- Magnetocaloric effect and heat capacity of high-spin manganese complexes in a disperse state
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Magnetothermal properties of high-spin chloro(2,3,7,8,12,13,17,18- octaethylporphyrinato)manganese(III), chloro(5,10,15,20-tetraphenylporphyrinato) manganese(III), bromo(5,10,15,20-tetraphenylporphyrinato)manganese(III), and (acetato)(5,10,15,20-tetraphenylporphyrinato)manganese(III) complexes as 6% water suspensions were determined by the microcalorimetric method at 298 K in a magnetic field of 0-1.0 T. It was established that when the magnetic field was applied, the temperature of the systems increases, leading to positive values of the magnetocaloric effect: the higher the magnetic field induction, the higher the values. It is shown that the dependences of the heat capacity of the complexes' solid particles on the magnetic field induction are of an extreme nature with a heat capacity in the area above 0.6 T less than that in the zero field. The regularities of the dynamics of the numerical values of the change in enthalpy and magnetic entropy of the manganese complexes when a growing magnetic field was applied and the regularities of the influence of the acidoligand in pentacoordinated complexes on their magnetothermal properties were considered.
- Korolev,Aref'Ev,Lomova,Klyueva,Zakharov,Korolev
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- A manganese porphyrin-α-cyclodextrin conjugate as an artificial enzyme for the catalytic epoxidation of polybutadiene
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We describe a manganese porphyrin-α-cyclodextrin conjugate as a catalyst for the epoxidation of cis-polybutadiene with trans-epoxide preference, which is a reverse stereoselectivity as compared to normal porphyrin catalysts. A clamp-like mechanism is prop
- Zhang, Qi-Wei,Elemans, Johannes A. A. W.,White, Paul B.,Nolte, Roeland J. M.
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- Hydrogen-bonded chain structure of a six-coordinate 5,10,15,20-tetraphenylporphinatomanganese(III) complex
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In methanolic solutions, disproportionation of the TCNQ anion radical to neutral TCNQ0 and the dianion TCNQ2- followed by aerobic oxidation of TCNQ2- results in the formation of methyl-4-dicyanomethylene benzoate anion (MDCB-). This anion coordinates to the manganese(III) atom of 5,10,15,20-tetraphenylporphinatomanganese(III) leading to the complex whose X-ray crystal structure is reported. The crystal had the monoclinic space group P21/n with unit cell dimensions a = 13.327(3), b = 20.236(6), c = 16.914(5) ? and β = 92.26(2)°. An important driving force behind the crystal packing is a hydrogen bonding interaction between non-identical ligands of adjacent molecules.
- Hill, Jonathan P.,Santiago, Julio,Sugino, Takushi,Shiro, Motoo,Shimizu, Yo
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- A rare μ-hydroxo-bridged species. Synthesis, structure, and properties of μ-hydroxo(tetraphenylporphyrinatomanganese(III))(phthalocyaninato-(azido) chromium(III)), [(TPP)Mn-O(H)-CrPc(N3)]
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A novel ditetrapyrrolic, heteroleptic, and heterometallic (Mn-Cr) μ-hydroxo-bridged complex has been prepared, and its structural and general properties have been studied. The species μ-hydroxo(tetraphenylporphyrin- atomanganese(III))(phthalocyaninato(azido)chromium(III)), [(TPP)Mn-O(H)- CrPc(N3)], isolated as a chloronaphthalene (CINP) solvate, has been structurally characterized by single-crystal X-ray work. The two (TPP)Mn and CrPc(N3) fragments are held together by the bridging μ-hydroxo ion with long Mn-O [1.993(5) A] and Cr-O [1.976(5) A] bond distances and a Mn-O(H)-Cr angle of 163.7(3)°. The five-coordinate Mn center in the (TPP)Mn fragment is displaced from the TPP rigorously planar central N 4 core by 0.128 A, and the environment is typical of a Mn III high-spin site. The six-coordinate CrIII in the CrPc(N3) moiety lies practically in the plane of the phthalocyanine macrocycle (displacement toward the azido group: 0.054 A). The average Mn-Npyr and Cr-Npyr bond distances are 2.011(6) and 1.982(6) A, respectively, and the Mn-Cr bond distance is 3.929(2) A. The porphyrin and phthalocyanine rings are in an almost eclipsed position [5.16(2)°], and the mean planes of the two macrocycles form a dihedral angle of 5.79(4)°. Crystal data for [(TPP)Mn-O(H)-CrPc(N3)] ·2CINP, C76H45CrMnN15O·2C 10H7Cl: a = 16.645(3) A, b = 17.692(4) A, c = 25.828(5) A, α = 90°, β= 98.79(3)°, γ= 90°, space group P21/c (No. 14), V = 7517(3) A3, Z= 4, R1 = 0.086, and wR2 = 0.267. IR-and UV-vis-near-IR spectral and room temperature magnetic susceptibility data of the [Mn-Cr] species are also presented.
- Donzello, Maria Pia,Bartolino, Laura,Ercolani, Claudio,Rizzoli, Corrado
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- Cycloaddition reaction of propylene oxide and carbon dioxide over NaX zeolite supported metalloporphyrin catalysts
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Metalloporphyrin catalysts has attracted extensive attention as the result of their outstanding biomimetic catalytic properties. In this paper, different kinds of unsupported (Co(TPP), MnIII(TPP)Cl and CoIII(TPP)Cl) and NaX zeolite supported metalloporphy
- Zhang, Fengyong,Xie, Yujia,Liu, Pingle,Hao, Fang,Yao, Zhengjie,Luo, He'An
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- Linkage Isomers of 4-Methylimidazolate Mn(II) Porphyrinates: Hindered or Unhindered?
