A new metal-organic coordination polymer [Zn(pzdc)(mbix)]n·nH2O(H2pzdc = pyrazine-2,3- dicarboxylic acid, mbix = 1,3-bis(imidazol-1-ylmethyl)-benzene) 1 has been hydrothermally synthesized and structurall...A new metal-organic coordination polymer [Zn(pzdc)(mbix)]n·nH2O(H2pzdc = pyrazine-2,3- dicarboxylic acid, mbix = 1,3-bis(imidazol-1-ylmethyl)-benzene) 1 has been hydrothermally synthesized and structurally characterized by elemental analysis, IR, TG, fluorescence spectrum and single-crystal X-ray diffraction. Yellow crystals crystallize in monoclinic system, space group P21/n with a = 8.5519(6), b = 14.8764(10), c = 16.4108(11) A, β = 103.4520(10)o, V = 2030.5(2)A^3, C(20)H(18)N6O5Zn, Mr = 487.77, Dc = 1.596 g/cm^3, F(000) = 1000, Z = 4, μ(MoK α) = 1.257 mm^-1, the final R = 0.0260 and w R = 0.0706 for 3445 observed reflections(I 〉 2σ(I)). The structure of 1 exhibits a one-dimensional chain-like structure. In addition, natural bond orbital(NBO) analysis was performed by the PBE0/LANL2DZ method in Gaussian 03 Program. The calculation results show obvious covalent interaction between the coordinated atoms and Zn(Ⅱ) ion.展开更多
On the basis of energy and shape method for the determination of the valence bond ( VB ) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole ...On the basis of energy and shape method for the determination of the valence bond ( VB ) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is ec^29907. (sc^0.4980 + dc^2.4927) ef^1.0098 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.展开更多
The valence bond structure of substitutional BCC based Ta-W alloys is studied using characteristic crystal (CC) theory. This theory is based on cluster statistics of random alloys. By studying the correlativity betw...The valence bond structure of substitutional BCC based Ta-W alloys is studied using characteristic crystal (CC) theory. This theory is based on cluster statistics of random alloys. By studying the correlativity between energy and volume of the CC in Ta- W alloys, the valence bond structure of CC is determined by the energy and shape method. Then, following additive law of CC, the valence bond structure of Ta-W alloys is calculated. It is found that the outer shell valence electronic distribution of Ta-W Mloys shows a continuous change in the whole composition range. The covalent electrons ec (dc, sc, and pc) increase, whereas near free electrons ef decrease with increasing W concentration. The bond length and single-bond radius decrease, whereas bond energy and bond valence increase with increasing W concentration. The mechanism of solid solution strengthening of Ta-W alloys is analyzed based on their valence bond structure.展开更多
Influence of aluminum addition on the structures and properties of SiO_2-B_2O_3-Al_2O_3-CaO vitrified bond at low sintering temperature and high strength was discussed. FTIR and XRD analyses were used to characterize ...Influence of aluminum addition on the structures and properties of SiO_2-B_2O_3-Al_2O_3-CaO vitrified bond at low sintering temperature and high strength was discussed. FTIR and XRD analyses were used to characterize the structures of the basic vitrified bond with different contents of aluminum. The bending strength and the thermal expansion coefficients were also tested. Meanwhile, the microstructures of composite specimens at sintering temperature of 660 ℃ were observed by scanning electron microscope(SEM). The experimental results showed that the properties of vitrified bond with 1wt% aluminum were improved significantly, where the bending strength, Rockwell hardness, and thermal expansion coefficient of the vitrified bond reached 132 MPa, 63 HRB, and 6.73×10^(-6) ℃^(-1), respectively.展开更多
A convenient method of synthesizing a tripeptide-containing N-methyl group amino acid was developed using O-benzotriazole-N,N,N',N'-tetramethyluronium-hexafluorophosphate as the condensing agent. The crystals of tri...A convenient method of synthesizing a tripeptide-containing N-methyl group amino acid was developed using O-benzotriazole-N,N,N',N'-tetramethyluronium-hexafluorophosphate as the condensing agent. The crystals of tripeptide had white needles belonging to the orthorhombic space group P2_12_12_1. The conformational preference for homochiral tripeptides with one N-methylated amide bond was also investigated. Crystal-structure analysis showed that homochiral tripeptides with an internal N-methylated amide bond preferred a trans-amide form, thereby giving the peptide β-fold characteristics. Intermolecular C-H···O and N-H···O hydrogen bonds linked the molecules into a one-dimensional chain and stabilized the structure.展开更多
A new energetic dipotassium 3,3-dinitro-5,5-bis-1,2,4-triazole-1,1-diolate [K2(DNOBT)] was synthesized, and structurally characterized by elemental analysis, IR spectra, 13 C NMR and single-crystal X-ray diffraction...A new energetic dipotassium 3,3-dinitro-5,5-bis-1,2,4-triazole-1,1-diolate [K2(DNOBT)] was synthesized, and structurally characterized by elemental analysis, IR spectra, 13 C NMR and single-crystal X-ray diffraction. K2(DNOBT)·2H2O crystallizes in monoclinic system, space group P21/n with a=6.0446(10), b=15.999(3), c=6.4169(11) , β=99.421(2)°, V=612.21(18) 3, Z=4, Dc=2.009 g·cm(-3), F(000)=372, μ=0.838 mm(-1), S=1.012, the final R=0.0248 and w R(I 〉 2σ(I))=0.0604. Thermal decomposition of the title compound was studied by using DSC and TG-DTG, and there is primarily one exothermic decomposition process at 371.5 ℃.展开更多
