O_2 SPECIES ON La_2O_3/MgO CATALYS FOR OXIDATIVE COUPLING OF METHANE AND ITS INTERACTION WITH CARBON DIOXIDE

The formation of O_2~- ions on La_2O_3/MgO Catalyst for oxidative cou-pling of methane and its interaction with CO_2 have been studied by EPR andFT-IR.The O_2~- ions with EPR parameters valued at g_(xx)=1.999,g_(yy)=2.018,g_n=2.061;A_(xx)=5.0G,A_(yy)=7.6G,are unstable at 573 K under vacuum.They could react with CO_2 at room temperature leading to the decrease of theirEPR signal intensities and the appearance of a new carbonate species with IRabsorption bands at 1628cm~(-1) and 1335 cm~(-1),in comparison with the CO_2 ab-sorption on the O_2~-free sample.It appears unlikely that the O_2~- ions are theactive oxygen species for the activation of methane.     

LIGAND FIELD PARAMETERS OF Nd~(3+) IN LASER CRYSTALS OF LiNdP_4O_(12)

A ligand—field calculation has been performed on laser crystal LiNdP_4O_(12) with C_(2v) point group. The parameters of ligand field of this crystal is obtained and discussed. The calculated Stark sublevels are in good agreement with the enperimental values within 6.7 cm~(-1).     

单晶Cr~(3+)/Na_3(AlMo_6O_(24)H_6)·8H_2O的EPR研究

本文研究了Na_3[CrMo_6O_(24)H_6]·8H_2O单晶磁性稀释在同构的Na_3[CrMo_6O_(24)H_6]·8H2O单晶后Cr(Ⅲ)离子在室温X波段的EPR波谱。从主轴平面上的EPR数据用最小二乘法获得了g张量的主值g_(ZZ)=1.904,g_(XX)=1.973,g_(YY)=1.933和零场分裂张量参数D=0.275cm~(-1),E=0.05cm~(-1)。根据这些实验参数,计算了磁场处在主轴平面上相对主轴的不同取向的磁性基态能级,并导出了主轴平面上EPR谱随磁场取向角度变化的等频曲线。这个计算曲线与主轴平面上实验数据曲线符合很好。     

Synthesis, Crystal Structure, and Properties of [Cu(tren)(im)Zn(tren)](ClO_4)_3·CH_3OH as a Model Compound of BESOD

This paper reports the synthesis,properties and crystal structure of the title model compound with the ESR parameters g_∥ =2.007,g_⊥=2.191, A_∥=0.0061 cm~(-1), and A_⊥=0.0114 cm~(-1). The crystal belongs to space group C_2~2-P2_1,a=8.924(2),b=11.590(4), c=16.356(6),β =91.40(2)°,Z=2.Cu(Ⅱ) and Zn(Ⅱ) are bridged by the imidazolate ring, with the distance of 5.84.The conductivity and electronic reflectance spectrum of the complex are described.pH dependence in an aqueous solution is also investigated by potentiometric titration, and fitted by a self-written computer program. The results indicate that the imidazolate bridge splits at the side facing Zn(Ⅱ) below pH 8.     

A new route to prepare the mixed oxo-ethylidynecapped trinuclear tungsten(Ⅳ)cluster and the crystal structure of H_2Na_3[W_3O(CCH_3)(O_2CCH_3)_6(H_2O)_3][H_2W_(12)O_(40)]·13.5H_2O

The synthesis and the structural characterization of the title compound H_2Na_3[W_3O(CCH_3)-(O_2CCH_3)_6(H_2O)_3][H_2W_(12)O_(40)]·13.5 H_2O are described.It is known that the mixed oxo-ethylidyne-capped tritungsten cluster can be obtained by Zn dust reduction of Na_2WO_4·2H_2O in acetic anhydride.The title compound has been characterized by X-ray diffraction,UV/VIS and ~1H NMR spectra.The tungsten atoms in the cluster cation and anion are in the oxidation states of W(IV)and W(VI)respectively.The crystal is rhombohedral with the space group R32,a=17.058(3),c=49.665(9),γ=120°,V=12516(9)~3,Z=6,final R=0.037 for 2071 reflections with I≥3σ(I).Boththe cluster cation and anion have a C_3 symmetry.The important interatomic distances in angstroms forthe cluster cation are:W—W,2.730(2);W—μ_3-O,2.00;W—O(carboxyl),2.12;W—O_t,2.18(2).     

