28110-70-5Relevant articles and documents
Laser photolysis of chromium(III) porphyrins with axial pyridines in dichloromethane and toluene solutions. Novel effects of a hydrogen bond in the ligand exchange reaction
Inamo, Masahiko,Nakaba, Hideyuki,Nakajima, Kiyohiko,Hoshino, Mikio
, p. 4417 - 4423 (2000)
Laser photolysis studies were carded out for (chloro)(pyridine)(5,10,15,20-tetraphenylporphyrinato)chromium-(III), [Cr(TPP)(Cl)(Py)], in both dichloromethane and toluene containing water. The five-coordinate [Cr(TPP)(Cl)] produced by the photoinduced dissociation of pyridine from [Cr(TPP)(Cl)(Py)] initially reacts with H2O to give [Cr(TPP)(Cl)(H2O)], which eventually exchanges the axial H2O with Py to regenerate [Cr(TPP)(Cl)(Py)]. The rate for the ligand exchange of [Cr(TPP)(Cl)(H2O)] with exogenous Py is found to exhibit a bell-shaped pyridine-concentration dependence. Kinetic studies revealed that at a high Py concentration, the exogenous Py probably makes a hydrogen bond with the axial H2O of [Cr(TPP)(Cl)(H2O)] to yield [Cr(TPP)(Cl)(HO-H···Py)] as a dead-end complex. A similar structure of the Cr-TPP complex having 2-methylpyridine molecules bound to the coordinated H2O ligand by a hydrogen bond was determined by X-ray structure analysis. The exchange reaction of the axial HO-H···Py in [Cr(TPP)(Cl)(HO-H···Py)] by Py follows the dissociative mechanism: The first step is the dissociation of Py from [Cr(TPP)(Cl)(HO-H···Py)], and the second step is the dissociation of H2O. The five-coordinate [Cr(TPP)(Cl)] thus produced reacts with Py to regenerate [Cr(TPP)(Cl)(Py)]. The direct ligand exchange reaction of the axial HO-H···Py in [Cr(TPP)(Cl)(HO-H···Py)] with exogenous Py does not occur. Probably, the hydrogen bond, HO-H···Py, increases the basicity of H2O, and thus, the bond energy between Cr and O in [Cr(TPP)(Cl)(HO-H···Py)] becomes much stronger than that in [Cr(TPP)(Cl)(H2O)]. The mechanism of the ligand substitution reaction of the chromium(III) porphyrins has been examined in detail on the basis of the laser photolysis studies of [Cr(TPP)(Cl)(L)] (L = pyridine, 3-cyanopyridine, and H2O).
Reactivity of Five-Coordinate Intermediate Generated by Laser Photolysis of Monoligated Chloro(5,10,15,20-tetraphenylporphinato)chromium(III) in Toluene
Inamo, Masahiko,Hoshino, Mikio,Nakajima, Kiyohiko,Aizawa, Sen-ichi,Funahashi, Shigenobu
, p. 2293 - 2304 (1995)
The Cr(III) porphyrin complexes (1) and (2) (tpp represents the dianion of 5,10,15,20-tetraphenylporphine) crystallized from a chloroform-toluene mixture in the tetragonal space group I4, Z = 2, a = 13.559(5), b = 13.559(5), c = 9.770(3) Angstroem, V = 1796(3) Angstroem3, and from a dichloroethane-toluene mixture containing a small amount of pyridine (py) in the monoclinic space group P21/n, Z = 4, a = 14.655(5), b = 23.498(4), c = 13.152(2) Angstroem, β = 101.54(1) deg, V = 4437(2) Angstroem3, respectively.The axial Cr-O bond length for 1 and the axial Cr-N bond length for 2 are 2.239(3) and 2.140(5) Angstroem, respectively.Laser irradiation of the toluene solution of causes the photodissociation of the axial ligand L, where L represents H2O or 3-cyanopyridine, to give the five-coordinate intermediate .The rate constant of the axial ligand recombination reaction falls into a narrow range around 1x109 mol-1 kg s-1 at 25.0 deg C for both reactions.The activation parameters indicate the very high reactivity of the five-coordinate intermediate.The diffusion-controlled process is regarded as a rate-determining step for the recombination.
