Azacalix[6]arene hexamethyl ether: synthesis, structure, and selective uptake of carbon dioxide in the solid state

To investigate dynamic solid-state complexation hitherto unexplored in nitrogen-bridged calixarene analogues, azacalix[6]arene hexamethyl ether has been prepared in three steps by applying a 5+1 fragment-coupling approach by using a Buchwald- Hartwig aryl amination reaction with the aid of our previously devised temporal N-silylation protocol. X-ray crystallographic analysis and NMR spectroscopic measurements have revealed that the azacalix[6]arene is well endowed with hydrogen-bonding ability, by which both the molecular and crystal structures are controlled. The azacalix[6]arene is conformationally flexible in solution on the NMR time scale, whereas it adopts a definite 1,2,3-alternate conformation with S2 symmetry in the solid state as a result of intramolecular bifurcated hydrogen-bonding interactions. In the crystal, molecules of the azacalix[6]arene are mutually interacted by intermolecular hydrogen bonds to establish one-dimensional hexane-filled nanochannel crystal architecture. Although the single crystal was broken after desolvation, the resultant polycrystalline powder material was capable of selectively adsorbing CO2 among the four main gaseous components of the atmosphere. In contrast, carbocyclic p-tert-butylcalix[6]arene hexamethyl ether, the crystal structure of which was also elucidated for the first time in the present study, gave rise to almost no uptake of CO2. Additional solid-gas adsorption experiments for another three gases, such as N2, O2, and Ar, suggested that quadrupole/induced-dipole interactions and/or hydrogen-bonding interactions played an important role in permitting the observed selective uptake of CO2 by this new azacalix[6]arene in the solid state.     

Spontaneous and selective CO2 sorption under ambient conditions in seemingly nonporous molecular crystal of azacalix[5]arene pentamethyl ether

Described are the syntheses, crystal structures, and solid-gas adsorption behaviors of azacalix[4]arene tetramethyl ether and azacalix[5]arene pentamethyl ether. While the former compound exhibited no adsorption of four main atmospheric components, the latter selectively and rapidly adsorbed CO(2) at ambient temperature and pressure. X-ray crystallographic and potential energy distribution analysis revealed that azacalix[5]arene created an energetically favorable space for CO(2) in its seemingly nonporous crystal, leading to the observed selective CO(2) uptake under ambient conditions.     

Exhaustively methylated azacalix[4]arene: preparation, conformation, and crystal structure with exclusively CH/pi-controlled crystal architecture

[structure: see text]. Described are the preparation, conformation, and crystal structure of exhaustively methylated azacalix[4]arene involving nitrogen atoms as bridging units. NMR and X-ray crystallographic analysis have demonstrated that this novel azacalix[4]arene adopts a 1,3-alternate conformation both in solution and in the solid state. The crystal structure has been characterized solely by intermolecular CH/pi interactions, by which the azacalix[4]arenes mutually interact with each other outside the cavity to furnish a two-dimensional network structure.     

Synthesis,structure, and conformation of terphenylene-derived azacalix[4]aromatics

Several novel azacalix[4]aromatics constituting terphenylene units have been synthesized via sequential nucleophilic aromatic substitution reactions of 5′-t-butyl-(1,1′:3′,1″-terphenyl)-3,3″-diamine 9 and 5′-t-butyl-(1,1′:3′,1″-terphenyl)– 4,4″-diamine 11 with 1,5-difluoro-2,4-dinitrobenzene and cyanuric chloride, respectively. The bridging –NH– functions of the tetra-nitro substituted azacalix[2]arene[2]terphenylenes 1 and 2 have been transformed to the corresponding –N(CH₃)– bridged azacalix[2]arene[2]terphenylenes 3 and 4 via N-alkylation. Single crystal X-ray analysis revealed that the terphenyl-3,3″-diamine derived azacalix[2]terphenylene[2]triazine 5 adopts a distorted chair conformation in the solid state, and the terphenyl-4,4″-diamine derived azacalix[2]terphenylene[2]triazine 6 was found to adopt a 1,3-alternate conformation.     

