首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Abstract

Chemical preparations, crystal structures, thermal analyses, and IR spectroscopic studies are given for two new hydrogen phosphates templated by 4-amino-2,2,6,6-tetramethylpiperidine: (C9H22N2)2·(H2PO4)·(HPO4)·(F)·H2O (I) and (C9H22N2)·(H2PO4)2(II). The structures are determined by single crystal X-ray diffraction. Both compounds crystallize in the P21/c (N°14) monoclinic space group with the unit cell parameters: a = 14.856 (1) Å, b = 14.092 (2) Å, c = 14.7166 (9) Å, β = 118.434 (7)°, V = 2709.2 (4) Å 3, and Z = 4 for (I) and a = 9.803 (2) Å, c = 0.466 (2) Å, c = 15.640 (8) Å, β = 94.990 (4), V = 1598.68 (7) Å3, and Z = 4 for (II).

The structure of I, refined to R = 0.042 and Rw = 0.067 for 6009 reflections (I ≥ 2σ (I)), exhibits infinite inorganic chains ((H2PO4)·(HPO4)·(F)·H2O)4? linked together through weak hydrogen bonds to form layers onto which the diprotonated [C9H22N2]2 + amine molecules are anchored.

The structure of II, refined to R = 0.060 and Rw = 0.086 for 1435 reflections (I ≥ 2σ (I)), consists of (H2PO4)? (100) layers between which [C9H22N2]2+ cations are inserted. A network of hydrogen bonds connects the different components. IR spectra of I and II show the characteristic bands of amine groups and phosphate anions.  相似文献   

2.
The heterogeneous phase reaction of excess sodium salt of 2-hydroxypyridine (OHpy) with [Ru(κ2C,O-RL)(PPh3)2(CO)Cl] (1) afforded complexes of the type [Ru(κ1C-RL)(PPh3)2(CO)(Opy)] (2) in excellent yield [κ2C,O-RL is 4-methyl-6-((N-R-arylimino)methyl)phenolato-C2,O), κ1C-RL is 4-methyl-6-((N-R-arylimino)methyl)phenol-C2) and R is H, Me, OMe, Cl]. The chelation of Opy is attended with the cleavage of Ru-O and Ru-Cl bonds and iminium-phenolato → imine-phenol prototropic shift. The 12 conversion is irreversible and the type 2 species are thermodynamically more stable than the acetate, nitrite, and nitrate complexes of 1. The spectral (UV-vis, IR, NMR) and electrochemical data of the complexes are reported. In dichloromethane solution the complexes display one quasi-reversible RuIII/RuII cyclic voltammetric response with E1/2 in the range 0.65–0.69 V versus Ag/AgCl. The crystal and molecular structures of [Ru(κ1C-HL)(PPh3)2(CO)(Opy)]·2C6H6·0.5H2O, 2(H)·2C6H6·0.5H2O and [Ru(κ1C-ClL)(PPh3)2(CO)(Opy)]·2C6H6·0.25H2O, 2(Cl)·2C6H6·0.25H2O are reported, which revealed a distorted octahedral RuC2P2NO coordination sphere. The pairs (P,P), (C,O), and (C,N) define the three trans directions. The electronic structures of the complexes are also scrutinized by density functional theory.  相似文献   

3.
Self-assembly of 4-aminoantipyrine (AAP) and 5-nitroisophthalic acid (H2NIP) with Co(CH3COO)2 or Cd(NO3)2 in CH3OH–H2O at room temperature generated {[Co2(AAP)(NIP)(H2O)8][Co(AAP)(NIP)2(H2O)2](H2O)4.5} (1) and {[Cd(AAP)(NIP)(H2O)](H2O)} n (2), which were further characterized by X-ray diffraction, IR spectra, elemental analysis and solid-state fluorescence spectra. The structure analysis indicates that 1 contains two individual fragments, one NIP-bridged six-coordinate binuclear CoII cation and a mononuclear CoII dianion. The binuclear units are connected into 1-D chains via O–H?···?O hydrogen bond interactions, which were further assembled into a 2-D supramolecular layer bridged by the mononuclear CoII unit. Complex 2 is a linear NIP bridged seven-coordinate CdII polymeric chain with the terminal AAP ligands as decorations, and are further extended into 2-D network by classic hydrogen bonds and π?···?π stacking interactions. Both solid complexes exhibit emission spectra from intraligand electron transfer at room temperature.  相似文献   