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Three different manganese(II) porphyrins have been exploited to react with 4-methylimidazolate (4-MeIm-), and the five-coordinate products are characterized by ultraviolet-visible, single-crystal X-ray, and electronic paramagnetic resonance spectroscopies. Interestingly, 4-MeIm- is found to bond to the metal center through either of the two N atoms (N1 or N3), which yielded two linkage isomers with either an unhindered or a hindered ligand conformation, respectively. Investigations revealed it is the large metal out-of-plane displacements (Δ24 and Δ4 ≥ 0.59 ?) that have rendered the equivalence of two isomers with a small energy difference (5.2-8.3 kJ/mol). The nonbonded intra- and intermolecular interactions thus become crucial factors in the balance of linkage isomerization. All of the products in both solution and solid states show the same characteristic resonances of high-spin Mn(II) (S = 5/2) with g⊥ ≈ 5.9 and g⊥ ≈ 2.0 at 4 K, consistent with the weak effects of the axial ligand on core conformation and metal electronic configurations. Zero-field splitting parameters obtained through simulations are also reported.
- Zhao, Jianping,Qian, Fei,Guo, Wenping,Li, Jianfeng,Lin, Zeyuan
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p. 7465 - 7474
(2021/05/26)
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- Nitrene Photochemistry of Manganese N-Haloamides**
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Manganese complexes supported by macrocyclic tetrapyrrole ligands represent an important platform for nitrene transfer catalysis and have been applied to both C?H amination and olefin aziridination catalysis. The reactivity of the transient high-valent Mn nitrenoids that mediate these processes renders characterization of these species challenging. Here we report the synthesis and nitrene transfer photochemistry of a family of MnIII N-haloamide complexes. The S=2 N-haloamide complexes are characterized by 1H NMR, UV-vis, IR, high-frequency and -field EPR (HFEPR) spectroscopies, and single-crystal X-ray diffraction. Photolysis of these complexes results in the formal transfer of a nitrene equivalent to both C?H bonds, such as the α-C?H bonds of tetrahydrofuran, and olefinic substrates, such as styrene, to afford aminated and aziridinated products, respectively. Low-temperature spectroscopy and analysis of kinetic isotope effects for C?H amination indicate halogen-dependent photoreactivity: Photolysis of N-chloroamides proceeds via initial cleavage of the Mn?N bond to generate MnII and amidyl radical intermediates; in contrast, photolysis of N-iodoamides proceeds via N?I cleavage to generate a MnIV nitrenoid (i.e., {MnNR}7 species). These results establish N-haloamide ligands as viable precursors in the photosynthesis of metal nitrenes and highlight the power of ligand design to provide access to reactive intermediates in group-transfer catalysis.
- Bhuvanesh, Nattamai,Das, Anuvab,Figgins, Matthew T.,Hicks, Madeline H.,Ozarowski, Andrew,Powers, David C.,Reid, Kaleb A.,Telser, Joshua,Van Trieste, Gerard P.
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supporting information
p. 26647 - 26655
(2021/11/18)
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- Method for synthesizing tetraaryl manganese porphyrin through synchronous aldehyde and pyrrole condensation and bivalent manganese salt oxidation insertion reaction
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The invention discloses a method for synthesizing tetraaryl manganese porphyrin by synchronous aldehyde and pyrrole condensation and bivalent manganese salt oxidation insertion reaction. Aromatic aldehyde, pyrrole and manganese dichloride are refluxed in
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Paragraph 0028-0029
(2020/09/08)
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- Surface molecular engineering of axial-exchanged Fe(III)Cl- and Mn(III)Cl-porphyrins towards enhanced electrocatalytic ORRs and OERs
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Herein, pyrene-pyridine (Pyr-Py) molecule was applied as the axial exchanged ligand to bridge Fe(III) and Mn(III)porphyrin immobilized on rGO. These axially exchanged metalloporphyrin functionalized nanocomposites revealed enhanced electrochemically catal
- Attatsi, Isaac Kwaku,Zhu, Weihua,Liang, Xu
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supporting information
(2020/03/23)
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- Crystallographic identification of a series of manganese porphyrin complexes with nitrogenous bases
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Studying the axial ligation behavior of metalloporphyrins with nitrogenous bases helps to better understand not only the biological function of heme-based protein systems, but also the catalytic properties of porphyrin-based reaction sites in other biomim
- Lahanas, Nicole,Kucheryavy, Pavel,Lalancette, Roger A.,Lockard, Jenny V.
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p. 304 - 312
(2019/02/20)
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- Spectral, Electrochemical, and ESR Characterization of Manganese Tetraarylporphyrins Containing Four β,β′-Pyrrole Fused Butano and Benzo Groups in Nonaqueous Media
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Two series of β,β′-pyrrole butano- A nd benzo-substituted mangenese(III) tetraarylporphyrins were synthesized and characterized with regard to their spectral and electrochemical properties. The investigated compounds have the general formula butano(Ar)su
- Fang, Yuanyuan,Wang, Liping,Xu, Weijie,Ou, Zhongping,Chen, Mingyuan,Cong, Lei,Shan, Wenqian,Ke, Xiangyi,Kadish, Karl M.
