32880-79-8

Basic information

• Product Name: {Co(III)(octaethylporphyrin)}radical⁽²⁺⁾(Br)2
• Synonyms: {Co(III)(octaethylporphyrin)}radical⁽²⁺⁾(Br)2
• CAS NO: 32880-79-8
• Molecular Weight: 751.573
• Mol File: 32880-79-8.mol

Chemical Properties

• CAS DataBase Reference: {Co(III)(octaethylporphyrin)}radical⁽²⁺⁾(Br)2(CAS DataBase Reference)
• NIST Chemistry Reference: {Co(III)(octaethylporphyrin)}radical⁽²⁺⁾(Br)2(32880-79-8)
• EPA Substance Registry System: {Co(III)(octaethylporphyrin)}radical⁽²⁺⁾(Br)2(32880-79-8)

Safety Data

• Hazardous Substances Data: 32880-79-8(Hazardous Substances Data)

Upstream product

• 17632-19-8 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine cobalt(II) 
• 7726-95-6 bromine 

Relevant articles and documents

Nuclear Magnetic Resonance Studies of Metalloporphyrin ?-Cation Radicals as Models for Compound I of Peroxidases

Hyperfine-shifted proton and deuterium NMR spectral studies are reported for ruthenium(II) and cobalt(III) octaethylporphyrin ?-cation radicals, II*CO>(+)*Br(-) (1), II*CO>(+)*ClO4(-) (2), III>(2+)*2Br(-) (3), and III>(2+)*2ClO4(-) (4) and their meso-deuterated analogues.The meso proton (or deuterium) resonances were not seriously broadened for these radicals and exhibited upfield or downfield shifts depending on the counterions and the central metal.Non-Curie law behaviors for the meso proton shifts were interpreted in terms of a thermal equilibrium between 2A1u and 2A2u ?-radical states which induce quite different electron spin distribution at the meso position.This thermal equilibrium was also confirmed by the variable-temperature UV spectral measurements.The thermodynamic parameters for this equilibrium were estimated and show that 2A1u and 2A2u states are energetically close and these two states are substantially mixed at room temperature.The downfield hyperfine shift of the meso proton for 2 was interpreted as arising from the ?-cation radical in the predominant 2A1u state, and the substantial upfield shift for 1 was explained as due to mixing of the 2A2u state to the 2A1u state.These assignments are in disagreement with the well-documented ones based on the UV-vis spectral studies.The effect of the axial ligand, imidazole, on the NMR spectra of 1 was also studied to mimic the electronic state of compounds I of peroxidases.

Resonance Raman Spectra of Metalloctaethylporphyrin Cation Radicals with a1u and a2u Orbital Character

Resonance Raman (RR) spectra are reported for radical cations of MIIOEP (OEP = octaethylporphyrin; M = Zn, Mg, Ni, Cu) and for the perchlorate and bromide salts of IIIOEP>+, produced by electrochemical and/or chemical oxidation.The enhancement patterns obtained with B (4067 angstroem) band excitation (except M = Zn and Mg, for which fluorescence overwhelms the Q band RR spectra) permitted assignment of most of the porphyrin skeletal models above 1000 cm-1, and frequency shifts relative to the unoxidized porphyrins have been cataloged.Those radicals, magnesium(II), zink(II), and cobalt(III) bromides, whose EPR spectra, have beenassigned on the basis of electron removal from an a1u molecular oribtal show a cammon pattern of shifts, while those with a2u-type EPR spectra, nickel(II), and cobalt(III) perchlorates, show a different pattern.The CuII radical, whose visible absorption spectrum resebles that of other a2u radicals, likewise has an a2u RR frequency shift pattern.The largest shifts are showen by the most prominent RR bands in the B-band-excited spectra, v4 (CaN breathing, primarily) and v2 (CbCb breathing, primarily).These shift up (+14 to +21 cm-1) and down (-19 to -38 cm-1), respectively, for the a1u radicals, but down (-12 to -22 cm-1) and up (+20 to +23 cm-1) for the a2u radicals.Thus an identification of the radical type is quite straighforvard in B-band-excited RR spectra.The directions of the shifts, however, are opposite to those expected from simple orbital simmetry arguments, since the a2u molecular orbital is bonding with respect to the Cb-Cb bonds and antibonding with respect to the Ca-N bonds, and vive versa for the a1u orbital.This discrepancy invites further examination via vibrational and electronic calculations.

