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1.
Nathalie Ségaud Elodie Anxolabéhère-Mallart Katell Sénéchal-David Laura Acosta-Rueda Marc Robert Frédéric Banse 《Chemical science》2015,6(1):639-647
Recent efforts to model the reactivity of iron oxygenases have led to the generation of nonheme FeIII(OOH) and FeIV(O) intermediates from FeII complexes and O2 but using different cofactors. This diversity emphasizes the rich chemistry of nonheme Fe(ii) complexes with dioxygen. We report an original mechanistic study of the reaction of [(TPEN)FeII]2+ with O2 carried out by cyclic voltammetry. From this FeII precursor, reaction intermediates such as [(TPEN)FeIV(O)]2+, [(TPEN)FeIII(OOH)]2+ and [(TPEN)FeIII(OO)]+ have been chemically generated in high yield, and characterized electrochemically. These electrochemical data have been used to analyse and perform simulation of the cyclic voltammograms of [(TPEN)FeII]2+ in the presence of O2. Thus, several important mechanistic informations on this reaction have been obtained. An unfavourable chemical equilibrium between O2 and the FeII complex occurs that leads to the FeIII-peroxo complex upon reduction, similarly to heme enzymes such as P450. However, unlike in heme systems, further reduction of this latter intermediate does not result in O–O bond cleavage. 相似文献
2.
Details of the reaction sequence used for the fluorimetric detection of phosphates by disassembly of transition metal Schiff base complexes were investigated for [FeIII(salen)(H2O)]+, [ZnII(salen)], [MnII(salen)(H2O)2], and [MnIII(salen)(H2O)]+. The reactivity of these compounds towards phosphorus oxoanions of differing charge, number of donor atoms and steric hindrance was detected by UV/Vis and fluorescence spectroscopy in both aprotic organic and aqueous media. Selectivity of [FeIII(salen)(H2O)]+ towards pyrophosphate over all other tested phosphorus-containing analytes was strongly supported. [ZnII(salen)] showed a faster reactivity but was much less selective. In contrast, [MnIII(salen)(H2O)]+ proved to be more stable than the iron complex but generally showed little reactivity towards phosphorus oxoanions. The influence of the charge of the central atom was investigated using the MnII analogue [MnII(salen)(H2O)2]. As expected, the reduced charge resulted in a reactivity comparable to the ZnII complex in organic solution but lead to hydrolysis of the complex in water. Finally, the reaction products of [FeIII(salen)(H2O)]+ with phosphates were characterized by IR spectroscopy and mass spectrometry, providing further insights into the reaction mechanism of the disassembly process. 相似文献
3.
Dr. Katharina Bleher Prof. Dr. Peter Comba Dr. Dieter Faltermeier Dr. Ashutosh Gupta Dr. Marion Kerscher Dr. Saskia Krieg Dr. Bodo Martin Dr. Gunasekaran Velmurugan Shuyi Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(4):e202103452
Oxidation of the iron(II) precursor [(L1)FeIICl2], where L1 is a tetradentate bispidine, with soluble iodosylbenzene (sPhIO) leads to the extremely reactive ferryl oxidant [(L1)(Cl)FeIV=O]+ with a cis disposition of the chlorido and oxido coligands, as observed in non-heme halogenase enzymes. Experimental data indicate that, with cyclohexane as substrate, there is selective formation of chlorocyclohexane, the halogenation being initiated by C−H abstraction and the result of a rebound of the ensuing radical to an iron-bound Cl−. The time-resolved formation of the halogenation product indicates that this primarily results from sPhIO oxidation of an initially formed oxido-bridged diiron(III) resting state. The high yield of up to >70 % (stoichiometric reaction) as well as the differing reactivities of free Fe2+ and Fe3+ in comparison with [(L1)FeIICl2] indicate a high complex stability of the bispidine-iron complexes. DFT analysis shows that, due to a large driving force and small triplet-quintet gap, [(L1)(Cl)FeIV=O]+ is the most reactive small-molecule halogenase model, that the FeIII/radical rebound intermediate has a relatively long lifetime (as supported by experimentally observed cage escape), and that this intermediate has, as observed experimentally, a lower energy barrier to the halogenation than the hydroxylation product; this is shown to primarily be due to steric effects. 相似文献
4.
