共查询到20条相似文献,搜索用时 36 毫秒
1.
《Magnetic resonance in chemistry : MRC》2003,41(12):1000-1008
The conformations of cis‐ ( 1 ) and trans‐cyclopentane‐1,3‐diol ( 2 ) have been studied by ab initio (Gaussian 98) and molecular mechanics (PCMODEL) calculations and by NMR spectroscopy. The calculations gave two low‐energy conformations for ( 1 ), 1A and 1B , both with axial hydroxyl groups. Two conformations with equatorial hydroxyl groups ( 1C and 1D ) were found but with much higher energy (ca 4.0 kcal mol?1). Five low‐energy conformers were found for 2 . Four were envelope conformations and one a half‐chair. The complete analysis of the 400 MHz 1H NMR spectra of 1 in a variety of solvents and 2 in chloroform was performed by extensive decoupling experiments, iterative computer analysis and spectral simulation. This gave all the H,H couplings in the molecule, including in 1 a long‐range 4J(H,H) coupling between H‐2cis and H‐4,5cis. The 3J(H,H) couplings were used to determine the conformer populations in these molecules. This was initially achieved using the Haasnoot, de Leeuw and Altona equation. to obtain the conformer couplings. It was found that this equation was not accurate for the C·CH2·CH2·C fragment in these molecules and the following equation was derived for this fragment from five‐ and six‐ membered cyclic compounds in fixed conformations: (1) The conformer populations were obtained by calculating the conformer couplings which were then compared with the observed couplings. Compound 1 in benzene solution is an approximately equal mixture of conformers 1A and 1B with small (<4%) amounts of 1C and 1D . In the polar solvents acetone and acetonitrile the populations of 1A and 1B are again equal, with 20% of 1C and <2% of 1D . In 2 the major conformers are 2B and 2D with small amounts of 2C , 2E and 2A . These novel findings are considered with previous data on cyclopentanol and cis‐ and trans‐cyclopentane‐1,2‐diol and it is shown that the axial hydroxyl substituent at the fold of the envelope appears to be a major factor in determining the conformational energies of these compounds. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
2.
Ulrich Girreser Ullvi Bluhm Bernd Clement Dieter Heber 《Magnetic resonance in chemistry : MRC》2013,51(11):714-721
The NMR spectroscopic data of a series of thirty‐four 3‐acylpyrido[1,2‐a]pyrimidinium salts are analyzed, which were prepared as either perchlorates or chlorides. Methyl group substituted 3‐aroyltetrahydropyrido[1,2‐a]pyrimidines with the methyl substituent in positions 6, 8 and 9 as well as both in positions 6 and 8 were investigated bearing various aroyl substituents. Unequivocal assignment of all resonances was achieved via two‐dimensional 1H,1H‐COSY measurements, 1H,13C and 1H,15N HSQC as well as HMBC experiments, and important diagnostic CH and NH couplings in the heteroaromatic ring system are evaluated. The influence of the methyl substituents was analyzed on the proton, carbon and nitrogen shifts. A significant effect of the counter ion on some chemical shifts of the nuclei under discussion of the pyridopyrimidines is found, allowing the indirect detection of the anion, which is confirmed by direct measurement of the 35Cl nucleus of the perchlorates. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
3.
Lívia O. A. Ferreira Ana Karoline S. M. Valdo Jos Antnio Nascimento Neto Leandro Ribeiro Jefferson R. D. da Silva Luiz H. K. Queiroz Caridad N. Perez Felipe T. Martins 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(6):694-701
We report a new polymorph of (1E,4E)‐1,5‐bis(4‐fluorophenyl)penta‐1,4‐dien‐3‐one, C17H12F2O. Contrary to the precedent literature polymorph with Z′ = 3, our polymorph has one half molecule in the asymmetric unit disordered over two 50% occupancy sites. Each site corresponds to one conformation around the single bond vicinal to the carbonyl group (so‐called anti or syn). The other half of the bischalcone is generated by twofold rotation symmetry, giving rise to two half‐occupied and overlapping molecules presenting both anti and syn conformations in their open chain. Such a disorder allows for distinct patterns of intermolecular C—H…O contacts involving the carbonyl and anti‐oriented β‐C—H groups, which is reflected in three 13C NMR chemical shifts for the carbonyl C atom. Here, we have also assessed the cytotoxicity of three symmetric bischalcones through their in vitro antitumour potential against three cancer cell lines. Cytotoxicity assays revealed that this biological property increases as halogen electronegativity increases. 相似文献
4.