A new coordination polymer, [Cd2(NIPH)(L)2(H2O)]n(1, HL = 3-(2-pyridyl)pyrazole and H2NIPH = 5-nitroisophthalic acid), has been synthesized. The structure of complex 1 has been characterized by X-ray single-...A new coordination polymer, [Cd2(NIPH)(L)2(H2O)]n(1, HL = 3-(2-pyridyl)pyrazole and H2NIPH = 5-nitroisophthalic acid), has been synthesized. The structure of complex 1 has been characterized by X-ray single-crystal diffraction, elemental analysis, IR spectrum analysis, thermogravimetric analysis and fluorescence spectrum analysis. Complex 1 belongs to the triclinic system, space group P1 with a = 8.9539(6), b = 11.6252(8), c = 12.2472(8) A^°, α = 80.011(2), β = 80.3850(10), γ = 86.773(2)°, V = 1237.37(14) A^°3, Z = 2, Dc = 1.987 g/cm^3, μ = 1.780 mm^-1, Mr = 740.25, F(000) = 724, the final R = 0.0295 and wR = 0.1015 with I 〉 2σ(I). Two H2NIPH as monodentate and bidentate ligands and two L ligands link four Cd(Ⅱ) ions to form a tetranuclear subunit. Each pair of the tetranuclear subunits is bridged by NIPH ligands to yield a one-dimensional double-chain structure. Furthermore, the 1D chains are linked into a 3D supramolecular framework with hydrogen bonds and π-π interactions. In addition, we analyzed Natural Bond Orbital(NBO) in using the PBE0/LANL2DZ method built in Gaussian 03 Program. The calculation results indicated the obvious covalent interaction between the coordinated atoms and Cd(Ⅱ) ion.展开更多
A series of lanthanide complexes LnCl_3·L(Ln=La,Pr,Nd;L=15-C-5 or 18-C-6)have been synthesized and their molecular configuration,electronic structure and bond character have been studied by XPS and quantum chemic...A series of lanthanide complexes LnCl_3·L(Ln=La,Pr,Nd;L=15-C-5 or 18-C-6)have been synthesized and their molecular configuration,electronic structure and bond character have been studied by XPS and quantum chemical calculation.The calculated results are in good agreement with that obtained in the experiments.Three Cl atoms are on the same side of Ln in LnCl_3·15-C-5 and the crown ring on the other side.forming a complex molecule with coordination number 8.LnCl_3·15-C-5 is easily hygroscopic in air because of its unsaturated coordination,which differs sharply from the stable Ln(NO_3)_3·15-C-5 com- plex of coordination number 11.The HOMO and neighboring occupied MOs are composed of Cl 3p and O2p, and the LUMO and neighboring unoccupied MOs are composed of Ln orbitals.The level structure easily pro- duces Ln3d satellite in XPS caused by L→Ln charge transfer transition.Due to the coordination,the absolute values of the charge are decreased at Ln and O atoms,but increased at Cl atoms,which is in agreement with XPS results.展开更多
The canonical and locatized molecutar orbiters of [NCCuS_2NoS_2]^(2-) cluster were calculated by means of CNDO quantum chemistry method. Then the energy and properties of corresponding chemicat bonds were discussed, e...The canonical and locatized molecutar orbiters of [NCCuS_2NoS_2]^(2-) cluster were calculated by means of CNDO quantum chemistry method. Then the energy and properties of corresponding chemicat bonds were discussed, especially, Cu-Sb-No three center conjugated π bonds and No-St-No conjugated π bonds were accounted for.展开更多
Ti-containing carbon films were deposited by using magnetron sputtering deposition. The composition and microstructure of the carbon films were characterized in detail by combining the techniques of Rutherford backsca...Ti-containing carbon films were deposited by using magnetron sputtering deposition. The composition and microstructure of the carbon films were characterized in detail by combining the techniques of Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is found that carbon films contain Ti 18 at pct; after Ti incorporation, the films consist of titanium carbide; C1s peak appears at 283.4 eV and it could be divided into 283.29 and 284.55 eV, representing sp2 and sp3, respectively, and sp2 is superior to sp3. This Ti-containing film with dominating sp2 bonds is nanocomposites with nanocrystalline TiC clusters embedded in an amorphous carbon matrix, which could be proved by XRD and TEM.展开更多
The crystal of aconitine has been obtained through an unexpected spontaneous change of the solid power of aconitine in air and characterized by single-crystal X-ray diffraction analysis and elemental analysis. Crystal...The crystal of aconitine has been obtained through an unexpected spontaneous change of the solid power of aconitine in air and characterized by single-crystal X-ray diffraction analysis and elemental analysis. Crystallographic data: orthorhombic, space group P2_12_12_1 with a = 17.0745(6), b = 15.5990(6), c = 12.2443(6) ?, V = 3261.2(2) ?~3, Z = 4, C_(34)H_(47)NO_(11), M_r = 645.73, D_c = 1.315 g/cm^3, F(000) = 1384, μ(MoKa) = 0.098 mm^(-1), R = 0.0605 and wR = 0.1311. Aconitine is diester diterpenoid alkaloid, and its main structure is composed of four six-membered and two five-membered rings. The intramolecular and intermolecular O–H···O and C–H···O hydrogen bonds extend the adjacent molecules into a one-dimensional chain and a two-dimensional framework, which may be the essential reason for the change.展开更多
