17632-19-8Relevant academic research and scientific papers
Cis-influence of hydroporphyrin macrocycles on axial ligation equilibria and alkyl exchange reactions of alkylcobalt(III) porphyrin complexes.
Stolzenberg,Summers
, p. 1518 - 1524 (2000)
Stability constants are reported for the coordination of pyridine and substituted pyridines to the alkylcobalt(III) complexes of octaethylporphyrin (OEP), t-octaethylchlorin (OEC), and ttt-octaethylisobacteriochlorin (OEiBC) in toluene solution. The stability constants correlate with the base strength of the nitrogenous ligand. A cis-influence of the macrocycle saturation level on the stability constants is observed. Stability constants for coordination of a given pyridine ligand to an alkylcobalt(III) complex are roughly 10 times smaller than the stability constants for the corresponding cobalt(II) complex. Analysis of a thermodynamic cycle demonstrates that this leads to decreased stability of the complex with respect to Co-C bond homolysis upon ligand coordination, a base-on effect. Alkyl exchange occurs between cobalt complexes of different tetrapyrroles. Equilibrium data establish that the exchange is nonstatistical and that the Co-C bond is stabilized by increasing the saturation of the tetrapyrrole macrocycle.
Metalloporphyrin Gas and Condenced-Phase Resonance Raman Studies: The Role of Vibrational Anharmonicities as Determinants of Raman Frequencies
Asher, Sanford A.,Murtaugh, James
, p. 7244 - 7251 (1983)
The first resonance Raman spectra of gas-phase porphyrins are reported.An extensive temperature-dependent study of the Raman spectra of nickel(II) and cobalt(II) octaethylporphyrine both in the gas phase and in condenced solution phases demonstrates a large temperature dependence of the Raman frequencies.The small frequency differences observed between the gas- and condenced phase samples indicate that the van der Waals interactions occuring in hydrocarbon solvents do not affect the heme frequencies.The temperature dependence of Raman frequencies shows an apparent activation energy.This temperature dependence is interpreted as arising from anharmonic interactions between high-frequency vibrations and thermally populated low-frequency vibrations.Frequency shifts as large as 15 cm-1 are observed between 40 and 600 K for the heme core size dependent Raman vibrations.These shifts may be interpreted as an expansion of the heme ring as low-frequency vibrations are thermally populated.The large temperature dependence of the heme vibrational frequencies may account for some of the spectral shifts observed in photochemically generated transient Raman studies in heme proteins.Transient heme temperature increases of greater than 100 K are expected to occur during photolysis of liganded heme complexes such as carbon monoxyhemoglobin and carbon monoxymyoglobin.This temperature increase will result in shifts to lower frequency for the heme Raman vibrations.
Synthesis and Spectral Properties of meso-Nitro-Substituted Octaethylporphyrins and Their Co(II) Complexes
Chizhova, N. V.,Mamardashvili, N. Zh.,Rusanov, A. I.
, p. 1878 - 1883 (2020)
Abstract: The reaction of 2,3,7,8,12,13,17,18-octaethylporphyrin with sodium nitrite in trifluoroacetic acid produced 5-nitro-2,3,7,8,12,13,17,18-octaethylporphyrin, 5,15-dinitro-2,3,7,8,12,13,17,18-octaethylporphyrin, and 5,10,15-trinitro-2,3,7,8,12,13,17,18-octaethylporphyrin. Reactions of octaethylporphyrin, mono-, di-, tri-, and tetranitro-substituted porphyrins coordination to cobalt(II) acetate in a chloroform–methanol mixture were studied. The corresponding Co(II) porphyrinates were obtained and identified. It was shown that, upon dissolution of Co(II) octaethylporphyrinates in dimethylformamide in the presence of NaOH, the Co(II)→Co(III) oxidation occurs in the coordination site of the macrocycle.
