Johns Hopkins School of Medicine
Author Institution: Department of Physiological chemistry, Johns Hopkins School of Medicine