One new polymer, [Na(NPHSNPAB)(CH3OH)]n, where NPHSNPAB stands for Nphenyl-2-[2-hydroxy-3-sulfo-5-nitrophenylhydrazone]butadione-1,3, has been synthesized and characterized by ^1H NMR and FTIR spectroscopy and sin...One new polymer, [Na(NPHSNPAB)(CH3OH)]n, where NPHSNPAB stands for Nphenyl-2-[2-hydroxy-3-sulfo-5-nitrophenylhydrazone]butadione-1,3, has been synthesized and characterized by ^1H NMR and FTIR spectroscopy and single-crystal X-ray diffraction. For this complex: C(17)H(17)N4NaO9S, Mr = 476.39, triclinic system, space group P1, a = 8.8741(18), b = 10.942(2), c = 12.039(2) A, α = 65.74(3), β = 77.49(3), γ = 84.30(3)o, V = 1040.3(4) A3, Z = 2, Dc = 1.521 g/cm^3, λ = 0.71073 A, F(000) = 492, S = 1.106, R = 0.0614 and w R = 0.1423 for 2945 observed reflections with I 〉 2(I). X-ray structural analysis revealed that the structure of NPHSNPAB framework was almost planar by C–H···O, N–H···O, O–H···O, and O–H···S hydrogen bonds. Moreover, sodium(I) center was bound by six O and one N atoms, forming the coordination polymer. The molecular packing diagram showed complicated hydrogen bonds and π···π stacking interaction in the polymer. The average bond distance of the two dicyclic units(3.768 A) indicated strong π···π stacking interaction. The complex displays greenyellow emission at room temperature.展开更多
A new Co(ll) coordination polymer has been successfully synthesized under hydrothermal conditions [Co(C2O4)(mbix)]n (1, H2C2O4 = oxalic acid, mbix = 1,3-bis(imidazol- l-ylmethyl)benzene). Its structure has b...A new Co(ll) coordination polymer has been successfully synthesized under hydrothermal conditions [Co(C2O4)(mbix)]n (1, H2C2O4 = oxalic acid, mbix = 1,3-bis(imidazol- l-ylmethyl)benzene). Its structure has been determined by elemental analyses, IR, UV spectroscopy and single-crystal X-ray diffraction analysis. Pink crystals crystallize in the triclinic system, space group PI with a = 8.8666(7), b = 9.5859(8), c = 10,8537(9) A,α = 67.6810(10),β= 66.1260(10), γ = 77.1300(10)°, V= 777.77(11), CI6HI4CoN404, Mr = 385.24, Dc = 1.645 g/cm3, F(000) = 394, Z= 2,/z(MoKa) = 1.134 mm% the final R = 0.0482 and wR = 0.1231 for 2968 observed reflections (I〉 2σ(I)). It shows a two-dimensional (2D) network structure. The intermolecular C-H…O hydrogen bonding and π-π stacking interactions extend complex 1 into a 3D supramolecular architecture and play an important role in stabilizing 1. In addition, Natural Bond Orbital (NBO) analysis was performed by using the PBE0/LANL2DZ method built in Gaussian 09 Program. The calculation results showed obvious covalent interaction between the coordinated atoms and Co(II) ion.展开更多
Two crystals of receptor 1, C(42)H(52)N(10)O4S2(anthracene-9,10-dicarbaldehyde bis-(phenyl-semithiocarbazone)) and-1-H2PO4, C(68)H(114)N(10)O(10)P2S2 were obtained at room temperature successfully, a...Two crystals of receptor 1, C(42)H(52)N(10)O4S2(anthracene-9,10-dicarbaldehyde bis-(phenyl-semithiocarbazone)) and-1-H2PO4, C(68)H(114)N(10)O(10)P2S2 were obtained at room temperature successfully, and their structures were characterized by X-ray crystallography diffraction. X-ray diffraction reveals that, receptor 1 crystallizes in monoclinic, space group P21/c, with a = 9.487(3),b = 20.674(6), c = 11.821(4)A, β = 113.416(8)o, Mr = 825.06, V = 2127.5(12) A^3, Z = 2, Dc = 1.288g/cm^3, μ = 0.18 mm^-1, F(000) = 876, MoK α radiation(λ = 0.71073 A), the final R = 0.0472 and wR = 0.0930. A total of 3758 unique reflections were collected, of which 3313 with I 〉 2σ(I) were observed. Compound 1-H2PO4^-crystallizes in triclinic, space group P21/n, with a = 8.767(1), b =13.6190(15), c = 16.615(2) ?, α = 98.727(14), β = 103.061(14), γ = 91.382(16)°, Mr = 1357.75, V =1906.6(4) A^3, Z = 1, Dc = 1.183 g/cm^3, μ = 0.17 mm-(-1), F(000) = 734, MoK α radiation(λ = 0.71073?), the final R = 0.0769 and wR = 0.1884. A total of 6699 unique reflections were collected, of which 2989 with I 〉 2σ(I) were observed. As it was observed in the crystal structure of 1-H2PO4^-, 1bound H2PO4^-at a 1:2 ratio by intermolecular interaction of N-H···O hydrogen bond obviously.Another interesting feature was that H2PO4--groups assembled chains themselves via intramolecular hydrogen bond O-H···O and connected the 1 molecules together through the interaction of H-bonds,which improved the planarity of 1 and increased the stability of the entire structure.展开更多
The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr2 Se4 at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity ex...The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr2 Se4 at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity experiments. With an increase in the magnetic field H, the antiferromagnetic transition temperature TN is observed to shift progressively toward lower temperatures. The corresponding high temperature cubic (Fd3m) to low temperature tetragonal (I41amd) structural transition is tuned simultaneously due to the inherent strong spin-lattice coupling. In the antiferromagnetic phase, an anomaly at Hc2 defined as a steep downward peak in the derivative of the M-H curve is dearly drawn. It is found that TN versus H and Hc2 versus T exhibit a consistent tendency, indicative of a field-induced tetragonal (I41amd) to cubic (Fd3m) structural transition. The transition is further substantiated by the field-dependent dielectric constant and thermal conductivity measurements. We modify the T-H phase diagram, highlighting the coexistence of the paramagnetic state and ferromagnetic clusters between 100K and TN.展开更多
