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91.
Krzystek J Fiedler AT Sokol JJ Ozarowski A Zvyagin SA Brunold TC Long JR Brunel LC Telser J 《Inorganic chemistry》2004,43(18):5645-5658
A variety of physical methods has been used to probe the non-Kramers, S = 1, V(III) ion in two types of pseudooctahedral complexes: V(acac)(3), where acac = anion of 2,4-pentanedione, and VX(3)(thf)(3), where thf = tetrahydrofuran and X = Cl and Br. These methods include tunable frequency and high-field electron paramagnetic resonance (HFEPR) spectroscopy (using frequencies of approximately 95-700 GHz and fields up to 25 T) in conjunction with electronic absorption, magnetic circular dichroism (MCD), and variable-temperature variable-field MCD (VTVH-MCD) spectroscopies. Variable-temperature magnetic susceptibility and field-dependent magnetization measurements were also performed. All measurements were conducted on complexes in the solid state (powder or mull samples). The field versus sub-THz wave quantum energy dependence of observed HFEPR resonances yielded the following spin Hamiltonian parameters for V(acac)(3): D = +7.470(1) cm(-1); E = +1.916(1) cm(-1); g(x) = 1.833(4); g(y) = 1.72(2); g(z) = 2.03(2). For VCl(3)(thf)(3), HFEPR detected a single zero-field transition at 15.8 cm(-1) (474 GHz), which was insufficient to determine the complete set of spin Hamiltonian parameters. For VBr(3)(thf)(3), however, a particularly rich data set was obtained using tunable-frequency HFEPR, and analysis of this data set gave the folowing: D = -16.162(6) cm(-1); E = -3.694(4) cm(-1); g(x) = 1.86(1); g(y) = 1.90(1); g(z) = 1.710(4). Analysis of the VTVH-MCD data gave spin Hamiltonian parameters in good agreement with those determined by HFEPR for both V(acac)(3) and VBr(3)(thf)(3) and in rough agreement with the estimate for VCl(3)(thf)(3) (D approximately 10 cm(-1), |E/D| approximately 0.18), together with the finding that the value of D is negative for both thf complexes. The electronic structures of these V(III) complexes are discussed in terms of their molecular structures and the electronic transitions observed by electronic absorption and MCD spectroscopies. 相似文献
92.
Cronin L McGregor PA Parsons S Teat S Gould RO White VA Long NJ Robertson N 《Inorganic chemistry》2004,43(25):8023-8029
The "one-pot" synthesis and characterization of a large 28-mer macrocycle (H(4)L(2)) with oxamido units capable of complexing guest ions through oxygen or nitrogen donor atoms is reported. Single-crystal structure determination of H(8)L(2)(NO(3))(4) and (Cu(2)[H(2)L(2)](H(2)O)(2))(NO(3))(2) demonstrated that the macrocycle contains two sites capable of complexing two nitrate anions or two copper(II) ions, involving a large structural reorganization in the conformation of the macrocyclic framework on coordination of the copper(II) ions when compared to the nitrate. Electrochemical and magnetic susceptibility measurements on the dinuclear Cu(II) complex and the related mononuclear and trinuclear Cu(II) complexes derived from the related 14-mer macrocycle were carried out and illustrate the role of the oxamido groups in mediating metal-metal interaction and delocalization. 相似文献
93.
A.A. Baker J.B. Headridge S.R. Keown G.D. Long P.A. Vergnano M.I. Wilson 《Analytica chimica acta》1979
The extraction method with hydrogen, hitherto used to determine mobile nitrogen in steels over the temperature range 350–450°C, has been employed at higher temperatures to determine nitrogen bound as aluminium nitride, or as titanium nitride or carbonitride. In steels containing only silicon and titanium as deoxidizers, the nitrogen remaining after passage of hydrogen at 600 or 750°C is present as titanium nitride or carbonitride and can be determined by difference. In steels containing only silicon and aluminium as deoxidizers, the nitrogen remaining after passage of hydrogen at 600°C is present as aluminium nitride and can also be determined by difference. This was verified by determining the aluminium nitride indirectly. The nitrogen released from both the aluminium and titanium steels in hydrogen at 600°C probably results from dissociation of submicroscopic particles of manganese silicon nitride. 相似文献
94.