4.
Two new ZnII complexes, {[Zn(L)(phen)(H2O)]?·?H2O} (1) and {[Zn(L)(4bpy)(H2O)]?·?H2O} (2) (L?=?5,6-dihydro-1,4-dithiin-2,3-dicarboxylate, phen?=?1,10-phenanthroline, and 4bpy?=?4,4′-bipyridine), have been prepared by in situ reaction of Zn(ClO4)2?·?6H2O with 5,6-dihydro-1,4-dithiin-2,3-dicarboxylic anhydrate in the presence of lithium hydroxide, together with incorporating chelating phen or bridging 4bpy as co-ligands. Their structures were determined by single-crystal X-ray diffraction. Complex 1 takes a 1-D helical structure that is further assembled into a 2-D network by O–H?···?O, C–H?···?O hydrogen bonds, and weak S?···?S interactions, and then an overall 3-D supramolecular framework was formed by π?···?π stacking interactions. Complex 2 possesses a 2-D (4,4)-layered structure. The structural difference between 1 and 2 can be attributed to the different N-donor auxiliary co-ligands. Both 1 and 2 are photoluminescent materials whose emission properties are closely related to their intrinsic structure.  相似文献   

5.
The complexes [Co(DH)2(Seu) y (Se-Seu) z ]2X · mSolv (DH is the dimethylglyoxime monoanion, Seu is selenourea, and X is [TiF6]2−, [ZrF6]2−) were obtained from the system CoX · 6H2O-DH2-Seu in DMF-MeOH or MeOH-H2O and examined by UV, IR, and NMR spectroscopy and X-ray diffraction. Unexpectedly, the ligand Se-Seu (the oxidized form of selenourea) was detected on the axial coordinate, partially replacing selenourea. The complexes were formulated as [Co(DH)2(Seu)1.75(Se-Seu)0.25]2[TiF6] · H2O (I) and [Co(DH)2(Seu)(Se-Seu)]2[ZrF6] · 3H2O (II). The complex cations in I and II have trans-octahedral structures. Their crystal structures are made up of the complex Co3+ cations and the outer-sphere MF62− anions (M = Ti(IV) (I) and Zr(IV) (II)) held together by electrostatic interactions and hydrogen bonds; water of crystallization is also involved in hydrogen bonding.  相似文献   

6.
In this work, the title complexes, (EnH2)1.5[ErIII(Ttha)] · 3H2O (I) and (EnH2)[ErIII(Egta)(H2O)]2 · 6H2O (II), where En = ethylenediamine, H6Ttha = triethylenetetramine-N,N,N′,N″,N″’,N″′-hexaacetic acid, H4Egta = ethyleneglycol-bis-(2-aminoethylether)-N,N,N′,N′-tetraacetic acid, have been successfully synthesized. Their structures have been characterized by IR spectroscopy and single-crystal X-ray diffraction techniques. The X-ray diffraction reveals that I is nine-coordinated and crystallizes in the monoclinic crystal space group P2/n with cell dimensions a = 17.6058(16), b = 9.6249(9), c = 20.560(2) ?, β = 109.7440(10)°, and V = 3279.1(5) ?3. Compound II is also nine-coordinated and crystallizes in the monoclinic crystal space group P21/n with the cell dimensions a = 12.938(6), b = 12.651(5), c = 14.943(6) ?, β = 105.441(5)°, and V = 2357.5(17) ?3. In I, each EnH22+ cation connects three adjacent [ErIII(Egta)(H2O)] complex anions through hydrogen bonds, while in I, there are two types of EnH2 2+ anions. One is highly symmetrical, forming hydrogen bonds with two neighboring [ErIII(Ttha)]3− complex anions. The other anion connects three adjacent [ErIII(Ttha)]3− complex anions through hydrogen bonds. These hydrogen bonds lead to the formation of 2D ladder-like layer structure.  相似文献   

