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1.
127I nuclear quadrupole resonance (NQR) spectroscopy is established as a rapid and robust method to indicate the formation of iodine–nitrogen halogen bonds in co‐crystalline powders. Once the relevant spectral frequency range has been established, diagnostic 127I NQR spectra can be acquired in seconds. The method is demonstrated for a series of co‐crystals of 1,4‐diiodobenzene. Changes in the 127I quadrupolar coupling constant (CQ) by up to 74.4 MHz correlate with the length of the C?I donor covalent bond and inversely with the I???N halogen‐bond length. The predictive power of this technique is validated on two previously unknown co‐crystalline powders prepared mechanochemically. Single‐crystal growth via co‐sublimation and structure determination by single‐crystal X‐ray diffraction cross‐validates the findings. Natural localized molecular‐orbital analyses provide insight into the origins of the quadrupolar coupling constants.  相似文献   

2.
The halogen bond, similar to the hydrogen bond, is an important noncovalent interaction and plays important roles in diverse chemistry‐related fields. Herein, bromine‐ and iodine‐based halogen‐bonding interactions between two benzene derivatives (C6F5Br and C6F5I) and dimethyl sulfoxide (DMSO) are investigated by using IR and NMR spectroscopy and ab initio calculations. The results are compared with those of interactions between C6F5Cl/C6F5H and DMSO. First, the interaction energy of the hydrogen bond is stronger than those of bromine‐ and chlorine‐based halogen bonds, but weaker than iodine‐based halogen bond. Second, attractive energies depend on 1/rn, in which n is between three and four for both hydrogen and halogen bonds, whereas all repulsive energies are found to depend on 1/r8.5. Third, the directionality of halogen bonds is greater than that of the hydrogen bond. The bromine‐ and iodine‐based halogen bonds are strict in this regard and the chlorine‐based halogen bond only slightly deviates from 180°. The directional order is iodine‐based halogen bond>bromine‐based halogen bond>chlorine‐based halogen bond>hydrogen bond. Fourth, upon the formation of hydrogen and halogen bonds, charge transfers from DMSO to the hydrogen‐ and halogen‐bond donors. The CH3 group contributes positively to stabilization of the complexes.  相似文献   

3.
The potassium salt of the [1‐H2N‐2‐F‐closo‐1‐CB11H10] anion ( 1 ) was obtained from an insertion reaction of Li3[7‐H2N‐nido‐7‐CB10H10] with BF3 · OEt2. Anion 1 was protonated to the neutral species 1‐H3N‐2‐F‐closo‐1‐CB11H10 (H 1 ) and it was iodinated with ICl to the [1‐H2N‐2‐F‐closo‐1‐CB11I10] anion ( 2 ). All species were characterized by multinuclear NMR, IR, and Raman spectroscopy as well as by elemental analysis. The structure of H 1· (CH3)2CO was studied by single‐crystal X‐ray diffraction and the experimentally determined bond lengths are compared to values derived from density functional calculations.  相似文献   

4.
Heterobimetallic Complexes of Lithium, Aluminum, and Gold with the N ‐[2‐ N ′, N ′‐(dimethylaminoethyl)‐ N ‐methyl‐aminoethyl]‐ferrocenyl Ligand (η5‐C5H5)Fe{η5‐C5H3[CH(CH3)N(CH3)CH2CH2NMe2]‐2} N‐[2‐N′,N′‐(dimethylaminoethyl)‐N‐methyl‐aminoethyl]ferrocene FcN,NH ( 1 ) reacts with nBuLi under formation of the lithium organyl (FcN,N)Li ( 2 ). At reactions of 2 with AlBr3 and AuCl · PPh3 the heterobimetallic organo derivatives (FcN,N)AlBr2 ( 3 ), (FcN,N)Au · PPh3 ( 4 ) are formed. A detailed characterization of 2 – 4 was carried out by single crystal x‐ray analyses as well as by NMR and Mößbauer spectroscopy.  相似文献   