Mechanistic Insight into the Nitric Oxide Dioxygenation Reaction of Nonheme Iron(III)–Superoxo and Manganese(IV)–Peroxo Complexes
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Dr. Seungwoo Hong Dr. Pankaj Kumar Dr. Kyung‐Bin Cho Dr. Yong‐Min Lee Prof. Dr. Kenneth D. Karlin Prof. Dr. Wonwoo Nam 《Angewandte Chemie (International ed. in English)》2016,55(40):12403-12407
Reactions of nonheme FeIII–superoxo and MnIV–peroxo complexes bearing a common tetraamido macrocyclic ligand (TAML), namely [(TAML)FeIII(O2)]2? and [(TAML)MnIV(O2)]2?, with nitric oxide (NO) afford the FeIII–NO3 complex [(TAML)FeIII(NO3)]2? and the MnV–oxo complex [(TAML)MnV(O)]? plus NO2?, respectively. Mechanistic studies, including density functional theory (DFT) calculations, reveal that MIII–peroxynitrite (M=Fe and Mn) species, generated in the reactions of [(TAML)FeIII(O2)]2? and [(TAML)MnIV(O2)]2? with NO, are converted into MIV(O) and .NO2 species through O?O bond homolysis of the peroxynitrite ligand. Then, a rebound of FeIV(O) with .NO2 affords [(TAML)FeIII(NO3)]2?, whereas electron transfer from MnIV(O) to .NO2 yields [(TAML)MnV(O)]? plus NO2?. 相似文献
5.
《Journal of Coordination Chemistry》2012,65(17):2893-2902
The complex [MnIV(napbh)2] (napbhH2 = N-(2-hydroxynaphthalen-1-yl)methylenebenzoylhydrazide) reacts with activated ruthenium(III) chloride in methanol in 1 : 1.2 molar ratio under reflux, giving heterobimetallic complexes, [MnIV(napbh)2RuIIICl3(H2O)] · [RuIII(napbhH)Cl2(H2O)] reacts with Mn(OAc)2·4H2O in methanol in 1 : 1.2 molar ratio under reflux to give [RuIII(napbhH)Cl2(H2O)MnII(OAc)2]. Replacement of aquo in these heterobimetallic complexes has been observed when the reactions are carried out in the presence of pyridine (py), 3-picoline (3-pic), or 4-picoline (4-pic). The molar conductances for these complexes in DMF indicates 1 : 1 electrolytes. Magnetic moment values suggest that these heterobimetallic complexes contain MnIV and RuIII or RuIII and MnII in the same structural unit. Electronic spectral studies suggest six coordinate metal ions. IR spectra reveal that the napbhH2 ligand coordinates in its enol form to MnIV and bridges to RuIII and in the keto form to RuIII and bridging to MnII. 相似文献
6.
The oxidation of transition metals such as manganese and copper by dioxygen (O2) is of great interest to chemists and biochemists for fundamental and practical reasons. In this report, the O2 reactivities of 1:1 and 1:2 mixtures of [(TPP)MnII] (1; TPP: Tetraphenylporphyrin) and [(tmpa)CuI(MeCN)]+ (2; TMPA: Tris(2-pyridylmethyl)amine) in 2-methyltetrahydrofuran (MeTHF) are described. Variable-temperature (−110 °C to room temperature) absorption spectroscopic measurements support that, at low temperature, oxygenation of the (TPP)Mn/Cu mixtures leads to rapid formation of a cupric superoxo intermediate, [(tmpa)CuII(O2•–)]+ (3), independent of the presence of the manganese porphyrin complex (1). Complex 3 subsequently reacts with 1 to form a heterobinuclear μ-peroxo species, [(tmpa)CuII–(O22–)–MnIII(TPP)]+ (4; λmax = 443 nm), which thermally converts to a μ-oxo complex, [(tmpa)CuII–O–MnIII(TPP)]+ (5; λmax = 434 and 466 nm), confirmed by electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy. In the 1:2 (TPP)Mn/Cu mixture, 4 is subsequently attacked by a second equivalent of 3, giving a bis-μ-peroxo species, i.e., [(tmpa)CuII−(O22−)−MnIV(TPP)−(O22−)−CuII(tmpa)]2+ (7; λmax = 420 nm and δpyrrolic = −44.90 ppm). The final decomposition product of the (TPP)Mn/Cu/O2 chemistry in MeTHF is [(TPP)MnIII(MeTHF)2]+ (6), whose X-ray structure is also presented and compared to literature analogs. 相似文献
7.