7.
The title compound, [Cu(C7H3O6S)2(C10H9N3)2][CuI(C10H9N3)2]2·2H2O, consists of anionic CuII moieties, cationic CuI species and uncoordinated water mol­ecules. The anionic dimeric unit consists of one crystallographically independent fully deprotonated 5‐sulfosalicylate (2‐oxido‐5‐sulfonatobenzoate) anion, a di‐2‐pyridylamine group and a CuII atom. Each CuII atom is five‐coordinate within a square‐pyramidal geometry. The anion lies on a special position of site symmetry. In the cationic monomer, the CuI atom adopts tetra­hedral geometry. The cations and anions are connected by O—H·O and N—H·O hydrogen bonds.  相似文献   

8.
A N-donor containing carboxylic ligand, 5-(pyridin-4-yl)isophthalic acid (H2L), was applied to construct two new coordination polymers [Cd(L)(DMF)] n (1, DMF?=?N,N-dimethylformamide) and {[Co(L)(H2O)2]?·?0.5CH3OH?·?1.5H2O} n (2) under different conditions. The complexes were characterized by IR, elemental, and thermogravimetric analyses, powder and single crystal X-ray diffraction. In 1 each L2? links four CdII to form a 3-D framework, while in 2 each L2? connects three metals to form a 2-D layer structure, which is further connected together by hydrogen bonds to form a 3-D architecture. The thermal stability of the complexes and the photoluminescence of 1 were investigated.  相似文献   

9.
Two complexes, [Cu2(TFSA)(2,2′-bpy)4]?·?TFSA?·?8H2O (1) and {[Cu(4,4′-bpy)(H2O)2]?·?TFSA?·?6H2O} n (2) (H2TFSA?=?tetrafluorosuccinic acid, 2,2′-bpy?=?2,2′-bipyridine, and 4,4′-bpy?=?4,4′-bipyridine), have been synthesized and structurally characterized by X-ray structural analyses. Complex 1 is a binuclear molecule bridged by TFSA ligands; 2 is a 1-D chain bridged by 4,4′-bpy ligands. The asymmetric units of the two complexes are composed of cationic complexes [Cu2(TFSA)(2,2′-bpy)4]2+ (1) and [Cu(4,4′-bpy)(H2O)2]2+ (2), free TFSA anion, and independent crystallization water molecules. A unique 2-D hybrid water–TFSA anionic layer by linkage of {[(H2O)8(TFSA)]2?} n fragments consisting of 1-D T6(0)A2 water tape and TFSA anionic units by hydrogen bonds in 1 was observed. Unique 2-D hybrid water–TFSA anionic layer generated by the linkage of {[(H2O)6(TFSA)]2?} n fragments consisting of cyclic water tetramers with appended water molecules and TFSA anionic units, and 1-D metal–water tape [Cu–H2O?···?(H2O)6?···?H2O?] n in 2 were found. 3-D supramolecular networks of the two complexes consist of cationic complexes and water–TFSA anionic assemblies connected by hydrogen bonds.  相似文献   

10.
Uranyl complexes with acetylenedicarboxylic acid, K(H5O2)[UO2L2H2O] · 2H2O (I) and Cs2[UO2L2H2O] · 2H2O (II), L2− = C4O 4 2− were prepared for the first time. The composition and structure of the complexes were determined by X-ray diffraction. The crystal data are as follows: a = 16.254(12) ?, b = 13.508(8) ?, c = 7.683(6) ?, β = 90.91(7)°, space group C2/c, V = 1687(2) ?3 (I); a = 7.0745(10), b = 18.4246(10), c = 13.1383(10) ?, space group Abm2, V = 1712.5(3) ?3 (II). The structures of I and II are based on [UO2L2H2O] n 2− anionic chains stretched along the [101] direction (I) or [010] direction (II). In I and II, the uranium coordination polyhedron is a pentagonal bipyramid in which the equatorial environment of the uranyl ions is formed by the oxygen atoms of the four L2− anions and the water molecule. The L2− anions in I and II are bidentate bridging ligands connecting two uranium atoms that are next to each other in the anionic chain; their coordination capacity is equal to 2. In I, the K+ and H5O 2 + cations are outer-sphere species. The latter form hydrogen bonds combining the anionic chains shifted by translation b with respect to each other. The [UO2L2H2O] n 2− chains in I are surrounded by the potassium and oxonium cations; in II, these are combined by hydrogen bonds into anionic layers between which Cs+ cations are arranged. The IR spectrum of compound II was measured and interpreted. Original Russian Text ? I.A. Charushnikova, A.M. Fedoseev, N.A. Budantseva, I.N. Polyakova, Ph. Moisy, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 1, pp. 63–69.  相似文献   