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p. 2576 - 2587
(2019/02/19)
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- Synthesis and photophysical properties of novel pyrene-metalloporphyrin dendritic systems
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A novel series of dendronized porphyrins bearing pyrene units in the periphery (Porph-O-Gn) and their metal complexes (M-[Porph-O-Gn]) are reported. The pyrene-containing Frechet-type dendrons up to the first generation were synthesized and further reacted with 5-phenol-10,15,20-triphenylporphyrin via an esterification reaction to afford the desired pyrene-labeled dendronized porphyrins. Later, these compounds were used as ligands to produce the corresponding complexes of Zn2+, Cu2+, Mg2+ and Mn3+. With the compounds in hand, the optical and photophysical properties of the dendritic metalloporphyrins were studied by absorption and fluorescence spectroscopy. The quantum yields, F?rster radius and efficiency of energy transfer were determined and discussed as a function of the structure and the donor-acceptor distances, finding an efficient energy transfer from the pyrene moiety to the metallated porphyrin core in each case.
- Rojas-Montoya, Sandra M.,Vonlanthen, Mireille,Porcu, Pasquale,Flores-Rojas, Gabriel,Ruiu, Andrea,Morales-Morales, David,Rivera, Ernesto
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p. 10435 - 10447
(2019/07/22)
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- Biomimetic Cleavage of Aryl–Nitrogen Bonds in N-Arylazoles Catalyzed by Metalloporphyrins
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The cleavage of C–N single bonds of N-containing compounds provides either an excellent nitrogen source or an excellent carbon source. In this study, an efficient metalloporphyrins/H2O2 cleavage of C–N bonds of arylpyrazoles was investigated. The effects of different factors, including different catalysts, catalyst dosages, H2O2 dosages, reaction temperature and reaction time were studied. The experimental results showed that the optimal catalyst was FeTPPCl, and the yield of pyrazole derivatives could reach up to 12.3%, which was fourfold higher than hemin catalyzed reaction and closed to ceric ammonium nitrate catalyzed reaction, respectively. Compared with transition-metal-catalyzed and strong-oxidization cleavage of C–N bonds, this protocol is characterized by environmentally-friendly, stable, mild reaction conditions and simplified operation procedures. Graphical Abstract: [Figure not available: see fulltext.].
- Yu, Zongjiang,Zhai, Guoqing,Xian, Mo,Lu, Ming,Wang, Pengcheng,Jiang, Tao,Xu, Chao,Sun, Weizhi
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p. 2636 - 2642
(2018/06/20)
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- Bromo-substituted Mn(II) and Mn(III)-tetraarylporphyrins: synthesis and properties
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Mono-, tetra-, and octa-bromo substituted Mn(II)- and Mn(III)-tetraarylporphyrins were synthesized by reactions of manganese(II) chloride with corresponding porphyrin ligands or their Cd(II)-complexes in DMF. With the use of the metal exchange reaction, the time of the Mn-porphyrins formation is significantly reduced with increase in yield of final products in comparison with the complexation reaction. Mn(III)-tetraarylporphyrins reduce to the Mn(II)-porphyrins in DMF in the presence of NaOH and in pure DMF. The obtained compounds were identified using UV–vis and 1H NMR spectroscopy, mass-spectrometry, and elemental analysis.
- Chizhova, Natalya Vasil’evna,Maltceva, Olga Valentinovna,Zvezdina, Svetlana Veniaminovna,Mamardashvili, Nugzar Zhoraevich,Koifman, Oscar Iosifovich
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p. 3222 - 3232
(2018/12/04)
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- Axial base-controlled catalytic activity, oxidative stability and product selectivity of water-insoluble manganese and iron porphyrins for oxidation of styrenes in water under green conditions
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A series of water-insoluble iron(III) and manganese(III) porphyrins, FeT(2-CH3)PPCl, FeT(4-OCH3)PPCl, FeT(2-Cl)PPCl, FeTPPCl, MnT(2-CH3)PPOAc, MnT(4-OCH3)PPOAc, MnT(2-Cl)PPOAc and MnTPPOAc, in the presence of imidazole (ImH), F?, Cl?, Br? and acetate were used as catalysts for the aqueous-phase heterogeneous oxidation of styrenes to the corresponding epoxides and aldehydes with sodium periodate. Also, the effect of various reaction parameters such as reaction time, molar ratio of catalyst to axial base, type of axial base, molar ratio of olefin to oxidant and nature of metal centre on the activity and oxidative stability of the catalysts and the product selectivity was investigated. Higher catalytic activities were found for the iron complexes. Interestingly, the selectivity towards the formation of epoxide and aldehyde (or acetophenone) was significantly influenced by the type of axial base. Furthermore, Br? and ImH were found to be the most efficient co-catalysts for the oxidation of olefins performed in the presence of the manganese and iron porphyrins, respectively. The optimized molar ratio of catalyst to axial base was different for various axial bases. Also, the order of co-catalyst activity of the axial bases obtained in aqueous medium was different from that reported for organic solvents. The use of a convenient axial base under optimum reaction catalyst to co-catalyst molar ratio in the presence of the manganese porphyrin gave the oxidative products with a conversion of ca 100% in a reaction time of less than 3?h. However, the catalytic activity of the iron porphyrins could not be effectively improved by increasing the catalyst to co-catalyst molar ratio.