A new three-dimensional nickel(Ⅱ) hydrogen-bonded molecular self assembly containing [(Ni(nicotinamide)2(thiocyanate)2(H2O)2] complex has been synthesized and characterized by single-crystal X-ray diffractio...A new three-dimensional nickel(Ⅱ) hydrogen-bonded molecular self assembly containing [(Ni(nicotinamide)2(thiocyanate)2(H2O)2] complex has been synthesized and characterized by single-crystal X-ray diffraction,FTIR spectroscopy,thermal analysis and magnetic measurements.Structural analysis reveals that the complex crystallizes in triclinic space group P1(crystal data a = 7.5574,b = 8.2683,c = 9.0056 A,α = 73.010,β = 69.698,γ = 66.51) and exhibits a distorted octahedral coordination sphere.Most interesting point in its structure is the involvement of sulphur atom of thiocyanate moiety in the trifurcated hydrogen bonding to build up the hydrogen-bonded self assembly.The magnetic behavior as determined by squid magnetometer(2~300 K temp.range) reveals dominating antiferromagnetic interaction followed by spin canting behavior below 20 K.展开更多
Various bond modes of the M-C(C5 ring) exist in metallocene compounds of group 14 heavier elements,mostly due to an intricate interaction between the lone electron pairs at the M center and the 6 p-electrons of the ...Various bond modes of the M-C(C5 ring) exist in metallocene compounds of group 14 heavier elements,mostly due to an intricate interaction between the lone electron pairs at the M center and the 6 p-electrons of the C5 ring.The tin(Ⅱ) metallocene complexes LSn R(L = HC[CMe(N-2,6-iPr2C6H3)]2,R = cyclopentadienyl,C5H5(1); indenyl,C9H7(2); fluorenyl,C(13)H9(3)) stabilized by the β-diketiminato ligand were prepared and utilized in the study on their solid and solution state structures.X-ray single-crystal diffraction data revealed an η~1-mode of the Sn-C(C5 ring) bond in each 1~3.However,the room temperature ~1H NMR spectral studies disclosed such a fluxional bonding mode in solution.The 119 Sn NMR studies suggested a quadruple coordination nature of the Sn center in 1 while the triple coordination manner was for the Sn atom in both 2 and 3.Then the variable-temperature(25~–75 ℃) ~1H NMR spectral studies for each 1~3 were performed,which detected the relaxation state structures of 1~3 at lower temperature.All of these results indicate a stereochemical activity of the lone electron pairs at the tin(Ⅱ) atom that definitely has an electronic interaction with the 6 p-electrons of the C5 ring.The observed Sn-C(C5 ring) bond modes appear influenced by either the metallocene size or the compound state existed.展开更多
Hydrogenated amorphous carbon(a-C:H)films are capable of providing excellent superlubricating properties,which have great potential serving as self-lubricating protective layer for mechanical systems in extreme workin...Hydrogenated amorphous carbon(a-C:H)films are capable of providing excellent superlubricating properties,which have great potential serving as self-lubricating protective layer for mechanical systems in extreme working conditions.However,it is still a huge challenge to develop a-C:H films capable of achieving robust superlubricity state in vacuum.The main obstacle derives from the lack of knowledge on the influencing mechanism of deposition parameters on the films bonding structure and its relation to their self-lubrication performance.Aiming at finding the optimized deposition energy and revealing its influencing mechanism on superlubricity,a series of highly-hydrogenated a-C:H films were synthesized with appropriate ion energy,and systematic tribological experiments and structural characterization were conducted.The results highlight the pivotal role of ion energy on film composition,nanoclustering structure,and bonding state,which determine mechanical properties of highly-hydrogenated a-C:H films and surface passivation ability and hence their superlubricity performance in vacuum.The optimized superlubricity performance with the lowest friction coefficient of 0.006 coupled with the lowest wear rate emerges when the carbon ion energy is just beyond the penetration threshold of subplantation.The combined growth process of surface chemisorption and subsurface implantation is the key for a-C:H films to acquire stiff nanoclustering network and high volume of hydrogen incorporation,which enables a robust near-frictionless sliding surface.These findings can provide a guidance towards a more effective manipulation of self-lubricating a-C:H films for space application.展开更多
A modern valence bond approach, namely bonded tableau unitary group approach, is applied to ozone, sulphur dioxide and nitrite systems, respectively. It is shown that the biradical structure is in the primary position...A modern valence bond approach, namely bonded tableau unitary group approach, is applied to ozone, sulphur dioxide and nitrite systems, respectively. It is shown that the biradical structure is in the primary position in descrbing the molecular structure of ozone. Thus three instead of two resonance structures are needed to describe the ground state of ozone. The case of sulphur dioxide is similar to that of ozone. It is found that, however, for the nitrite anion four resonance structures are needed.展开更多