Infrared Spectra of ?-Cation Radicals of Magnesium, Zinc, and Cobalt Octaethylporphyrins

Infrared spectra in the 1700-250-cm-1 region were measured for the bromide salts of the ?-cation radicals of MOEP (M=Mg(II) and Zn(II), OEP=octaethylporphyrin) and for the bromide and perchlorate salts of CoIIIOEP+, all of which were prepared by chemical oxidation.By comparing the infrared spectra of the ?-cation radicals with those of the parent molecules, assignments were made for the in-plane stretching and bending modes as well as the out-of-plane bending modes of the porphyrin ring of the radicals and the frequency shifts of these modes relative to the unoxidized molecules were determined.Common shift patterns were observed for the Mg(II) and Zn(II) radicals, which are known to be in a 2A1u state from the ESR study.These patterns were, however, quite different from the corresponding shift patterns observed for the perchlorate salt of the Co(III) radical, which is in a 2A2u state, suggesting that the measurement of the infrared spectra is one of the straightforward methods for determining the ground electronic structure of the ?-cation radicals of metalloporphyrins.The infrared spectrum of the bromide salt of the ?-cation radical of the Co(III) complex, whose ground electronic structure is also in a 2A1u state, however, shows features much simpler than those observed for the Mg(II) and Zn(II) radicals.This result suggests the existence of a vibronic coupling effect in the Co(III) radical, which reduces the intensities of some infrared bands due to porphyrin ring modes.

Temperature dependence in the magnetic circular dichroism spectrum of the π-cation-radicaI species of cobalt octaethylporphyrin

The oxidation of metalloporphyrins can result in the formation of π-cation-radical species for which two ground states are possible, namely the 2A1u and 2A2u states. Two-electron oxidation of cobalt(II) octaethylporphyrin yields the π-cation-radical species [CoIIIOEP]?2+(X-)2, which exhibits absorption and MCD spectra, in solution and at room temperature, that depend on the counteranion X-. Complexation with bromide and perchlorate counterions forms different [CoIIIOEP]?2+ species that adopt the 2A1u and 2A2u ground states, respectively. The MCD spectral characteristics of the [CoIIIOEP]?2+(Br-)2 and [CoIIIOEP]?2+(ClO4-) 2 complexes differentiate between the two ground states. The MCD spectra in the visible-UV region of both [CoIIIOEP]?2+(Br-)2 and [CoIIIOEP]?2+(ClO4-) 2 are shown, for the first time, to be temperature dependent between 4.2 and 100 K. The temperature dependence in the MCD spectrum is interpreted in terms of spin-orbit coupling in the excited π-π* states that results when charge-transfer states that involve the cobalt lie close to the π-π* states. The spin-orbit coupling coefficient modifies the energies of the initially, equally spaced L·S components of the porphyrin 2Eg excited state. The MCD C terms that are measured can be characterized as being spin-dependent C terms.

Vibrational, Electronic, and Structural Properties of Cobalt, Copper, and Zinc Octaethylporphyrin ? Cation Radicals

Optical and resonance Raman (RR) spectroscopic characterization of the oxidation products of several metallooctaethylporphyrins has been carried out.One-electron oxidation of the macrocycle yields a series of divalent metal substituted octaethylporphyrin ? cation radicals, MIIOEP.+ClO4- (M = Ni, Co, Cu, and Zn).The porphyrin core vibrational frequencies above 1450 cm-1 of these complexes are described by a linear function of center to pyrrole nitrogen distances.A comparison of these structural correlations and of Raman depolarization ratios with those of the parent MOEP compounds is used to established vibrational mode assignments for the cations.The agreement between the correlation parameters of the MOEP and MOEP.+ClO4- suggests similar potential energy distributions in the normal modes of both species.We find that the frequencies of the stretching modes with dominantly CbCb character increase, whereas those with CaCm and CaN character decrease in the cation radical relative to the neutral metalloporphyrin.Similar trends in Soret band maxima for the ? cation radicals and their parent compounds reflect changes in the relative energy of the a2u(?) orbital.These structural correlations seem to be essentially insensitive to 2A2u vs 2A1u radical designation.With the vibrational mode correlations as a guide to evaluation of porphyrin core geometry, we have carried out a detailed analysis of the oxidation products of CoIIOEP and we suggest structures for the two-electron-oxidized species CoIIIOEP.+2ClO4- and CoIIIOEP.+2Br-.Differences in the high-frequency vibrations of these two compounds are interpreted in terms of expansion or possible ruffling of the porphyrrin core in the latter relative to the former compound.RR excitation in the 600-680-nm region of the CoIIIOEP.+2Br- absorptions shows a lack of anomalously polarized scattering and produces spectra similar to those obtained with near-UV excitation.This suggests the absence of strong Herzberg-Teller coupling between the excited electronic states of this ? cation radical.