- Zakavi, Saeed,Hashemi-Amiri, Akbar,Asadi, Fatemeh
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- Catalytic Aerobic Oxidation of Biomass-based Furfural into Maleic Acid in Aqueous Phase with Metalloporphyrin Catalysts
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Catalytic oxidation of renewable furfural into valuable maleic acid in aqueous solutions using metalloporphyrin catalysts was investigated for the first time. The synthesized catalysts were characterized by FT-IR, UV–vis, 1H NMR, elemental analysis, and TGA. The catalysts varied in metal active sites and functional groups, which had different effects on their catalytic activity. Furthermore, the effects of temperatures, reaction time, catalyst loading, and oxygen pressure were studied in detail. Maleic acid could be achieved in 44% yield by using FeT(p-Cl)PPCl as catalyst under optimal conditions. Finally, FeT(p-Cl)PPCl could be reused in five consecutive runs without a significant loss of activity.
- Huang, Yi,Wu, Chunyan,Yuan, Wenwen,Xia, Yongmei,Liu, Xiang,Yang, Huamei,Wang, Haijun
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p. 786 - 794
(2017/07/24)
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- Effects of porphyrin deformation on the 13 C and 1H NMR chemical shifts in high-spin five-and six-coordinate manganese(III) porphyrin complexes
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As an extension of our study to reveal the effect of porphyrin deformation on the 13C and 1H NMR chemical shifts, both five-and six-coordinate high-spin (S = 2) Mn(III) complexes such as Mn(Por)Cl and [Mn(Por)(CD3OD)2]Cl h
- Ikezaki, Akira,Nakamura, Mikio
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p. 318 - 330
(2016/07/07)
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- Preparation and spectral properties of β-bromo-substituted Mn(III) tetraphenylporphyrinates
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Interaction of 5,10,15,20-tetraphenylporphyrin, 2-bromo-5,10,15,20-tetraphenylporphyrin, and 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin with manganese(II) chloride in dimethylformamide has been studied by means of spectrophotometry. The corresponding chloride acido complexes of manganese(III) has been so prepared and identified. The complexes could be reduced into manganese(II) tetraphenylporphyrinates in the presence of potassium hydroxide in dimethylformamide.
- Chizhova,Zvezdina,Kataleva,Mamardashvili
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p. 1132 - 1135
(2015/06/25)
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- Syntheses, spectroscopic and AFM characterization of some manganese porphyrins and their hybrid silica nanomaterials
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The present work is concerned with the manganese complexes of 5,10,15,20-tetraphenylporphyrin and of 5,10,15,20-tetra(3-hydroxyphenyl) porphyrin, which were prepared by metallation of the corresponding porphyrin ligands, and the study of their spectroscop
- Eugenia, Fagadar-Cosma,Mirica, Marius Constantin,Balcu, Ionel,Bucovicean, Carmen,Cretu, Carmen,Armeanu, Ileana,Gheorghe, Fagadar-Cosma
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experimental part
p. 1370 - 1388
(2010/03/30)
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- 'Click' silica immobilisation of metallo-porphyrin complexes and their application in epoxidation catalysis
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We present the synthesis, via Adler condensation reactions, of mono- and tetrakis-4-(ethynyl-phenyl)porphyrin ligands and the zinc and manganese complexes thereof. The formed complexes were immobilised on silica by reacting the ethynyl groups with azide-f
- McDonald, Aidan R.,Franssen, Nicole,van Klink, Gerard P.M.,van Koten, Gerard
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p. 2153 - 2162
(2009/10/23)
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- Immobilization of Fe, Mn and Co tetraphenylporphyrin complexes in MCM-41 and their catalytic activity in cyclohexene oxidation reaction by hydrogen peroxide
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Metalloporphyrin catalysts are able to carry out selective oxidation of organic substrates with several oxidizing agents. Recently, mesoporous materials have been studied as supports because they present high specific surface area, better dispersion and regeneration properties. This work presents the results of synthesis, characterization and application of three metalloporphyrin catalysts (FeTPPCl, MnTPPCl and CoTPP, where TPP = tetraphenylporphyrin) anchored on MCM-41, in the reaction of cyclohexene oxidation with hydrogen peroxide. A modified sol-gel preparation was chosen for the synthesis of the MCM-41 mesoporous material, as well as the anchoring was followed by Soxhlet extraction to ensure strong adsorption of the complex. The supported materials were much more stable than pure metalloporphyrins. The synthesized catalysts were characterized by UV-vis, FTIR, XRD, ICP-AES, 29Si MAS-NMR and thermal analysis, before and after incorporation. Evidence of the metalloporphyrin immobilization was confirmed by elemental analysis and their activity in the oxidation reaction. FeTPPCl/MCM-41 showed higher conversion than CoTPP/MCM-41 and MnTPPCl/MCM-41. However, MnTPPCl/MCM-41 even in low concentration on the support showed a good conversion for the direct oxidation of cyclohexene with the highest turnover number (1.54 × 105). All catalysts showed similar selectivity that favors allylic oxidation products over epoxidation. No leaching of the metalloporphyrins was observed after the reaction.
- Costa, Andréia A.,Ghesti, Grace F.,de Macedo, Julio L.,Braga, Valdeilson S.,Santos, Marcello M.,Dias, José A.,Dias, Sílvia C.L.