Peter W. A. Howe 《Magnetic resonance in chemistry : MRC》2012,50(10):705-708
Fluorine‐containing compounds are rare in biological systems, so fluorine NMR spectroscopy can selectively detect and quantify fluorinated xenobiotics in crude biological extracts. The high sensitivity of fluorine NMR allows the detection of compounds containing isolated trifluoromethyl groups at nanogramme levels. However, it only provides limited structural information about trifluoromethyl‐containing compounds owing to the difficulty of interpreting fluorine chemical shifts and the low sensitivity of HOESY experiments used to correlate fluorine nuclei with protons in the same compound. This paper demonstrates that long‐range fluorine–proton J‐couplings can be used to correlate isolated trifluoromethyl groups with nearby protons with significantly higher sensitivity than HOESY. Fluorine‐observe fluorine–proton HMQC can even give correlations when the fluorine–proton J‐couplings are less than the observed fluorine resonance linewidth, so it provides a useful alternative source of structural information about fluorinated xenobiotics. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
5.
《Magnetic resonance in chemistry : MRC》2002,40(11):738-742
An unsymmetrical heterocyclic diamine, 1,2‐dihydro‐2‐(4‐aminophenyl)‐4‐[4‐(4‐aminophenoxy)‐4‐phenyl]‐(2H)phthalazin‐1‐one, was synthesized. Its 1H and 13C NMR spectra were completely assigned by utilizing the two‐dimensional heteronuclear 13C–1H multiple‐bond coherence (HMBC) spectroscopy, and heteronuclear 13C–1H one‐bond correlation spectroscopy, homonuclear shift correlation spectroscopy (H,H‐COSY) and rotating frame Overhauser enhancement spectroscopy (ROESY). The structure of the compound was shown to be the phthalazinone rather than the phthalazine ether from cross peaks and chemical shifts of the protons. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
6.
Influence of dibenzoylmethane's substituents in meta and para positions on chemical shift values of tautomers' characteristic protons was investigated in four solvents with 1H NMR spectroscopy: acetone‐d6, benzene‐d6, CDCl3 and deuterated dimethyl sulfoxide (DMSO‐d6). It was proved that the influence of substituents on chemical shifts strongly depends on the kind of the solvent; the greatest changes were observed in benzene‐d6 and the smallest in CDCl3. In acetone‐d6 and DMSO‐d6, the influence of substituents on chemical shifts is similar and the most regular. It allowed a fair correlation of chemical shifts of para‐substituted dibenzoylmethane derivatives' characteristic protons with Hammett substituent constants in these solvents. In CDCl3, characteristic protons' chemical shifts were near 1H NMR spectroscopy measurement error limits, and, therefore, correlation with Hammett substituent constants in this solvent was unsatisfactory. In benzene, although the changes of chemical shifts are the most evident, the changes are also the most irregular, and, therefore, correlation in this solvent failed completely. Results of meta‐substituted derivatives were much more irregular, and their correlation with Hammett substituent constants was poor in all investigated solvents. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
7.
