Absolute one-handed chiral quinoline tetramers andoctamers containing different oxazolylanilines at the C-terminus have been synthesized.The absolute one-handed sense and diastereomeric excess values were valued by^1H...Absolute one-handed chiral quinoline tetramers andoctamers containing different oxazolylanilines at the C-terminus have been synthesized.The absolute one-handed sense and diastereomeric excess values were valued by^1H NMR.X-ray crystal diffractionand CD studies reveal that the S-oxazolylaniline always induces a P-handed helicity and the absolute helicity is driven by the stable three-center hydrogen bonding between protons in the amide and N atoms in oxazolylaniline and adjacent quinoline ring.CPL investigations demonstrated that S-CQn-a-d are CPL active and its g(lum)values are dependent on its length.Interestingly,the sizes of the substituents in the chiral centers are different,howeve r,they exert no effect on the dissymmetric factors g(abs)and g(lum)of quinoline oligoamide foldamers.展开更多
Two naphthalene（NP） and bipyridinium（BIPY^2＋） alternately incorporated polymers P1 and P2 have been prepared through the formation of dynamic hydrazone bonds. The polymers formed NP–BIPY^2＋donor–acceptor inter...Two naphthalene（NP） and bipyridinium（BIPY^2＋） alternately incorporated polymers P1 and P2 have been prepared through the formation of dynamic hydrazone bonds. The polymers formed NP–BIPY^2＋donor–acceptor interaction-induced pleated secondary structure. Upon reducing the BIPY^2＋units to radical cation BIPY＋, intramolecular dimerization of the BIPY＋units induced the backbones to afford another pleated secondary structure. Adding electron-rich macrocyclic polyether bis-1,5-dinaphtho[38]crown-10 or electron-deficient cyclobis（paraquat-p-phenylene） cyclophane did not break the first foldamer by complexing the BIPY^2＋or NP units of the polymers, whereas the di（radical cationic）ring of the second cyclophane could break the second foldamer by forming threading complexes with the BIPY＋units of the polymers.展开更多
A phosphorescent supramolecular foldamer is conveniently constructed by the 1:1 host-vip complexation with cucurbit[8]uril and 1,2-diaminocyclohexane-bridged 4-(4-bromophenyl)-pyridinium salt. The tightly compact ho...A phosphorescent supramolecular foldamer is conveniently constructed by the 1:1 host-vip complexation with cucurbit[8]uril and 1,2-diaminocyclohexane-bridged 4-(4-bromophenyl)-pyridinium salt. The tightly compact host-vip complexation in molecular foldamer can greatly suppress the fluorescence emissive channel and promote the intersystem crossing from singlet to triplet states, thus leading to the green phosphorescence at ambient temperature in aqueous solution. More intriguingly, the phosphorescence emission shows very rapid and sensitive responsiveness to different antibiotics in both inanimate milieu and living cells. Remarkably, the limit of detection of such binary inclusion complex toward sulfamethazine can reach as low as 1.86 × 10^(-7) mol/L. Thus, it is envisaged that this supramolecular nanoplatform featuring unique complexation-enhanced phosphorescence emission may hold great promise in sensing and detecting many other biological targets under physiological environment.展开更多
π-conjugated polymers(CPs)hold great promise for optoelectronics,energy,and biomedicine,yet bioinspired folded architectures remain underexplored due to limited coupling strategies.Here,we report a scalable synthesis...π-conjugated polymers(CPs)hold great promise for optoelectronics,energy,and biomedicine,yet bioinspired folded architectures remain underexplored due to limited coupling strategies.Here,we report a scalable synthesis of helical polymer nanotubes via homogeneous Suzuki-Miyaura cross-coupling.Their helical conformation is stabilized by electrostatic repulsion between heteroatoms or intramolecular hydrogen bonding,confirmed by AFM,single-crystal X-ray diffraction,CD spectroscopy,and theoretical modeling.The nanotubes(~5 nm in length)feature hydrophilic,electron-rich lumens and hydrophobic alkyl exteriors,enabling spontaneous insertion into lipid bilayers.They display distinct,pore-size-dependent transport:wider pores facilitate glucose permeation,while narrower channels with defined coordination sites show selective K^(+)transport.K^(+)selectivity was validated through vesicle-based kinetics and symmetric/asymmetric bilayer lipid membrane(BLM)assays.Notably,the F3 system achieved a K^(+)/Na^(+)selectivity ratio of 26.8 in asymmetric BLMs.This work introduces a new class of aromatic helical polymers and highlights the role of coordination site density in ion selectivity.π-conjugated helical polymers are demonstrated for the first time to exhibit both ion selectivity and small-molecule transport,offering a blueprint for designing artificial K^(+)-specific nanopores with bio-medical potential,especially for treating channelopathies.展开更多