CRYSTAL STRUCTURE OF 18-TUNGSTODIVANADATE ANION IN Na_2H_2[H_2V_2W_(18)O_(62)].12H_2O

The structure of Na_2H_2[H_2V_2W_(18)O_(62)]12H_2O has been determined by x-rayanalysis.The crystals are trigonal,space group R3m,with cell parametersa=37.613(11),c=12.972(7)A,V=15901(13)A~3,and Z=9.The structure model wasrefined by full-matrix least square to R=0.065 for 1702 reflections with F>4σ(F).The existence of the[H_2V_2W_(18)O_(62)]~(4-)heteropolyanion in the crystals has beenconfirmed.It is composed of two VO_4 tetrahedra and eighteen WO_6 octahedralinked to gve the Dawson-type structure.     

EXPERIMENTAL STUDY AND THEORETICAL INTERPR ETATION OF ELECTRONIC STRUCTURE OF CRYSTAL OF ETHYLENEDIAMINE COMPLEX OF NICKEL(Ⅱ)-SILVER(Ⅰ) THIOCYANATE

d-d electronic absorption spectrum of Ni(en)_3 [Ni (en)_2Ag_2(NCS)_6]·H_2O, ENST, was measured. Absorption bands are at 11,300, 13,150, 18,650, 23,000 and 28,700 cm~(-1). The electronic energy levels were calculated by means of ligand field theory. Its EPR spectrum was measured directly at 77 K without dilution with diamagnetic medium. Zero-field splitting and half-field transition were observed g=2.169±0.020, g= 2.164 ± 0.020 and |D|=0.095±0.003cm~(-1). This paper discusses synthetically and theoretically the experimental results of electronic structure and crystal structure of this complex crystal.     

MOLECULAR AND CRYSTAL STRUCTURES OF TETRANUCLEAR MOLYBDENUM CLUSTER[Mo_4(μ_3-O)_2O_4Cl_2(o-CH_3C_6H_4COO)~6]■

The new cluster[Mo_4(μ_3-O)_2O_4Cl_2(o-CH_3C_6H_4COO)_6]has been prepared by thereaction of molybdenum pentachloride and o-methylbenzoic acid.The crystal andmolecular structures were determined by the X-ray diffraction method.It crystallizesin the orthorhombic space group Pnna with cell parameters:Mr=1361.6,a=13.792(4),b=17.957(3),c=20.974(9) ,V=5194(2) ~3,Z=4,Dc=1.74/cm~3,F(OOO)=2704,μ(MoK )=11.0/cm,R=0.074.     

SYNTHESIS AND CHARACTERIZATION OF Co(Ⅱ) COMPLEX OF 14-MEMBERED HEXAAZA MACROCYCLIC LIGAND WITH AXIALLY COORDINATED BROMIDES

The macrocyclic ligand complex, [Co(C_(18)H_(18)N_6) Br_2]·1/2H_2O, has been synthesized by the template condensation of 2, 6-diacetylpyridine with hydrazine in the presence of cobalt (Ⅱ) dibromide and characterized by IR, ESR, electronic spectra and magnetic properties. Based on these data, the complex is proposed to be an approximate elongated octahedron with low spin state. The absorption bands of d-d transition are assigned, and the values of various ligand field parameters have been evaluated and are discussed in terms of their chemical utilities. ESR study on the complex has been carried out. The values of g(?)and g(?) have been determined. From ligand field parameter values and gvalues, μ_(eff)=2.06 BM has been obtained, which is consistent with the experimental value(2.04BM).     