Electrogeneration of oxidized corrole dimers. Electrochemistry of (OEC)M where M = Mn, Co, Ni, or Cu and OEC is the trianion of 2,3,7,8,12,13,17,18- octaethylcorrole
Kadish, Karl M.,Adamian, Victor A.,Van Caemelbecke, Eric,Gueletii, Elena,Will, Stefan,Erben, Christoph,Vogel, Emanuel
, p. 11986 - 11993 (1998)
The electrochemistry of (OEC)M where M = Mn, Co, Ni, or Cu and OEC is the trianion of 2,3,7,8,12,13,17,18-octaethylcorrole was investigated in dichloromethane, benzonitrile, or pyridine, and the oxidized compounds were characterized by UV-visible and/or ESR spectroscopy. The first two oxidations of the Co, Ni, and Cu corroles involve the reversible stepwise abstraction of 1.0 electron per two (OEC)M units and lead to [(OEC)M]2+ and [(OEC)M]22+, which are assigned as π-π dimers containing oxidized corrole macrocycles and divalent central-metal ions on the basis of the electrochemical and spectroscopic data. The ESR spectrum of [(OEC)Cu]2+ suggests the presence of one ESR-active Cu(II) center in the singly oxidized dimer. Further bulk electrooxidation of [(OEC)CU]2+ at potentials positive of the second oxidation results in the abstraction of a second electron from the dimeric unit and leads to a triplet ESR spectrum typical of a copper(II) dimer, from which a Cu-Cu distance of 3.88 A? is calculated. The ESR spectrum of [(OEC)Co]2+ in frozen CH2Cl2 at 77 K has a major line at g is perpendicular to = 2.40 with a weak signal at g is parallel with = 1.89 and is typical of Co(II) ion. The doubly oxidized dimer, [(OEC)Co]22+ is ESR silent in CH2Cl2 or PhCN, thus suggesting that the two unpaired electrons of the two Co(II) ions in [(OEC)Co]22+ are coupled. The absolute potential difference between E( 1/2 ) for generation of [(OEC)M]2+ and [(OEC)M]22+ can be related to the degree of interaction between the two (OEC)M units of the dimer and follows the order Co (ΔE( 1/2 ) = 460 mV) > Ni (ΔE(2) = 260 mV) > Cu (ΔE( 1/2 ) = 140 mV). No evidence is seen for dimerization of (OEC)Mn after oxidation to its Mn(IV) form in the first electron-transfer step, and the occurrence of this metal-centered reaction may be the reason for the absence of dimerization.
Generation of an (alkoxycarbonyl)rhodium complex in an alcohol analog of the water-gas shift reaction
Miller, Roy G.,Kyle, Jeffrey A.,Coates, Geoffrey W.,Anderson, D. Joe,Fanwick, Phillip E.
, p. 1161 - 1166 (1993)
(Octaethylporphyrinato)rhodium(II) dimer ((OEPRh)2, 1) reacts with CO and ethanol in CH2Cl2 to give (octaethylporphyrinato)rhodium(III) chloride (5), (ethoxycarbonyl)(octaethylporphyrinato)rhodium(III) (OEPRh(CO)OEt, 6), and formyl(octaethylporphyrinato)rhodium(III) (2). The structure of 6 was clarified by X-ray diffraction analysis. Complex 6 crystallized in the monoclinic space group P21/n (No. 14) with a = 14.581 (1) ?, b = 14.181 (2) ?, c = 17.4530 (9) ?, V = 3608.8 (9) ?3, Z = 4, R = 0.046, Rw = 0.051, and T = 293 K for 415 parameters and 4864 reflections. The 1H and 13C spectral properties of 2 and 6 in CD2Cl2 were determined and the behaviors of 1, 2, (octaethylporphyrinato)rhodium(III) hydride (3), and 6 in CH2Cl2 solvent were examined. Photolysis of 2 in CH2Cl2 at 300 nm afforded (octaethylporphyrinato)rhodium(III) chloride. Treatment of OEPCoNa with acetic anhydride in ethylene glycol dimethyl ether afforded acetyl(octaethylporphyrinato)cobalt(III) and an analogous experiment with acetic formic anhydride generated an acyl(octaethylporphyrinato)cobalt(III) complex.
Cobalt(II) Nitrosyl Cation Radicals of Porphyrins, Chlorins, and Isobacteriochorins. Models for Nitrite and Sulfite Reductases and Implications for A1u Heme Radicals
Fujita, Etsuko,Chang, C. K.,Fajer, Jack
, p. 7665 - 7669 (1985)
Oxidation of cobalt(II) nitrosyl complexes of porphyrins (P), chlorins (C), and isobacteriochlorins (iBC) yields CoIINO ?-cation radicals.The radicals are stable and recyclable to the parent compound without loss of NO.The oxidized species have
Chelation, formulation, encapsulation, retention, and in vivo biodistribution of hydrophobic nanoparticles labelled with 57Co-porphyrin: Oleylamine ensures stable chelation of cobalt in nanoparticles that accumulate in tumors
Hervella, Pablo,Dam, Johan Hygum,Thisgaard, Helge,Baun, Christina,Olsen, Birgitte Brinkmann,H?ilund-Carlsen, Poul Flemming,Needham, David
, p. 11 - 25 (2018)