Binding of propylene oxide to porphyrin- and salen-M(III) cations, where M = Al, Ga, Cr, and Co
Chen, Peter,Chisholm, Malcolm H.,Gallucci, Judith C.,Zhang, Xiangyang,Zhou, Zhiping
, p. 2588 - 2595 (2005)
The binding of propylene oxide (PO) to a series of metal cations LM(III)+, where for L = tetraphenylporphyrin (TPP) M = Al, Ga, Cr, and Co, and for L = (R,R)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2- cyclohexenediamine (salen) M = Al and Cr, was studied in the gas phase by electrospray tandem mass spectroscopy, and the relative stabilities of LM(PO)2+ and LM(PO)+ cations were determined. The chromium(III) and aluminum(III) cations most tenaciously bind PO, and for M = Al, coordination to the TPP ligated metal center was favored relative to salen. For (TPP)M(PO)2+, the dissociation of PO followed the order M = Al > Cr, but for (TPP)M(PO)+ the dissociation was M = Cr > Al. The single-crystal structural determinations on (R,R-salen)AlOCHMe(S)CH2Cl-0.5PO and (R,R-salen)AlO 2CMe-1.5py grown in neat PO and pyridine, respectively, reveal five-coordinate aluminum(III) centers with the alkoxide/acetate ligands in the axial position of a square-based pyramid. These results are discussed in terms of the reactivity of these metal complexes in ring-opening polymerizations and copolymerizations with PO and CO2, respectively.
Origins of photoacoustic effect in solutions with a single non-pulsed continue wave laser beam; study on the CrTPP solutions
Ghasedi, A.,Koushki, E.,Tayebee, R.
, (2022/01/28)
The influential parameters on the photoacoustic (PA) effect, as one of the most beneficial phenomena, have not been appropriately investigated. Since PA exhibited a laser-dependent characteristic, we came up with the idea that PA must be a multi-factorial phenomenon in which a comprehensive study is necessary. Several parameters including beam characteristic (continuous-wave or pulsed laser), wavelength, pulse duration of the light source, light-matter interaction properties such as absorption, Raman scattering, and stimulated Raman scattering (RS and SRS), and solution features exhibited themselves as demonstrative factors. Although each of the properties mentioned above contributes to a specific PA mechanism, but they will not be the only reason for generating PA signals. This work comprehensively delved the decisive parameters influencing PA mechanism and probed the thermodynamic-dependent PA effect.
Probing 'spin-forbidden' oxygen-atom transfer: Gas-phase reactions of chromium-porphyrin complexes
Crestoni, Maria Elisa,Fornarini, Simonetta,Lanucara, Francesco,Warren, Jeffrey J.,Mayer, James M.
, p. 4336 - 4343 (2010/05/14)
Oxygen-atom transfer reactions of metalloporphyrin species play an important role in biochemical and synthetic oxidation reactions. An emerging theme in this chemistry is that spin-state changes can play important roles, and a 'two-state' reactivity model
Inter-Metal Nitrogen Atom Transfer Reactions between Nitridochromium(V) and Chromium (III) Porphyrins
Neely, Frank L.,Bottomley, Lawrence A.
, p. 5432 - 5434 (2008/10/09)
Reactions of nitridochromium(V) porphyrins with chromium(III) porphyrins resulted in reversible, inter-metal nitrogen atom transfer between the two chromium porphyrin complexes. The progress of these reactions was followed spectrophotometrically. Kinetic analysis of the spectral data obtained over time for a variety of substituted porphyrins showed the reactions to be first order in each of the reactants and second order overall. Equilibrium constants were computed from the spectral data and ranged from 0.56 to 2.1 for the reactions between nitridochromium(V) octaethylporphyrin and a series of chlorochromium(III) tetraphenylporphyrins possessing phenyl ring substituents. Forward rate constants were determined for this reaction series and ranged from 6.8 to 1420 M-11 s-1. Electron-withdrawing substituents enhanced the forward rates but diminished the equilibrium constants. It is proposed that the reactions proceed by nucleophilic attack of the nitridochromium porphyrin donor on the cationic chromium(III) porphyrin nitrogen atom acceptor facilitating a net, two-electron redox process mediated by a homobimetallic μ-nitrido intermediate.
Stereoelectronic Aspects of Inter-Metal Nitrogen Atom Transfer Reactions between Nitridomanganese(V) and Chromium(III) Porphyrins
Bottomley, Lawrence A.,Neely, Frank L.
, p. 5435 - 5439 (2008/10/09)
Reactions of nitridomanganese(V) porphyrins with chromium(III) porphyrins resulted in the irreversible formation of nitridochromium(V) porphyrins and manganese(III) porphyrins. The progress of these reactions has been followed spectrophotometrically, electrochemically, and spectroscopically by EPR. Kinetic analysis of the spectrophotometric data obtained during these reactions for a variety of substituted porphyrins showed the reactions to be first order in each of the reactants. Rate constants were dependent upon the electronic and steric effects of the porphyrin substituent, upon the identity of the anion bound to the chromium(III) reactant, and upon the solvent dielectric constant. We propose that the mechanism of these nitrogen atom transfer reactions involves the nucleophilic attack of the nitridomanganese porphyrin donor on the cationic chromium(III) porphyrin acceptor facilitating a net, two-electron redox process mediated by a heterobimetallic μ-nitrido intermediate. This report represents the first systematic study of the stereoelectronic effects involved in the complete, inter-metal nitrogen atom transfer between two metalloporphyrins.