Growth and Characterization of Crystal Nd_(0.06)Y_(0.94)Sr_6Sc(BO_3)_6

<正>The crystal of Nd0.06Y0.94Sr6Sc(BO3)6 with the dimensions up to 35 mm × 28 mm × 13 mm was grown by a top-seeded solution growth method from Li6B4O9 flux. The grown crystal was characterized by X-ray powder diffraction. The optical absorption of the crystal shows that it has a strong absorption band at 8070 A, and the absorption coefficient is 2.17cm-1 with a FWHM of 41 A, which can match with the wavelength of the diode-laser (LD) and is suitable for the LD pumping. Based on the Judd-Ofelt theory, the three parameters of line oscillator strength Ω(λ) (λ = 2, 4 and 6) of the Nd3+ion in the crystal were calculated as follows: Ω2= 1.194 × 10-20, Ω4= 4.186 × 10-20 and Ω6 = 3.351 × 10-20cm2, which are relatively larger. The results indicate that the crystal Nd0.06Y0.94Sr6Sc(BO3)6 may be a kind of high-efficient laser material for diode-pumped.     

Theoretical studies of the reactions of O(~3p) with halogenated methyl (Ⅰ)——Reaction mechanism of the O(~3p) CH_2Cl reaction

The reaction of O(~3P) with CH_2Cl radical has been studied using ab initio molecular orbital theory. G2 (MP2) method is used to calculate the geometrical parameters, vibrational frequencies and energies of various stationary points on the potential energy surface. The reaction mechanism is revealed. The addition of O(~3P) with CH_2Cl leads to the formation of an energy rich intermediate OCH_2Cl which can subsequently undergo decomposition or isomerization to the final products. The calculated heat of reaction for each channel is in agreement with the experimental value. The production of H CHClO and Cl CH_2O are predicted to be the major channels. The overall rate constants are calculated using transition state theory on the basis of ab initio data. The rate constant is pressure independent and exhibits negative temperature dependence at lower temperatures, in accordance with the experimental results.     

Synthesis,Fluorescence and Magnetic Properties of a New Europium(Ⅲ) Complex Eu(C_(14)H_9O_3)_2(C_(12)H_8N_2)_2(NO_3)

A new europium(III)complex Eu(C_(14)H_9O_3)_2(C_(12)H_8N_2)_2(NO_3)has been synthesized with 2-benzoylbenzoic acid and 1,10-phenanthroline as ligands.Crystal data for the complex are as follows:monoclinic,space group P2_1/c,a=9.6733(6),b=22.9521(14),c=19.7701(12)?,β=94.9800(10)o,V=4372.8(5)?~3,D_c=1.557 g/cm~3,Z=4,μ(Mo Kα)=1.501 mm~(-1),F(000)=2064,the final R=0.0214 and w R=0.0510.The Eu(III)ion is coordinated by ten atoms to give a bicapped square antiprism coordination geometry.The complex shows two intense fluorescence emission bands arising from the transitions of Eu~(3+):~5D_0→~7F_1(594 nm)and ~5D_0→~7F_2(618 nm).In addition,its X_(m )T decreases from 1.29767 cm~3?mol~(-1)?K at 300 K to 0.01531 cm~3?mol~(-1)?K at 2 K.     

MOLYBDENUM-IRON MIXED METAL CLUSTERS (Ⅰ)——THE SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF (η~5-C_5H_5)_2Mo_2Fe_2(μ_4-Te)(μ_3-Te)_2(CO)_6

The reaction of Fe_2(μ_3-Te)_2(CO)_9 with Mo_2(CO)_6(η~5-C_5H_5) affords the title compound. Its X-ray analysis shows a butterfly structure for the Mo_2Fe_2 core; the two molybdenum atoms occupy the hinge with a Mo—Mo bond distance of 2.819 and the two iron atoms are on the tops of the wings with an average Mo—Fe bond distance of 2.932(2). Each molybdenum is bonded to a Cp ring, and three CO ligands are terminally bonded to each iron atom. One tellurium atom quadruply bridges Mo_Fe_2 with Mo—Te(μ_4)=2.625(2). and Fe—Te(μ_4)=2.713(2). Two tellurium atoms triply bridge the two triangular Mo_2Fe faces with Mo—Te(μ_3)=2.678(1) and Fe—Te(μ_3)=2.513(3). The molecule has C_(2v) symmetry and a bicapped triangle bipyramidal skeleton. Crystallographic parameters are as follows: space groupImm2(orthorhombic), a=14.562(3), b=10.391(1), c=7.139(4), V=1080.2(i)~3, Z=2, ρ(cald)=1.819g·cm~(-3). The final R factor was 2.2％ for 620 independent reflections(I>2σ(I)).     