The cerium‐containing MCM‐41 (Ce‐MCM‐41) has been synthesized by direct hydrothermal method. The low‐angle XRD patterns revealed the typical five major peaks of MCM‐41 type hexagonal structures. The interplanar spacing d100 = 38.4 Å was obtained that can be indexed on a hexagonal unit cell parameter with ao = 44.3 Å which was larger than that of pure siliceous MCM‐41 (Si‐MCM‐41). Transmission electron micrograph shows the regular hexagonal array of uniform channel characteristics of MCM‐41. The BET surface area of Ce‐MCM‐41 was 840 m2/g, which is much reduced as compared to that of Si‐MCM‐41, with the pore size of 26.9 Å and mesopore volume of 0.78 cm3/g were measured by nitrogen adsorption‐desorption isotherm at 77 K. Along with the results, the synthesized Ce‐MCM‐41 exhibited a well‐ordered MCM‐41‐type mesoporous structure with the incorporation of cerium. Using Ce‐MCM‐41 as a support, the Rh (0.5 wt%) catalyst exhibited very high activity for the NO/CO reactions. 相似文献
95.
Two copper complexes [Cu(TTA)2(4,4′‐azpy)] (1) and [Cu‐(TTA)2(3,3′‐azpy)] (2) (HTTA = 1,1,1‐trifluoro‐3‐(2‐thenoyl)‐acetone, 4,4′‐azpy = 4,4′‐azobispyridine, 3,3′‐azpy = 3,3′‐azobispyridine) were synthesized and characterized. The crystal structures were determined by X‐ray diffraction analysis. The crystal 1 belongs to triclinic with space group P1 , a = 0.8515(2) nm, b = 0.9259(2) nm, c = 0.9468(2) nm, a = 66.126(9)°, β = 79.667(9)°, γ = 90.13(1)°, Z = 1, V = 0.6692(2) nm3, Dc = 3.425 g/cm3, γ = 2.113 mm?1, F(000) = 694, R1 = 0.0594, wR2 = 0.1499. The crystal 2 belongs to monoclinic with space group P21/c, a = 1.0661(2) nm, b = 1.4296(3) ran, c = 1.0041(3) nm, β = 114.50(3)°, V = 1.3926(5) nm3, Z = 2, Dc = 1.646 g/ cm3, μ = 1.015 mm?1, F(000) = 694, R1, = 0.0535, wR2 = 0.1113. In the crystals of complexes 1 and 2, the copper atoms have distorted octahedral symmetry. The two compounds possess very similar one‐dimensional linear chains linked through the rodlike 4,4′‐azpy ligands or 3,3′‐azpy ligands. 相似文献
96.
Qi‐Wei Zhang Yi‐Hang Wen Yun‐Long Feng 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(6):m255-m257
The title compound, [Zn2(C5H6O4)2(C13H14N2)]n or [Zn2(glu)2(bpp)]n, is a novel zinc polymer based on mixed flexible glutarate (glu) and 1,3‐di‐4‐pyridylpropane (bpp) ligands. The ZnII center has a distorted tetrahedral geometry and the central atom of the bpp ligand is located at a special site with a C2 axis passing through it. A layer is formed by Zn–glu bonding. Such layers are pillared by bpp ligands, forming a three‐dimensional framework with large channels. The inverted interpenetration of two three‐dimensional frameworks completes the molecular structure. 相似文献
97.
Preparation and Characterization of Microencapsulated Hexadecane Used for Thermal Energy Storage 总被引:3,自引:0,他引:3
GuangLongZOU ZhiChengTAN XiaoZhengLAN LiXianSUN TaoZHANG 《中国化学快报》2004,15(6):729-732
Polyurea microcapsules about 2.5μm in diameter containing phase change material for thermal energy storage application were synthesized and characterized by interfacial polycondensation method with toluene-2,4-diisocyanate and ethylenediamine as monomers in an emulsion system. Hexadecane was used as a phase change material and OP, which is nonionic surfactant, and used as an emulsifier. The chemical structure and thermal behavior of the microcapsules were investigated by FTIR and thermal analysis respectively. The results show encapsulated hexadecane has a good potential as a solar energy storage material. 相似文献
98.
Ye Xu Dr. Huifeng Yao Lijiao Ma Ling Hong Jiayao Li Qing Liao Yunfei Zu Jingwen Wang Mengyuan Gao Prof. Long Ye Prof. Jianhui Hou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9089-9095
Decreasing the energy loss is one of the most feasible ways to improve the efficiencies of organic photovoltaic (OPV) cells. Recent studies have suggested that non-radiative energy loss ( ) is the dominant factor that hinders further improvements in state-of-the-art OPV cells. However, there is no rational molecular design strategy for OPV materials with suppressed . Herein, taking molecular surface electrostatic potential (ESP) as a quantitative parameter, we establish a general relationship between chemical structure and intermolecular interactions. The results reveal that increasing the ESP difference between donor and acceptor will enhance the intermolecular interaction. In the OPV cells, the enhanced intermolecular interaction will increase the charge-transfer (CT) state ratio in its hybridization with the local exciton state to facilitate charge generation, but simultaneously result in a larger . These results suggest that finely tuning the ESP of OPV materials is a feasible method to further improve the efficiencies of OPV cells. 相似文献
99.