Karunanithi Anandababu Ramamoorthy Ramasubramanian Prof. Dr. Hubert Wadepohl Prof. Dr. Peter Comba Neethinathan Johnee Britto Prof. Dr. Madhavan Jaccob Prof. Dr. Ramasamy Mayilmurugan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(40):9540-9547
The iron(II) complexes [Fe(L)(MeCN)3](SO3CF3)2 (L are two derivatives of tris(2-pyridyl)-based ligands) have been synthesized as models for cysteine dioxygenase (CDO). The molecular structure of one of the complexes exhibits octahedral coordination geometry and the Fe−Npy bond lengths [1.953(4)–1.972(4) Å] are similar to those in the Cys-bound FeII-CDO; Fe−NHis: 1.893–2.199 Å. The iron(II) centers of the model complexes exhibit relatively high FeIII/II redox potentials (E1/2=0.988–1.380 V vs. ferrocene/ferrocenium electrode, Fc/Fc+), within the range for O2 activation and typical for the corresponding nonheme iron enzymes. The reaction of in situ generated [Fe(L)(MeCN)(SPh)]+ with excess O2 in acetonitrile (MeCN) yields selectively the doubly oxygenated phenylsulfinic acid product. Isotopic labeling studies using 18O2 confirm the incorporation of both oxygen atoms of O2 into the product. Kinetic and preliminary DFT studies reveal the involvement of an FeIII peroxido intermediate with a rhombic S= FeIII center (687–696 nm; g≈2.46–2.48, 2.13–2.15, 1.92–1.94), similar to the spectroscopic signature of the low-spin Cys-bound FeIIICDO (650 nm, g≈2.47, 2.29, 1.90). The proposed FeIII peroxido intermediates have been trapped, and the O−O stretching frequencies are in the expected range (approximately 920 and 820 cm−1 for the alkyl- and hydroperoxido species, respectively). The model complexes have a structure similar to that of the enzyme and structural aspects as well as the reactivity are discussed. 相似文献
8.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(31):9219-9223
Ceric ammonium nitrate (CAN) or CeIV(NH4)2(NO3)6 is often used in artificial water oxidation and generally considered to be an outer‐sphere oxidant. Herein we report the spectroscopic and crystallographic characterization of [(N4Py)FeIII‐O‐CeIV(OH2)(NO3)4]+ ( 3 ), a complex obtained from the reaction of [(N4Py)FeII(NCMe)]2+ with 2 equiv CAN or [(N4Py)FeIV=O]2+ ( 2 ) with CeIII(NO3)3 in MeCN. Surprisingly, the formation of 3 is reversible, the position of the equilibrium being dependent on the MeCN/water ratio of the solvent. These results suggest that the FeIV and CeIV centers have comparable reduction potentials. Moreover, the equilibrium entails a change in iron spin state, from S =1 FeIV in 2 to S =5/2 in 3 , which is found to be facile despite the formal spin‐forbidden nature of this process. This observation suggests that FeIV=O complexes may avail of reaction pathways involving multiple spin states having little or no barrier. 相似文献
9.
Dr. Apparao Draksharapu Waqas Rasheed Dr. Johannes E. M. N. Klein Prof. Dr. Lawrence Que Jr. 《Angewandte Chemie (International ed. in English)》2017,56(31):9091-9095
Ceric ammonium nitrate (CAN) or CeIV(NH4)2(NO3)6 is often used in artificial water oxidation and generally considered to be an outer-sphere oxidant. Herein we report the spectroscopic and crystallographic characterization of [(N4Py)FeIII-O-CeIV(OH2)(NO3)4]+ ( 3 ), a complex obtained from the reaction of [(N4Py)FeII(NCMe)]2+ with 2 equiv CAN or [(N4Py)FeIV=O]2+ ( 2 ) with CeIII(NO3)3 in MeCN. Surprisingly, the formation of 3 is reversible, the position of the equilibrium being dependent on the MeCN/water ratio of the solvent. These results suggest that the FeIV and CeIV centers have comparable reduction potentials. Moreover, the equilibrium entails a change in iron spin state, from S=1 FeIV in 2 to S=5/2 in 3 , which is found to be facile despite the formal spin-forbidden nature of this process. This observation suggests that FeIV=O complexes may avail of reaction pathways involving multiple spin states having little or no barrier. 相似文献
10.