IR AND ESR STUDIES OF THE REDUCED HETEROPOLYMOLYBDOVANADOPHOS PHORIC ACIDS H_(3+n)PMo_(12-n)V_nO_(40) (n=0,2,4)

The reducibility and isotope exchange ability of different oxygen bonds (O_b, O_p, O_t) in the Keggin structure of heteropolymolybdates (H_(3+n)PMo_(12-n)V_nO_(40)) containing zero, two or four vanadium atoms as well as the changes of structure of heteropolyacids during reduction were investigated by IR, ESR and ~(18)O isotope exchange. The results obtained showed that the order in the reducibility of different oxygen bonds is O_b>>O_p≈O_t, the replacement of Mo by V affects obviously the reducibility of various oxygen bonds: O_b increases while O_p and O_t decrease. ~(18)O exchange rate of O_b, O_p, O_t is not different, comparatively speaking, the isotope exchange of oxygen of the heteropolyacids containing vanadium atoms is more difficult than PMo_(12). The ESR spectra indicate that two kinds of Mo~(5+) ions with different coordinations are present in PMo_(12) (n=0) during reducing process, their g values are g_⊥~A=1.971, g_(?)~A=1.912 and g_⊥~B=1.965, g_(?)~B=1.861 belonging respectively to the d     

Synthesis and Fluorescent and Magnetic Properties of a New Europium Complex Eu(C_(20)H_(14)O_3N)_3(2,2'-bipy)(H_2O)·H_2O

A new europium(Ⅲ) complex Eu(C_(20)H_(14)O_3N)_3(2,2?-bipy)(H_2O)·H_2O has been synthesized with2-diphenylanine carbonyl benzoic acid and 2,2?-bipyridine as ligands.Crystal data for the complex are as follows:triclinic,space group ■,a=11.3334(5),b=16.0883(7),c=17.0116(8)?,α=70.411(4)o,β=82.435(4)o,γ=85.095(4)o,V=2894.0(2)?~3,D_c=1.484 g/cm~3,Z=2,μ=1.15 mm~(-1),F(000)=1320 and the final R=0.0447 and w R=0.0578.The Eu(Ⅲ) ion is coordinated by nine atoms to give a monocapped square antiprism coordination geometry.The complex shows two intense fluorescence emission bands arising from the transitions of Eu~(3+):~5D_0→~7F_1 (592 nm) and ~5D_0→~7F_2 (616 nm),respectively.Also reported is the magnetic property of the complex.The complex exhibits antiferromagnetism in the temperature range of 300～2 K.     

Synthesis,Structure and Properties of a New Terbium(Ⅲ) Complex Tb_2(C_(15)H_(11)O_3)_6(phen)_2

A new terbium(Ⅲ) complex Tb_2(C_(15)H_(11)O_3)_6(phen)_2 has been synthesized with 2-(4-methylbenzoyl)benzoic acid and 1,10-phenanthroline as ligands.Crystal data for the complex are as follows:monoclinic,space group P2_1/n,a=15.0786(6),b=13.5762(5),c=22.9683(9) A,β=104.130(4)°,V=4559.6(3) A~3,D_c=1.540_g/cm~3,Z=2,μ(MoKα)=1.615 mm~(-1),F(000)=2136,the final R=0.0528 and wR=0.0740.The Tb(Ⅲ) ion is coordinated by eight atoms to give a distorted square antiprism coordination geometry.The complex shows four fluorescence emission bands arising from the transitions of Tb~(3+5)D_4→~7F_6(490 nm),~5D_4→~7F_5(546 nm),~5D_4→~7F_4(588 nm) and ~5D_4→~7F_3(622 nm).The complex is an antiferromagnet in the range of 300～2 K.Also reported in the paper is the thermal stability property of the title complex.     