5.
Reaction of [Au(DAPTA)(Cl)] with RaaiR’ in CH2Cl2 medium following ligand addition leads to [Au(DAPTA)(RaaiR’)](Cl) [DAPTA=diacetyl-1,3,5-triaza-7-phosphaadamantane, RaaiR’=p-R-C6H4-N=N- C3H2-NN-1-R’, (1—3), abbreviated as N,N’-chelator, where N(imidazole) and N(azo) represent N and N’, respectively; R=H (a), Me (b), Cl (c) and R’=Me (1), CH2CH3 (2), CH2Ph (3)]. The 1H NMR spectral measurements in D2O suggest methylene, CH2, in RaaiEt gives a complex AB type multiplet while in RaaiCH2Ph it shows AB type quartets. 13C NMR spectrum in D2O suggest the molecular skeleton. The 1H-1H COSY spectrum in D2O as well as contour peaks in the 1H-13C HMQC spectrum in D2O assign the solution structure.  相似文献   

6.
Co‐crystallisation of, in particular, 4‐iodotetrafluorophenol with a series of secondary and tertiary cyclic amines results in deprotonation of the phenol and formation of the corresponding ammonium phenate. Careful examination of the X‐ray single‐crystal structures shows that the phenate anion develops a C?O double bond and that the C?C bond lengths in the ring suggest a Meissenheimer‐like delocalisation. This delocalisation is supported by the geometry of the phenate anion optimised at the MP2(Full) level of theory within the aug‐cc‐pVDZ basis (aug‐cc‐pVDZ‐PP on I) and by natural bond orbital (NBO) analyses. With sp2 hybridisation at the phenate oxygen atom, there is strong preference for the formation of two non‐covalent interactions with the oxygen sp2 lone pairs and, in the case of secondary amines, this occurs through hydrogen bonding to the ammonium hydrogen atoms. However, where tertiary amines are concerned, there are insufficient hydrogen atoms available and so an electrophilic iodine atom from a neighbouring 4‐iodotetrafluorophenate group forms an I???O halogen bond to give the second interaction. However, in some co‐crystals with secondary amines, it is also found that in addition to the two hydrogen bonds forming with the phenate oxygen sp2 lone pairs, there is an additional intermolecular I???O halogen bond in which the electrophilic iodine atom interacts with the C?O π‐system. All attempts to reproduce this behaviour with 4‐bromotetrafluorophenol were unsuccessful. These structural motifs are significant as they reproduce extremely well, in low‐molar‐mass synthetic systems, motifs found by Ho and co‐workers when examining halogen‐bonding interactions in biological systems. The analogy is cemented through the structures of co‐crystals of 1,4‐diiodotetrafluorobenzene with acetamide and with N‐methylbenzamide, which, as designed models, demonstrate the orthogonality of hydrogen and halogen bonding proposed in Ho’s biological study.  相似文献   

7.
The title compound has been prepared from [Ti(η5‐C5Me5)Cl3] and cis‐cis‐(t‐BuSi(OH)—CH2)3 in hexane solution in the presence of Et3N. The pale yellow complex was characterized by NMR and MS spectra, as well as by a crystal structure determination. The two crystallographic independent molecules in the triclinic unit cell (space group P1¯, No. 2, Z = 4) both have a nearly identical adamantane‐like TiO3Si3C3 cage of approximate C3v symmetry. The exocyclic C—C—C bond angles in the Cp‐ligand range from 123° to 129°. A quantum chemical calculation of the free molecule predicts this range to be 124° to 127°. The arrangement of the molecules in the crystal is characteristic for an offset face‐to‐face ππ stacking of the aromatic η5‐C5Me5 rings.  相似文献   

8.
A study of the strong N?X????O?N+ (X=I, Br) halogen bonding interactions reports 2×27 donor×acceptor complexes of N‐halosaccharins and pyridine N‐oxides (PyNO). DFT calculations were used to investigate the X???O halogen bond (XB) interaction energies in 54 complexes. A simplified computationally fast electrostatic model was developed for predicting the X???O XBs. The XB interaction energies vary from ?47.5 to ?120.3 kJ mol?1; the strongest N?I????O?N+ XBs approaching those of 3‐center‐4‐electron [N?I?N]+ halogen‐bonded systems (ca. 160 kJ mol?1). 1H NMR association constants (KXB) determined in CDCl3 and [D6]acetone vary from 2.0×100 to >108 m ?1 and correlate well with the calculated donor×acceptor complexation enthalpies found between ?38.4 and ?77.5 kJ mol?1. In X‐ray crystal structures, the N‐iodosaccharin‐PyNO complexes manifest short interaction ratios (RXB) between 0.65–0.67 for the N?I????O?N+ halogen bond.  相似文献   

9.
Two [N???I+???N] halogen‐bonded dimeric capsules using tetrakis(3‐pyridyl)ethylene cavitands with different lower rim alkyl chains are synthesized and analyzed in solution and the gas phase. These first examples of symmetrical dimeric capsules making use of the iodonium ion (I+) as the main connecting module are characterized by 1H NMR spectroscopy, diffusion ordered NMR spectroscopy (DOSY), electrospray ionization mass spectrometry (ESI‐MS), and ion mobility‐mass spectrometry (TW‐IMS) experiments. The synthesis and effective halogen‐bonded dimerization proceeds through analogous dimeric capsules with [N???Ag+???N] binding motifs as the intermediates as evidenced by the X‐ray structures of (CH2Cl2)2@[ 3 a 2?Ag4?(H2O)2?OTs4] and (CH2Cl2)2@[ 3 a 2?Ag4?(H2O)4?OTs4], two structurally different capsules.  相似文献   

10.
Synthesis and Characterization of InIII–SnII‐Halogenido‐Alkoxides and of Indiumtri‐ tert ‐butoxide Through sodium halide elimination between Indium(III) halides and sodium‐tri‐tert‐butoxistannate(II) or sodium‐tri‐tert‐butoxigermanate(II) the three new heterometallic and heteroleptic alkoxo compounds THF · Cl2In(OtBu)3Sn ( 1 ), THF · Br2In(OtBu)3Sn ( 2 ), and THF · Cl2In‐ (OtBu)3Ge ( 3 ), have been synthesized. The molecular structures of 1 and 2 in the solid state follow from single crystal X‐ray structure determinations while structural changes in solution may be derived from temperature dependant NMR spectroscopy. The crystal structures of compounds 1 and 2 are despite different halide atoms isostructural. Both crystallize in the ortho‐rhombic crystal system in space group Pbca with eight molecules per unit cell. The heavy atoms occupy the apical positions of empty trigonal bipyramids of almost point symmetry Cs(m) and are connected through oxygen atoms occupying the equatorial positions. The indium atoms in both compounds are in the centers of distorted octahedra from 4 oxygen and 2 halogen atoms whereas the tin atoms are coordinated by three oxygen atoms in a trigonal pyramidal fashion. Although the coordinative bonding of THF to indium leads to an asymmetry of the molecule the NMR spectra in solution are simple showing a more complex pattern at lower temperatures. Tri(tert‐butoxi)indium [In(OtBu)3]2 ( 4 ), is obtained through alcoholysis of In(N(Si(CH3)3)2)3 using tert‐butanol in toluene and is crystallized from hexane. The X‐ray structure determination of 4 seems to be the first one of a homoleptic and homometallic indiumalkoxide. Compound 4 crystallizes in the monoclinic crystal system in a dimeric form with eight molecules in the unit cell of space group C2/c. The dimeric units have C2 symmetry and an almost planar In2O2 ring which originates from oxygen bridging of the monomers. Through this mutual Lewis acid base interaction the indium atoms get four oxygen ligands in a distorted tetrahedral environment.  相似文献   

11.
The irreversible inhibition of δ‐chymotrypsin with the enantiomerically pure, P(3)‐axially and P(3)‐equatorially X‐substituted cis‐ and trans‐configurated 2,4‐dioxa‐3‐phospha(1,5,5‐2H3)bicyclo[4.4.0]decane 3‐oxides (X=F, 2,4‐dinitrophenoxy) was monitored by 31P‐NMR spectroscopy. 1H‐Correlated 31P{2H}‐NMR spectra enabled the direct observation of the vicinal coupling (3J) between the P‐atom of the inhibitor and the CH2O moiety of Ser195 (=‘Ser195’(CH2O)), thus establishing the covalent nature of the ‘Ser195’(CH2O? P) bond in the inhibited enzyme. The stereochemical course of the phosphorylation is dependent on the structure of the inhibitor, and neat inversion, both inversion and retention, as well as neat retention of the configuration at the P‐atom was found.  相似文献   