Singh Nand K. Kushawaha Surendra K. Ayyagari Archana 《Transition Metal Chemistry》2001,26(1-2):140-146
A new ligand, N-phenyl-N
-2-furanthiocarbohydrazide (HPhfth), and its complexes with VOIV, MnIII, FeIII, CoII, NiII, CuII and ZnII have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, i.r., n.m.r., u.v.–vis., mass and FAB mass spectral data. The room temperature e.s.r. spectra of the VOIV, FeIII and CuII complexes yield <g> values characteristic of square pyramidal VOIV, octahedral FeIII and square planar CuII, respectively. The NiII and CuII complexes semiconduct, but the ZnII complex is an insulator at room temperature. However, the conductivity increases as the temperature increases from 303–383 K, with a band gap of 0.21–1.01 eV. HPhfth and its soluble complexes have been screened against several bacteria and fungi. 相似文献
11.
Danick Reynard Dr. Sunny Maye Dr. Pekka Peljo Vimanshu Chanda Prof. Hubert H. Girault Dr. Solène Gentil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(32):7250-7257
The MnIII/MnII redox couple with a standard potential of +1.51 V versus the standard hydrogen electrode (SHE) has attracted interest for the design of V/Mn redox flow batteries (RFBs). However, MnIII disproportionation leads to a loss of capacity, an increase in pressure drop, and electrode passivation caused by the formation of MnO2 particles during battery cycling. In this work, the influence of TiIV or/and VV on MnIII stability in acidic conditions is studied by formulating four different electrolytes in equimolar ratios (Mn, Mn/Ti, Mn/V, Mn/V/Ti). Voltammetry studies have revealed an ECi process for MnII oxidation responsible for the electrode passivation. SEM and XPS analysis demonstrate that the nature and morphology of the passivating oxides layer depend strongly on the electrolyte composition. Spectroelectrochemistry highlights the stabilization effect of TiIV and VV on MnIII. At a comparable pH, the amount of MnIII loss through disproportionation is decreased by a factor of 2.5 in the presence of TiIV or/and VV. Therefore, VV is an efficient substitute for TiIV to stabilize the MnIII electrolyte for RFB applications. 相似文献
12.
Shreedhar N. Shetti A. Sitaramachandra Murty Gopal L. Tembe 《Transition Metal Chemistry》1993,18(5):467-472
Summary Complexes of the potentially tetradentate ligand isonitroso-acetylacetone dithiosemicarbazone (inbtH2) of formulae [Ti(inbtH2)Cl2]Cl2, [M(inbt)], where M = VIV O, MnII, NiII or ZnII, [M(inbtH2)X2], where M = CoII and X = Cl, or M = NiII and X = Cl, Br or I, and [M(inbtH2)Cl2]Cl, where M = CrIII or FeIII, have been prepared and characterized by physico-chemical and spectroscopic methods. In all the compounds the metal is coordinated by the thiocarbonyl sulphur and imine nitrogen, as revealed by i.r. studies. The n.m.r. spectra of the complexes of NiII and ZnII confirm coordination through nitrogen. Possible structures for the complexes are proposed. The Mössbauer spectrum of the FeIII complex is discussed. 相似文献
13.
The catalytic systems [(BPMEN)FeII(CH3CN)2](ClO4)2/H2O2/CH3OOH and [(TPA)FeII(CH3CN)2](ClO4)2/H2O2/CH3OOH, where BPMEN = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-1,2-diaminoethane and TPA = tris(2-pyridylmethyl)amine, provide selective olefin epoxidation. Proton NMR studies showed that the mononuclear iron(IV) oxo complexes [(L)FeIV=O]2+, with L = BPMEN or TPA, are present in the cited catalytic systems. These intermediates are the decomposition products of the acylperoxo complexes [(L)FeIII-O3CCH3]2+. Such a complex was observed by the 2H NMR technique at low temperatures. The [(L)FeIV=O]2+ and [(L)FeV=O]3+ oxo complexes are possible active species in the studied catalytic systems. 相似文献
14.
C. Robert Lucas Kamala Mitra Subhendu Biswas Shyamal Kumar Chattopadhyay Bibhutosh Adhikary 《Transition Metal Chemistry》2005,30(2):185-190
A series of mononuclear MnII and MnIV complexes of general formulae [MnL2(NCS)2] (1a–1d) and [Mn(L)2(NCS)2] (2a–2c) have been prepared where L are Schiff bases obtained by the condensation of pyridine-2-aldehyde with para-alkyl-substituted aniline, and L are the corresponding amide ligands. The room temperature magnetic susceptibility data of (1a–1d) indicate that MnII is in a high spin state. The cyclic voltammograms of (1a–1d) exhibit a one-electron quasi-reversible MnIIMnIII oxidation. A linear correlation has been found when E0[MnIII/MnII] is plotted against Hammett p parameters. X-ray crystallographic data of (1b) shows that the central MnII ion adopts a distorted octahedral geometry with six different Mn–N distances. Upon oxidation of MnII complexes (1b–1d) by H2O2, the corresponding MnIV complexes (2a–2c) were obtained, and the Schiff base ligands were oxidized to the corresponding amides. The lowest energy LMCT bands of these MnIV complexes correlate linearly with Hammett p parameters. The redox behavior of the MnIV complexes has been investigated by cyclic voltammetry. E.p.r. spectra of the MnII and MnIV complexes are also reported. 相似文献
15.