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p. 149 - 157
(2009/01/21)
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- A green process for oxidation of p-nitrotoluene catalyzed by metalloporphyrins under mild conditions
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A novel synthetic technology of p-nitrobenzoic acid has been investigated with dioxygen by using metalloporphyrins RTPP-MIIICl (M = Fe, Co, Mn) as biomimetic catalysts. Oxidation of p-nitrotoluene to p-nitrobenzoic acid under 2.0 MPa of O2 in the presence of a microamount of metalloporphyrins (RTPP-MIIICl) at 55 °C was achieved with the highest (up to 90.4%) yield. Further research results show that the catalytic activities were relative to the nature of the substituted groups and the central metal ions of metalloporphyrins. For the metalloporphyrins with the same center metal ions, the greater the electron-withdrawing degree of groups in the porphyrin ring, the higher the catalytic activities of the metalloporphyrins. The catalytic activities for metalloporphyrins with different center metal ions followed the order RTPPMn IIICl > RTPP Fe IIICl > RTPP Co IIICl.
- Wang, Lanzhi,She, Yuanbin,Zhong, Rugang,Ji, Hongbing,Zhang, Yanhui,Song, Xufeng
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p. 757 - 761
(2012/12/22)
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- Effect of octabromo substitution on the coordination properties of manganese(III) octaphenyltetraazaporphyrin
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Comparative studies of the kinetics of formation of manganese(III) complexes with octaphenyltetraazaporphyrin and its octabromo derivative, of their dissociation and axial ligand exchange were carried out. The effect of octabromo substitution on the coordination properties of the compounds is determined by the -I effect of bromine atoms. The different effects on the kinetic parameters of the reactions [increase in the rate and significant decrease in the activation energy upon complex formation, slowing down of dissociation, and acceleration of acido ligand exchange with nitrido(tetraphenyporphyrin)manganese(V) are caused by the involvement of different reaction centers in the limiting stages (different mechanisms of the processes).
- Klyueva,Repina,Chizhova
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p. 975 - 979
(2007/10/03)
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- The patterns of nitrogen atom transfer between manganese(V) and manganese(III) complexes with porphyrins and tetraazaporphyrins
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The kinetics of intermetallic nitride nitrogen atom transfer between manganese(V) and manganese(III) complexes with tetraphenylporphin and octaphenyltetraazaporphin were studied. The interaction between the nitridomanganese(V)tetraphenylporphyrin and Mn(I
- Stuzhin,Repina,Klyueva,Fedotova
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p. 864 - 870
(2007/10/03)
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- Effect of the composition of the H2SO4-AcOH binary solvent on the dissociation kinetics of metal porphyrins
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The kinetics and mechanism of dissociation of copper(II) complexes with octaethylporphyrin and of manganese(III) with tetraphenylporphyrin were studied in relation to the composition of an H2SO4-AcOH binary solvent. Concentration ran
- Klueva,Suslova,Lomova
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p. 1303 - 1308
(2007/10/03)
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- Photoluminescent properties of cadmium selenide in contact with solutions and films of metalloporphyrins: Nitric oxide sensing and evidence for the aversion of an analyte to a buried semiconductor-film interface
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The band-edge photoluminescence (PL) intensity of etched n-CdSe single crystals is quenched reversibly by adsorption of the trivalent metalloporphyrins, MTPPCl (TPP = tetraphenylporphyrin; M = Mn, Fe, Co) in nitrogen-saturated methylene chloride solution. The PL responses are concentration dependent and can be fit to the Langmuir adsorption isotherm model to yield binding constants of ～103-104 M-1. The MTPPCl compounds react irreversibly with NO in solution to form nitrosyl adducts, and these compounds reversibly enhance the CdSe PL intensity when adsorbed onto the semiconductor surface, also with binding constants of ～103-104 M-1. Films of MTPPCl were prepared on CdSe substrates by solvent evaporation. These coatings serve as transducers for NO detection: while the bare CdSe surface shows no response to NO gas relative to N2, the coated surfaces reversibly enhance the PL intensity (CoTPPCl) or quench it (MnTPPCl and FeTPPCl), with binding constants on the order of ～1 atm-1. In contrast to the PL results, which are particularly sensitive to the semiconductor-film interface, electronic and IR spectral changes of the bulk film induced by NO binding were irreversible. The UV-vis and IR spectra could be spectroscopically mimicked by preformed nitrosyl adduct films that were prepared by solvent evaporation of MTPPCl (M = Co, Fe) and MTPP (M = Co) solutions that had been exposed to NO. These films, however, lack transduction capability, as the PL intensity is the same in NO and N2 ambients. For the films prepared from FeTPPCl and CoTPPCl, the saturation of IR and UV-vis spectral changes occurs at NO pressures at least 10-fold lower than observed for PL changes. These results indicate that NO has a strong aversion to binding at the semiconductor-film interface as opposed to the bulk film environment. Steric and electronic contributions to these observed effects are discussed.
- Ivanisevic, Albena,Reynolds, Mark F.,Burstyn, Judith N.,Ellis, Arthur B.
