共查询到20条相似文献,搜索用时 453 毫秒
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Majeed Z Mondal KC Kostakis GE Lan Y Anson CE Powell AK 《Dalton transactions (Cambridge, England : 2003)》2010,39(20):4740-4743
Using glycerol (H?gly) as a primary ligand, the decanuclear aggregate [Mn(II)?Mn(III)?Dy?(μ?-OH)?(Hgly)?(H?gly)?-(PhCO?)??(H?O)?]·10CH?CN (1) has been synthesised; it has a structure built up from two Mn?Dy? heterocubane units linked through a central Dy?(μ-benzoate)? paddle-wheel dimer and shows slow relaxation of its magnetisation. 相似文献
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Kareis CM Lapidus SH Her JH Stephens PW Miller JS 《Journal of the American Chemical Society》2012,134(4):2246-2254
The aqueous reaction of Mn(II) and NaCN leads to the isolation of the 3-D Prussian blue analogue (PBA) Na(2)Mn[Mn(CN)(6)]·2H(2)O (1·H(2)O), which under careful dehydration forms 1. 1·H(2)O is monoclinic [P2(1)/n, a = 10.66744(32) ?, b = 7.60223(23) ?, c = 7.40713(22) ?, β = 92.4379(28)°], while 1 is rhombohedral [R ?3, a = 6.6166(2) ?, c = 19.2585(6) ?], and both structures are atypical for PBAs, which are typically face centered cubic. Most notably, the average ∠Mn-N-C angles are 165.3(3)° and 142.4(4)° for 1·H(2)O and 1, respectively, which are significantly reduced from linearity. This is attributed to the ionic nature of high-spin Mn(II) accommodating a reduced ∠Mn-N-C to minimize void space. Both 1 and 1·H(2)O magnetically order as ferrimagnets below their ordering temperature, T(c), of 58 and 30 K, respectively, as determined from the average of several independent methods. 1 and 1·H(2)O are hard magnets with 5 K coercive fields of 15,300 and 850 Oe, and remnant magnetizations of 9075 and 102 emu·Oe/mol, respectively. These data along with previous T(c)'s reported for related materials reveal that T(c) increases as the ∠Mn-N-C deviates further from linearity. Hence, the bent cyanide bridges play a crucial role in the superexchange mechanism by increasing the coupling via shorter Mn(II)···Mn(II) separations, and perhaps an enhanced overlap. 相似文献
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Romain S Rich J Sens C Stoll T Benet-Buchholz J Llobet A Rodriguez M Romero I Clérac R Mathonière C Duboc C Deronzier A Collomb MN 《Inorganic chemistry》2011,50(17):8427-8436
A new pentanuclear bis(triple-helical) manganese complex has been isolated and characterized by X-ray diffraction in two oxidation states: [{Mn(II)(μ-bpp)(3)}(2)Mn(II)(2)Mn(III)(μ-O)](3+) (1(3+)) and [{Mn(II)(μ-bpp)(3)}(2)Mn(II)Mn(III)(2)(μ-O)](4+) (1(4+)). The structure consists of a central {Mn(3)(μ(3)-O)} core of Mn(II)(2)Mn(III) (1(3+)) or Mn(II)Mn(III)(2) ions (1(4+)) which is connected to two apical Mn(II) ions through six bpp(-) ligands. Both cations have a triple-stranded helicate configuration, and a pair of enantiomers is present in each crystal. The redox properties of 1(3+) have been investigated in CH(3)CN. A series of five distinct and reversible one-electron waves is observed in the -1.0 and +1.50 V potential range, assigned to the Mn(II)(4)Mn(III)/Mn(II)(5), Mn(II)(3)Mn(III)(2)/Mn(II)(4)Mn(III), Mn(II)(2)Mn(III)(3)/Mn(II)(3)Mn(III)(2), Mn(II)Mn(III)(4)/Mn(II)(2)Mn(III)(3), and Mn(III)(5)/Mn(II)Mn(III)(4) redox couples. The two first oxidation processes leading to Mn(II)(3)Mn(III)(2) (1(4+)) and Mn(II)(2)Mn(III)(3) (1(5+)) are related to the oxidation of the Mn(II) ions of the central core and the two higher oxidation waves, close in potential, are thus assigned to the oxidation of the two apical Mn(II) ions. The 1(4+) and 1(5+) oxidized