16591-56-3Relevant articles and documents
MECHANISTIC CONSIDERATIONS IN THE PHOTODIPPROPORTIONATION OF μ-OXO-BIS ((TETRAPHENYLPORPHINATO)IRON(III))
Peterson, Mark W.,Rivers, David S.,Richman, Robert M.
, p. 2907 - 2915 (1985)
The photochemistry of μ-oxo-bis((tetraphenylporphinato)iron(III)) has been studied.Both continuous and photolysis establish a photochemical disproportionation to fom the ferrous complex FeTPP and the ferryl complex FeOTTP: Using triphenylphosp
Electrochemistry and spectroscopy of sulfate and thiosulfate complexes of iron porphyrins
Crawford, Philip W.,Ryan, Michael D.
, p. 13 - 22 (2002)
The electrochemical and spectroscopic properties of the complex formed by the addition of thiosulfate to ferric porphyrins were examined. The NMR spectrum of the thiosulfate-ferric porphyrin complex was consistent with a high-spin ferric complex, while the EPR spectrum at liquid nitrogen temperatures indicated that the complex under these conditions was low-spin. Such behavior has been previously observed for other ferric porphyrin complexes. The visible spectra were characterized by a shift in the Soret band to higher energies, with smaller changes in the longer wavelength region. The complex was reasonably stable in DMF, but slowly reduced over several hours to FeII(TPP) and S4O62-. The voltammetric behavior of the thiosulfate complex in DMF consists of two waves, the first of which was irreversible. The ferric/ferrous reduction in the presence of thiosulfate was shifted negatively about 400 mV, compared to the Fe(TPP)(Cl) reduction. The visible, NMR and EPR spectra were most consistent with a Fe-S bonded ferric porphyrin-thiosulfate complex, Fe(P)(S-SO3)-. The kinetics of the reduction of ferric porphyrin by thiosulfate in DMSO indicated an autocatalytic mechanism, where the first step is the formation of the catalyst. The identity of the catalyst could not be determined because it must be present at low concentrations, but it is formed from the reaction of the ferric complex with thiosulfate. Coordination of thiosulfate to the porphyrin was not necessary for the reduction to occur, and the reduction of Fe(TPP)(Cl) by thiosulfate was accelerated by the addition of sulfate. Under these conditions, sulfate had replaced thiosulfate as the axial ligand for the ferric porphyrin. In the presence of sulfate, the reduction occurred in a single kinetic pseudo-first order step.
Hydrogen-Bonding Effects in Five-Coordinate High-Spin Imidazole-Ligated Iron(II) Porphyrinates
Hu, Chuanjiang,Noll, Bruce C.,Schulz, Charles E.,Scheidt, W. Robert
, p. 793 - 803 (2018)
The influence of hydrogen binding to the N-H group of coordinated imidazole in high-spin iron(II) porphyrinates has been studied. The preparation and characterization of new complexes based on [Fe(TPP)(2-MeHIm)] (TPP is the dianion of tetraphenylporphyrin) are reported. The hydrogen bond acceptors are ethanol, tetramethylene sulfoxide, and 2-methylimidazole. The last acceptor, 2-MeHIm, was found in a crystalline complex with two [Fe(TPP)(2-MeHIm)] sites, only one of which has the 2-methylimidazole hydrogen bond acceptor. This latter complex has been studied by temperature-dependent M?ssbauer spectroscopy. All new complexes have also been characterized by X-ray structure determinations. The Fe-NP and Fe-NIm bond lengths, and displacement of the Fe atom out of the porphyrin plane are similar to, but marginally different than, those in imidazole-ligated species with no hydrogen bond. All the structural and M?ssbauer properties suggest that these new hydrogen-bonded species have the same electronic configuration as imidazole-ligated species with no hydrogen bond. These new studies continue to show that the effects of hydrogen bonding in five-coordinate high-spin iron(II) systems are subtle and challenging to understand.
Sinyakov, G. N.,Shul'ga, A. M.
, (1993)
Nakamoto, K.,Watanabe, T.,Ama, T.,Urban, M. W.