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p. 3731 - 3738
(2007/10/03)
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- Synthesis, Chemical-Physical Characterization, and Redox Properties of a New Mixed-Ligand Heterobimetallic N-Bridged Dimer: (μ-Nitrido)[((tetraphenylporphyrinato)manganese)((phthalocyaninato)iron)]
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A new mixed-ligand heterobimetallic μ-nitrido bridged complex of the formula (TPP)Mn-N-Fe(Pc) (I) has been prepared from (TPP)MnN3 and (Pc)Fe (TPP = tetraphenylporphyrinato anion, Pc = phthalocyaninato anion) and its molecular and electronic structure were investigated by EPR, IR, Raman, UV-visible and Moessbauer spectroscopy as well as by electrochemistry and magnetic susceptibility measurements. The complex, formally a mixed-valence Mn-Fe d8 system, is low-spin (diamagnetic). Moessbauer data indicate an unbalanced positive charge distribution for the two metal centers and an approach to the formally mixed-valence species (TPP)-MnIV=N-FeIII(Pc). This assignment differs from findings for the related complex (TPP)FeIII1/2-N-FeIII1/2(Pc) (II) and other similar N-bridged analogues, including (TPP)FeIV=N-RuIII(Pc). A metal centered one-electron oxidation occurs by reaction of I with dilute HClO4 and leads to formation of a Mn(IV)=N-Fe(IV) species, I-ClO4. Pyridine can coordinate with I to give a mono(pyridine) adduct and the formation constant for this reaction has been determined spectrophotometrically in CH2Cl2 solutions. The singly oxidized complex, I-ClO4, also reacts with pyridine and is converted to a bis-pyridine derivative containing the fragment [(py)(TPP)Mn-N-Fe(Pc)(py)]+. Complex I can undergo five reversible one-electron oxidations in CH2Cl2 and up to six electrons can be extracted from the neutral complex in pyridine. Both sets of reactions were characterized by cyclic voltammetry which was used to determine the half-wave potentials for each electrode reaction and also to evaluate formation constants for pyridine binding to the neutral and singly oxidized forms of the complex.
- Donzello, Maria Pia,Ercolani, Claudio,Kadish, Karl M.,Ou, Zhongping,Russo, Umberto
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p. 3682 - 3688
(2008/10/08)
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- Special Features of the Electronic Effects of Substituents in Manganese(III) Porphyrins
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Spectrophotometry was applied to study of the kinetics of dissociation and state in concentrated sulfuric acid solutions of bromine-substituted manganese(III) tetraphenylporphyrins featuring σ,π donor-acceptor metal-nitrogen interaction. The effects of identical substituents in the pyrrole and phenyl rings of the ligand on the kinetic stability of the tetraphenylporphine complexes differ not only quantitatively, but can be opposite in sign. A mechanism is considered of the electronic effects of substituents on the state of the electron pairs of the Mn-N bonds and of the n-electron pairs of the nitrogen atoms which add protons in the course of dissociation of the complex. These effects are unsimilar for subsituents in the macroring and in the phenyl rings of the ligand tetraphenylporphine.
- Klyueva,Lomova,Berezin
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p. 499 - 504
(2007/10/03)
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- Carbon-13 NMR spectroscopy, electron spin distributions, and valence state of pentacoordinate manganese tetraphenylporphyrin complexes
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The solution optical and NMR spectra of (TPP)MnX (X = F-, NCO-, CH3CO2-, HCO2-, N3-, Cl-, Br-, NO2-, NO3-, NCS-, CN-, I-, ClO4-, BF4-, B(C6H5)4-) indicate that ionic bonding may be particularly important in manganese tetraphenylporphyrin complexes. A Karplus-Fraenkel equation utilization of 13C NMR spectra for the calculation of electron spin densities at the porphyrin nuclei uncovers an unexpectedly high positive π density at the pyrrole α-carbon sites. The densities for the acetato, nitrato, and perchlorato complexes are 0.049, 0.056, and 0.063, respectively. Such high densities are unlikely to be covalent in origin, and accordingly an axial ligand dependent mixture of the [MnII(SI = 3/2, 4A2)P(S = 1/2, 2A2)?-]+ + [MnIII(S = 2, 5A1)P2-]+ electronic states is proposed for the ground valence state of manganese tetraphenylporphyrin complexes. The calculations probably underestimate the α-carbon spin densities, so the C2v (dx2-y2)0 (dz2)1 (dxz dyz)2 (dxy)2 (a2(π))2 (a1(π))2 [MnIIP?-]+ valence state is likely to be the principal ground-state contributor. The electron spin at the α-carbon sites dominates the carbon-13 spectroscopy through polarization and correlation. In contrast to previous deductions of negative p(π) density, but in accord with the hyperporphyrin optical spectra, a high positive p(π) density is present at the meso sites. This spin density is effectively undermined by the greater spin at the α-carbon location. The phenyl residue NMR reflects an axial ligand dependent balance of spin polarization and positive spin delocalization from the meso position. The carbon-13 spectra of the Br-, Cl-, and CN- complexes indicate asymmetry in the porphyrin-phenyl residue interaction. The behavior of the axial ligand sensitive optical ε(III)/ε(IV) ratio, suggests that the a2(π) orbital is the HOMO in manganese tetraphenylporphyrin complexes.
- Turner, Peter,Gunter, Maxwell J.
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p. 1406 - 1415
(2008/10/08)
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- Metalloporphyrin photochemistry with matrix isolation
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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.
- Suslick, Kenneth S.,Bautista, Jocelyn F.,Watson, Randall A.
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p. 6111 - 6114
(2007/10/02)
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- The use of perchlorato(tetraphenylporphinato)manganese(III) as a reagent for the spectrophotometric determination of anions in nonaqueous solvents
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Perchlorato(tetraphenylporphinato)manganese(III) (TPPMnClO4) is shown to be a useful reagent for the determination of a variety of anions in nonaqueous media.The analysis is based on the displacement of coordinated perchlorate by more strongly coordinating anions as monitored spectrophotometrically.The procedure is demonstrated for the determination of tetra-alkylammonium salts of nitrate, nitrite, chloride, bromide, iodide, acetate, trifluoroacetate, cyanate, and thiocyanate in acetonitrile.Relative precisions and accuracies of the order of five parts per thousand are indicated.Key words: perchlorato(tetraphenylporphinato)manganese(III), spectrophotometric determination of anions, anions in nonaqueous media.
- Hinman, A. Scott,McGarty, Karen,Tang, Clement,Pavelich, Brad J.
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p. 545 - 550
(2007/10/02)
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- Electrochemical reactivity of manganese(II) porphyrins. Effects of dioxygen, benzoic anhydride, and axial ligands
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Currents for electrochemical reductions of manganese(III) porphyrins in oxygenated, aprotic media correspond to passage of between one and two electrons per porphyrin, depending on the experimental time scale, the axial base present, and the particular porphyrin. The two-electron process corresponds to an ECE reaction sequence involving formation and subsequent reduction of an intermediate Mn(II)-dioxygen adduct. The formal potential of the second electron step is shown to be ca. -0.17 V vs. NaSCE for Mn(TPP)benzoate. Passage of the second electron is suppressed by strong axial bases and by competitive axial binding but is promoted by use of an axial anion that gives the most negative potential for passage of the first electron, Mn(TPP)benzoate being a specific example. The overall rate constant for the intermediate chemical step is estimated. In the presence of the added electrophile benzoic anhydride, and on a slower time scale, reduction by more than two electrons occurs by a process postulated to involve heterolysis of the O-O bond by the electrophile, producing an even more easily reduced, high-valent manganese-oxo porphyrin. The rate of electrophile attack is slower than that for dioxygen binding.
- Creager,Murray, Royce W.
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p. 2612 - 2618
(2008/10/08)
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- Synthesis and Characterization of a MnIII Porphyrin Cation Radical and Its Conversion to MnIV by Ligand Metathesis
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The complex (5,10,15,20-tetraphenylporphinato)manganese chloro hexachloroantimonate, 1, MnTPP(Cl)(SbCl6), was synthesized by the oxidation of MnTPP(Cl) with phenoxathiin hexachloroantimonte in dichloromethane.The assignment of 1 as a manganese(III) porphyrin ?-cation radical species was based on its X-ray crystal structure, visible and infrared spectra, and magnetic properties.The crystal structure was determined as a tetrachloroethane solvate.The manganese in the compound is five-coordinated with the chloride anion axially bound to the Mn with 50percent occupancy at sites above and below the porphyrin ring.The second anion, SbCl6(1-), is displaced from the Mn with a Mn-Cl-Sb angle of 132 deg.The porphyrin core carbon and nitrogen atoms as well as Mn are coplanar.Variable-temperature magnetic susceptibility measurements on the solid gave μeff = 4.9 μB which is close to that expected for a MnIII cation (d4) S = 2, ?-cation radical S = 1/2, with independent spin states.Magnetic susceptibility measurements on solutions of 1 gave a range of values for μeff between 5.7 and 6.7 μB.This suggests that the spin independent state of 1 in the solid changes into a ferromagnetically coupled state, resultant spin of five-halves, in the solution phase.The IR spectrum of 1, with four solvent molecules (C2H2Cl4) present, shows a peak at 1280 cm-1.A band in this region has been suggested as diagnostic of metallotetraphenylporphyrin ?-cation radical species.The 1280-cm-1 band observed for 1 disappeared when all the solvent molecules from 1 were removed under vacuum.The crystalline nature of the solid was lost by the removal of the solvent molecules; however, magnetic moment (4.7 μB) and the visible spectrum remained virtually unchanged.We believe that the 1280-cm-1 band in 1 is associated with the solvent molecules; neat C2H2Cl4 also shows strong absorption in the 1280-cm-1 region.Treatment of 1 with basic methanol or oxidation of MnTPP(Cl) with phenoxathiin hexachloroantimonate in the presence of basic methanol gave another species whose visible and EPR spectra are identical with that reported for MnIVTPP(OCH3)2.These results suggest that the site of oxidation in MnTPP(Cl) is shifted from the ligand to the metal in the presence of the strong ?-donating ligand, CH3O(1-).
- Spreer, Larry O.,Maliyackel, Anthony C.,Holbrook, Stephen,Otvos, J. W.,Calvin, Melvin
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p. 1949 - 1953
(2007/10/02)
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- Study of (Tetraphenylporphinato)manganese(III)-Catalyzed Epoxidation and Demethylation Using p-Cyano-N,N-dimethylaniline N-Oxide as Oxygen Donor in a Homogeneous System. Kinetics, Radiochemical Ligation Studies, and Reaction Mechanism for a Model of Cytochrome P-450
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Oxygen transfer from p-cyanodimethylaniline (p-CNDMANO) to cyclohexene as well as "intramolecular" oxygen transfer accompained by demethylation to yield p-cyanomonomethylaniline (p-CNMMA) are strongly catalyzed by ligated (tetraphenylporphinato)MnIII (i.e., XMnIIITPP).These reactions have been studied in dry, oxygen-free benzonitrile.Radiochemical studies show that H2O (or TOH) is not bound to XMnIIITPP in aprotic solvents so that the MnIII moiety is pentacoordinate.Oxygen transfer occurs through the reversible formation of the hexacoordinated species p-CNDMANO*MnIII(X)TPP.This species decomposes to p-cyanodimethylaniline (p-CNDMA) + O=MnV(X)TPP.Reactions of cyclohexene with O=MnV(X)TPP yields cyclohexene epoxide and XMnIIITPP whereas p-CNMMA is formed directly from the p-CNDMANO*MnIII(X)TPP complex.The rates of product formation are shown to be dependent upon the nature of the ligand (X- = F-, Cl-, Br-, I-, OCN-).In the absence of the axial ligand X-, the rates of reaction are extremely slow.Thus, the MnIII C2-cap-porphyrin (XMnIIICAPTPP), which can only form an O=MnV porphyrin species wherein the Mn moiety is not complexed to X- as a sixth ligand, shows almost no tendency to act as a catalyst for oxygen transfer.The necessary presence of the axial ligand X- and the dependence of rate upon X- requires the structure of the oxygen transfer species to be quivalent to O=MnV(X)TPP.A kinetic analysis is presented (Scheme III) which has allowed the determination of the influence of the ligands X- upon the various rate constants (Table IV) involved in the overall oxidations.By employing p-CNDMANO as oxygen donor, multiple catalytic turnovers without loss of porphyrin have been realized.