11.
Different tautomeric and zwitterionic forms of chelidamic acid (4‐hydroxypyridine‐2,6‐dicarboxylic acid) are present in the crystal structures of chelidamic acid methanol monosolvate, C7H5NO5·CH4O, (Ia), dimethylammonium chelidamate (dimethylammonium 6‐carboxy‐4‐hydroxypyridine‐2‐carboxylate), C2H8N+·C7H4NO5, (Ib), and chelidamic acid dimethyl sulfoxide monosolvate, C7H5NO5·C2H6OS, (Ic). While the zwitterionic pyridinium carboxylate in (Ia) can be explained from the pKa values, a (partially) deprotonated hydroxy group in the presence of a neutral carboxy group, as observed in (Ib) and (Ic), is unexpected. In (Ib), there are two formula units in the asymmetric unit with the chelidamic acid entities connected by a symmetric O—H...O hydrogen bond. Also, crystals of chelidamic acid dimethyl ester (dimethyl 4‐hydroxypyridine‐2,6‐dicarboxylate) were obtained as a monohydrate, C9H9NO5·H2O, (IIa), and as a solvent‐free modification, in which both ester molecules adopt the hydroxypyridine form. In (IIa), the solvent water molecule stabilizes the synperiplanar conformation of both carbonyl O atoms with respect to the pyridine N atom by two O—H...O hydrogen bonds, whereas an antiperiplanar arrangement is observed in the water‐free structure. A database study and ab initio energy calculations help to compare the stabilities of the various ester conformations.  相似文献   

12.
Three new transition metal complexes, [FeII(H2O)6][(C9H7NO3)2FeII] · H2O (1), H[K(H2O)3][(C9H7NO3)2CoII] · H2O (2), and [CoII(H2O)6][(C9H7NO3)2CoII] · H2O (3), with salicylideneglycine have been synthesized and characterized by elemental analysis, IR spectra, UV-Vis spectroscopy, and X-ray crystallography. The structure analyses indicate that the tridentate salicylideneglycine binds through aliphatic nitrogen, phenoxy, and carboxylic oxygen in the anion. There are many inter- and intra-molecular hydrogen bonds among lattice water, the anion, and the cation to form a 3-D network. The thermogravimetric analyses and the quantum chemistry calculations of compounds 1, 2, and 3 are also discussed.  相似文献   

13.
The (enH2)[GdIII 2(pdta)2(H2O)2]?·?8H2O (1) (en?=?ethylenediamine and H4pdta?=?propylenediamine-N,?N,?N′,?N′-tetraacetic acid) and (enH2)[GdIII(egta)(H2O)]2?·?6H2O (2) (H4egta?=?ethyleneglycol-bis-(2-aminoethylether)-N,?N,?N′,?N′-tetraacetic acid) complexes were synthesized and characterized by infrared spectrum, thermal analysis, and single-crystal X-ray diffraction. The complex (enH2)[GdIII 2(pdta)2(H2O)2]?·?8H2O has a binuclear eight-coordinate structure with pseudo square antiprism and crystallizes in the monoclinic crystal system with C2/c space group. Through a carboxylate bridge, an infinite 1-D zigzag polymeric binuclear [GdIII 2(pdta)2(H2O)2]2? complex anion is formed. All infinite zigzag polymeric complex anions link through hydrogen bonds, yielding a layer structure. (enH2)[GdIII(egta)(H2O)]2?·?6H2O has a mononuclear nine-coordinate structure with pseudo monocapped square antiprism and crystallizes in the monoclinic crystal system with P21/n space group. Each enH2 2+ cation, through hydrogen bonds, connects two adjacent [GdIII(egta)(H2O)]? complex anions.  相似文献   