, p. 3744 - 3745 (1982)
Just a proton: Distinguishing the two electronic states of five-coordinate high-spin iron(ll) porphyrinates with imidazole/ate coordination
Hu, Chuanjiang,Sulok, Corinne D.,Paulat, Florian,Lehnert, Nicolai,Twigg, Anna I.,Hendrich, Michael P.,Schulz, Charles E.,Scheidt, W. Robert
, p. 3737 - 3750 (2010)
We report detailed studies on two S = 2 electronic states of high-spin iron(ll) porphyrlnates. These two states are exemplified by the five-coordinate derivatives with either neutral imidazole or anionic imidazolate as the axial ligand. The application of several physical methods all demonstrate distinctive differences between the two states. These Include characteristic molecular structure differences, Moessbauer spectra, magnetic circular dichroism spectroscopy, and Integer-spin EPR spectral distinctions. These distinctions are supported by DFT calculations. The two states are characterized by very different spatial properties of the doubly occupied orbital of the high-spin that are consonant with the physical properties.
Reactions of nitrogen oxides with heme models. Spectral and kinetic study of nitric oxide reactions with solid and solute FeIII(TPP)(NO 3)
Kurtikyan, Tigran S.,Gulyan, Gurgen M.,Martirosyan, Garik G.,Lim, Mark D.,Ford, Peter C.
, p. 6216 - 6224 (2005)
The reaction(s) of nitric oxide (nitrogen monoxide) gas with sublimed layers containing the nitrato iron(III) complex FeIII(TPP) (η2-O2NO) (1, TPP = meso-tetraphenyl porphyrinate 2-) leads to formation of several iron porphyrin species that are ligated by various nitrogen oxides. The eventual products of these low-temperature solid-state reactions are the nitrosyl complex Fe(TPP)(NO), the nitro-nitrosyl complex Fe(TPP)(NO2)(NO), and 1 itself, and the relative final quantities of these were functions of the NO partial pressure. It is particularly notable that isotope labeling experiments show that the nitrato product is not simply unreacted 1 but is the result of a series of transformations taking place in the layered material. Thus, the nitrato complex formed from solid Fe(TPP)(η2-O2NO) maintained under a 15NO atmosphere was found to be the labeled analogue Fe(TPP)(η2-O215NO). The reactivities of the layered solids are compared to the behaviors of the same species in ambient temperature solutions. To interpret the reactions of the labeled nitrogen oxides, the potential exchange reactions between N2O3 and 15NO were examined, and complete isotope scrambling was observed between these species under the reaction conditions (T = 140 K). Overall it was concluded from isotope labeling experiments that the sequence of reactions is initiated by reaction of 1 with NO to give the nitrato nitrosyl complex Fe(TPP)(η1-ONO2)(NO) (2) as an intermediate. This is followed by a reaction in the presence of excess NO that is equivalent to the loss of the nitrate radical NO3. to give Fe(TPP)(NO) as another transient species. A plausible pathway involving NO attack on the coordinated nitrate of 2 resulting in the release of N2O4 concerted with electron transfer to the metal center is proposed.
Reagen, William K.,Radonovich, Lewis J.
, p. 5274 - 5275 (1987)
Photoreduction of ferric-tetraphenylporphyrin in oxygen-containing solvents revealed by resonance Raman and absorption spectroscopy
Terekhov, Sergei N.,Kruglik, Sergei G.
, p. 268 - 272 (1995)
Photoreduction is observed for Fe(III)(TPP)Cl (TPP is tetraphenylporphyrin) in some oxygen (O)-containing solvents under anaerobic conditions using resonance Raman (RR) and absorption spectroscopy. This process is found to be initiated by visible light in the 390-450 nm region. The coincidence of RR and absorption spectra of photoinduced species and of chemically reduced ones reveals that the final product of photoreduction is the high-spin Fe(II)(TPP)L complex, where L = THF (tetrahydrofuran), DMF(dimethyl formamide) or 1,4-dioxane. Such a photoreduction is not observed under anaerobic conditions for the Fe(III)(TPP)Cl complex in benzene, pyridine or CH2Cl2, nor in the abovementioned solvents under anaerobicconditions. No photoreduction is observed for Fe(III)(OEP)Cl (OEP = octaethylporphyrin). A mechanism for the photoinduced phenomenon observed for Fe(III)(TPP)Cl in O-containing solvents under anaerobic conditions isproposed.