Chiral supramolecules prepared by the additive-driven self-assembly of block copolymers provide a facile method to construct helical nanostructures. In this study, we investigated the chiral transfer from chiral tarta...Chiral supramolecules prepared by the additive-driven self-assembly of block copolymers provide a facile method to construct helical nanostructures. In this study, we investigated the chiral transfer from chiral tartaric acid to poly(styrene)-b-poly(ethylene oxide) using small-angle X-ray scattering,transmission electron microscopy, circular dichroism, and vibrational circular dichroism. The results showed that the chirality was transferred to both the segments of block copolymer irrespective of the interaction with the chiral additives and formation of helical phase structure. However, the chirality transfer was carried out using different methods: for poly(ethylene oxide) segments, the chirality transfer was carried out via direct hydrogen bond formation; for polystyrene segments, the chirality transfer was carried out via the cooperative motion of block copolymers during the thermal annealing.展开更多
基金supported by the Science and Technology Development Project of Jilin Provincial Science&Technology Department(201205080)the Science and Technology Research Projects of the Education Office of Jilin Province(No.2013.384)
文摘A new metal-organic coordination polymer [Zn(pzdc)(mbix)]n·nH2O(H2pzdc = pyrazine-2,3- dicarboxylic acid, mbix = 1,3-bis(imidazol-1-ylmethyl)-benzene) 1 has been hydrothermally synthesized and structurally characterized by elemental analysis, IR, TG, fluorescence spectrum and single-crystal X-ray diffraction. Yellow crystals crystallize in monoclinic system, space group P21/n with a = 8.5519(6), b = 14.8764(10), c = 16.4108(11) A, β = 103.4520(10)o, V = 2030.5(2)A^3, C(20)H(18)N6O5Zn, Mr = 487.77, Dc = 1.596 g/cm^3, F(000) = 1000, Z = 4, μ(MoK α) = 1.257 mm^-1, the final R = 0.0260 and w R = 0.0706 for 3445 observed reflections(I 〉 2σ(I)). The structure of 1 exhibits a one-dimensional chain-like structure. In addition, natural bond orbital(NBO) analysis was performed by the PBE0/LANL2DZ method in Gaussian 03 Program. The calculation results show obvious covalent interaction between the coordinated atoms and Zn(Ⅱ) ion.
基金supported by the National Natural Science Foundation of China(No.50271085).
文摘On the basis of energy and shape method for the determination of the valence bond ( VB ) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is ec^29907. (sc^0.4980 + dc^2.4927) ef^1.0098 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.
基金supported by Xiangtan University Doctor Research Foundation(GrantNo.08QDZ32)
文摘The valence bond structure of substitutional BCC based Ta-W alloys is studied using characteristic crystal (CC) theory. This theory is based on cluster statistics of random alloys. By studying the correlativity between energy and volume of the CC in Ta- W alloys, the valence bond structure of CC is determined by the energy and shape method. Then, following additive law of CC, the valence bond structure of Ta-W alloys is calculated. It is found that the outer shell valence electronic distribution of Ta-W Mloys shows a continuous change in the whole composition range. The covalent electrons ec (dc, sc, and pc) increase, whereas near free electrons ef decrease with increasing W concentration. The bond length and single-bond radius decrease, whereas bond energy and bond valence increase with increasing W concentration. The mechanism of solid solution strengthening of Ta-W alloys is analyzed based on their valence bond structure.
基金Funded by the National“Twelfth Five-Year”Plan for Science&Technology Support of China(2012BAA08B00)
文摘Influence of aluminum addition on the structures and properties of SiO_2-B_2O_3-Al_2O_3-CaO vitrified bond at low sintering temperature and high strength was discussed. FTIR and XRD analyses were used to characterize the structures of the basic vitrified bond with different contents of aluminum. The bending strength and the thermal expansion coefficients were also tested. Meanwhile, the microstructures of composite specimens at sintering temperature of 660 ℃ were observed by scanning electron microscope(SEM). The experimental results showed that the properties of vitrified bond with 1wt% aluminum were improved significantly, where the bending strength, Rockwell hardness, and thermal expansion coefficient of the vitrified bond reached 132 MPa, 63 HRB, and 6.73×10^(-6) ℃^(-1), respectively.
基金supported by the National Natural Science Foundation of China(No.21272052,21472034)Natural Science Foundation of Hebei Province(No.14272604D B2014208138)+1 种基金the Foundation of the Education Department of Hebei Province(No.ZH2012025,ZD2014017)National Basic Research Program of China(2011CB512007 and 2012CB723501)
文摘A convenient method of synthesizing a tripeptide-containing N-methyl group amino acid was developed using O-benzotriazole-N,N,N',N'-tetramethyluronium-hexafluorophosphate as the condensing agent. The crystals of tripeptide had white needles belonging to the orthorhombic space group P2_12_12_1. The conformational preference for homochiral tripeptides with one N-methylated amide bond was also investigated. Crystal-structure analysis showed that homochiral tripeptides with an internal N-methylated amide bond preferred a trans-amide form, thereby giving the peptide β-fold characteristics. Intermolecular C-H···O and N-H···O hydrogen bonds linked the molecules into a one-dimensional chain and stabilized the structure.