Imidazobenzimidazole fused azacalix[4]arenes: Synthesis,structure, and Zn2+-selective colorimetric-fluorometric sensor

Tetra(amino)azacalix[4]arene skeleton was functionalized at the bridging NH sites using various aromatic aldehydes via formation of imidazobenzimidazole fused heterocycles. X-ray single crystal analysis revealed distorted 1,3-alternate conformations for the resulting macrocycles. Anthracenyl and pyrenyl modified imidazobenzimidazole fused azacalix[4]arenes existed as dimers in the solid state, associated mainly through π-π stacking interactions between the planar polycyclic fluorophores. The tetrapyrenyl modified product was further used as a Zn²⁺-selective sensor, which showed naked-eye detected color change and enhanced excimer emission. The stoichiometry between the sensor and Zn²⁺ was determined to be 1:1 and the association constant was 1.1 × 10⁵ L/mol. The sensing process was highly selective and showed strong anti-interference with presence of other cations. The UV-vis spectral changes in the sensing process were completely reversible by alternate addition of Zn²⁺ and F⁻, showing an efficient ‘‘on–off-on’’ result.     

Hydrogen-bonded 1D and 2D Assemblies of Tetraiso-butyl-resorcin[4]arene in the Crystalline State

1 INTRODUCTION There is continuing interest in the assembly of molecular capsules based on concomitant formation of multiple hydrogen bonds between smaller mole- cular components[1]. A particularly attractive buil- ding block is calix[4]resorcinarenes with eight pen- dant hydroxyl functional groups[2]. In a crystal engi- neering design strategy for molecular self-assembly, cocrystallization of C-methylcalix[4]resorcinarenes with nitrogen-donor molecules such as pyridines in the presence …     

C(aryl)-C(alkyl) bond formation from Cu(ClO(4))(2)-mediated oxidative cross coupling reaction between arenes and alkyllithium reagents through structurally well-defined Ar-Cu(iii) intermediates

The stable and structurally well-defined Ar-Cu(iii) intermediates, that are prepared almost quantitatively from the reaction of azacalix[1]arene[3]pyridines with Cu(ClO(4))(2)·6H(2)O under aerobic conditions, reacted smoothly with a number of alkyllithium reagents under mild conditions to form C(aryl)-C(alkyl) bonds.     

Synthesis and characterization of diametrically substituted tetra-O-n-butylcalix[4]arene ligands and their chelated complexes of titanium,molybdenum, and palladium

The ligation properties of three new upper-rim-substituted calix[4]arene ligands, 5,17-bis(hydroxymethyl)-tetra-n-butoxycalix[4]arene ((HOCH2)2-nBu4Clx, 7), 5,17-bis((diphenylphosphinito)methoxy)-tetra-n-butoxycalix[4]arene ((PPh2OCH2)2-nBu4Clx, 8), and 5,17-bis((diphenylphosphino)methyl)-tetra-n-butoxycalix[4]arene ((PPh2CH2)2-nBu4Clx, 10) are reported herein. The newly prepared compounds differ from previously reported diametrically substituted calix[4]arene derivatives in that the lower-rim substituent was n-butyl. The presence of this lower-rim substituent did not reduce the inherent crystallinity of these complexes as purification of all materials occurred via simple crystallizations. The key precursor for the syntheses of 8 and 10 was 7, acquisition of which occurred in six steps starting from tetra-tert-butylcalix[4]arene, 1. Calix[4]arene derivatives include, tetra-n-butoxycalix[4]arene (nBu4Clx, 3), 5,11,17,23-tetrabromo-tetra-n-butoxycalix[4]arene (Br4-nBu4Clx, 4), 5,17-dibromo-tetra-n-butoxycalix[4]arene (Br2-nBu4Clx, 5), 5,17-bis(formyl)-tetra-n-butoxycalix[4]arene ((CHO)2-nBu4Clx, 6), and 5,17-bis(chloromethyl)-tetra-n-butoxycalix[4]arene ((ClCH2)2-nBu4Clx, 9), all of which were synthesized using modifications of existing procedures. Characterization of all compounds occurred, when possible, using 1H, 13C, and 31P NMR, elemental analyses, FAB-MS, ESI-MS, FT-IR, and X-ray crystallography. The solid-state structures of all calix[4]arene intermediates and ligands showed that the annulus adopted the pinched-cone conformation in which the average C(5)...C(17) intraannular separation was 4.5 +/- 0.4 A. Reaction of 7 with CpTiMe3 yielded the cis-chelate, CpTi(Me)[(OCH2)2-nBu4Clx] (11), quantitatively. Data obtained using ESI-MS (positive-ion mode) confirmed the monomer formulation showed above, and 1H NMR spectra provided sufficient information to deduce the nature of the Ti coordination sphere. Reaction of 8 with cis-Cl2Pd(NCPh)2 in refluxing benzene afforded cis-Cl2Pd[(PPh2OCH2)2-nBu4Clx] (12) in good yields. The monomeric identity of this compound was verified by both X-ray crystallography and positive-ion ESI-MS. The cis-bidentate calix[4]arene ligand did not undergo any noticeable contortion upon chelation of the PdCl2 fragment. Acid-promoted decomposition of 12 occurred in the presence of adventitious HCl and gaseous HCl, and the products of this decomposition were 9 and [mu2-ClPd(PPh2OH)(PPh2O)]2. In addition, chelates of 8 that contained Mo(CO)3L (L = NCMe (14a), NCEt (14b), and CO (14c)) showed that the mode of coordination was relatively insensitive to the identity of the metal. X-ray crystallography afforded views of the solid-state structures of 14b,c and, like 12, showed that the Mo(CO)3L fragment resided above the pinched-cone of the calix[4]arene. 1H NMR revealed that C-H/pi interactions existed between L (14a,b) and a phenyl ring of the coordinated phosphinite. Finally, the bis(diphenylphosphine)calix[4]arene ligand (10) readily coordinated the Mo(CO)3L species, but the reaction did not go to completion, as evidenced by 1H NMR, even after a 5 day reaction time. Data suggest that the product is similar to that observed for 12 and 14, but the incomplete reaction complicated attempts to obtain pure material and prohibited definitive assignment of the coordination array.     