Metalloporphyrin photochemistry with matrix isolation
Suslick, Kenneth S.,Bautista, Jocelyn F.,Watson, Randall A.
, p. 6111 - 6114 (1991)
The photochemistry of a number of metalloporphyrin oxoanion complexes has been examined by matrix isolation techniques, using both frozen solvent glasses and polymer films. After an extensive search for a noncoordinating, unreactive, glassing solvent, a 3:1 mixture of 2,2-dimethylbutane and tert-butylbenzene was found to work well at temperatures below 70 K. Alternatively, the photochemistry of metalloporphyrins was monitored in polymer films by the evaporation on a sapphire window of metalloporphyrin solutions in toluene containing either poly(methyl methacrylate) or poly(α-methylstyrene). The polymer films have the added advantage of a greatly increased temperature range, providing diffusional isolation even at room temperature. The photoreduction of the metal by homolytic α-bond cleavage and loss of the axial ligand appears to be a general mechanism for all metalloporphyrin complexes examined. The formation of metal-oxo species from photolysis of metalloporphyrin oxoanion complexes in solution derives from secondary, thermal reactions.
Experimental and Theoretical Evidence for an Unusual Almost Triply Degenerate Electronic Ground State of Ferrous Tetraphenylporphyrin
Tarrago, Maxime,R?melt, Christina,Nehrkorn, Joscha,Schnegg, Alexander,Neese, Frank,Bill, Eckhard,Ye, Shengfa
, p. 4966 - 4985 (2021)
Iron porphyrins exhibit unrivalled catalytic activity for electrochemical CO2-to-CO conversion. Despite intensive experimental and computational studies in the last 4 decades, the exact nature of the prototypical square-planar [FeII(TPP)] complex (1; TPP2- = tetraphenylporphyrinate dianion) remained highly debated. Specifically, its intermediate-spin (S = 1) ground state was contradictorily assigned to either a nondegenerate 3A2g state with a (dxy)2(dz2)2(dxz,yz)2 configuration or a degenerate 3Egθ state with a (dxy)2(dxz,yz)3(dz2)1/(dz2)2(dxy)1(dxz,yz)3 configuration. To address this question, we present herein a comprehensive, spectroscopy-based theoretical and experimental electronic-structure investigation on complex 1. Highly correlated wave-function-based computations predicted that 3A2g and 3Egθ are well-isolated from other triplet states by ca. 4000 cm-1, whereas their splitting ΔA-E is on par with the effective spin-orbit coupling (SOC) constant of iron(II) (≈400 cm-1). Therfore, we invoked an effective Hamiltonian (EH) operating on the nine magnetic sublevels arising from SOC between the 3A2g and 3Egθ states. This approach enabled us to successfully simulate all spectroscopic data of 1 obtained by variable-temperature and variable-field magnetization, applied-field 57Fe M?ssbauer, and terahertz electron paramagnetic resonance measurements. Remarkably, the EH contains only three adjustable parameters, namely, the energy gap without SOC, ΔA-E, an angle θ that describes the mixing of (dxy)2(dxz,yz)3(dz2)1 and (dz2)2(dxy)1(dxz,yz)3 configurations, and the ?rd-3?expectation value of the iron d orbitals that is necessary to estimate the 57Fe magnetic hyperfine coupling tensor. The EH simulations revealed that the triplet ground state of 1 is genuinely multiconfigurational with substantial parentages of both 3A2g (12%), owing to their accidental near-triple degeneracy with ΔA-E = +950 cm-1. As a consequence of this peculiar electronic structure, 1 exhibits a huge effective magnetic moment (4.2 μB at 300 K), large temperature-independent paramagnetism, a large and positive axial zero-field splitting, strong easy-plane magnetization (g⊥ ≈ 3 and g∥ ≈ 1.7) and a large and positive internal field at the 57Fe nucleus aligned in the xy plane. Further in-depth analyses suggested that g⊥ ? g∥ is a general spectroscopic signature of near-triple orbital degeneracy with more than half-filled pseudodegenerate orbital sets. Implications of the unusual electronic structure of 1 for CO2 reduction are discussed.