12.
The polymers with functionalized alkoxy groups and with narrow molecular weight distribution (Mw/Mn < 1.12) are obtained from the living polymerization of 2‐alkoxy‐1‐methylenecyclopropanes using π‐allylpalladium complex, [(PhC3H4)Pd(μ‐Cl)]2, as the initiator. The polymers with oligoethylene glycol groups in the alkoxy substituent are soluble in water, and hydroboration of the C?C double bond and ensuing addition of the OH groups to C?N bond of alkyl isocyanate produce the polymers with urethane pendant groups. The reaction decreases solubility of the polymer in water significantly. Di‐ and triblock copolymers of the 2‐alkoxy‐1‐methylenecyclopropanes are prepared by consecutive addition of the two or three 2‐alkoxy‐1‐methylenecyclopropane monomers to the Pd initiator. The polymers which contain both hydrophobic butoxy or tert‐butoxy group and hydrophilic oligoethylene glycol group dissolve in water and/or organic solvents, depending on the substituents. The 1H NMR spectrum of poly( 1a ‐b‐ 1h ) (? (CH2C(?CH2)CHOBu)n? (CH2C(?CH2)CH(OCH2CH2)3OMe)m? ) in D2O solution exhibits peaks because of the butoxy and ?CH2 hydrogen in decreased intensity, indicating that the polymer forms micelle particles containing the hydrophilic segments in their external parts. Aqueous solution of the polymer with a small amount of DPH (DPH = 1,6‐diphenyl‐1,3,5‐hexatriene) shows the absorbance due to DPH at concentration of the polymer higher than 5.82 × 10?5 g mL?1. Other block copolymers such as poly( 1b ‐b‐ 1h ) and poly( 1a ‐b‐ 1g ) also form the micelles that contain DPH in their core. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 959–972, 2009  相似文献   

13.
Cellulose ( 1 ) was converted for the first time to 6‐phenyl‐6‐deoxy‐2,3‐di‐O‐methylcellulose ( 6 ) in 33% overall yield. Intermediates in the five‐step conversion of 1 to­ 6 were: 6‐O‐tritylcellulose ( 2 ), 6‐O‐trityl‐2,3‐di‐O‐methylcellulose ( 3 ), 2,3‐di‐O‐methylcellulose ( 4 ); and 6‐bromo‐6‐deoxy‐2,3‐di‐O‐methylcellulose ( 5 ). Elemental and quantitative carbon‐13 analyses were concurrently used to verify and confirm the degrees of substitution in each new polymer. Gel permeation chromotography (GPC) data were generated to monitor the changes in molecular weight (DPw) as the synthesis progressed, and the compound average decrease in cellulose DPw was ~ 27%. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the decomposition of all polymers. The degradation temperatures ( °C) and percent char at 500 °C of cellulose derivatives 2 to 6 were 308.6 and 6.3%, 227.6 °C and 9.7%, 273.9 °C and 30.2%, 200.4 °C and 25.6%, and 207.2 °C and 27.0%, respectively. The glass transition temperature (Tg) of­6‐O‐tritylcellulose by dynamic mechanical analysis (DMA) occurred at 126.7 °C and the modulus (E′, Pa) dropped 8.9 fold in the transition from ?150 °C to + 180 °C (6.6 × 109 to 7.4 × 108 Pa). Modulus at 20 °C was 3.26 × 109 Pa. Complete proton and carbon‐13 chemical shift assignments of the repeating unit of the title polymer were made by a combination of the HMQC and COSY NMR methods. Ultimate non‐destructive proof of carbon–carbon bond formation at C6 of the anhydroglucose moiety was established by generating correlations between resonances of CH26 (anhydroglucose) and C1′, H2′, and H6′ of the attached aryl ring using the heteronuclear multiple‐bond correlation (HMBC) method. In this study, we achieved three major objectives: (a) new methodologies for the chemical modification of cellulose were developed; (b) new cellulose derivatives were designed, prepared and characterized; (c) unequivocal structural proof for carbon–carbon bond formation with cellulose was derived non‐destructively by use of one‐ and two‐dimensional NMR methods. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