Inspired by natural Ca^(2+)channels,we design and synthesize a type of artificial Ca^(2+)carriers using o-phenanthroline-oxadiazole-based foldamers.Through the incorporation of negative charges into cavity-containing ...Inspired by natural Ca^(2+)channels,we design and synthesize a type of artificial Ca^(2+)carriers using o-phenanthroline-oxadiazole-based foldamers.Through the incorporation of negative charges into cavity-containing foldamers,highly selective calcium ion transmembrane transport can be achieved,leading to the identification of two highly efficient Ca^(2+)carriers.Systematic investigation revealed a positive correlation between the number of negative charges on the foldamers and the foldamers‘cation-binding affinity.Furthermore,the size-selective effect,achieved through precise matching between the foldamer cavity dimensions and Ca^(2+)ion size,resulted in an unprecedented Ca^(2+)/Mg^(2+)selectivity ratio(S_(Ca/Mg)),reaching record S_(Ca/Mg) values greater than 100–the highest of all artificial Ca^(2+)carriers reported to date.Moreover,artificial Ca^(2+)carriers show high Ca^(2+)transport activity(EC_(50)=190 nM).This simple and modular approach enables tailored design of divalent cation transporters,thus providing promising applications for artificial divalent cation transporters in the fields of biochemistry and material chemistry.展开更多
By introducing two and three zinc porphyrin units to one side of hydrogen bonding-induced aromatic amide foldamers, two new molecular tweezers 1 and 2 have been prepared. To explore new possible binding patterns, a le...By introducing two and three zinc porphyrin units to one side of hydrogen bonding-induced aromatic amide foldamers, two new molecular tweezers 1 and 2 have been prepared. To explore new possible binding patterns, a leucine-based pyridine ligand 3 that bears a pentafluorophenyl group has been prepared. UV-Vis and IH NMR ex- periments reveal that 1 and 2 favorably complex one or two molecules of 3. UV-Vis titration experiments show that the apparent association constants of the complexes of the zinc porphyrin units of the two receptors and 3 are con- siderably higher than that of the complex between a simple control zinc porphyrin and 3. In the presence of excess of 3, the left zinc porphyrin unit of 1 and 2 can bind one more molecule of 3, which is, however, stabilized only by the single Zn-N coordination.展开更多
Conjugation,as an essential chemical term used to describe electron delocalization,can be roughly grouped into two categories,through-bond conjugation(TBC)and through-space conjugation(TSC).A hybrid conjugation system...Conjugation,as an essential chemical term used to describe electron delocalization,can be roughly grouped into two categories,through-bond conjugation(TBC)and through-space conjugation(TSC).A hybrid conjugation system integrating both TBC and TSC is rarely studied and utilized,for lack of a well-established model and difficulty of structure modification and property tuning,despite its theoretical significance and potential applications.Herein,various foldamers with a tetraphenylethene(TPE)core are employed as hybrid conjugation models to investigate structure–property correlation by introducing heterocycles of furan/thiophene into theπ-stacking TSC component.For comparison,two kinds of TPE-cored foldamers with different stacking models,a benzene–heterocycle stacking model and a benzene–benzene stacking model,are designed.Combining experimental measurements and theoretical calculations,the impact of benzene–heterocycle interaction on the hybrid conjugation natures and photophysical properties has been studied systematically.The results reveal that the benzene–heterocycle stacking model can fabricate a hybrid conjugation nature with an improved TSC component to make a more dominant contribution to the electronic transition natures than the benzene–benzene stacking model,leading to the distinguishing photophysical behavior.This work provides valuable guidance for the design of new functional materials with hybrid conjugation systems.展开更多