Sergei V. Chapyshev Evgeny N. Ushakov Alexander V. Chernyak 《Magnetic resonance in chemistry : MRC》2013,51(9):562-568
2,4,6‐Triazido‐s‐triazine, 2,4,6‐triazidopyrimidine and six different 2,4,6‐triazidopyridines were studied by 15N NMR spectroscopy. The assignment of signals in the spectra was performed using the gauge‐independent atomic orbital (GIAO)–Tao‐Perdew‐Staroverov‐Scuseria exchange‐correlation functional (TPSS)h/6‐311+G(d,p) calculations on the M06‐2X/6‐311+G(d,p) optimized molecular geometries. The Truhlar and coworkers' continuum solvation model called SMD was applied to treat solvent effects. With this approach, the root mean square error in estimations of the 15N chemical shifts for the azido groups was just 1.9 ppm. It was shown that the different reactivity of the α‐ and γ‐azido groups in pyridines correlates well with the chemical shifts of the Nα signals of these groups. Of two nonequivalent azido groups of azines, the azido group with the most shielded Nα signal is the most electron‐deficient and reactive toward electron‐rich reagents. By contrast, the azido group of azines with the most deshielded Nα signal is the most reactive toward electron‐poor reagents. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
8.
The Substituent Effect of 1‐Arylazonaphthen‐2‐ols on Azo‐hydrazone Tautomerization According to NMR Analysis
下载免费PDF全文
![点击此处可从《中国化学会会志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The substituent effect on azo‐hydrazone tautomerization of 1‐arylazonaphthen‐ols is studied by means of NMR analysis. Among the 13C chemical shifts, the C(2) of this series compound is the most sensitive to the variation in the nature of substituent on the phenyl ring. Therefore, the variation in the chemical shifts of C(2) is used to probe the substituent effect by using the substituent chemical shifts and free energy vs. Hammett’s constant (χρ+). Both methods give a negative correlation slope, indicating the electron‐with‐ drawing groups favor the hydrazone tautomer form. The effect on the chemical shifts of C(2) of compound 8 in ten solvents can be classified as the solvent with a proton‐donor, proton‐acceptor and arenes system. The substituent with electron‐donating character is more sensitive to the nature of solvent and it favors the hydrazone form. Free energy obtained from the dynamic NMR technique indicates the tautomerization favors the hydrazone‐form for the substituent with electron‐withdrawing character. 相似文献
9.
Nader Noroozi Pesyan 《Magnetic resonance in chemistry : MRC》2011,49(9):592-599
Isotopic effect on tautomeric behaviors of the synthesized 5‐phenoxy‐ (1a), 5‐(2,6‐dimethylphenoxy)‐ (1b), 5‐(2,6‐diisopropylphenoxy)‐ (1c), 5‐(2,6‐dimethoxyphenoxy)‐ (1d) and 5‐(4‐methylphenoxy)‐tetrazole (1e) were investigated in DMSO‐d6 by adding one drop of D2O. Among 1a–e, 1a, 1d and 1e show small rotational barrier around C5? O1 and O1? C6 while in 1b and 1c there are distinguishable rotational barrier about that bonds. The 1H NMR spectra of 1b and 1c show slightly different chemical shifts for two methyl and isopropyl groups on those phenyl ring, respectively, while the chemical shifts difference (Δδ) between two methyl and two isopropyl groups were enhanced by adding D2O. The 13C NMR spectra of 1b show two overlapped singlets for methyl groups after adding D2O. Representatively, the calculations of compound 1c were performed with GAUSSIAN‐03and the rotational barrier about C5? O1 and between isopropyl group and phenyl ring in 1c was calculated with B3LYP/6‐31G(d) basis set. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
10.
《Magnetic resonance in chemistry : MRC》2002,40(5):371-376
1H, 13C and two‐dimensional NMR analyses were applied to determine the NMR parameters of 6‐(2′,3′‐dihydro‐1′H‐inden‐1′‐yl)‐1H‐indene. The measurements were accomplished with 0.5 mg of the substance, this quantity being sufficient to determine the chemical shifts of all the H and C atoms, and also the appropriate coupling constants and to give the complete NMR resonance assignments of the molecule. The predicted patterns of the four different H atoms of the methylene groups of the indane structural element coincided completely with the complex patterns in the NMR spectra. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
11.