14.
Two new coordination supramolecular complexes based on a versatile and unsymmetrical 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) and MnII and NiII have been synthesized and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of MnCl2?· 4H2O with Hpot afforded a neutral mononuclear complex [Mn(pot)2(H2O)4]?·?2H2O (1), which exhibits a three-dimensional (3-D) supramolecule through versatile intermolecular O–H?···?X (X=O, N and S) hydrogen bond interactions. When using NiCl2?·?6H2O instead of MnCl2?· 4H2O under similar reaction conditions, a neutral mononuclear complex [Ni(pot)2(H2O)4] (2) is also obtained, which does not exhibit intermolecular hydrogen bonds and π–π stacking interactions. It is very interesting that the pot anion exhibits different coordination modes in complexes 1 and 2. The IR spectra and the TGA for 1 and 2 have been investigated and discussed in detail.  相似文献   

15.
Crystal structures of [Co(Promp)(Hpromp)] · H2O (I) (where Promp and Hpromp are deprotonated and monoprotonated anions of S-proline-N-mono-3-propionic acid) and (H3O)[Co(Hedta)(CN)] · H2O (II) (where HEdta is monoprotonated anion of ethylenediaminetetraacetic acid) are determined by X-ray diffraction method. The Co coordination octahedron in compound I is formed by two N atoms in trans-positions and by four O atoms of two tridentate ligands, i.e., anions of H2Promp acid, one of which is fully deprotonated, while the other one has protonated carboxyl group of a six-membered aminopropionate metal cycle. Neutral [Co(Promp)(Hpromp)] complexes and water molecules are united by hydrogen bonds into chains along 21 screw axis. Crystals II consist of the complex anions [Co(Hedta)(CN)], hydroxonium cations, and water molecules. The Co coordination octahedron includes two N atoms and three O atoms of ion of ethylenediaminetetraacetic acid, whose one acetate group is not coordinated but protonated; cyanide ion lies in the NCoN plane. Crystals II contain two types of H3O+ ions that are involved in hydrogen bonds in different way.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 596–605.Original Russian Text Copyright © 2005 by Poznyak, Burshtein.  相似文献   

16.
A dinuclear copper(II) compound, [Cu(btssb)(H2O)]2 · 4(H2O) (1), and a 1-D chain copper(II) compound, [Cu(ctssb)(H2O)] n (2) [where H2btssb is 2-[(5-bromo-2-hydroxy-benzylidene)-amino]-ethanesulfonic acid and H2ctssb is 2-[(3,5-dichloro-2-hydroxy-benzylidene)-amino]-ethanesulfonic acid], were prepared and characterized. Compound 1 crystallizes in the monoclinic space group P21/c, with a = 10.109(2) Å, b = 20.473(4) Å, c = 6.803(1) Å, β = 100.32(3)°, V = 1385.1(5) Å3, and Z = 2; R 1 for 1796 observed reflections [I > 2σ(I)] was 0.0357. The geometry around each copper(II) can be described as slightly distorted square pyramidal. The CuII ··· CuII distance is 5.471(1) Å. Compound 1 formed a 1-D network through O–H ··· O hydrogen bonds and 1-D water chains exist. The 1-D chain complex 2 crystallizes in the triclinic space group P 1, with a = 5.030(2) Å, b = 7.725(2) Å, c = 17.011(5) Å, α = 92.706(4)°, β = 97.131(4)°, γ = 102.452(3)°, V = 638.6(3) Å3, and Z = 2; R 1 for 1897 observed reflections [I > 2σ(I)] was 0.0171. In 2, Cu(II) was also a slightly distorted square pyramid formed by two oxygens and one nitrogen from ctssb, one oxygen from another ctssb, and one water molecule. The complex formed a 1-D chain through O–S–O bridge of ctssb ligand. The 1-D chain further constructed a double chain through O?H ··· O hydrogen bonds.  相似文献   

17.

The asymmetric unit of compound (I), 4-fluoroanilinium picrate, C6H7NF+.C6H2N3O7? contain one 4-fluoroanilinium cation and one picrate anion whereas in compound (II), dicyclohexylaminium picrate, C12H22N+.C6H2N3O7? the asymmetric unit contains two sets of dicyclohexylaminium cation and picrate anion due to conformational difference between the molecules. In (I), all three nitro groups of the picrate anion are positionally disordered over two sites refined to major and minor components. The molecular ions of (I), interlinked through N–H???O and C–H???O hydrogen bonds forming two-dimensional supramolecular sheet along (-1 0 1) plane. Whereas in (II), the symmetry-independent molecules labeled as A and B molecule form independent one-dimensional supramolecular tape extending along (1 1 0) and (1 0 0) direction. The supramolecular tapes are interlinked through C–H???O interaction to form three-dimensional network in the crystalline solid in (II).

