Novel dual molecular‐ and ion‐recognition responsive poly(N‐isopropylacrylamide‐co‐benzo‐12‐crown‐4‐acrylamide) (PNB12C4) linear copolymers with benzo‐12‐crown‐4 (B12C4) as both guest and host units are prepared. The copolymers exhibit highly selective sensitivities toward γ‐cyclodextrin (γ‐CD) and Na+. The presence of γ‐CD induces the lower critical solution temperature (LCST) of PNB12C4 copolymer to shift to a higher value due to the formation of 1:1 γ‐CD/B12C4 host‐guest inclusion complexes, while Na+ causes a negative shift in LCST due to the formation of 2:1 “sandwich” B12C4/Na+ host‐guest complexes. Regardless of the complexation order, when γ‐CD and Na+ coexist with PNB12C4, competitive complexation actions of B12C4 as both guest and host units toward γ‐CD and Na+ finally form equilibrium 2:2:1 γ‐CD/B12C4/Na+ composite complexes, and the final LCST values of PNB12C4 copolymer reach almost the same level. The results provide valuable guidance for designing and applying PNB12C4‐based smart materials in various applications.
The inclusion of the fluorescent organic dye, ethyl 3‐(7‐hydroxy‐2‐oxo‐2H‐chromen‐3‐yl)‐3‐oxopropanoate ( 1 ) by the host β‐cyclodextrin (β‐CD), and its response toward mercuric ions (Hg2+), was studied by UV/Vis, fluorescence, and 1H NMR spectroscopic analyses, mass spectrometry and molecular modeling studies. 1H NMR measurements together with molecular modeling studies for dye 1 demonstrate that it exhibits two tautomeric forms (keto and enol); however, when the dye is included into the β‐CD cavity, the enol form predominates. Moreover, by using spectroscopic and spectrometry techniques, a 1:1 stoichiometry was determined for the complexes formed between dye 1 (enol form) and β‐CD, with a binding constant (Kb1=1.8×104 m ?1) and for the dye 1 (keto form)‐Hg2+ (Kb2=2.3×103 m ?1). Interestingly, in the presence of 1 –β‐CD complex and mercuric ions, a ternary supramolecular system (Hg– 1 –β‐CD complex) was established, with a 1:1:1 stoichiometry and a Kb3 value of 4.3×103 m ?1, with the keto form of the dye being the only one present in this assembly. The three‐component system provides a starting point for the development of novel and directed supramolecular assemblies. 相似文献
This study shows that stereochemical factors largely determine the extent to which 6-(4′-t-butylphenylamino)-naphthalene-2-sulphonate, BNS? and its dimer, (BNS? )2, are complexed by β-cyclodextrin, βCD, and a range of linked βCD dimers. Fluorescence and 1H NMR studies, respectively, show that BNS? and (BNS? )2 form host–guest complexes with βCD of the stoichiometry βCD.BNS? (10? 4K1 = 4.67 dm3 mol? 1) and βCD.BNS22 ? (10? 2K2′ = 2.31 dm3 mol? 1), where the complexation constant K1 = [βCD.BNS? ]/([βCD][BNS? ]) and K2′ = [βCD. (BNS? )2]/([βCD.BNS? ][BNS? ]) in aqueous phosphate buffer at pH 7.0, I = 0.10 mol dm3 at 298.2 K. (The dimerisation of BNS? is characterised by 10? 2Kd = 2.65 dm3 mol? 1.) For N,N-bis((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)succinamide, 33βCD2su, N-((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)-N′-(6A-deoxy-6A-β-cyclodextrin)urea, 36βCD2su, N,N-bis(6A-deoxy-6A-β-cyclodextrin)succinamide, 66βCD2su, N-((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)-N′-(6A-deoxy-6A-β-cyclodextrin)urea, 36βCD2ur, and N,N-bis(6A-deoxy-6A-β-cyclodextrin)urea, 66βCD2ur, the analogous 10? 4K1 = 11.0, 101, 330, 29.6 and 435 dm3 mol? 1 and 10? 2K2′ = 2.56, 2.31, 2.59, 1.82 and 1.72 dm3 mol? 1, respectively. A similar variation occurs in K1 derived by UV–vis methods. The factors causing the variations in K1 and K2 are discussed in conjunction with 1H ROESY NMR and molecular modelling studies. 相似文献
In the crystal structure of the title compound, [LiPd2Cl4(C12H12N2)2](C24F20B)·1.196CD2Cl2 or [{(Me2bipy)PdCl2}2(μ‐Li)]+·B(C6F5)4−·1.196CD2Cl2 (Me2bipy is 4,4′‐dimethyl‐2,2′‐bipyridine), an Li+ cation is stabilized by complexation with two (Me2bipy)PdCl2 units through weak Li—Cl interactions. This compound is thus a rare example of a complex that exhibits an arrested Cl− abstraction. 相似文献
The β‐diketone 3‐(4‐cyanophenyl)pentane‐2,4‐dione crystallizes as the enol tautomer 4‐(2‐hydroxy‐4‐oxopent‐2‐en‐3‐yl)benzonitrile, C12H11NO2, (I), with an intramolecular O—H⋯O hydrogen bond [O⋯O = 2.456 (2) Å]. Reaction of (I) with copper acetate monohydrate in the presence of triethylamine leads to the formation of the copper(II) complexbis[3‐(4‐cyanophenyl)pentane‐2,4‐dionato‐κ2O,O]copper(II), [Cu(C12H10NO2)2], (II). In the structure of (II), the Cu atom is coordinated by four β‐diketonate O atoms in a slightly distorted square‐planar geometry, with Cu—O distances in the range 1.8946 (11)–1.9092 (11) Å. The nitrile moieties in (II) make it a candidate for reaction with other metal ions to produce supramolecular structures. 相似文献
A series of 2‐amino‐7‐methoxy‐4‐aryl‐4H‐chromene‐3‐carbonitrile compounds 2 were obtained by condensation of 3‐methoxyphenol with β‐dicyanostyrenes 1 in absolute ethanol containing piperidine. The intermediate enamines 3 were prepared by compounds 2 with 5‐substituted‐1,3‐cyclohexanedione using p‐toluenesuflonic acid (TsOH) as catalyst. The title compounds 11‐amino‐3‐methoxy‐8‐substituted‐12‐aryl‐8,9‐dihydro‐7H‐chromeno[2,3‐b]quinolin‐10(12H)‐one 4 were synthesized by cyclization of the intermediate enamines 3 in THF with K2CO3 /Cu2Cl2 as catalyst. The structures of all compounds were characterized by elemental analysis, IR, MS, and 1H NMR spectra. The crystal structure of compound 4i was determined by single‐crystal X‐ray diffraction analysis. 相似文献
The noncovalent interactions between 4′, 6‐diamidino‐2‐phenylindole (DAPI) and sulfobutylether β‐cyclodextrin (SBE7β‐CD) are evaluated by using photochemical measurements and compared with that of native β‐CD. Contrasting recognition behavior and intriguing modulations in the photochemical behavior of DAPI were observed. In particular, a large enhancement in the fluorescence emission and excited‐state lifetime were seen upon binding to SBE7β‐CD, with the SBE7β‐CD inclusion complex being approximately 1000 times stronger than that of β‐CD. The ensuing fluorescence “turn on” was demonstrated to be responsive to chemical stimuli, such as metal ions and adamantylanmine (AD). Upon addition of Ca2+/AD, nearly quantitative dissociation of the complex was established to regenerate the free dye and result in fluorescence “turn off”. The SO3? groups are believed to be critical for the strong and selective binding of the chromophore and the stimuli‐responsive tuning. This is as an important design criterion for the optimization of host–guest properties through supramolecular association, which is relevant for drug‐delivery applications. 相似文献
This work reports the elusive structural evidence for the [4]pseudorotaxane of β‐cyclodextrin (β‐CD) with coffee chlorogenic acid (CGA), a conjugate of caffeic acid (CFA) and quinic acid (QNA). A single‐crystal X‐ray structure analysis of the inclusion complex β‐cyclodextrin–chlorogenic acid–water (2/2/17), 2C42H70O35·2C16H18O9·17H2O, reveals that CGA threads through β‐CD and assembles via O—H…O hydrogen bonds and parallel‐displaced π–π interactions in the twofold symmetry‐related dimer yielding a [4]pseudorotaxane, which is crystallographically observed for the first time in CD inclusion complexes. The encapsulation of the aromatic ring and C=C—C(=O)O chain in the β‐CD dimeric cavity indicates that the CFA moiety plays a determinant role in complexation. This is in agreement with the DFT‐derived relative thermodynamic stabilities of the trimodal β‐CD–CGA inclusion complexes, that is, β‐CD complexed with different CGA components: C=C—C(=O)O chain > cyclohexane ring > aromatic ring. The complexation stability is further enhanced in the dimeric β‐CD–CGA complex, with the CFA moiety totally enclosed in the β‐CD dimeric cavity. 相似文献