Francis E. Porbeni I. Daniel Shin Xintao Shuai Xingwu Wang Jeffery L. White Xin Jia Alan E. Tonelli 《Journal of Polymer Science.Polymer Physics》2005,43(15):2086-2096
A biodegradable diblock copolymer of poly(ϵ‐caprolactone) (PCL) and poly(L ‐lactide) (PLLA) was synthesized and characterized. The inclusion compound (IC) of this copolymer with α‐cyclodextrin (α‐CD) was formed and characterized. Wide‐angle X‐ray diffraction showed that in the IC crystals α‐CDs were packed in the channel mode, which isolated and restricted the individual guest copolymer chains to highly extended conformation. Solid‐state 13C NMR techniques were used to investigate the morphology and dynamics of both the bulk and α‐CD‐IC isolated PCL‐b‐PLLA chains. The conformation of the PCL blocks isolated within the α‐CD cavities was similar to the crystalline conformation of PCL blocks in the bulk copolymer. Spin–lattice relaxation time (T1C) measurements revealed a dramatic difference in the mobilities of the semicrystalline bulk copolymer chains and those isolated in the α‐CD‐IC channels. Carbon‐observed proton spin–lattice relaxation in the rotating frame measurements (T1ρH) showed that the bulk copolymer was phase‐separated, while, in the IC, exchange of proton magnetization through spin‐diffusion between the isolated guest polymer chains and the host α‐CD was not complete. The two‐dimensional solid‐state heteronuclear correlation (HetCor) method was also employed to monitor proton communication in these samples. Intrablock exchange of proton magnetization was observed in both the bulk semicrystalline and IC copolymer samples at short mixing times; however, even at the longest mixing time, interblock proton communication was not observed in either sample. In spite of the physical closeness between the isolated included guest chains and the host α‐CD molecules, efficient proton spin diffusion was not observed between them in the IC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2086–2096, 2005 相似文献
12.
Alexandru T. Balaban Donald C. Young Janez Plavec Klemen Pečnik Matevž Pompe Jeremy E. Dahl Robert M. K. Carlson 《Magnetic resonance in chemistry : MRC》2015,53(12):1003-1018
Tetramantanes, and all diamondoid hydrocarbons, possess carbon frameworks that are superimposable upon the cubic diamond lattice. This characteristic is invaluable in assigning their 1H and 13C NMR spectra because it translates into repeating structural features, such as diamond‐cage isobutyl moieties with distinctively complex methine to methylene signatures in COSY and HMBC data, connected to variable, but systematic linkages of methine and quaternary carbons. In all tetramantane C22H28 isomers, diamond‐lattice structures result in long‐range 4JHH, W‐coupling in COSY data, except where negated by symmetry; there are two highly symmetrical and one chiral tetramantane (showing seven 4JHH). Isobutyl‐cage methines of lower diamondoids and tetramantanes are the most shielded resonances in their 13C spectra (<29.5 ppm). The isobutyl methylenes are bonded to additional methines and at least one quaternary carbon in the tetramantanes. W‐couplings between these methines and methylenes clarify spin‐network interconnections and detailed surface hydrogen stereochemistry. Vicinal couplings of the isobutyl methylenes reveal positions of the quaternary carbons: HMBC data then tie the more remote spin systems together. Diamondoid 13C NMR chemical shifts are largely determined by α and β effects, however γ‐shielding effects are important in [123]tetramantane. 1H NMR chemical shifts generally correlate with numbers of 1,3‐diaxial H–H interactions. Tight van der Waals contacts within [123]tetramantane's molecular groove, however, form improper hydrogen bonds, deshielding hydrogen nuclei inside the groove, while shielding those outside, indicated by Δδ of 1.47 ppm for geminal hydrogens bonded to C‐3,21 . These findings should be valuable in future NMR studies of diamondoids/nanodiamonds of increasing size. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
13.
《Magnetic resonance in chemistry : MRC》2002,40(5):353-360
The 15N NMR chemical shifts of N7‐ and N9‐substituted purine derivatives were investigated systematically at the natural abundance level of the 15N isotope. The NMR chemical shifts were determined and assigned using GSQMBC, GHMBC, GHMQC and GHSQC experiments in solution. 15N cross‐polarization magic angle spinning data were recorded for selected compounds in order to study the principal values of the 15N chemical shifts. Geometric parameters obtained by using RHF/6–31G** and single‐crystal x‐ray structural analysis were used to calculate the chemical‐shielding constants (GIAO and IGLO) which were then used to assign the nitrogen resonances observed in the solid‐state NMR spectra and to determine the orientation of the principal components of the shift tensors. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
14.
《Magnetic resonance in chemistry : MRC》2002,40(3):237-240
The complete 1H NMR chemical shift assignments of 1,2,3,4,5,6,7,8‐octahydroacridine ( 1 ), 1,2,3,4,5,6,7,8‐octahydro‐9‐(3‐pyridyl)acridine ( 2 ), 1,2,3,4,5,6,7,8‐octahydro‐9‐(4‐pyridyl)acridine ( 3 ) and the corresponding N(10)‐oxides 1a , 2a and 3a , respectively, were achieved on the basis of 400 MHz 1H NMR spectra and proton–proton decoupling, HMQC and NOEDIFF experiments. The spectral data for the above compounds provided the first experimental evidence of the difference in the anisotropy effect of the two non‐symmetrical moieties of the pyridine nucleus, and allowed us to ascertain that the shielding effect of the moiety defined by the C(2′)—N—C(6′) atoms is weaker than that of the C(3′)—C(4′)—C(5′) moiety. The 13C NMR spectra of 1 – 3 and 1a – 3a and the effect of N(10)‐oxidation on the 13C NMR chemical shifts are also discussed. The N‐oxidation of 2 and 3 with m‐chloroperbenzoic acid occurred regiospecifically, affording the N(10)‐oxides 2a and 3a free of N(1′)‐oxide isomers. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
15.
Paul Leonard 《Magnetic resonance in chemistry : MRC》2013,51(1):9-15
The 1H NMR spectra of 35 cyclic and acyclic esters are analysed to give the 1H chemical shifts and couplings. The substituent chemical shifts of the ester group were analysed using three‐bond (γ) effects for near protons and the electric field, magnetic anisotropy and steric effect of the ester group for more distant protons. The electric field is calculated from the partial atomic charges on the O?C = O atoms, and the asymmetric magnetic anisotropy of the carbonyl group acts at the midpoint of the C = O bond. The values of the anisotropies Δχparl and Δχperp were for the aliphatic esters 10.35 and ?18.84 and for the conjugated esters 7.33 and ?15.75 (×10?6 Å3/molecule). The oxygen steric coefficients found were 104.4 (aliphatic C = O), 45.5 (aromatic C = O) and 16.0 (C–O) (×10?6 Å6/molecule). After parameterisation, the overall RMS error for the data set of 280 entries was 0.079 ppm. The strongly coupled 1H NMR spectra of the 2‐methyl, 3‐methyl and 4‐methyl γ‐butyrolactones were analysed and the methyl conformational equilibrium obtained from the observed couplings. The observed versus calculated density functional theory (DFT) ΔG(ax‐eq) was 1.0 (1.01), 0.34 (0.54) and 0.65 (0.71) kcal/mol res. The shielding effect of a methyl cis to a proton in the five‐membered lactone rings is ?0.40 ±0.05 ppm and deshielding trans effect 0.12 ±0.05 ppm, which is common to both five and six membered rings. The cis/trans isomerism in the vinyl esters methyl acrylate, crotonate and methacrylate and methyl furoate was examined using the 1H chemical shifts. The calculated shifts of both the cis and trans isomers were in good agreement with the observed shifts. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
16.
Monoalkylated acylguanidines are important functional groups in many biologically active compounds and additionally applied in coordination chemistry. Yet a straightforward assignment of the individual NH chemical shifts and the acylguanidine conformations is still missing. Therefore, in this study, NMR spectroscopic approaches for the chemical and especially the conformational assignment of protonated monoalkylated acylguanidines are presented. While NOESY and 3JH, H scalar couplings cannot be applied successfully for the assignment of acylguanidines, 4JH, H scalar couplings in 1H,1H COSY spectra allow for an unambiguous chemical shift and conformational assignment. It is shown that these 4JH, H long‐range couplings between individual acylguanidinium NH resonances are observed solely across all‐trans (w) pathways. Already one cis orientation in the magnetisation transfer pathway leads to signal intensities below the actual detection limit and significantly lower than cross‐peaks from 2JNH, NH couplings or chemical exchange. However, it should be noted that also in the case of conformational exchange being fast on the NMR time scale, averaged cross‐peaks from all‐trans 4JH, H scalar couplings are detected, which may lead at first glance to an incomplete or even wrong conformational analysis. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
17.
Mehdi Rimaz Nader Noroozi Pesyan Jabbar Khalafy 《Magnetic resonance in chemistry : MRC》2010,48(4):276-285
The tautomerism of the synthesized 3‐arylpyrimido[4,5‐c]pyridazine‐5,7(6H,8H)‐diones ( 1a–d ) and 3‐aryl‐7‐thioxo‐7,8‐dihydro‐6H‐pyrimido[4,5‐c]pyridazine‐5‐ones ( 2a–d ) was studied in dimethyl sulfoxide (DMSO)‐d6. 1H NMR spectra of 1a–d showed a clustered water molecule in the structure backbone that is attached by strong intermolecular H bonding. The relation between the temperature and H bonding of the clustered water molecule with 1a was also studied as representative. The relation between the electronegativity (χ) of the substituent on phenyl ring and the chemical shifts of clustered water protons in 1a–d was also studied. All of 1a–d and also 2d compounds existed in lactam ( I ) form, whereas 2a–c compounds have two distinguished tautomers in DMSO‐d6 [lactam ( I ) and lactim ( II ) forms]. The solvent‐substrate proton exchange was examined in compounds 1a–d and 2a–d by adding one drop of D2O. All compounds (except 1d ) showed proton/deuterium exchange of the clustered water protons in DMSO by adding one drop of D2O. Some compounds (but not all of them) that are easily soluble in DMSO‐d6 containing D2O showed isotopic splitting (β‐isotope effect) in their 13C NMR spectra. Among them, compound 1a was the best evidence to help the spectral assignments and structure determination of predominant tautomer by carbon‐13 splitting (β‐isotope effect). Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
18.
《Magnetic resonance in chemistry : MRC》2003,41(4):301-303
4‐Methyl‐6,8‐dihydroxy‐7H‐benz[de]anthracen‐7‐one was isolated from the sap of Aloe by column chromatography. Its 1H and 13C NMR spectra were completely assigned by utilizing two‐dimensional 1H‐detected heteronuclear one‐bond (HMQC) and multiple‐bond (HMBC) chemical shift correlation experiments together with 1H–1H COSY and DEPT techniques. These techniques were also valuable in assigning the protons and carbons of those benzanthrone compounds which were previously incompletely reported because of the overlap of proton signals. The molecular structure was elucidated by 2D NMR analysis. The spectral properties (MS, IR and UV) are also presented. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
19.
《Magnetic resonance in chemistry : MRC》2003,41(1):53-60
The use of Eu(fod)3 in the analysis of the 1H and 13C NMR spectra of cis and trans‐fused β‐hydroxydecalones is described. The relative configuration of the substituents is discussed using the PMLIS algorithm to determine the lanthanide (Eu) ion position in the complex in an effective axially symmetric model. The conformations of two cis‐decalones are also discussed. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
20.
Dr. Ana Pérez Dr. Diana de Saá Prof. Alfredo Ballesteros Prof. José Luis Serrano Dr. Teresa Sierra Dr. Pilar Romero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(31):10271-10279
The self‐assembly of polycatenar molecules derived from 1,6‐diphenyl‐3,4‐dipropyl‐3‐hexen‐1,5‐diyne has been studied in detail by solution NMR spectroscopy. The analysis of the concentration‐ and temperature‐dependent evolution of the chemical shifts and the diffusion coefficients in [D12]cyclohexane agrees well with an isodesmic model of association in this solvent. The association constants for the stacking and entropy and enthalpy of the process have been obtained. The driving force for the aggregation process is provided by a negative enthalpy (ΔH), which is partially compensated by a negative entropy (ΔS). A structural study of the self‐assembly in solution has been carried out with the help of NOESY NMR spectroscopic experiments. 相似文献