species and the reduced Mn(4)(II) (1(2+)) species are quantitatively generated by bulk electrolyses demonstrating the high stability of the pentanuclear structure in four oxidation states (1(2+) to 1(5+)). The spectroscopic characteristics (X-band electron paramagnetic resonance, EPR, and UV-visible) of these species are also described as well as the magnetic properties of 1(3+) and 1(4+) in solid state. The powder X- and Q-band EPR signature of 1(3+) corresponds to an S = 5/2 spin state characterized by a small zero-field splitting parameter (|D| = 0.071 cm(-1)) attributed to the two apical Mn(II) ions. At 40 K, the magnetic behavior is consistent for 1(3+) with two apical S = 5/2 {Mn(II)(bpp)(3)}(-) and one S = 2 noninteracting spins (11.75 cm(3) K mol(-1)), and for 1(4+) with three S = 5/2 noninteracting spins (13.125 cm(3) K mol(-1)) suggesting that the {Mn(II)(2)Mn(III)(μ(3)-O)}(5+) and {Mn(II)Mn(III)(2)(μ(3)-O)}(6+) cores behave at low temperature like S = 2 and S = 5/2 spin centers, respectively. The thermal behavior below 40 K highlights the presence of intracomplex magnetic interactions between the two apical spins and the central core, which is antiferromagnetic for 1(3+) leading to an S(T) = 3 and ferromagnetic for 1(4+) giving thus an S(T) = 15/2 ground state. 相似文献
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Structural and electronic properties of the λ-MnO(2)(001) surface are investigated applying density functional theory approach. The calculations show that all Mn ions at unreconstructed smooth surface preserve the +4 oxidation state observed in the bulk. Upon the λ-MnO(2)(001) reconstruction, one fourth of Mn ions at the surface undergo a change of the oxidation state from +4 to +3, although the reconstruction does not change the Mn coordination number with oxygen. This is accompanied with the filling of initially empty 3d(z(2) ) states localized on cations with one electron denoted by two neighboring O atoms. Although the reconstruction leads to an energy gain of 0.04 eV per surface unit cell, it is not a spontaneous process since it proceeds with an activation energy of 0.12 eV. 相似文献
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平衡电极电势实验确定了25℃,1.5 mol@L-1醋酸钾+醋酸-醋酐(3:l体积比)溶液中Mn(Ⅲ)/Mn(Ⅱ)的条件电极电势为0.719 V(vs SCE);采用电势扫描和旋转圆盘电极技术研究了醋酸-醋酐溶液中铂电极上Mn(Ⅲ)/Mn(Ⅱ)电对的阳极氧化动力学.结果表明:Mn(Ⅱ)阳极氧化成Mn(Ⅲ)的电极反应控制步骤属电荷传递过程,阳极传递系数β=0.347,交换电流密度ia=5.84×10-6A@cm-2,阳极标准反应速率常数ka=1.35 ×10-8m@s-1,Mn(Ⅱ)和OAc-的反应级数均为一级. 相似文献
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铂电极上醋酸-醋酐溶液中Mn(III)/Mn(II)电对研究 总被引:2,自引:0,他引:2
平衡电极电势实验确定了25 ℃, 1.5 mol•L-1醋酸钾+醋酸-醋酐(3:1体积比)溶液中Mn(III)/Mn(II)的条件电极电势为0.719 V(vs SCE);采用电势扫描和旋转圆盘电极技术研究了醋酸-醋酐溶液中铂电极上Mn(III)/Mn(II)电对的阳极氧化动力学. 结果表明:Mn(II)阳极氧化成Mn(III)的电极反应控制步骤属电荷传递过程, 阳极传递系数β=0.347,交换电流密度i0=5.84×10-6 A•cm-2,阳极标准反应速率常数ka=1.35×10-8 m•s-1, Mn(II)和OAc-的反应级数均为一级. 相似文献
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Evolved gas analysis?Cion-attachment mass spectrometry (EGA?CIAMS) indicates that Mn(CO)5 and Mn2(CO)9 free radicals are produced in the gas phase by pyrolysis of Mn2(CO)10 in an infrared image furnace. The Li+-adduct mass spectra of the pyrolysis products contained peaks at m/z 202 and 369 for Mn(CO)5Li+ and Mn2(CO)9Li+, respectively, providing direct evidence that d-metal complex radicals were formed in the furnace. We studied the effect of temperature on the rate of production of the radicals, and confirmed the presence of the compounds Mn(CO)5 and Mn2(CO)9, which were reported in earlier studies based on electron-impact mass spectrometry, electron spin resonance spectroscopy, and Fourier transform infrared spectroscopy. 相似文献