Synthesis and structure of N-methylated azacalix[4]pyridines and azacalix[1]arene[3]pyridines

Reaction of azacalix[4]pyridine and azacalix[1]arene[3]pyridine with methyl iodide afforded N-methylated products selectively and highly efficiently. Crystal structures revealed that the modified electronic nature of the pyridines could change the conjugation between the bridging nitrogen and the neighbouring aromatics.     

Synthesis of tetraazacalix[2]arene[2]triazines: tuning the cavity by the substituents on the bridging nitrogen atoms

[Structure: see text] A number of tetraazacalix[2]arene[2]triazines bearing different substituents on the bridging nitrogen atoms were synthesized efficiently using a fragment coupling strategy. The N-arylation of the parent azacalix[2]arene]2]triazine afforded tetra(arylaza)calix[2]arene[2]triazine in 91% yield. The introduction of different substituents on the bridging positions led to the regulation of the cavity of the resulting macrocyclic molecules.     

Electronic structure, molecular electrostatic potentials, vibrational spectra in substituted calix[n]arenes (n = 4, 5) from density functional theory

Electronic structure, molecular electrostatic potential, and vibrational frequencies of para-substituted calix[n]arene CX[n]-R (n = 4, 5; R = H, NH(2), t-Bu, CH(2)Cl, SO(3)H, NO(2)) and their thia analogs (S-CX[n]-R; with R = H and t-Bu) in which sulfur bridges two aromatic rings of CX[n] have been derived from the density functional theory. A rotation around CH(2) groups connecting the phenol rings engenders four, namely, cone, partial cone, 1,2-alternate, and 1,3-alternate CX[n]-R conformers. Of these, the cone conformer comprising of large number of O1-H1···O1' interactions turns out to be of lowest energy. Normal vibration analysis reveal the O1-H1 stretching frequency of unsubstituted CX[n] shifts to higher wavenumber (blue shift) on substitution of electron-withdrawing (NO(2) or SO(3)H) groups, while electron-donating substituents (NH(2), t-Bu) engender a shift of O1-H1 vibration in the opposite direction (red shift). The direction of frequency shifts have been analyzed using natural bond orbital analysis and molecular electrostatic potential (MESP) topography. Furthermore, calculated (1)H NMR chemical shift (δ(H)) in modified CX[n] hosts follow the order: H1 > H3/H5 > H7(a) > H7(b). The δ(H) values in CX[4] are in consonant with the observed (1)H NMR spectra.     

