Back-Bonding in Ruthenium Porphyrins As Monitored by Resonance Raman Spectroscopy

Dongho Kim, Y. Oliver Su, Thomas G. Spiro

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Abstract

Resonance Raman spectra are reported for Ru11complexes of octaethylporphyrin (OEP) and tetraphenylporphine (TPP) with pyridine, methanol, and CO axial ligands, using both B- and Q-band excitation. For the porphyrin skeletal mode frequencies above 1370 cm-1 agree remarkably well with the values calculated on the basis of the porphyrin core size by using parameters derived earlier for iron protoporphyrin complexes. These frequencies shift both positively and negatively when the CO is replaced by pyridine due to from Ru to the porphyrin orbitals. The shift pattern is the same as that observed for the adduct of iron(II) protoporphyrin, relative to the core size predictions, and the extent of the shifts is very similar in the two cases. Thus, to the porphyrin appears to be quantitatively similar for Ru11and shifts are also reported for RunTPP(py)2. For the stretching, bending, and C-O stretching modes are observed at 513, 578, and 1930 cm-1. For Fe11porphyrins, the M-CO and C-0 frequencies are somewhat lower and higher, respectively, implying greater back-donation to the bound CO for Ru11than for Fe11.

Original languageEnglish
Pages (from-to)3993-3997
Number of pages5
JournalInorganic Chemistry
Volume25
Issue number22
DOIs
Publication statusPublished - 1986 Jan 1

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All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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