基金Financially supported by the National Natural Science Foundation of China(No.21373157)
文摘A new energetic dipotassium 3,3-dinitro-5,5-bis-1,2,4-triazole-1,1-diolate [K2(DNOBT)] was synthesized, and structurally characterized by elemental analysis, IR spectra, 13 C NMR and single-crystal X-ray diffraction. K2(DNOBT)·2H2O crystallizes in monoclinic system, space group P21/n with a=6.0446(10), b=15.999(3), c=6.4169(11) , β=99.421(2)°, V=612.21(18) 3, Z=4, Dc=2.009 g·cm(-3), F(000)=372, μ=0.838 mm(-1), S=1.012, the final R=0.0248 and w R(I 〉 2σ(I))=0.0604. Thermal decomposition of the title compound was studied by using DSC and TG-DTG, and there is primarily one exothermic decomposition process at 371.5 ℃.
基金supported by the Science and Technology Development Project of Jilin Provincial Science&Technology Department(201205080)the Science and Technology Research Projects of the Education Office of Jilin Province(No.2013.384)
文摘A new coordination polymer, [Cd2(NIPH)(L)2(H2O)]n(1, HL = 3-(2-pyridyl)pyrazole and H2NIPH = 5-nitroisophthalic acid), has been synthesized. The structure of complex 1 has been characterized by X-ray single-crystal diffraction, elemental analysis, IR spectrum analysis, thermogravimetric analysis and fluorescence spectrum analysis. Complex 1 belongs to the triclinic system, space group P1 with a = 8.9539(6), b = 11.6252(8), c = 12.2472(8) A^°, α = 80.011(2), β = 80.3850(10), γ = 86.773(2)°, V = 1237.37(14) A^°3, Z = 2, Dc = 1.987 g/cm^3, μ = 1.780 mm^-1, Mr = 740.25, F(000) = 724, the final R = 0.0295 and wR = 0.1015 with I 〉 2σ(I). Two H2NIPH as monodentate and bidentate ligands and two L ligands link four Cd(Ⅱ) ions to form a tetranuclear subunit. Each pair of the tetranuclear subunits is bridged by NIPH ligands to yield a one-dimensional double-chain structure. Furthermore, the 1D chains are linked into a 3D supramolecular framework with hydrogen bonds and π-π interactions. In addition, we analyzed Natural Bond Orbital(NBO) in using the PBE0/LANL2DZ method built in Gaussian 03 Program. The calculation results indicated the obvious covalent interaction between the coordinated atoms and Cd(Ⅱ) ion.
文摘A series of lanthanide complexes LnCl_3·L(Ln=La,Pr,Nd;L=15-C-5 or 18-C-6)have been synthesized and their molecular configuration,electronic structure and bond character have been studied by XPS and quantum chemical calculation.The calculated results are in good agreement with that obtained in the experiments.Three Cl atoms are on the same side of Ln in LnCl_3·15-C-5 and the crown ring on the other side.forming a complex molecule with coordination number 8.LnCl_3·15-C-5 is easily hygroscopic in air because of its unsaturated coordination,which differs sharply from the stable Ln(NO_3)_3·15-C-5 com- plex of coordination number 11.The HOMO and neighboring occupied MOs are composed of Cl 3p and O2p, and the LUMO and neighboring unoccupied MOs are composed of Ln orbitals.The level structure easily pro- duces Ln3d satellite in XPS caused by L→Ln charge transfer transition.Due to the coordination,the absolute values of the charge are decreased at Ln and O atoms,but increased at Cl atoms,which is in agreement with XPS results.
文摘The canonical and locatized molecutar orbiters of [NCCuS_2NoS_2]^(2-) cluster were calculated by means of CNDO quantum chemistry method. Then the energy and properties of corresponding chemicat bonds were discussed, especially, Cu-Sb-No three center conjugated π bonds and No-St-No conjugated π bonds were accounted for.
文摘Ti-containing carbon films were deposited by using magnetron sputtering deposition. The composition and microstructure of the carbon films were characterized in detail by combining the techniques of Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is found that carbon films contain Ti 18 at pct; after Ti incorporation, the films consist of titanium carbide; C1s peak appears at 283.4 eV and it could be divided into 283.29 and 284.55 eV, representing sp2 and sp3, respectively, and sp2 is superior to sp3. This Ti-containing film with dominating sp2 bonds is nanocomposites with nanocrystalline TiC clusters embedded in an amorphous carbon matrix, which could be proved by XRD and TEM.
基金Supported by the Scientific Research Project of Education Department of Shaanxi Provincial Government in 2014(No.14JK1045)the key project of Baoji University of Arts and Sciences in 2014(No.ZK14009)
文摘The crystal of aconitine has been obtained through an unexpected spontaneous change of the solid power of aconitine in air and characterized by single-crystal X-ray diffraction analysis and elemental analysis. Crystallographic data: orthorhombic, space group P2_12_12_1 with a = 17.0745(6), b = 15.5990(6), c = 12.2443(6) ?, V = 3261.2(2) ?~3, Z = 4, C_(34)H_(47)NO_(11), M_r = 645.73, D_c = 1.315 g/cm^3, F(000) = 1384, μ(MoKa) = 0.098 mm^(-1), R = 0.0605 and wR = 0.1311. Aconitine is diester diterpenoid alkaloid, and its main structure is composed of four six-membered and two five-membered rings. The intramolecular and intermolecular O–H···O and C–H···O hydrogen bonds extend the adjacent molecules into a one-dimensional chain and a two-dimensional framework, which may be the essential reason for the change.
