Back-bonding in ruthenium porphyrins as monitored by Resonance Raman spectroscopy
Resonance Raman spectra are reported for Ru/sup II/ complexes of octaethylporphyrin (OEP) and tetraphenylporphine (TPP) with pyridine, methanol, and CO axial ligands, using both B- and Q-band excitation. For Ru/sup II/ OEP(CO)(MeOH) the porphyrin skeletal mode frequencies above 1370 cm/sup -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 ..pi..-back-donation from Ru to the porphyrin ..pi.. orbitals. The shift pattern is the same as that observed for the bis(imidazole) 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, ..pi..-back-bonding to the porphyrin appears to be quantitatively similar for Ru/sup II/ and Fe/sup II/. ..pi..-Back-bonding shifts are also reported for Ru/sup II/TPP(py)/sub 2/. For Ru/sup II/OEP(CO)(py) the Ru-CO stretching, Ru-C-O bending, and C-O stretching modes are observed at 513, 578, and 1930 cm/sup -1/. For Fe/sup II/ porphyrins, the M-CO and C-O frequencies are somewhat lower and higher, respectively, implying greater back-donation to the bound CO for Ru/sup II/ than for Fe/sup II/.
- Research Organization:
- Princeton Univ., NJ
- DOE Contract Number:
- AC02-81ER10861
- OSTI ID:
- 7252284
- Journal Information:
- Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 25:22; ISSN INOCA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
CARBONYLS
CARBOXYLIC ACIDS
CHEMICAL BONDS
COMPLEXES
DATA
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
LASER SPECTROSCOPY
LIGANDS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PORPHYRINS
RAMAN SPECTROSCOPY
RUTHENIUM COMPLEXES
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES