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1.
《化学:亚洲杂志》2017,12(15):1909-1914
A dodecavanadate, [V12O32]4−, is an inorganic bowl‐type host with a cavity entrance with a diameter of 4.4 Å in the optimized structure. Linear, bent, and trigonal planar anions are tested as guest anions and the formation of host–guest complexes, [V12O32(X)]5− (X=CN, OCN, NO2, NO3, HCO2, and CH3CO2), were confirmed by X‐ray crystallographic analyses and a 51V NMR spectroscopy study. The degree of distortion of the bowl from a regular to an oval shape depends on the type of guest anion. In 51V NMR spectroscopy, all chemical shifts of the host–guest complexes are clearly shifted after guest incorporation. The incorporation reaction rates for OCN, NO2, HCO2, and CH3CO2 are much larger than those of NO3 and halides. The incorporated nonspherical molecular anions in the dodecavanadate host are easily dissociated or exchanged for other anions, whereas spherical halides in the host are preserved without dissociation, even in the presence of the tested anions.  相似文献   

2.
Several bis‐triazolium‐based receptors have been synthesized and their anion‐recognition capabilities have been studied. The central chiral 1,1′‐bi‐2‐naphthol (BINOL) core features either two aryl or ferrocenyl end‐capped side arms with central halogen‐ or hydrogen‐bonding triazolium receptors. NMR spectroscopic data indicate the simultaneous occurrence of several charge‐assisted aliphatic and heteroaromatic C?H noncovalent interactions and combinations of C?H hydrogen and halogen bonding. The receptors are able to selectively interact with HP2O73?, H2PO4?, and SO42? anions, and the value of the association constant follows the sequence: HP2O73?>SO42?>H2PO4?. The ferrocenyl end‐capped 72+?2 BF4 ? receptor allows recognition and differentiation of H2PO4? and HP2O73? anions by using different channels: H2PO4? is selectively detected through absorption and emission methods and HP2O73? by using electrochemical techniques. Significant structural results are the observation of an anion???anion interaction in the solid state (2:2 complex, 62+? [ H2P2O7 ] 2? ), and a short C?I???O contact is observed in the structure of the complex [ 8 2+][SO4]0.5[BF4].  相似文献   

3.
Binding of novel biphene[n]arene hosts to antiaromatic 7,7,8,8‐tetracyanoquinodimethane (TCNQ) are investigated by DFT. Biphene[4]arene favors the inclusion complex through noncovalent interactions, such as hydrogen bonding, π–π stacking, C?H???π, and C?H???H?C dihydrogen bonding. Donor–acceptor complexation renders aromatic character to the guest through charge transfer. The formation of TCNQ anionic radicals through supramolecular π stacking significantly influences its chemical and photophysical behavior. Electron density reorganization consequent to encapsulation of TCNQ reflects in the shift of characteristic vibrations in the IR spectra. The accompanying aromaticities arising from the induced ring currents are analyzed by employing nucleus‐independent chemical shifts based profiles.  相似文献   

4.
Mixed‐valence polyoxovanadates(IV/V) have emerged as one of the most intricate class of supramolecular all‐inorganic host species, able to encapsulate a wide variety of smaller guest templates during their self‐assembly formation process. As showcased herein, the incorporation of guests, though governed solely by ultra‐weak electrostatic and van der Waals interactions, can cause drastic effects on the electronic and magnetic characteristics of the shell complex of the polyoxovanadate. We address the question of methodology for the magnetochemical analysis of virtually isostructural {VIV/V22O54}‐type polyoxoanions of D2d symmetry enclosing diamagnetic VO2F2? (C2v), SCN? (C∞v), or ClO4? (Td) template anions. These induce different polarization effects related to differences in their geometric structures, symmetry, ion radii, and valence shells, eventually resulting in a supramolecular modulation of magnetic exchange between the V(3d) electrons that are partly delocalized over the {V22O54} shells. We also include the synthesis and characterization of the novel [VVO2F2@HVIV8VV14O54]6? system that comprises the rarely encountered discrete difluorovanadate anion as a quasi‐isolated guest species.  相似文献   