  相似文献   

18.
New host-guest compounds are synthesized and studied by X-ray diffraction analysis: (18-crown-6) potassium 0.84(diiodobromide) 0.16(dibromoiodide), [K(18-crown-6)]+ · (Br1.16I1.84), (I) and diaqua (18-crown-6)chlororubidium, [RbCl(18-crown-6)(H2O)2], (II). The crystals of compound I are monoclinic (space group P21/n, a = 9.157 ?, b = 8.589 ?, c = 14.072 ?, β = 102.27°, Z = 2). The structure of compound II is orthorhombic (space group Pnma, a = 9.813 ?, b = 15.231 ?, c = 12.629 ?, Z = 4). The structures are solved by a direct method and refined by the full-matrix anisotropic least squares to R = 0.062 (I) and 0.079 (II) for 3149 (I) and 2840 (II) independent reflections (CAD-4 automated diffractometer, λMoK α radiation). The crystal structures of compounds I and II are different: compound I is built of infinite chains of the alternating cations [K(18-crown-6)]+ and mixed halide anions linked by weak coordination bonds K-Br or K-I, whereas individual molecules [RbCl(18-crown-6)(H2O)2] form structure II. Original Russian Text ? A.N. Chekhlov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 8, pp. 1385–1391.  相似文献   

19.
Cyanide-bridged trinuclear heterometallic Ag(I)-Mn(III) complex {[Mn(TClPP)(H2O)]2[Ag(CN)2]}2 · 2Br · 2C3H6O · 3H2O (I) and ion-pair complex {[Mn(TClPP)(CH3OH)2][Ag(CN)2]} · 0.5H2O (II) have been synthesized with [Mn(TClTPP)(H2O)2]Br (H2TClTPP = meso-tetra(4-chlorophenyl)porphyrin) as assembling segment and K[Ag(CN)2] as building block by using different crystallization method. These two complexes have been characterized by elemental analysis, IR spectroscopy and X-ray structure determination. In the trinuclear complex I, [Ag(CN)2]? as bidentate ligand coordinates with the two central Mn(III) atom of [Mn(TClPP)(H2O)2]+ through its two trans cyanide groups to form the complex cation of [Mn(TClPP)(H2O)]2[Ag(CN)2]+, which further constructs the neutral complexes with the help of one Br? as balanced anion. For the ion-pair complex II composed by free [Mn(TClPP)(CH3OH)2]+ cation and free [Ag(CN)2]? anion, it can be linked into one-dimensional supramolecular structure with the dependence of the intermolecular O-H...N and O-H...O hydrogen bond interactions.  相似文献   

20.
Synthesis and structure of a supramolecular dimer and inorganic–organic cocrystal of composition [{CuIIL1?(H2O)}2(C8H6O4)] (1) are described (H2L1= N,N′-ethylenebis(3-ethoxysalicylaldimine); C8H6O4 = terephthalic acid). Crystal engineering has been utilized for the designed synthesis of the title compound. Compound 1 crystallizes in a triclinic system with P 1 space group. The structure consists of terephthalic acid and two symmetry related inclusion products [CuIIL1?(H2O)], in which the water molecule is encapsulated in the O4 compartment by forming bifurcated hydrogen bonds involving two hydrogen of water and phenolate and ethoxy oxygens of the compartmental ligand. Hydrogen bonding between encapsulated water molecules and terephthalic acid forms the supramolecular dimer. The title compound is an example of an inorganic–organic cocrystal as well. Weak interactions, such as semicoordination of phenoxo oxygen of one unit to the metal center of a symmetry related unit and C–H ··· O, and O–H ··· O hydrogen bonds result in generation of an overall 3-D topology in the title compound. The 3-D topology can be understood as interlinking of two different 2-D sheets.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号