Vibrational spectra of dioxygen adducts and oxo complexes of ruthenium tetraphenylporphine (RuTPP)

Infrared Spectra of RuTPP, RuCOTPP, and Ru(CO)2TPP Isolated in Solid Argon

Infrared spectra of unstable species such as CO-free ruthenium tetraphenylporphyrin RuTPP and RuCOTPP (species with vacant coordination sites) isolated in solid argon at 8 K have been recorded. Selective deposition conditions allow the isolation of either RuTPP and RuCOTPP or RuCOTPP and Ru(CO)2TPP. This depends on the preparation conditions of the sample. A specific Ru-CO bending mode has been characterized at 590.1 cm(-1) for Ru(CO)2TPP. The behavior of each vibrational mode of RuTPP, RuCOTPP, and Ru(CO)2TPP has been analyzed. Modes such as gamma8 at 721.3 cm(-1) (out-of-plane stretching mode gamma(Cbeta-H)sym) and nu41 at 1342.8 cm(-1) (nuCalpha-N coupled with deltaCalpha-Cm) reflect the charge transfer in the porphyrin. Indeed, the addition of one or two CO ligands to RuTPP reduces the charge transfer between the metal center and the porphyrin, which appears as an increase in the frequency of the nu41 mode and in a decrease in that of the gamma8 mode.

Structural characterization of Ru-bleomycin complexes by resonance Raman, circular dichroism, and NMR spectroscopy

A series of spectroscopic techniques including absorption and CD spectra, resonance Raman spectra, and (1)H NMR as well as electrospray mass spectrometry have shown that Ru(II) ion binds to bleomycin, forming an equimolar complex, similarly to Fe(II), i.e., via the secondary amine nitrogen, the pyrimidine ring nitrogen, the deprotonated peptide bond nitrogen of the histydyl residue, and the histidine imidazole nitrogen, which are bound in the equatorial positions, and the alpha-amino nitrogen of beta-aminoalanine, which coordinates in the apical position above pH 7. The reaction of Ru(II)-BLM with O(2), H(2)O(2),or PhIO leads to formation of the oxy species in which only one oxygen atom is bound to metal ion. According to our data, the reaction of Ru(II)-BLM complex with oxygen species leads to different product than that suggested for Fe(II)-BLM. The formation of the BLM-Ru-O-Ru-BLM dimeric unit, similar to that found for sterically unhindered Ru porphyrins, seems to be the most likely.