Photoreductive self-assembly from [Mo7O24]6- to carboxylates-coordinated {Mo142} Mo-blue nanoring in the presence of carboxylic acids

The primary steps of the photoredox reaction between [Mo7O24]6- and carboxylic acid electron (and proton) donors in aqueous solutions are investigated by the chemically induced dynamic electron spin polarization (CIDEP) spectroscopy. The excitation of the O-->Mo ligand-to-metal charge-transfer (LMCT) bands of [Mo7O24]6- in the presence of CH3CO2H induces the emissive electron spin polarization (ESP) of *CH2CO2 and *CH3 radicals with an accompanying formation of the one-electron reduced species [Mo7O23(OH)]6-, which is demonstrated by the triplet mechanism involving the O --> Mo LMCT triplet states. The prolonged photolysis of the solution containing [Mo7O24]6- and CH3CO2H at pH = 3.4 leads to the formation of the acetate/propionate-coordinated {Mo142} Mo-blue nanoring, [MoV28MoV(I)114O429H10(H2O)(49)(CH3)CO2 triple bond Ac5(C2H5CO2 triple bond Pr)]30- (1a) through the formation of the cis-configured dimeric dehydrative condensation to two-electron reduced Mo-blue [(Mo7O23)2]10- ({Mo14}). 1a is isolated as a [NH4]+/[Me3NH]+-mixed salt which is formulated as [NH4]27[Me3NH]3[Mo(V)28Mo(VI)114O429H10(H2O)49(CH3CO2)5(C2H5CO2)].150 +/- 10H2O (1) by results of elementary analysis, single-crystal X-ray analysis, 1H NMR, IR, and UV/Vis measurements, and manganometric redox titration. Based on the building-block sequence of for 1a, the bottom-up processes from [Mo7O24]6- to the {Mo142} ring in the coexistence of beta-[Mo8O26]4- are discussed by (i) the stabilization of the molecular curvature of {Mo14} through both the intramolecular transfer of monomolybdates and the intermolecular transfer of monomolybdates as degradation fragments of beta-[Mo8O26]4-, to yield {Mo21} and {Mo20} building blocks, (ii) the outer-ring formation resulting from seven successive two-electron-photoreductive condensations among {Mo21} and {Mo20}, and (iii) inner-ring formation resulting from eight successive dehydrative condensations between monomolybdate linkers attached to the neighboring head Mo sites.     

Origins of cooperative noncovalent host-guest chemistry in mixed valence complexes

The electronic effects resulting from noncovalent host-guest interactions between calix[6]arene and a ruthenium dimer, [Ru3O(OAc)6(CO)(ppy)]2-mu-pz (ppy=4-phenyl pyridine, pz=pyrazine), are presented. The noncovalent interaction is between the calix[6]arene and the ppy ligands of the dimer. The dimer can bind 2 equiv of calix[6]arene. The complex [Ru3O(OAc)6(CO)(ppy)]2-mu-pz forms a highly stable mixed valence ion with strong electronic coupling between the two Ru3 clusters. The strength of the electronic interaction is found to be moderated by calix[6]arene binding. Addition of calix[6]arene to the mixed valence ion causes the electronic coupling to decrease. The binding of calix[6]arene is found to be cooperative. The origins of cooperative binding are developed in terms of the potential energy surfaces associated with the symmetric and asymmetric mixed valence ion. In particular, it is found that symmetry breaking (through the binding of a single calix[6]arene) destabilizes the mixed valence state. Restoration of symmetry (through the binding of a second calix[6]arene) increases the stability of the mixed valence ion and provides an additional driving force for the binding of the second calix[6]arene.     

A New Coordinated Transition-metal Linked Network Compound Constructed by Octamolybdate Chain

1 INTRODUCTION The polyoxometalates have aroused extensive in-terest due to their alluring topologies and potentialapplications in various fields (e.g. catalysis, biology,medicine and materials science)[1]. A variety of po-lyoxometalate anions and related fragments withoxygen-rich compositions can serve as inorganic li-gands to coordinate secondary transition metal ions(so-called heterometals, such as Cu2 , Ni2 , Co2 andMn2 )[2]. Thus, larger discrete species and infinitelyextending ar…     

Rigidity and/or flexibility of calixarenes. effect of the p-sulfonatocalix[n]arenes (n = 4, 6, and 8) on the electron transfer process [Ru(NH3)5pz]2+ + Co(C2O4)3(3-)