基金supported by the Soft Science project of Shanxi Province(No.2013041020-03)the National Natural Science Foundation of China(No.51174275)
文摘One new polymer, [Na(NPHSNPAB)(CH3OH)]n, where NPHSNPAB stands for Nphenyl-2-[2-hydroxy-3-sulfo-5-nitrophenylhydrazone]butadione-1,3, has been synthesized and characterized by ^1H NMR and FTIR spectroscopy and single-crystal X-ray diffraction. For this complex: C(17)H(17)N4NaO9S, Mr = 476.39, triclinic system, space group P1, a = 8.8741(18), b = 10.942(2), c = 12.039(2) A, α = 65.74(3), β = 77.49(3), γ = 84.30(3)o, V = 1040.3(4) A3, Z = 2, Dc = 1.521 g/cm^3, λ = 0.71073 A, F(000) = 492, S = 1.106, R = 0.0614 and w R = 0.1423 for 2945 observed reflections with I 〉 2(I). X-ray structural analysis revealed that the structure of NPHSNPAB framework was almost planar by C–H···O, N–H···O, O–H···O, and O–H···S hydrogen bonds. Moreover, sodium(I) center was bound by six O and one N atoms, forming the coordination polymer. The molecular packing diagram showed complicated hydrogen bonds and π···π stacking interaction in the polymer. The average bond distance of the two dicyclic units(3.768 A) indicated strong π···π stacking interaction. The complex displays greenyellow emission at room temperature.
基金supported by the Science and Technology Development Project of Jilin Provincial Science&Technology Department(201205080)the Science and Technology Research Projects of the Education Office of Jilin Province(No.2013.384)
文摘A new Co(ll) coordination polymer has been successfully synthesized under hydrothermal conditions [Co(C2O4)(mbix)]n (1, H2C2O4 = oxalic acid, mbix = 1,3-bis(imidazol- l-ylmethyl)benzene). Its structure has been determined by elemental analyses, IR, UV spectroscopy and single-crystal X-ray diffraction analysis. Pink crystals crystallize in the triclinic system, space group PI with a = 8.8666(7), b = 9.5859(8), c = 10,8537(9) A,α = 67.6810(10),β= 66.1260(10), γ = 77.1300(10)°, V= 777.77(11), CI6HI4CoN404, Mr = 385.24, Dc = 1.645 g/cm3, F(000) = 394, Z= 2,/z(MoKa) = 1.134 mm% the final R = 0.0482 and wR = 0.1231 for 2968 observed reflections (I〉 2σ(I)). It shows a two-dimensional (2D) network structure. The intermolecular C-H…O hydrogen bonding and π-π stacking interactions extend complex 1 into a 3D supramolecular architecture and play an important role in stabilizing 1. In addition, Natural Bond Orbital (NBO) analysis was performed by using the PBE0/LANL2DZ method built in Gaussian 09 Program. The calculation results showed obvious covalent interaction between the coordinated atoms and Co(II) ion.
基金supported by the China Postdoctoral Science Foundation(No.2014M551053)Natural Science Foundation of Hebei Province(No.B2015203124)Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education),Nankai University
文摘Two crystals of receptor 1, C(42)H(52)N(10)O4S2(anthracene-9,10-dicarbaldehyde bis-(phenyl-semithiocarbazone)) and-1-H2PO4, C(68)H(114)N(10)O(10)P2S2 were obtained at room temperature successfully, and their structures were characterized by X-ray crystallography diffraction. X-ray diffraction reveals that, receptor 1 crystallizes in monoclinic, space group P21/c, with a = 9.487(3),b = 20.674(6), c = 11.821(4)A, β = 113.416(8)o, Mr = 825.06, V = 2127.5(12) A^3, Z = 2, Dc = 1.288g/cm^3, μ = 0.18 mm^-1, F(000) = 876, MoK α radiation(λ = 0.71073 A), the final R = 0.0472 and wR = 0.0930. A total of 3758 unique reflections were collected, of which 3313 with I 〉 2σ(I) were observed. Compound 1-H2PO4^-crystallizes in triclinic, space group P21/n, with a = 8.767(1), b =13.6190(15), c = 16.615(2) ?, α = 98.727(14), β = 103.061(14), γ = 91.382(16)°, Mr = 1357.75, V =1906.6(4) A^3, Z = 1, Dc = 1.183 g/cm^3, μ = 0.17 mm-(-1), F(000) = 734, MoK α radiation(λ = 0.71073?), the final R = 0.0769 and wR = 0.1884. A total of 6699 unique reflections were collected, of which 2989 with I 〉 2σ(I) were observed. As it was observed in the crystal structure of 1-H2PO4^-, 1bound H2PO4^-at a 1:2 ratio by intermolecular interaction of N-H···O hydrogen bond obviously.Another interesting feature was that H2PO4--groups assembled chains themselves via intramolecular hydrogen bond O-H···O and connected the 1 molecules together through the interaction of H-bonds,which improved the planarity of 1 and increased the stability of the entire structure.
基金Supported by the National Basic Research Program of China under Grant No 2011CBA00111the National Natural Science Foundation of China under Grant No U1332143
文摘The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr2 Se4 at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity experiments. With an increase in the magnetic field H, the antiferromagnetic transition temperature TN is observed to shift progressively toward lower temperatures. The corresponding high temperature cubic (Fd3m) to low temperature tetragonal (I41amd) structural transition is tuned simultaneously due to the inherent strong spin-lattice coupling. In the antiferromagnetic phase, an anomaly at Hc2 defined as a steep downward peak in the derivative of the M-H curve is dearly drawn. It is found that TN versus H and Hc2 versus T exhibit a consistent tendency, indicative of a field-induced tetragonal (I41amd) to cubic (Fd3m) structural transition. The transition is further substantiated by the field-dependent dielectric constant and thermal conductivity measurements. We modify the T-H phase diagram, highlighting the coexistence of the paramagnetic state and ferromagnetic clusters between 100K and TN.