5.
The scaffold geometries, stability and magnetic features of the (pyridine‐2‐yl)methanolate (L) supported wheel‐shaped transition‐metal complexes with compositions [M6L12] ( 1 ), [Na?(ML2)6]+ ( 2 ), and [M′?(ML2)6]2+ ( 3 ), in which M=CoII, NiII, CuII, and ZnII were investigated with density functional theory (DFT). The goals of this study are manifold: 1) To advance understanding of the magnetism in the synthesized compounds [Na?(ML2)6]+ and [M′?(ML2)6]2+ that were described in Angew. Chem. Int. Ed.­ 2010 , 49, 4443 ( I ‐{Na?Ni6}, I ‐{Ni′?Ni6}) and Dalton Trans.­ 2011 , 40, 10526 ( II ‐{Na?Co6}, II ‐{Co′?Co6}); 2) To disclose how the structural, electronic, and magnetic characteristics of 1 , 2 , and 3 change upon varying MII from d7 (Co2+) to d10 (Zn2+); 3) To estimate the influence of the Na+ and M′2+ ions (XQ+) occupying the central voids of 2 and 3 on the external and internal magnetic coupling interactions in these spin structures; 4) To assess the relative structural and electrochemical stabilities of 1 , 2 , and 3 . In particular, we focus here on the net spin polarization, the determination of the strength and the sign of the exchange coupling energies, the rationalization of the nature of the magnetic coupling, and the ground‐state structures of 1 , 2 , and 3 . Our study combines the broken symmetry DFT approach and the model Hamiltonian methodology implemented in the computational framework CONDON 2.0 for the modeling of molecular spin structures, to interpret magnetic susceptibility measurements of I ‐{Na?Ni6} and I ‐{Ni′?Ni6}. We illustrate that whereas the structures, stability and magnetism of 1 , 2 , and 3 are indeed influenced by the nature of 3d transition‐metals in the {M6} rims, the XQ+ ions in the inner cavities of 2 and 3 impact these properties to an even larger degree. As exemplified by I ‐{Ni′?Ni6}, such heptanuclear complexes exhibit ground‐state multiplets that cannot be described by simplistic model of spin‐up and spin‐down metal centers. Furthermore, we assess how future low‐temperature susceptibility measurements at high magnetic fields can augment the investigation of compound 3 with M=Co, Ni.  相似文献   

6.
Formation of either a dimetallic compound or a 1 D coordination polymer of adiponitrile adducts of [Fe(bpte)]2+ (bpte=[1,2‐bis(pyridin‐2‐ylmethyl)thio]ethane) can be controlled by the choice of counteranion. The iron(II) atoms of the bis(adiponitrile)‐bridged dimeric complex [Fe2(bpte)22‐(NC(CH2)4CN)2](SbF6)4 ( 2 ) are low spin at room temperature, as are those in the polymeric adiponitrile‐linked acetone solvate polymer {[Fe(bpte)(μ2‐NC(CH2)4CN)](BPh4)2 ? Me2CO} ( 3? Me2CO). On heating 3? Me2CO to 80 °C, the acetone is abruptly removed with an accompanying purple to dull lavender colour change corresponding to a conversion to a high‐spin compound. Cooling reveals that the desolvate 3 shows hysteretic and abrupt spin crossover (SCO) S=0?S=2 behaviour centred at 205 K. Non‐porous 3 can reversibly absorb one equivalent of acetone per iron centre to regenerate the same crystalline phase of 3? Me2CO concurrently reinstating a low‐spin state.  相似文献   

7.
8.
We report the synthesis of the water‐soluble cryptophanol derivative 1 and the study of the chiroptical properties of its two enantiomers (>99 % ee) by polarimetry, electronic circular dichroism (ECD), and vibrational circular dichroism (VCD). We show that cryptophanol 1 exhibits unusual chiroptical properties in water under basic conditions (pH>12). For instance, the shapes of the ECD and VCD spectra of 1 in water were strongly dependent on the nature of the alkali metal ions (Li+, Na+, K+, Cs+) surrounding the cryptophane and whether or not a guest molecule is present inside the cavity of the host. To the best of our knowledge, this is the first example in which the nature of these counterions governs the chiroptical properties of a host molecule. Moreover, specific ECD spectra were obtained depending on the size of the guest molecules. This makes 1 a good sensor for small neutral molecules in aqueous solvent. Finally, VCD experiments associated with DFT calculations show that the chiroptical changes can be directly correlated to the presence of charges close to the aromatic rings and with a conformational change of the alkyl chains upon encapsulation.  相似文献   

9.
A full account of our studies of 2,4,6‐trinitrophenol (TNP) sensing is provided. A series of chemosensors 2 , 3 , 4 , 5 with a variety of aromatic chromophores for specific recognition of TNP has been designed and then realized through the fluorescence “on/off” mechanism. These chemosensors demonstrated highly selective, sensitive, and fluorescent quenching of TNP with remarkable visual changes through the intramolecular charge‐transfer (ICT) process. Their host–guest interactions were investigated by 1H NMR spectroscopic titrations and their corresponding co‐crystal structures, which showed that the 1:1 host–guest complexes were formed by multiple hydrogen‐bond interactions in solution or in the solid state. The origins of the significant affinity demonstrated during the fluorescence recognition process were further disclosed through DFT calculations of corresponding compounds.  相似文献   

10.
By exploiting the breathing behavior of nanopores, we have studied for the first time the dependency of the guest‐induced proton conductivity of an interpenetrated CuI metal–organic framework (CuI‐MOF, [ 1 ]) on various guest molecules. Proton conductivities of over 10?3 S cm?1 under humid conditions were induced by a series of guest molecules, namely N,N‐dimethylformamide, dimethyl sulfoxide, diethylamine, 1,4‐dinitrobenzene, nitrobenzene, pyridine, and 1H‐1,2,4‐triazole. A detailed investigation of the guest‐incorporated complexes revealed that low‐energy proton conduction occurs under humid conditions through the Grotthuss mechanism in [ 1 ?NB] and through the vehicle mechanism in the rest of the complexes. Single‐point energy computations revealed considerable stabilization upon guest encapsulation. To the best of our knowledge, [ 1 ] represents the first example in which considerably high protonic conductivity is triggered upon the facile incorporation of small molecules of such a variety. The investigation portrayed herein may be a stepping stone towards the rational design of proton‐conducting materials for practical applications.  相似文献   

11.
A computational study is performed to identify the origin of the room‐temperature stability, in aqueous solution, of functionalized π‐[R‐TTF]22+ dimers (TTF=tetrathiafulvalene; R=(CH2OCH2)5CH2OH) included in the cavity of a cucurbit[8]uril (CB[8]) molecule. π‐[R‐TTF]22+ dimers in pure water are weakly stable, and are mostly dissociated at room temperature. Upon addition of CB[8] to an aqueous π‐[R‐TTF]22+ solution, a (π‐[R‐TTF]2?CB[8])2+ inclusion complex is formed. The same complex is obtained after the sequential inclusion of two [R‐TTF].+ monomers in the CB[8] molecule. Both processes are thermodynamically and kinetically allowed. π‐[R‐TTF]22+ dimers dissolved in pure water present a [TTF].+???[TTF].+ long, multicenter bond, similar to that already identified in π‐[TTF]22+ dimers dissolved in organic solvents. Upon their inclusion in CB[8], the strength and other features of the [TTF].+???[TTF].+ long, multicenter bond are preserved. The room temperature stability of the π‐[R‐TTF]22+ dimers included in CB[8] is shown to originate in the π‐[R‐TTF]22+???CB[8] interaction, the strength of which comes from a strongly attractive electrostatic component and a dispersion component. Such a dominant electrostatic term is caused by the strongly polarized charge distribution in CB[8], the geometrical complementarity of the π‐[R‐TTF]22+ and CB[8] geometries, and the amplifying effect of the 2+ charge in π‐[R‐TTF]22+.  相似文献   

12.
A first principles methodology, aimed at understanding the roles of molecular conformation and energetics in host–guest binding interactions, is developed and tested on a system that pushes the practical limits of ab initio methods. The binding behavior between the [2.2.2]‐cryptand host (4,7,13,16,21,24‐hexaoxa‐1,10‐diaza‐bicyclo[8.8.8]hexacosane) and alkali metal cations (Li+, Na+, and K+) in gas, water, methanol, and acetonitrile is characterized. Hartree–Fock and density functional theory methods are used in concert with crystallographic information to identify gas phase, energy‐minimized conformations. Gas phase free energies of binding, with vibrational contributions, are compared to solution‐state binding constants through relative binding selectivity analysis. Calculated relative binding free energies qualitatively correlated with solution state experiments only after gas phase metal desolvation is considered. The B3LYP exchange–correlation functional improves theoretical correlations with experimental relative binding free energies. The relevance of gas phase calculations towards understanding binding in condensed phases is discussed. Natural bond orbital methods highlights previously unidentified intramolecular and intermolecular M+(222) chemistries, such as an intramolecular n′O→σ*CH hydrogen bond.  相似文献   

13.
The construction of efficient synthetic functional receptors with tunable cavities, and the self‐organization of guest molecules within these cavities through noncovalent interactions can be challenging. Here we have prepared a double‐cavity molecular cup based on hexaethynylbenzene that possesses a highly π‐conjugated interior for the binding of electron‐rich guests. X‐ray crystallography, NMR spectroscopy, UV/Vis spectroscopy, fluorescent spectroscopy, cyclic voltammetry, and SEM were used to investigate the structures and the binding behaviors. The results indicated that the binding of a guest in one cavity would affect the binding of the same or another guest in the other cavity. The effect of electron transfer in this system suggests ample opportunities for tuning the optical and electronic properties of the molecular cup and the encapsulated guest. The encapsulation of different guests would also lead to different aggregate nanostructures, which is a new way to tune their supramolecular architectures.  相似文献   

14.
A cyclophane is reported incorporating two units of a heptagon‐containing extended polycyclic aromatic hydrocarbon (PAH) analogue of the hexa‐peri‐hexabenzocoronene (HBC) moiety (hept‐HBC). This cyclophane represents a new class of macrocyclic structures that incorporate for the first time seven‐membered rings within extended PAH frameworks. The saddle curvature of the hept‐HBC macrocycle units induced by the presence of the nonhexagonal ring along with the flexible alkyl linkers generate a cavity with shape complementarity and appropriate size to enable π interactions with fullerenes. Therefore, the cyclophane forms host–guest complexes with C60 and C70 with estimated binding constants of Ka=420±2 m ?1 and Ka=(6.49±0.23)×103 m ?1, respectively. As a result, the macrocycle can selectively bind C70 in the presence of an excess of a mixture of C60 and C70.  相似文献   

15.
The dynamic positions of the dimetallic cluster inside the mid‐sized spherical cages of C80–C82 have been seldom studied, despite the high abundance of M2@C2n (2n=80, 82) species among various endohedral metallofullerenes. Herein, using crystallographic methods, we first unambiguously map the metal positions for both Ce2@D5h‐C80 and Ce2@Ih‐C80, showing how the symmetry or geometrical change in cage structure can influence the motional behavior of the cluster. Inside the D5h cage, the primary cerium sites have been identified along a cage belt of the contiguous hexagons, which suggests the significant influence of such a cage motif on endohedral cluster motion. Further analysis revealed a distorted D5h cage owing to the “punch‐out” effect of cerium atoms. The consequence is the presence of two localized electrostatic potential minima inside the cage of (D5h‐C80)6?, thus reflecting the primary ionic cerium–cage interaction. In contrast, a different motional behavior of Ce2 cluster was observed inside the Ih cage. With the major cerium sites, the molecule of Ce2@Ih‐C80 presented an approximate D2h configuration. With the combined theoretical study, we propose that the additional unidentified influence of NiII(OEP) (OEP=octaethylporphyrin) might be also relevant for the location of cerium sites inside the Ih cage.  相似文献   

16.
The photophysical properties of a multicomponent [1]rotaxane bearing a β‐cyclodextrin ring covalently connected to an axle comprising an azobenzene photoisomerisable moiety and a naphthalimide‐type fluorescent stopper are investigated by a combined experimental and computational study. The absorption and fluorescence spectra, and particularly the induced circular dichroism (ICD) signal, are determined. The latter shows a sign relation that cannot be rationalised in terms of the simple general rules commonly employed to analyse the ICD spectra of achiral guests encircled by chiral hosts. To assist the interpretation of experimental results, DFT and time‐dependent (TD) DFT calculations are performed to explore the availability of low‐energy conformations and to model their spectroscopic response. Molecular dynamics simulations performed in water show the interconversion of a number of conformers, the contribution of which to the ICD signal is in agreement with the observation.  相似文献   

17.
Treatment of the open‐cage fullerene C63H4NO2(Ph)2(Py)(N2C6H4) ( 1 ) with methanol at 150 °C results in an orifice‐enlargement reaction to give C69H8NO(CO2Me)(Ph)(Py)(N2C6H4) ( 2 ). The overall yield from C60 to isolated 2 is 6.1 % (four steps). Compound 2 contains a 24‐membered elliptic orifice that spans 8.45 Å along the major axis and 6.37 Å along the minor axis. The skeleton of 2 resembles the hypothetic C60H10 (5,5)‐carbon nanotube endcap. The cup‐shaped structure of 2 is able to include water, hydrogen cyanide, and acetylene, forming H2O@ 2 , HCN@ 2 , and C2H2@ 2 , respectively. The molecular structures of H2O@ 2 and HCN@ 2 have been determined by X‐ray crystallography. The 1H NMR spectra reveal substantial upfield shifts for the endohedral species, such as δ=?10.30 (for H2O), ?2.74 and ?14.26 (for C2H2), and ?1.22 ppm (for HCN), owing to the strong shielding effects of the fullerene cage.  相似文献   

18.
Engineering self‐templating inorganic architectures is critical for the development of bottom‐up approaches to nanoscience, but systems with a hierarchy of templates are elusive. Herein we describe that the cluster‐anion‐templated (CAT) assembly of a {CAT}?{Mo24Fe12} macrocycle forms a giant ca. 220 nm3 unit cell containing 16 macrocycles clustered into eight face‐shared tetrahedral cluster‐of‐clusters assemblies. We show that {CAT}?{Mo24Fe12} with different CATs gives the compounds 1 – 4 for CAT=Anderson {FeMo6} ( 1 ), Keggin {PMo12} ( 2 ), Dawson {P2W18} ( 3 ), and {Mo12O36(HPO3)2} ( 4 ) polyoxometalates. “Template‐free” assembly can be achieved, whereby the macrocycle components can also form a template in situ allowing template to macrocycle to superstructure formation and the ability to exchange the templates. Furthermore, the transformation of template clusters within the inorganic macrocycle {Mo24Fe12} allows the self‐generation of an uncapped {Mo12O36(HPO3)2} in compound 4 .  相似文献   

19.
Novel dynamic molecular tweezers (DMTs) 3 a , 3 b , 4 a , 4 b , and 5 b , composed of two tub‐shaped dibenzocyclooctatetraene (DBCOT) units, were designed and synthesized. The cyclooctatetraene (COT) rings of these DMTs readily invert in solution, and the molecular structure shows rigid syn and anti forms in an equilibrium mixture in solution. The syn and anti conformers can be observed by NMR. The isomerization barriers of 3 a , 3 b , 4 a , 4 b , and 5 b are in the range of 16.5–21.3 kcal mol?1, depending on steric repulsion between substituents of the COT rings and protons of the central benzene ring. These DMTs form complexes with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) and 1,2,4,5‐tetracyano‐benzene (TCNB) in solution and in the solid state. The binding abilities of these DMTs increase with electron‐donating substituents on COT, which increase the electron densities of the cavity of the syn form, as supported by theoretical calculations. In addition, elongation of the terminal alkoxy chains of the DMTs was found to cause the enhancement of van der Waals contact with guest molecules. Therefore, 5 b , which has CH2OMe groups on the COT rings and longer ethoxy groups on the terminal benzene rings, showed the highest electron density of the cavity and hence the highest binding ability with the electron‐deficient guest molecules. Interestingly, solutions of 3 b , 4 b , and 5 b show thermochromism in the presence of DDQ. A solution of 3 b or 4 b with DDQ in CHCl3 is green due to charge‐transfer interaction at room temperature and the color changes from green to yellow upon heating to 60 °C and from green to blue upon cooling to ?40 °C, whereas the high complexation ability of 5 b with DDQ only shows a change in the shade of blue.  相似文献   

20.
Iminosulfane(phosphane)carbon(0) derivatives (iSPCs; Ar3P→C←SPh2(NMe); Ar=Ph ( 1 ), 4‐MeOC6H4 ( 2 ), 4‐(Me2N)C6H4 ( 3 )) have been successfully synthesized and the molecular structure of 3 characterized. Carbone 3 is the first thermally and hydrolytically stable carbone stabilized by phosphorus and sulfur ligands. DFT calculations reveal the electronic structures of 1 – 3 , which have two lone pairs of electrons at the carbon center. First and second proton affinity values are theoretically calculated to be in the range of 286.8–301.1 and 189.6–208.3 kcal mol?1, respectively. Cyclic voltammetry measurements reveal that the HOMO energy levels follow the order of 3 > 2 > 1 and the HOMO of 3 is at a higher energy than those of bis(chalcogenane)carbon(0) (BChCs). The reactivities of these lone pairs of electrons are demonstrated by the C‐diaurated and C‐proton‐aurated complexes. These results are the first experimental evidence of phosphorus‐ and sulfur‐stabilized carbones behaving as four‐electron donors. In addition, the reaction of hydrochloric salts of the carbones with Ag2O gives the corresponding AgI complexes. The resulting silver(I) carbone complexes can be used as carbone transfer agents. This synthetic protocol can also be used for moisture‐sensitive carbone species.  相似文献   

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