The reaction [Ru(NH3)5pz]2+ + Co(C2O4)33- has been studied in aqueous solutions of p-sulfonatocalix[n]arene (n = 4, 6, and 8). The results are interpreted by using the pseudophase model. Results show that the rigidity and/or flexibility of the assembled rings have a great effect on the thermodynamics of inclusion of the guest into the host and, therefore, on the kinetics of the electron transfer processes that take place in these media. The obtained results are discussed from the viewpoint of two types of interactions: electrostatic and nonelectrostatic. From surface potential measurements, the guest-host interactions have been demonstrated to be mainly due to nonelectrostatic interactions, although the species are charged. So, the nonelectrostatic contribution to the equilibrium constant in all the calixarenes studied is 1 order of magnitude higher than the electrostatic one (Knel = 144 and 884 mol-1 dm3 for p-sulfonatocalix[n]arene (n = 4 and 6, respectively) and Kel approximately 10 mol-1 dm3). Electrostatic interactions also affect the kinetic results.     

Synthesis,structures, and conformational characteristics of calixarene monoanions and dianions

The synthesis, complete characterization, and solid state structural and solution conformation determination of calix[n]arenes (n = 4, 6, 8) is reported. A complete series of X-ray structures of the alkali metal salts of calix[4]arene (HC4) illustrate the great influence of the alkali metal ion on the solid state structure of calixanions (e.g., the Li salt of monoanionic HC4 is a monomer; the Na salt of monoanionic HC4 forms a dimer; and the K, Rb, and Cs salts exist in polymeric forms). Solution NMR spectra of alkali metal salts of monoanionic calix[4]arenes indicate that they have the cone conformation in solution. Variable-temperature NMR spectra of salts HC4.M (M = Li, Na, K, Rb, Cs) show that they possess similar coalescence temperatures, all higher than that of HC4. Due to steric hindrance from tert-butyl groups in the para position of p-tert-butylcalix[4]arene (Bu(t)C4), the alkali metal salts of monoanionic Bu(t)C4 exist in monomeric or dimeric form in the solid state. Calix[6]arene (HC6) and p-tert-butylcalix[6]arene (Bu(t)C6) were treated with a 2:1 molar ratio of M(2)CO(3) (M = K, Rb, Cs) or a 1:1 molar ratio of MOC(CH(3))(3) (M = Li, Na) to give calix[6]arene monoanions, but calix[6]arenes react in a 1:1 molar ratio with M(2)CO(3) (M = K, Rb, Cs) to afford calix[6]arene dianions. Calix[8]arene (HC8) and p-tert-butylcalix[8]arene (Bu(t)()C8) have similar reactivity. The alkali metal salts of monoanionic calix[6]arenes are more conformationally flexible than the alkali metal salts of dianionic calix[6]arenes, which has been shown by their solution NMR spectra. X-ray crystal structures of HC6.Li and HC6.Cs indicate that the size of the alkali metal has some influence on the conformation of calixanions; for example, HC6.Li has a cone-like conformation, and HC6.Cs has a 1,2,3-alternate conformation. The calix[6]arene dianions show roughly the same structural architecture, and the salts tend to form polymeric chains. For most calixarene salts cation-pi arene interactions were observed.     

Tautomerization of methyldiazene to formaldehyde-hydrazone in ruthenium and osmium complexes

Mixed-ligand hydrazine complexes [M(CO)(RNHNH2)P4](BPh4)2 (1, 2) [M = Ru, Os; R = H, CH3, C6H5; P = P(OEt)3] with carbonyl and triethyl phosphite were prepared by allowing hydride [MH(CO)P4]BPh4 species to react first with HBF4.Et2O and then with hydrazines. Depending on the nature of the hydrazine ligand, the oxidation of [M(CO)(RNHNH2)P4](BPh4)2 derivatives with Pb(OAc)4 at -30 C gives acetate [M(kappa1-OCOCH3)(CO)P4]BPh4 (3a), phenyldiazene [M(CO)(C6H5N=NH)P4](BPh4)2 (3c, 4c), and methyldiazene [M(CO)(CH3N=NH)P4](BPh4)2 (3b, 4b) derivatives. Methyldiazene complexes 3b and 4b undergo base-catalyzed tautomerization of the CH3N=NH ligand to formaldehyde-hydrazone NH2N=CH2, giving the [M(CO)(NH2N=CH2)P4](BPh4)2 (5, 6) derivatives. Complexes 5 and 6 were characterized spectroscopically and by the X-ray crystal structure determination of the [Ru(CO)(NH2N=CH2)[P(OEt)3]4](BPh4)2 (5) derivative. Acetone-hydrazone [M(CO)[NH2N=C(CH3)2]P4](BPh4)2 (7, 8) complexes were also prepared by allowing hydrazine [M(CO)(NH2NH2)P4](BPh4)2 derivatives to react with acetone.     