Octahedral coordination of molybdenum(III) is achieved by limiting the amount of cyanide available upon complex formation. Reaction of Mo(CF(3)SO(3))(3) with LiCN in DMF affords Li(3)[Mo(CN)(6)] x 6DMF (1), featuring the previously unknown octahedral complex [Mo(CN)(6)](3-). The complex exhibits a room-temperature moment of mu(eff) = 3.80 mu(B), and assignment of its absorption bands leads to the ligand field parameters Delta(o) = 24800 cm(-1) and B = 247 cm(-1). Further restricting the available cyanide in a reaction between Mo(CF(3)SO(3))(3) and (Et(4)N)CN in DMF, followed by recrystallization from DMF/MeOH, yields (Et(4)N)(5)[Mo(2)(CN)(11)] x 2DMF x 2MeOH (2). The dinuclear [Mo(2)(CN)(11)](5-) complex featured therein contains two octahedrally coordinated Mo(III) centers spanned by a bridging cyanide ligand. A fit to the magnetic susceptibility data for 2, gives J = -113 cm(-1) and g = 2.33, representing the strongest antiferromagnetic coupling yet observed through a cyanide bridge. Efforts to incorporate these new complexes in magnetic Prussian blue-type solids are ongoing. 相似文献
100.
The M?ssbauer effect spectra for a series of small [Fe(eta(5)-C(5)H(5))(CO)(x)()] substituted metallaborane complexes are reported, where x = 1 or 2. The pentaborane cage in compounds [Fe(eta(5)-C(5)H(5))(CO)(2)B(5)H(7)P(C(6)H(5))(2)] (1), [Fe(eta(5)-C(5)H(5))(CO)(2)B(5)H(8)] (2), and [(Fe(eta(5)-C(5)H(5))(CO)(2))(2)B(5)H(7)] (3) was found to act as a significantly better donor ligand than the ligands in a comparison group of previously reported [Fe(eta(5)-C(5)H(5))(CO)LX] complexes, where L = CO or PPh(3) and X = halide, pseudohalide, or alkyl ligands. These metallaborane complexes were found to most resemble their silyl analogues in M?ssbauer spectral parameters and the electronic distribution around the iron centers. In addition, the M?ssbauer data showed that the [&mgr;-2,3-(P(C(6)H(5))(2)B(5)H(7)](-) ligand was a superior donor to the corresponding unsubstituted [B(5)H(8)](-) ligand. The M?ssbauer spectral results for the metallaborane complexes studied were found to be in general agreement with the anticipated donor and accepting bonding considerations for the cage ligands based upon their infrared and (11)B NMR spectra and X-ray structural features. The M?ssbauer data for the [Fe(eta(5)-C(5)H(5))(CO)B(4)H(6)(P(C(6)H(5))(2))] (4) and [Fe(eta(5)-C(5)H(5))(CO)B(3)H(7)(P(C(6)H(5))(2))] (5) complexes, in comparison with compound 1, showed that as the borane cage becomes progressively smaller, it becomes a poorer donor ligand. A qualitative relationship was found between the observed M?ssbauer isomer shift data and the number of boron cage vertices for the structurally related [Fe(eta(5)-C(5)H(5))(CO)(x)B(y)H(z)P(C(6)H(5))(2)] complexes, where x = 1 or 2, y = 3-5, and z = 6 or 7. The X-ray crystallographic data for compounds 1, 2, 5, and [Fe(eta(5)-C(5)H(5))(CO)B(5)H(8)] (6) were also found to agree with the trends observed in the M?ssbauer spectra which showed that the s-electron density on the iron nucleus increases in the order 5 < 6 < 2 < 1. The X-ray crystal structure of complex 2 is also reported. Crystallographic data for 2: space group P2(1)/c (No. 14, monoclinic), a = 6.084(3) ?, b = 15.045(8) ?, c = 13.449(7) ?, beta = 99.69(5) degrees, V = 1213(1) ?(3), Z = 4 molecules/cell. 相似文献