文摘A new three-dimensional nickel(Ⅱ) hydrogen-bonded molecular self assembly containing [(Ni(nicotinamide)2(thiocyanate)2(H2O)2] complex has been synthesized and characterized by single-crystal X-ray diffraction,FTIR spectroscopy,thermal analysis and magnetic measurements.Structural analysis reveals that the complex crystallizes in triclinic space group P1(crystal data a = 7.5574,b = 8.2683,c = 9.0056 A,α = 73.010,β = 69.698,γ = 66.51) and exhibits a distorted octahedral coordination sphere.Most interesting point in its structure is the involvement of sulphur atom of thiocyanate moiety in the trifurcated hydrogen bonding to build up the hydrogen-bonded self assembly.The magnetic behavior as determined by squid magnetometer(2~300 K temp.range) reveals dominating antiferromagnetic interaction followed by spin canting behavior below 20 K.
基金supported by the National Natural Science Foundation of China(21473142 and 21673191)the National Innovative Research Team of China(IRT_14R31 and J1310024)
文摘Various bond modes of the M-C(C5 ring) exist in metallocene compounds of group 14 heavier elements,mostly due to an intricate interaction between the lone electron pairs at the M center and the 6 p-electrons of the C5 ring.The tin(Ⅱ) metallocene complexes LSn R(L = HC[CMe(N-2,6-iPr2C6H3)]2,R = cyclopentadienyl,C5H5(1); indenyl,C9H7(2); fluorenyl,C(13)H9(3)) stabilized by the β-diketiminato ligand were prepared and utilized in the study on their solid and solution state structures.X-ray single-crystal diffraction data revealed an η~1-mode of the Sn-C(C5 ring) bond in each 1~3.However,the room temperature ~1H NMR spectral studies disclosed such a fluxional bonding mode in solution.The 119 Sn NMR studies suggested a quadruple coordination nature of the Sn center in 1 while the triple coordination manner was for the Sn atom in both 2 and 3.Then the variable-temperature(25~–75 ℃) ~1H NMR spectral studies for each 1~3 were performed,which detected the relaxation state structures of 1~3 at lower temperature.All of these results indicate a stereochemical activity of the lone electron pairs at the tin(Ⅱ) atom that definitely has an electronic interaction with the 6 p-electrons of the C5 ring.The observed Sn-C(C5 ring) bond modes appear influenced by either the metallocene size or the compound state existed.
基金The authors would like to thank Dongzhou ZHAN for technological support during friction experiment.This work was supported by the National Natural Science Foundation of China(Nos.51925506,51975314,51935006,and 51527901).
文摘Hydrogenated amorphous carbon(a-C:H)films are capable of providing excellent superlubricating properties,which have great potential serving as self-lubricating protective layer for mechanical systems in extreme working conditions.However,it is still a huge challenge to develop a-C:H films capable of achieving robust superlubricity state in vacuum.The main obstacle derives from the lack of knowledge on the influencing mechanism of deposition parameters on the films bonding structure and its relation to their self-lubrication performance.Aiming at finding the optimized deposition energy and revealing its influencing mechanism on superlubricity,a series of highly-hydrogenated a-C:H films were synthesized with appropriate ion energy,and systematic tribological experiments and structural characterization were conducted.The results highlight the pivotal role of ion energy on film composition,nanoclustering structure,and bonding state,which determine mechanical properties of highly-hydrogenated a-C:H films and surface passivation ability and hence their superlubricity performance in vacuum.The optimized superlubricity performance with the lowest friction coefficient of 0.006 coupled with the lowest wear rate emerges when the carbon ion energy is just beyond the penetration threshold of subplantation.The combined growth process of surface chemisorption and subsurface implantation is the key for a-C:H films to acquire stiff nanoclustering network and high volume of hydrogen incorporation,which enables a robust near-frictionless sliding surface.These findings can provide a guidance towards a more effective manipulation of self-lubricating a-C:H films for space application.
基金State Major Key Project for Basic Researches also supported by the National Natural Science Foundation of China
文摘A modern valence bond approach, namely bonded tableau unitary group approach, is applied to ozone, sulphur dioxide and nitrite systems, respectively. It is shown that the biradical structure is in the primary position in descrbing the molecular structure of ozone. Thus three instead of two resonance structures are needed to describe the ground state of ozone. The case of sulphur dioxide is similar to that of ozone. It is found that, however, for the nitrite anion four resonance structures are needed.
基金supported by National Natural Science foundation of China(Nos.21374060 and 21574081)
文摘Chiral supramolecules prepared by the additive-driven self-assembly of block copolymers provide a facile method to construct helical nanostructures. In this study, we investigated the chiral transfer from chiral tartaric acid to poly(styrene)-b-poly(ethylene oxide) using small-angle X-ray scattering,transmission electron microscopy, circular dichroism, and vibrational circular dichroism. The results showed that the chirality was transferred to both the segments of block copolymer irrespective of the interaction with the chiral additives and formation of helical phase structure. However, the chirality transfer was carried out using different methods: for poly(ethylene oxide) segments, the chirality transfer was carried out via direct hydrogen bond formation; for polystyrene segments, the chirality transfer was carried out via the cooperative motion of block copolymers during the thermal annealing.