Background and motivation: While small molecules can be used in cancer diagnosis there is a need for imageable diagnostic NanoParticles (NPs) that act as surrogates for the therapeutic NPs. Many NPs are composed of hydrophobic materials so the challenge is to formulate hydrophobic imaging agents. To develop individualized medical treatments based on NP, a first step should be the selection of patients who are likely responders to the treatment as judged by imaging tumor accumulation of NPs. This requires NPs with the same size and structure as the subsequent therapeutic NPs but labelled with a long-lived radionuclide. Cobalt isotopes are good candidates for NP labelling since 55Co has half-life of 17.5 h and positron energy of 570 keV while 57Co (t1/2 271.6 d) is an isotope suited for preclinical single photon emission tomography (SPECT) to visualize biodistribution and pharmacokinetics of NPs. We used the hydrophobic octaethyl porphyrin (OEP) to chelate cobalt and to encapsulate it inside hydrophobic liquid NPs (LNPs). We hypothesized that at least two additional hydrophobic axial ligands (oleylamine, OA) must be provided to the OEP-Co complex in order to encapsulate and retain Co inside LNP. Results: 1. Cobalt chelation by OEP and OA. The association constant of cobalt to OEP was 2.49 × 105 M?1 and the formation of the hexacoordinate complex OEP-Co-4OA was measured by spectroscopy. 2. NP formulation and characterization: LNPs were prepared by the fast ethanol injection method and were composed of a liquid core (triolein) surrounded by a lipid monolayer (DSPC:Cholesterol:DSPE-PEG2000). The size of the LNPs loaded with the cobalt complex was 40 ± 5 nm, 3. Encapsulation of OEP-Co-OA: The loading capacity of OEP-Co-OA in LNP was 5 mol%. 4. Retention of OEP-57Co-4OA complex in the LNPs: the positive effect of the OA ligands was demonstrated on the stability of the OEP-57Co-4OA complex, providing a half-life for retention in PBS of 170 h (7 days) while in the absence of the axial OA ligands was only 22 h. 5 Biodistribution Study: the in vivo biodistribution of LNP was studied in AR42J pancreatic tumor-bearing mice. The estimated half-life of LNPs in blood was about 7.2 h. Remarkably, the accumulation of LNPs in the tumor was as high as 9.4% ID/g 24 h after injection with a doubling time for tumor accumulation of 3.22 h. The most important result was that the nanoparticles could indeed accumulate in the AR42J tumors up to levels greater than those of other NPs previously measured in the same tumor model, and at about half the values reported for the molecular agent 57Co-DOTATATE. Conclusions: The additional hydrophobic chelator OA was indeed needed to obtain a stable octahedral OEP-Co-4OA. Cobalt was actually well-retained inside LNP in the OEP-Co-4OA complex. The method described in the present work for the core-labelling of LNPs with cobalt is now ready for labeling of NPs with 55Co, or indeed other hexadentate radionuclides of interest for preclinical in vivo PET-imaging and radio-therapeutics.
Mechanochemical insertion of cobalt into porphyrinoids using Co2(CO)8as a cobalt source
Damunupola, Dinusha,Chaudhri, Nivedita,Atoyebi, Adewole O.,Brückner, Christian
supporting information, p. 3643 - 3652 (2020/07/30)
Cobalt porphyrinoids find broad use as catalysts or electrode materials. Traditional solution state cobalt insertion reactions into a free base porphyrinoid to generate the corresponding cobalt complex generally require fairly harsh conditions, involving the heating of the reactants in high-boiling solvents for extended period of times. We report here an alternative method of cobalt insertion: A solvent-free (at least for the insertion step) mechanochemical method using a planetary ball mill with Co2(CO)8as a cobalt source. The scope and limits of the reaction were investigated with respect to the porphyrinic substrate susceptible to the reaction conditions, the influences of different grinding aids, and bases added. While the mechanochemical method is, like other metal insertion methods into porphyrinoids, not universally suitable for all substrates tested, it is faster, milder, and greener for several others, when compared to established solution-based methods.
Structure of Phenyl Derivatives of Octaethylporphyrin and Dissociation Kinetics of Their Mn3+, Co2+, and Cu2+ Complexes in Acetic Acid
Kuvshinova,Kuz'min,Pukhovskaya,Semeikin,Golubchikov
, p. 652 - 654 (2007/10/03)
Octaethyl-, 5-phenyloctaethyl-, 5,15-diphenyloctaethyl-, 5,10,15,20-tetraphenyloctaethyl, and dodecaphenylporphyrins were prepared, and their geometries were optimized by the method of molecular mechanics. The deformation of the porphyrin macroring grows
Dissociation kinetics of copper and cobalt complexes with sterically distorted porphyrins
Kuvshinova,Kuz'min,Dudkina,Pukhovskaya,Semeikin,Golubchikov
, p. 133 - 136 (2007/10/03)
The dissociation kinetics of the cobalt and copper complexes with octaethylporphyrin, its 5-phenyl, 5,15-diphenyl, and 5,10,15,20-tetraphenyl derivatives, and dodecaphenylporphyrin in acetic acid with small additions of trifluoroacetic acid were studied. In this series of complexes, the steric distortion of the tetrapyrrole macrocycle sequentially increases, which results in a regular decrease in the kinetic stability of the metal porphyrins: The dissociation rate increases by three orders of magnitude.