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Jeon IeR Ababei R Lecren L Li YG Wernsdorfer W Roubeau O Mathonière C Clérac R 《Dalton transactions (Cambridge, England : 2003)》2010,39(20):4744-4746
In an attempt to develop novel coordination networks of SMMs, a Cu(II) picolinate complex has been used to coordinate S(T) = 9 tetranuclear Mn-based SMMs resulting in an intriguing 2D framework exhibiting a magnet-like behavior at low temperature. 相似文献
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Rose-Munch F Marti A Cetiner D Tranchier JP Rose E 《Dalton transactions (Cambridge, England : 2003)》2011,40(7):1567-1575
First Suzuki-Miyaura coupling reactions applied to (η(5)-chloro-cyclohexadienyl)Mn(CO)3 complexes are described and lead to the syntheses of (η(5)-aryl-cyclohexadienyl)Mn(CO)3 and of cationic (η(6)-arene)Mn(CO)3 complexes after rearomatization. The structures of two of the new complexes have been investigated by X-ray diffraction study. 相似文献
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鲁米诺与K2S2O8在碱性介质中能产生稳定的化学发光信号,Mn2+对鲁米诺过硫酸钾体系的化学发光产生微弱的抑制作用,而Ag+能增强Mn2+对发光体系的抑制作用,据此建立测定了废水中微量Mn2+的流动注射化学发光分析方法。Mn2+的浓度在1.0×10-10~1.0×10-7mol/L范围内与相对发光强度(ΔI)呈良好的线性关系,检出限为1.0×10-12mol/L;对1.0×10-7mol/LMn2+进行11次平行测定,其相对标准偏差RSD为1.3%。方法已用于测定废水中Mn2+的含量。 相似文献
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催化荧光法测定痕量Mn(Ⅱ)的研究 总被引:3,自引:0,他引:3
利用Mn(Ⅱ)对高碘酸钾氧化还原型罗丹明B的催化作用,建立了荧光增强测定痕量锰的新方法,用初始速率法研究了最佳反应条件。在此条件下,方法的线性范围为0.08~2.0ng·ml~(-1),检出限为0.028ng·ml~(-1),方法直接用于化学试剂硫酸钾中锰的测定,结果满意。 相似文献
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催化光度法测定痕量Mn(Ⅱ)的研究——Mn(Ⅱ)-铍试剂Ⅲ-H_2O_2体系 总被引:2,自引:0,他引:2
研究了0.10mol·L~(-1)氨水介质中,Mn(Ⅱ)催化H_2O_2氧化铍试剂Ⅲ退色的反应,选择了最佳反应条件下。方法的检出限为2.0×10~(-10)g·ml~(-1),线性范围为0.4~20.0ng·ml~(-1)。本法简单灵敏、选择性较好,可直接测定茶叶中Mn(Ⅱ)含量。 相似文献
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《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1993,49(12):1801-1807
EPR of Mn(II)-doped single crystals of cis-catena-μ-sulphato-aquotris(imidazole)cadmium(II) has been studied in the temperature range 300-90 K. Mn(II) replaces Cd(II) substitutionally giving rise to two magnetically inequivalent sites. The large magnitude and high asymmetry component of the D-tensor is in accordance with the low symmetry of the substitutional site. Due to the non-first order nature of the spectrum all the work had to be carried out at Q-band frequency. Forbidden transitions corresponding to ΔmI = ± 1 and ±2 are observed for a number of orientations and their positions have been calculated by perturbation theory taking into account the second order admixtures due to cross terms in D and hyperfine coupling constant A. The spin—Hamiltonian parameters at 300 K are A = −83.5, D = −790.0, E = −80.4 (all in units of 10−4 cm−1) and g = 2.0014. 相似文献
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以改性玉米苞叶纤维为载体(MCF),负载Mn(II)和Fe(II)制备了Mn(II)-Fe(II)-MCF复合材料,催化H2O2氧化水中染料。通过傅立叶变换红外/近红外成像系统和扫描电子显微镜对其结构和形貌进行表征。实验结果表明:当染料浓度为10 mg·L-1,Mn(II)-Fe(II)-MCF用量为4 g·L-1,H2O2初始浓度为1.56 mmol·L-1,Mn(II)-Fe(II)-MCF对四种染料的催化效率明显不同。阳离子蓝X-GRRL(CBX-GRRL)降解效果最好,其次是甲基橙(MO)、次甲基蓝(MB)和罗丹明B(RhB)。对染料的氧化反应进行动力学分析,MO的降解反应为二级反应,CBX-GRRL、MB和RhB的降解反应均为一级反应。Mn(II)-Fe(II)-MCF适合催化氧化偶氮染料废水。 相似文献
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采用流动注射光度法对海水化学需氧量(CODMn,高锰酸盐指数)进行快速测定。实验以KMnO4作氧化剂,淀粉-KI作显色剂,葡萄糖作标准物质;对流动注射分析流路进行了设计,优化了反应圈长度、反应温度、反应物浓度、进样量、泵速等实验条件;并通过自动加热装置对反应器进行在线加热;在最优条件下,测定方法的线性范围为0~6mg·L-1(实际需氧量),最低检出限为0.13mg·L-1,实际海水测定时加标回收率在96%~104%范围内,对1mg·L-1的COD标准溶液进行了11次连续测定,相对标准偏差(RSD)为1.88%。该方法操作简单、方便、灵敏度高,用于海水实际样品分析时,其测定值与国标法测定值一致。 相似文献