- Powell, Michael F.,Pai, Emil F.,Bruice, Thomas C.
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p. 3277 - 3285
(2007/10/02)
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- Carbon-13 and deuterium NMR spectroscopy of high-spin manganese(III) porphyrin halide and pyridine complexes
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Carbon-13 NMR spectroscopic measurements have been performed for high-spin manganese(III) porphyrins to evaluate effects of axial ligand binding and to correlate isotropic shift patterns with d-orbital occupation. A qualitative description of unpaired spin delocalization mechanisms is offered. No particular ordering of resonances is apparent for F-, Cl-, and I- adducts, but absolute shift values for the F- complex are larger and approach those for the stronger field 4-methylpyridine ligand. Resonances for α-pyrrole carbon atoms are downfield and cover a range from 383 to 492 ppm. Corresponding β-pyrrole carbon signals are upfield in the region from -72 to -166 ppm. The meso carbon signal exhibits a small upfield shift, which increases in magnitude with 4-methylpyridine displacement of the halide ligand. Previously elucidated carbon-13 shift correlations are consistent with predominant unpaired π-spin density at β-pyrrole and meso carbon sites of manganese(III) porphyrins. Negative π-spin density at the meso carbon atom is to be contrasted with earlier Hu?ckel calculations that predict large positive spin density at this position. Deuterium NMR spectroscopy revealed large downfield shifts for α-and β-deuterium atoms of coordinated pyridine-d5. Corresponding carbon-13 signals are also far downfield. These observations are readily explained by transmission of σ-spin density from the singly occupied dz2 orbital to the axial pyridine ligand.
- Goff, Harold M.,Hansen, Andrew P.
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p. 321 - 326
(2008/10/08)
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- Isolation, Purification, and Characterization of Intermediate (Iodosylbenzene)metalloporphyrin Complexes from the (Tetraphenylporphinato)manganese(III)-Iodosylbenzene Catalytic Hydrocarbon Functionalization System
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A second-type of high-valent complex has been isolated from the reaction of (tetraphenylporphinato)manganese(III) derivatives, XMnIIITPP, with iodosylbenzene.This new type of complex, isolated from the XMnIIITPP-iodosylbenzene system
- Smegal, John A.,Schardt, Bruce C.,Hill, Craig L.
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p. 3510 - 3515
(2007/10/02)
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- Hydrocarbon Functionalization by the (Iodosylbenzene)manganese(IV) Porphyrin Complexes from the (Tetraphenylporphinato)manganese(III)-Iodosylbenzene Catalytic Hydrocarbon Oxidation System. Mechanism and Reaction Chemistry
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The two types of complexes isolated from the reaction of (tetraphenylporphinato)manganese(III) derivatives, XMnIIITPP, with iodosylbenzene - IVTPP(OIPh)>2O, 1, X = Cl- or Br-, and IVTPP>2O, 2, X = N3- - are capable of oxidizing alkane substrates in good yields at room temperature.Several lines of evidence establish the intermediacy of free alkyl radicals in the reactions of 1 and 2 with alkanes.Oxygen exchange with water in both the iodosyl (Mn-O-I) and μ-oxo (Mn-O-Mn) moieties of 1 suggests the formation of oxo manganese porphyrin complexes from these moieties.Hydrogen abstraction from the alkane substrate by an oxo manganese porphyrin intermediate is postulated to be mechanism for reaction of 1 and 2 with alkanes.Observation of a monomeric manganese(IV) porphyrin intermediate by EPR spectroscopy during the reactions of 1 with alkanes is consistent with the formation of a hydroxymanganese(IV) porphyrin complex resulting from substrate hydrogen abstraction by an oxo intermediate.The formation of RX product from oxidation of RH by 1 has been determined to result from ligand-transfer oxidation of free alkyl radicals by the porphyrin complexes in solution.Through competition reactions and time-dependent product formation studies, ligand-transfer oxidation by XMnIIITPP was found to be the major pathway for RX production.Observation of MnIITPP by EPR spectroscopy during the reactions of 1 with alkanes supports this conclusion.Formation of ROH product may result from ligand-transfer oxidation of free radicals or from the collapse of an intermediate caged radical pair.The mechanism of ROH product formation in the caged radical pair is postulated to be an outer-sphere electron-transfer process due to the expected slow rate of inner-sphere ligand transfer for the high-spin d3 hydroxymanganese(IV) porphyrin complex.Thus the ability of the substrate radical to undergo electron-transfer oxidation determines the ratio of radicals that undergo cage escape to give free radicals to radicals that undergo oxidation and subsequent formation of alcohol product in the caged species.Studies with tertiary substrates support these conclusions.
- Smegal, John A.,Hill, Craig L.
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p. 3515 - 3521
(2007/10/02)
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