A Facile Method of Synthesis of a Calix[4]arene Amide and the Crystal Structure of a Self-assembled Calix[4]arene Amide via van Der Waals Interaction

A new facile method of synthesis of calix[4]arene amide via the aminolysis of the calix[4]arene esters was reported. One ethyl ester of the compound (2) was aminolysized byn-butylamine. The crystal structure of compound (1)shows that one ethyl ester of compound (1) enters into thecavity of another compound (1) forming a long chainhost-guest supramolecule. From the 2D NMR data, the compound(1) does not assemble in THF or CHCl₃ solution. The CH- interaction and crystallization energy might be theimportant driving forces for forming the self-assembledcalix[4]arene.     

2001年全国高中学生化学竞赛（决赛）理论试题答案

第 1题1- 1　Ａ :ＮＨ4 ＨＣＯ3[或 (ＮＨ4 ) 2 ＣＯ3]　Ｂ :ＫＣｌ　Ｃ :Ｋ2 ＳＯ4 　Ｄ :ＮＨ4 Ｃｌ　Ｅ :Ｆｅ2 Ｏ3　Ｆ :ＣＯ21- 2　反应 (1) :(ｍ +ｎ)ＦｅＳＯ4 + 2 (ｍ +ｎ)ＮＨ4 ＨＣＯ3=Ｆｅｍ +ｎ(ＯＨ) 2ｎ(ＣＯ3) ｍ↓ + (ｎ +ｍ) (ＮＨ4 ) 2 ＳＯ4 + (2ｎ +ｍ)ＣＯ2 ↑ +ｍＨ2 ＯＮＨ4 ＨＣＯ3 写成 (ＮＨ4 ) 2 ＣＯ3,Ｆｅｍ +ｎ(ＯＨ) 2ｎ(ＣＯ3) ｍ 写成 (1)Ｆｅ2 (ＯＨ) 4-2ｍ(ＣＯ3) ｍ,(2 )Ｆｅ2 (ＯＨ) 2 ＣＯ3,(3)Ｆｅ(ＯＨ) 2 和ＦｅＣＯ3 且配平的 ,也给分。反应 (2 ) :2Ｆｅｍ +ｎ(ＯＨ) 2ｎ(ＣＯ3) ｍ+ ｍ +ｎ2 Ｏ2…     

以新型[Mo_8Na_2O_(28)]~(6-)多阴离子为建筑单元的2D→3D互锁配位聚合物的组装、结构及性质

以NiCl2、(NH4)6Mo7O24、NaOH及柔性配体1,3-二(1,2,4-三氮唑-1-)丙烷(Btp)为原料,采用水热技术合成了一个结构新颖的基于多金属氧酸盐(多酸)[Mo8Na2O28]6–的二维有机-无机杂化配位聚合物[Ni(Btp)2(H2O)Mo8Na2O26(μ2-OH)2]0.5·H2O(1).通过元素分析、IR、TG和X-射线单晶衍射等对化合物1进行了表征.X-射线单晶结构分析表明,该化合物属于单斜晶系,P21/c空间群,晶胞参数a=11.6871(8)?,b=21.7506(15)?,c=14.9208(8)?,Z=4,R1=0.0487,wR2=0.1409.化合物1中含有一种新型的多酸阴离子簇[Mo8Na2O28]6–,可以看作是由β-[Mo8O26]4–转化成的具有[V10O28]6–结构特征的新型多酸.该多酸被镍和Btp形成的二维(2D)层夹在中间,形成一种夹心型的2D柱状层结构.二维柱状层之间相互穿插形成了一个二维→三维(2D→3D)的互锁结构,柱状层之间的氢键作用又进一步稳固了整个框架.此外,该化合物具有较好的电催化和光催化性能.