Macrocycle- And metal-centered reduction of metal tetraphenylporphyrins where the metal is copper(ii), nickel(ii) and iron(ii)
Andronov, Mikhail G.,Khasanov, Salavat S.,Kitagawa, Hiroshi,Konarev, Dmitri V.,Kuzmin, Aleksey V.,Nazarov, Dmitry I.,Otsuka, Akihiro,Shestakov, Alexander F.,Yamochi, Hideki,Yudanova, Evgeniya I.
, p. 15620 - 15632 (2021/12/02)
The reduction of metal(ii) tetraphenylporphyrins, where metal(ii) is copper, nickel or iron, has been performed in toluene solution in the presence of a cryptand. Cesium anthracenide was used as a reductant. Crystalline salts {cryptand(Cs+)}2{CuII(TPP4-)}2- (1) and {cryptand(Cs+)}{NiI(TPP2-)}-·C6H5CH3 (2) have been obtained. The two-electron reduction of {CuII(TPP2-)}0 is centered on the macrocycle allowing one to study for the first time the structure and properties of the TPP4- tetraanions in the solid state. Tetraanions have a diamagnetic state and show essential C-Cmeso bond alternation. New bands attributed to TPP4- appear at 670, 770 and 870 nm. Unpaired S = 1/2 spin is localized on CuII. The one-electron reduction of {NiII(TPP2-)}0 centered on nickel provides the formation of {NiI(TPP2-)}- with unpaired S = 1/2 spin localized on NiI at 100(2) K. The effective magnetic moment of 2 is 1.68μB at 120 K and a broad asymmetric EPR signal characteristic of NiI is observed for 2 and also for (Bu3MeP+){NiI(TPP2-)}-·C6H5CH3 (3) in the 4.2-120 K range. Since dianionic TPP2- macrocycles are present at 100(2) K, no alternation of C-Cmeso bonds is observed in 2. The excited quartet S = 3/2 state according to the calculations is positioned close to the ground S = 1/2 state. In the excited state, charge transfer from NiI to the macrocycle takes place resulting in the formation of NiII with S = 1 and TPP3- with S = 1/2 in the {NiII(TPP3-)}- anions. Therefore, the increase in the magnetic moment of 2 above 150 K is attributed to the population of the excited quartet state with a gap of 750 K. Salt 2 is EPR silent above 150 K and manifests absorption bands characteristic of TPP3- at RT. The reduction of NiII(TPP2-) and FeII(TPP2-) by cesium anthracenide in the presence of Bu3MeP+ yields crystals of 3 and (Bu3MeP+){FeI(TPP2-)}-·C6H5CH3 (4) whose crystal structures and optical properties are also presented. DFT calculations have been carried out for {MII(TPP2-)} (M = Cu, Ni and Fe) and their anions to interpret the experimental results obtained for 1-4. This journal is
Selective nitrogen reduction to ammonia on iron porphyrin-based single-site metal-organic frameworks
Cong, Meiyu,Chen, Xuyang,Xia, Kai,Ding, Xin,Zhang, Linlin,Jin, Yu,Gao, Yan,Zhang, Lixue
supporting information, p. 4673 - 4678 (2021/03/09)
Constructing efficient catalysts for N2reduction into value added ammonia under ambient conditions is a considerable challenge. Herein, well-defined single-site metal-organic frameworks (MOFs, M-TCPP; M = Fe, Co, or Zn) were constructed and evaluated as electrocatalysts for N2reduction. The prepared Fe-TCPP exhibited prominent performance with a high NH3yield of 44.77 μg h?1mgcat.?1and a faradaic efficiency of 16.23%, superior to that of all the reported molecular and MOF catalysts. The superior performance was ascribed to the highly effective N2activation at the Fe site, and benefited from the overall reaction thermodynamics advantage in the key reaction step of *NNH formation. This study gives an understanding of the intrinsic activity of well-defined catalysts in the electrocatalytic N2reduction, and provides atomic-level insights into the rational design and engineering of highly active catalysts for artificial N2fixation.