A comparative kinetic study of the reactions of two mixed valence manganese(III,IV) complexes with macrocyclic ligands, [L1MnIV(O)2MnIIIL1], 1 (L1 = 1,4,7,10‐tetraazacyclododecane) and [L2MnIV(O)2MnIIIL2], 2 (L2 = 1,4,8,11‐tetraazacyclotetradecane) with 2‐mercaptoethanol (RSH) has been carried out by spectrophotometry in aqueous buffer at (30 ± 0.1)°C. Rate of the reactions between the oxidants and the reductant was found to be negligibly slow with no systematic dependence on either redox partners. Externally added copper(II) (usually 5 × 10?7 mol dm?3), however, increases the rate of the reduction of 1 and 2 significantly. In the presence of catalytic amount of copper(II), the rate of the reaction is nearly proportional to [RSH] at lower concentration of the reductant but follows a saturation kinetics at higher concentration of the latter for the reaction between 1 and the thiol. Reaction rate was found to be strongly influenced by the variation of acidity of the medium and the observed kinetics suggests that the two reductant species ([Cu(RSH)]2+ and [Cu(RS)]+) are significant for the reaction between 1 and the thiol. The dependence of the rate on [RSH] for the reduction of 2 by the thiol was complex and rationalized considering two equilibria involving the catalyst (Cu2+) and the reductant. The pH rate profile suggests that both the μ‐O protonated [MnIII(O)(OH)MnIV] and the deprotonated [MnIII(O)2MnIV] forms of the oxidant 2 become important. The kinetic results presented in this study indicate the domination of outer‐sphere path. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 129–137, 2004 相似文献
16.
1-Isonicotinoyl-4-benzoyl-3-thiosemicarbazide (IBtsc) and its CrIII, MnII, FeIII, CoII, NiII, CuII and ZnII complexes have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, u.v.–vis., i.r., n.m.r. and FAB mass spectral data. The room temperature e.s.r. spectra of the CrIII, FeIII and CuII complexes yield values, characteristic of octahedral, tetrahedral and square-planar complexes, respectively. The Mössbauer spectra of [Fe(IBtsc-H)Cl2] at room temperature and at 78 K suggest the presence of high-spin FeIII. The NiII, CrIII and CuII complexes show semiconducting behaviour in the solid state, but the ZnII complex is an insulator at room temperature. IBtsc and its soluble complexes have been screened against several bacteria, fungi and tumour cell lines. 相似文献
17.
Dr. David Bengio Dr. Thomas Dumas Sylvie Arpigny Dr. Richard Husar Dr. Eric Mendes Dr. Pier Lorenzo Solari Dr. Michel L. Schlegel Dr. Daniel Schlegel Dr. Stéphane Pellet-Rostaing Prof. Philippe Moisy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(63):14385-14396
Separation processes based on room temperature ionic liquids (RTIL) and electrochemical refining are promising strategies for the recovery of lanthanides from primary ores and electronic waste. However, they require the speciation of dissolved elements to be known with accuracy. In the present study, Eu coordination and EuIII/EuII electrochemical behavior as a function of water content in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIm][NTf2]) was investigated using UV–visible spectrophotometry, time-resolved laser fluorescence spectroscopy, electrochemistry, and X-ray absorption spectroscopy. In situ measurements were performed in spectroelectrochemical cells. Under anhydrous conditions, EuIII and EuII were complexed by NTf2, forming Eu−O and Eu−(N,O) bonds with the anion sulfoxide function and N atoms, respectively. This complexation resulted in a greater stability of EuII, and in quasi-reversible oxidation–reduction with an E0’ potential of 0.18 V versus the ferrocenium/ferrocene (Fc+/Fc) couple. Upon increasing water content, progressive incorporation of water in the EuIII coordination sphere occurred. This led to reversible oxidation–reduction reactions, but also to a decrease in stability of the +II oxidation state (E0’=−0.45 V vs. Fc+/Fc in RTIL containing 1300 mm water). 相似文献
18.
