Resonance Raman excitation of oxygen (O2) stretching vibrations of oxy(tetraphenylporphyrinato)cobalt(II) at 457.9 nm

Bajdor, Krzysztof; Nakamoto, K.; Kincaid, James R.

doi:10.1021/ja00341a090

Cited by 14 publications

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“…Binding of dioxygen has received the most attention, and matrix isolation techniques have been used to facilitate these studies , whereas resonance enhancement of the lower frequency Co−O 2 vibrations make these frequencies readily available from Raman measurements. , Thus, it is useful to use both techniques in order to establish all metal−ligand vibrational frequencies. Vibrational assignments are necessarily verified by isotopic substitutions on the ligand atoms, which affects the vibrational frequencies in these simple systems in a relatively straightforward manner …”

Section: Introductionmentioning

confidence: 99%

Room Temperature Binding of CO to Cobaltous Porphyrin π Cation Radical: Spectroscopic Characterization of Mono and Bis CO Complexes with Cobaltic Porphyrin

et al. 1996

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When CO(g) is added to solutions of the cobaltous porphyrin π cation radical [Co(II)OEP•]ClO4, prepared by oxidation of CoOEP by AgClO4 in anhydrous CH2Cl2, room temperature binding of CO to the metal center occurs. Two distinct products result, [(CO)Co(III)OEP]ClO4 and [(CO)2Co(III)OEP]ClO4. These compounds exhibit Soret maxima at 366 and 414 nm, respectively. Resonance Raman (RR) spectra measured before the addition of CO are used to characterize the cobaltous porphyrin π cation radical, and, after the addition of CO, RR spectra obtained by using 363.8 nm excitation confirm the occurrence of the five-coordinate Co(III) porphyrin complex. This complex, along with halide ligated analogs, displays some structure-sensitive vibrational frequencies which suggest that an unusual distortion of the porphyrin core occurs in CH2Cl2 solution. RR spectra obtained by using 413.1 nm excitation after the addition of CO are used to identify the second product as a typical six-coordinate cobaltic porphyrin. Titrations with CO reveal that the five- and six-coordinate complexes, [(CO)Co(III)OEP]ClO4 and [(CO)2Co(III)OEP]ClO4, form with P 1/2 values of 36 ± 3 and 4000 ± 300 Torr of CO, respectively. Isosbestic points in the UV−vis spectra occur at 368 nm for binding of the first CO and at 385 nm during binding of the second CO ligand. FTIR and RR spectra of [(CO)Co(III)OEP]ClO4 reveal vibrations at 2110 and 441 cm-1 which shift upon substitution of 13CO or C18O for the natural abundance CO. Isotope sensitive vibrations of [(CO)2Co(III)OEP]ClO4 were measured at 2137 and 468 cm-1. In each case the modes above 2100 cm-1 correspond to C⋮O stretching frequencies, while the lower frequency features are assigned to Co−C stretching motions. The resonance Raman enhancement of these isotope sensitive frequencies confirm CO binding to the metal center. The selective presence of these features in the Raman and FTIR data is consistent with that expected from symmetry based selection rules for five- and six-coordinate CO complexes. The relatively high C⋮O stretching frequencies observed are suggestive of weak metal dπ → ligand π* backbonding that results from the oxidation of Co(II) to Co(III).

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Section: Introductionmentioning

confidence: 99%

Room Temperature Binding of CO to Cobaltous Porphyrin π Cation Radical: Spectroscopic Characterization of Mono and Bis CO Complexes with Cobaltic Porphyrin

et al. 1996

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“…However, at the ambient temperature unprotected porphyrins of the bivalent metals are rapidly oxidized by dioxygen, demanding low-temperature conditions for stabilization of oxy-complexes. [6] While six-coordinate cobalt porphyrin dioxygen complexes with axial N-donor have been a subject of many investigations, [7][8][9][10] a little is known on the complexes bearing S-donor ligands. On the best of our knowledge, the only six-coordinate cobalt porphyrin dioxygen complexes with trans S-donors were studded by Kazuo Nakamoto group, who made an invaluable contribution to the field of coordination chemistry of porphyrins and other organometallic compounds.…”

Section: Introductionmentioning

confidence: 99%

Low Temperature Spectroscopic Study of the Sulfides Binding by Dioxygen Adduct of Cobalt Porphyrin

Martirosyan¹,

Hovhannisyan²,

Azizyan³

et al. 2021

MHC

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Dedicated to the blessed memory of our beloved leader, colleague and friend Tigran KutikyanThe interaction of dimethyl sulfide ((CH 3 ) 2 S) and hydrogen sulfide (H 2 S) with cobalt porphyrin and its five-coordinate dioxygen complex was studied at low temperatures in sublimated porphyrin layers using electronic and infrared absorption spectroscopy. Upon addition of sulfides to a cryostat containing Co(TTP)O 2 (TTP is meso-tetratolylporphyrinato dianion) at low temperatures, the FTIR and Vis electronic spectral changes were observed which are consistent with sulfide binding in axial trans-position to dioxygen. Density functional theory (DFT) computational analysis also supports formation of the six-coordinate adducts. These complexes are stable only at low temperatures and dissociate upon heating.

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ChemInform Abstract: RESONANCE RAMAN EXCITATION OF OXYGEN (O2) STRETCHING VIBRATIONS OF OXY(TETRAPHENYLPORPHYRINATO)COBALT(II) AT 457.9 NM

Bajdor¹,

Nakamoto²,

Kincaid³

1983

Chemischer Informationsdienst

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Resonance Raman excitation of oxygen (O2) stretching vibrations of oxy(tetraphenylporphyrinato)cobalt(II) at 457.9 nm

Cited by 14 publications

References 0 publications

Room Temperature Binding of CO to Cobaltous Porphyrin π Cation Radical: Spectroscopic Characterization of Mono and Bis CO Complexes with Cobaltic Porphyrin

Room Temperature Binding of CO to Cobaltous Porphyrin π Cation Radical: Spectroscopic Characterization of Mono and Bis CO Complexes with Cobaltic Porphyrin

Low Temperature Spectroscopic Study of the Sulfides Binding by Dioxygen Adduct of Cobalt Porphyrin

ChemInform Abstract: RESONANCE RAMAN EXCITATION OF OXYGEN (O2) STRETCHING VIBRATIONS OF OXY(TETRAPHENYLPORPHYRINATO)COBALT(II) AT 457.9 NM

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