14.
Iodine (I2) acts as a bifunctional halogen‐bond donor connecting two macrocyclic molecules of the bowl‐shaped halogen‐bond acceptor, N‐cyclohexyl ammonium resorcinarene chloride 1 , to form the dimeric capsule [(1,4‐dioxane)3@ 1 2(I2)2]. The dimeric capsule is constructed solely through halogen bonds and has a single cavity (V=511 Å3) large enough to encapsulate three 1,4‐dioxane guest molecules.  相似文献   

15.
The reaction of HON(tBu)CH2CH2N(tBu)OH with tri‐tert‐butyl gallium affords a hydroxylaminato complex of the formula [tBu2Ga{ON(tBu)CH2CH2N(H)(tBu)O}], which contains a monoanionic bishydroxylaminato ligand with one anionic and one neutral, but tautomeric aminoxide end, both linked to gallium by their oxygen atoms leading to a seven‐membered ring. The compound was characterised by elemental analysis, 1H and 13C NMR and determination of its crystal structure.  相似文献   

16.
A class of extended 2,5‐disubstituted‐1,3,4‐oxadiazoles R1‐C6H4‐{OC2N2}‐C6H4‐R2 (R1=R2=C10H21O 1 a , p‐C10H21O‐C6H4‐C?C 3 a , p‐CH3O‐C6H4‐C?C 3 b ; R1=C10H21O, R2=CH3O 1 b , (CH3)2N 1 c ; F 1 d ; R1=C10H21O‐C6H4‐C?C, R2=C10H21O 2 a , CH3O 2 b , (CH3)2N 2 c , F 2 d ) were prepared, and their liquid‐crystalline properties were examined. In CH2Cl2 solution, these compounds displayed a room‐temperature emission with λmax at 340471 nm and quantum yields of 0.730.97. Compounds 1 d , 2 a – 2 d , and 3 a exhibited various thermotropic mesophases (monotropic, enantiotropic nematic/smectic), which were examined by polarized‐light optical microscopy and differential scanning calorimetry. Structure determination by a direct‐space approach using simulated annealing or parallel tempering of the powder X‐ray diffraction data revealed distinctive crystal‐packing arrangements for mesogenic molecules 2 b and 3 a , leading to different nematic mesophase behavior, with 2 b being monotropic and 3 a enantiotropic in the narrow temperature range of 200210 °C. The structural transitions associated with these crystalline solids and their mesophases were studied by variable‐temperature X‐ray diffractometry. Nondestructive phase transitions (crystal‐to‐crystal, crystal‐to‐mesophase, mesophase‐to‐liquid) were observed in the diffractograms of 1 b, 1 d , 2 b, 2 d , and 3 a measured at 25200 °C. Powder X‐ray diffraction and small‐angle X‐ray scattering data revealed that the structure of the annealed solid residue 2 b reverted to its original crystal/molecular packing when the isotropic liquid was cooled to room temperature. Structure–property relationships within these mesomorphic solids are discussed in the context of their molecular structures and intermolecular interactions.  相似文献   

17.
Sodium in dry methanol reduces 2‐cyanopyridine in the presence of 3‐piperidylthiosemicarbazide and produces 2‐pyridine‐formamide‐3‐piperidylthiosemicarbazone, HAmpip. Complexes with zinc(II), cadmium(II), and mercury(II) have been prepared and characterized by elemental analyses and spectroscopic techniques. In addition, the crystal structures of [Zn(Ampip)2], [Zn(Ampip)(Oac)]2, [Cd(HAmpip)Cl2]·(CH3)2SO, [Cd(HAm‐pip)Br2] · (CH3)2SO, [Cd(HAmpip)I2]·(CH3)2SO, [Cd(Ampip)2] and [Hg(HAmpip)Br2]·(CH3)2SO have been solved. Coordination of the anionic and neutral thiosemicarbazone ligand is via the pyridyl nitrogen, imine nitrogen and thiolato/thione sulfur atom, respectively. In [Zn(Ampip)(OAc)]2 one of the bridging acetato ligands has monodentate coordination and the other bridges in a bidentate manner. 113Cd NMR studies were carried out on the [Cd(HAmpip)X2](X = Cl, Br or I) and [Cd(Ampip)(OAc)]2 complexes. The 113Cd chemical shifts are affected by the halogen and range from 411 to 301 ppm, and the spectrum of [Cd(Ampip)(OAc)]2 shows two signals at 450 and 251 ppm. The 199Hg NMR spectrum of [Hg(HAmpip)Cl2] also is discussed.  相似文献   