Intermediates in the Epoxidation of Alkenes by Cytochrome P-450 Models. 3. Mechanism of Oxygen Transfer from Substituted Oxochromium(V) Porphyrins to Olefinic substrates
Garrison, J. Mark,Bruice, Thomas C.
, p. 191 - 198 (2007/10/02)
Studies were initiated with the following chromium(IV) oxo porphyrin species: chromium(IV) oxide ((TPP)Cr(IV)(O)), chromium(IV) oxide ((Me12TPP)Cr(IV)(O)), chromium(IV) oxide ((Cl8TPP)Cr(IV)(O)), chromium(IV) oxide ((F8TPP)Cr(IV)(O)), and chromium(IV) oxide ((F20TPP)Cr(IV)(O)).Cyclic voltammetric (CH2Cl2, V, SCE) 1e oxidationpotentials for the couples (Porph)Cr(IV)(O)/(Porph)Cr(V)(O)(ClO4) have been determined 12TPP)Cr(IV)(O), 0.825; (Cl8TPP)Cr(IV)(O), 0.895; (F8TPP)Cr(IV)(O), 0.975; (F20TPP)Cr(IV)(O), chemically irreversible>.Standard solutions of (TPP)Cr(V)(O)(ClO4), (Me12TPP)Cr(V)(O)(ClO4), (Cl8TPP)Cr(V)(O)(ClO4), and (F8TPP)Cr(V)(O)(ClO4) were obtained by controlled-potential bulk electrolysis of the corresponding chromium(IV) oxo porphyris, and these solutions were employed in kinetic and product studies of the oxidation of a number of alkenes (CH2Cl2 solvent; 30 deg C).Under the pseudo-first-order condition of >> , the following reactions have been show to take place: (i) (Porph)Cr(V)(O)(ClO4)+alkene --> (Porph)Cr(III)(X)+epoxide (k1); (ii) (Porph)Cr(V)(O)(ClO4)+(Porph)Cr(III)(X) (Porph)Cr(IV)(O)+(Porph)Cr(IV)(X) (k2/k3); and (iii) spontaneous conversion of (Porph)Cr(V)(O) to (Porph)Cr(IV)(O) possibly by oxidation of solvent or supporting electrolyte (k4).The reversibility (k2/k3) of (ii) must be related to the formation of two different chromium(IV) porphyrinspecies, one of which is stabilized by oxo axial ligation ((Porph)Cr(IV)(O)) and one of which is not ((Porph)Cr(IV)(X); where X=Cl(-) or ClO4(-)).This is supported by the observation that the spectrum of (Me12TPP)Cr(IV)(O) remains unchanged in CH2Cl2 solutions of norbornene.Values of the second-order rate constants (k1) for alkene epoxidations were determined by both the slopes of plots of vs the pseudo-first-order rate constants (kobsd) for disappearance of and by computer simulation of the time courses for disappearance and appearance of the species (Porph)Cr(V)(O)(ClO4), (Porph)Cr(III)(X), and (Porph)Cr(IV)(O) according to reactions (i)-(iii).The two methods provided like values of k1.Values of k1 (M-1 s-1), determined from dependence of kobsd on , for reactions with (Me12TPP)Cr(V)(O)(ClO4) are the following: 5.4x1E-2, norbornene; 8.78x1E-4, cis-cyclooctene; 6.82x1E-3, cis-stilbene; and 5.19x1E-13, cyclohexene.With (Cl8TPP)Cr(V)(O)(ClO4) the values of k1 (M-1 s-1) are 9.56x1E-1 for norbornene and 2.13x1E-2 for cis-cyclooctene.Use of computer simulation of...
Oxochromium compounds. 2. Reaction of oxygen with chromium(II) and chromium(III) porphyrins and synthesis of a μ-oxo chromium porphyrin derivative
Liston, David J.,West, Bruce O.
, p. 1568 - 1576 (2008/10/08)
The reaction of oxygen with Cr(II) porphyrin complexes in solution has been found to result in the formation of CrIVO(P) compounds when oxygen is in excess. Solid CrII(P) also react irreversibly with oxygen, and the products dissolve in toluene to form CrIVO(P). The complex (TPP)CrOCr(TPP) has been isolated from the reaction of CrO(TPP) and CrII(TPP) and shown to undergo further reaction with oxygen to give CrO(TPP). The complex shows an IR absorption at 860 cm-1, considered to indicate the presence of the CrOCr linkage, and has μeff = 1.61 μB per Cr at 300 K, indicating substantial antiferromagnetic coupling. Similar μ-oxo complex formation has been demonstrated spectroscopically between other CrO(P)/Cr(P′) combinations where P and P′ may be the same or different. (P)CrOCr(P) complexes can be detected as intermediates in the reaction of CrII(P) with oxygen when the amount of oxygen is restricted. CrIII(P)Cl also reacts with oxygen in chloroform in the presence of HCl to give intermediates that are converted to CrIVO(P) in the presence of basic alumina. A Cr-porphyrin π-cation radical is proposed as the intermediate.