STARK ENERGY LEVELS OF ~5D_4,~7F_J(J=0—6)OF Tb~(3+) IONS IN TbP_5O_(14)

In the present paper, the polarized fluorescence spectra and the infrared absorptionspectra of single crystals of terbium pentaphosphate, TbP_5O_(14), were measured at 77 K. Most ofthe observed transitions were identified and the energy level structure of the ~7F multipletwas also defined. The result of structure analysis indicates that the coordination of the cationto oxygen atoms is eightfold with the geometry of a slightly distorted square antiprism. In otherwords, the local symmetry of the Tb~(3+) in TbP_5O_(14) belongs to C_(4v). The crystal field calculationswere performed for such symmetry and gave a respectable fit for the observed Stark splittingof the ~7F_J (J = 0--6) multiplet. The comparison between the experimental and the calculatedenergy levels shows that the rms deviation and the maximum deviation are 8cm~(-1) and 17cm~(-2),respectively.     

Crystal structure and single crystal EPR of (NH_4)_2(15-crown-5)_3[Cu(mnt)_2] and (NH_4)_2(benzo-15-crown-5)_4[Cu(mnt)_2]·0.5H_2O

The X-ray crystal structures of (NH4)2(15-crown-5)3[Cu(mnt)2] (1) and (NH4)2(benzo-15-crown-5)4- [Cu(mnt)2]·0.5H2O (2) were determined. Two single crystals are composed of distinct structures of ammonium-crown ether supramolecular cation and [Cu(mnt)2]2? anion. The triple-decker dication in complex 1 and a sandwich dimmer in complex 2 were observed. X-Band EPR studies on the single crystals of both complex 1 and complex 2 have been carried out at room temperature, which revealed that complex 2 showed a perfect hyperfine structure of Cu whereas that of complex 1 could not be observed. The principal values and direction cosines of the principal axes of the g and A tensors were computed by a least-squares fitting procedure. The spin density of Cu(II) was estimated according to the principal values of the A tensors and compared well with the results calculated based on DFT method.     

SYNTHESIS AND STRUCTURE OF TWO-ELECTRON HETEROPOLY BLUE K_2H_4SiMo(Ⅴ)_2Mo(Ⅵ)_(10)O_(40)·12H_2O WITH α-KEGGIN STRUCTURE

The single crystal of two-electron heteropoly blue with Si as the heteroatom and α-Keggin structure K_2H_4SiMo(Ⅴ)_2Mo(Ⅵ)_(10)O_(40)·12H_2O was obtained by electrolytic reduction. It crystallizes in a triclinic system with space group P , Mr=2117.73, a= 13.702(4), b=14.107(3), c=14.184(2) ; α=119.27(1), β=93.14(2), ;γ=110. 3(2)°, V=2154.29~3, Z=2, F(000)=1999, μ=36.39cm~(-1), Dc=3.26 g/cm~3. Final R factor is 0.0515. Mo(Ⅴ) is situated in two different edge-shared Mo_3O_(13) groups. The heteropoly blue was characterized by IR, UV, polarography, X-ray photoelectron spectra and ESR. All the results show that the structure of the heteropoly anion with Keggin structure remains unchanged basically in the process of reduction.     

RESEARCH ON TRINUCLEAR MOLYBDENUM CLUSTER COMPOUNDS——CRYSTAL AND MOLECULAR STRUCTURE OF (C_5H_7S_2)_3[Mo_3(μ_3-S)(μ_2-S_2)_3Cl_7]

The space group of the title crystal is Pnam. The unit cell parameters are: a=17.226(4), b=14.306(7), c=15.074(4); z=4, Dobs=2.03g·cm~(-3), D_(calc)=2.063g·cm~(-3). The crystal structure was solved by the heavy atom method and refined by the full-matrix least-squares until the final conventional discrepancy factor was reduced to 0.068. The results of the investigation show that the crystal consists of trinuclear Mo cluster anions [Mo_3(μ_3-S)(μ_2-S_2)_3Cl_7]~(3-) together with planar (C_5H_7S_2)~ monocations, surrounding the cluster anions. In the cluster anion three Mo atoms, forming a nearly equilateral triangle (2.755(1), 2.755(1), 2.743(1)), are bound by a μ_3-S bridging atom, while each pair of Mo atoms is bridged further by a μ_2-S_2 ligand. Besides, each Mo atom is coordinated to two terminal Cl atoms, so that the coordination sphere of each Mo atom approaches closely a pentagonal bipyramid. In addition, a single Gl atom, not at all involved in the coordination spheres of the three Mo atom