18.
The MP2 ab initio quantum chemistry methods were utilized to study the halogen‐bond and pnicogen‐bond system formed between PH2X (X = Br, CH3, OH, CN, NO2, CF3) and BrY (Y = Br, Cl, F). Calculated results show that all substituent can form halogen‐bond complexes while part substituent can form pnicogen‐bond complexes. Traditional, chlorine‐shared and ion‐pair halogen‐bonds complexes have been found with the different substituent X and Y. The halogen‐bonds are stronger than the related pnicogen‐bonds. For halogen‐bonds, strongly electronegative substituents which are connected to the Lewis acid can strengthen the bonds and significantly influenced the structures and properties of the compounds. In contrast, the substituents which connected to the Lewis bases can produce opposite effects. The interaction energies of halogen‐bonds are 2.56 to 32.06 kcal·mol?1; The strongest halogen‐bond was found in the complex of PH2OH???BrF. The interaction energies of pnicogen‐bonds are in the range 1.20 to 2.28 kcal·mol?1; the strongest pnicogen‐bond was found in PH2Br???Br2 complex. The charge transfer of lp(P) ? σ*(Br? Y), lp(F) ? σ*(Br? P), and lp(Br) ? σ*(X? P) play important roles in the formation of the halogen‐bonds and pnicogen‐bonds, which lead to polarization of the monomers. The polarization caused by the halogen‐bond is more obvious than that by the pnicogen‐bond, resulting in that some halogen‐bonds having little covalent character. The symmetry adapted perturbation theory (SAPT) energy decomposition analysis showes that the halogen‐bond and pnicogen‐bond interactions are predominantly electrostatic and dispersion, respectively.  相似文献   

19.
Reaction of Ti(OCH2CH2OR)4 (R?CH3 and C2H5) with 8‐hydroxyquinoline in benzene at room temperature resulted in the formation of Ti(C9H6NO)2(OCH2CH2OR)2, characterized by IR, 1H‐NMR, UV and mass spectroscopies. The molecular structure of Ti(C9H6NO)2(OCH2CH2OCH3)2 has been determined by single‐crystal X‐ray structure analysis. The geometry at titanium is a distorted octahedron, with the nitrogen atoms of quinolinate occupying the trans position with respect to oxygens of the 2‐methoxyethoxy groups. The prepared quinolinate derivatives of titanium alkoxides are very stable towards hydrolysis and harsh conditions are required for hydrolytic cleavage. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

20.
The adsorption behaviour of the CdII–MOF {[Cd(L)2(ClO4)2]·H2O ( 1 ), where L is 4‐amino‐3,5‐bis[3‐(pyridin‐4‐yl)phenyl]‐1,2,4‐triazole, for butan‐2‐one was investigated in a single‐crystal‐to‐single‐crystal (SCSC) fashion. A new host–guest system that encapsulated butan‐2‐one molecules, namely poly[[bis{μ3‐4‐amino‐3,5‐bis[3‐(pyridin‐4‐yl)phenyl]‐1,2,4‐triazole}cadmium(II)] bis(perchlorate) butanone sesquisolvate], {[Cd(C24H18N6)2](ClO4)2·1.5C4H8O}n, denoted C4H8O@Cd‐MOF ( 2 ), was obtained via an SCSC transformation. MOF 2 crystallizes in the tetragonal space group P43212. The specific binding sites for butan‐2‐one in the host were determined by single‐crystal X‐ray diffraction studies. N—H…O and C—H…O hydrogen‐bonding interactions and C—H…π interactions between the framework, ClO4? anions and guest molecules co‐operatively bind 1.5 butan‐2‐one molecules within the channels. The adsorption behaviour was further evidenced by 1H NMR, IR, TGA and powder X‐ray diffraction experiments, which are consistent with the single‐crystal X‐ray analysis. A 1H NMR experiment demonstrates that the supramolecular interactions between the framework, ClO4? anions and guest molecules in MOF 2 lead to a high butan‐2‐one uptake in the channel.  相似文献   

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