Juan Chen Stepan Stepanovic Dr. Apparao Draksharapu Prof. Dr. Maja Gruden Prof. Dr. Wesley R. Browne 《Angewandte Chemie (International ed. in English)》2018,57(12):3207-3211
Non‐heme (L)FeIII and (L)FeIII‐O‐FeIII(L) complexes (L=1,1‐di(pyridin‐2‐yl)‐N,N‐bis(pyridin‐2‐ylmethyl)ethan‐1‐amine) underwent reduction under irradiation to the FeII state with concomitant oxidation of methanol to methanal, without the need for a secondary photosensitizer. Spectroscopic and DFT studies support a mechanism in which irradiation results in charge‐transfer excitation of a FeIII?μ‐O?FeIII complex to generate [(L)FeIV=O]2+ (observed transiently during irradiation in acetonitrile), and an equivalent of (L)FeII. Under aerobic conditions, irradiation accelerates reoxidation from the FeII to the FeIII state with O2, thus closing the cycle of methanol oxidation to methanal. 相似文献
19.
Dr. Matthias Tombers Jun. Prof. Dr. Jennifer Meyer Dr. Jonathan Meyer Dr. Arkadiusz Lawicki Dr. Vicente Zamudio-Bayer Dr. Konstantin Hirsch Prof. Dr. J. Tobias Lau Prof. Dr. Bernd von Issendorff Prof. Dr. Akira Terasaki Prof. Dr. Thomas A. Schlathölter Prof. Dr. Ronnie A. Hoekstra Dr. Sebastian Schmidt Prof. Dr. Annie K. Powell Dr. Eva Kessler Dr. Marc H. Prosenc Prof. Dr. Christoph van Wüllen Prof. Dr. Dr. Gereon Niedner-Schatteburg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(2):e202102592
The phenomenon of single molecule magnet (SMM) behavior of mixed valent Mn12 coordination clusters of general formula [MnIII8MnIV4O12(RCOO)16(H2O)4] had been exemplified by bulk samples of the archetypal [MnIII8MnIV4O12(CH3COO)16(H2O)4] (4) molecule, and the molecular origin of the observed magnetic behavior has found support from extensive studies on the Mn12 system within crystalline material or on molecules attached to a variety of surfaces. Here we report the magnetic signature of the isolated cationic species [Mn12O12(CH3COO)15(CH3CN)]+ (1) by gas phase X-ray Magnetic Circular Dichroism (XMCD) spectroscopy, and we find it closely resembling that of the corresponding bulk samples. Furthermore, we report broken symmetry DFT calculations of spin densities and single ion tensors of the isolated, optimized complexes [Mn12O12(CH3COO)15(CH3CN)]+ (1) , [Mn12O12(CH3COO)16] (2) , [Mn12O12(CH3COO)16(H2O)4] (3) , and the complex in bulk geometry [MnIII8MnIV4O12(CH3COO)16(H2O)4] (5) . The found magnetic fingerprints – experiment and theory alike – are of a remarkable robustness: The MnIV4 core bears almost no magnetic anisotropy while the surrounding MnIII8 ring is highly anisotropic. These signatures are truly intrinsic properties of the Mn12 core scaffold within all of these complexes and largely void of the environment. This likely holds irrespective of bulk packing effects. 相似文献
20.
Singh Nand K. Kushawaha Surendra K. Thomas Michael J. K. 《Transition Metal Chemistry》2000,25(6):648-658
A new potential tetradentate ligand, N-nicotinoyl-N-2-furanthiocarbohydrazide (H2Nfth), and its complexes with VOIV, MnII, FeII,III, CoII, NiII, CuII and ZnII have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, u.v.–vis, i.r., n.m.r., ES+ and FAB mass spectral data. The room temperature e.s.r spectra of the VOIV and FeIII complexes yield g values, characteristic of octahedral complexes. The Mössbauer spectra of [Fe(HNfth)2] and [Fe2(Nfth)3] at room temperature and at 78 K suggest the presence of high-spin iron(II) and iron(III), respectively. The complexes are electrically insulating at room temperature, however, their conductivities increase as the temperature increases from 333–383 K, with a band gap of 0.46–0.77 eV, indicating their semiconducting behaviour. H2Nfth and its soluble complexes have been screened against several bacteria and fungi. 相似文献