Recent studies have started to provide initial insights into the aggregation and assembly of two classes of back-rigidified foldamers with flat,curved backbones consisting of aromatic residues.With their persistent sh...Recent studies have started to provide initial insights into the aggregation and assembly of two classes of back-rigidified foldamers with flat,curved backbones consisting of aromatic residues.With their persistent shape that presents large,well-defined aromatic surface areas,these crescent foldamers were found to undergo size-dependent aggregation in solution and pack into 1D assemblies in the solid state.Crescent aromatic oligoamides undergo stacking interactions not only in polar solvents but also in nonpolar ones,a unique property that is not associated with many other molecules that associate via π-π stacking interaction.The stacking of oligo(m-phenylene ethynylenes) is similar to aromatic hydrocarbons,being promoted in polar solvents such as methanol while being discouraged in nonpolar solvents such as halohydrocarbons.The ready synthetic availability of crescent foldamers makes it possible to directly control the intermolecular interaction by tuning surface areas.Besides,the columnar assembly of these cavity-containing molecules provides a new strategy for constructing supramolecular nanotubular structures.展开更多
A series of aromatic oligoamide foldamers based on 8-fluoro amino-quinoline carboxyl acid have been synthe- sized and characterized. Studies show that these foldamers self-assemble to form well-defined twisted helical...A series of aromatic oligoamide foldamers based on 8-fluoro amino-quinoline carboxyl acid have been synthe- sized and characterized. Studies show that these foldamers self-assemble to form well-defined twisted helical mi- crofibers in chloroform-methanol （1 ： 1, V/V） binary solvent due to the intermolecular π-π stacking and van der Waals forces of aliphatic chains, which are supported by SEM, TEM and XRD. It is also revealed that the assembly morphologies show strong dependence on the length of alkyl chains.展开更多
The crystal structures of three intramolecularly hydrogen bonded rigid aromatic amide derivatives,which all bear one iodine atom at one end as the donor and one pyridine unit at the other end as the acceptor,have been...The crystal structures of three intramolecularly hydrogen bonded rigid aromatic amide derivatives,which all bear one iodine atom at one end as the donor and one pyridine unit at the other end as the acceptor,have been described to reveal the utility of halogen bonding in inducing the formation of supramolecular macrocycles.All the three compounds formed intermolecular I···N halogen bonding.For short compound 1,halogen bonding induced the formation of an extended supramolecular array.For longer folded compounds 2 and 3,halogen bonding could hold two molecules to form supramolecular macrocycles even by adopting a highly distorted,energetically less favorable conformation(for 3).Depending on the solvent for the growth of crystals,compound 3 could also gave rise to a halogen bonded supramolecular double helix.展开更多
Two benzene/2,2＇-bipyridine-alternately incorporated amide polymers have been prepared, which are driven by hydrophobicity to form two different helical conformations. Both helices exhibit twist sense bias in water i...Two benzene/2,2＇-bipyridine-alternately incorporated amide polymers have been prepared, which are driven by hydrophobicity to form two different helical conformations. Both helices exhibit twist sense bias in water induced by chiral valine side chains and the coordination of the 2,2＇-bipyridine unit to the Ni2＋ ions.展开更多
The complexing behaviour of two linear compounds 1 and 2 toward the trifluoroacetic acid （TFA） salts of n-dodecylamine, di-n-octylamine, n-dodecyl D- and L-phenylalaninates （3, 4, and D- and L-5） in chloroform has...The complexing behaviour of two linear compounds 1 and 2 toward the trifluoroacetic acid （TFA） salts of n-dodecylamine, di-n-octylamine, n-dodecyl D- and L-phenylalaninates （3, 4, and D- and L-5） in chloroform has been described. Compounds 1 and 2 consist of two folded amide moieties with two pyridyls at the terminals which are connected directly or with an acetylene linker. The rigidified folded moieties are stabilized by intramolecular hydrogen bonding, while the whole molecules can adopt an ＂S＂- or a ＂C＂-styled conformation depending on the relative orientation of the two rigidified moieties. ^1H NMR, UV-Vis, fluorescent and circular dichroism investigations revealed that 1 and 2 could bind primary and secondary ammonium cations with their ＂C＂-styled conformation. In the presence of 1 equiv, of TFA, the binding stability was increased significantly as a result of promoted formation of the ＂C＂-styled conformation due to the monoprotonation of the peripheral pyridyl units in 1 and 2. In contrast, the addition of 2 equiv, of TFA substantially weakened the binding stability because the ＂S＂-styled conformation was favored as a result of protonation of both of their pyridyl units. Moreover, remarkable induced circular dichroisms were also displayed for the complexes of 1 and 2 with chiral D- and L-5.展开更多
Two aromatic hydrazide haptamers have been prepared,with both consisting of two hydrogen bonded folded segments. Compared to their fully hydrogen bonded analogues,the flexibility of their backbones increases due to la...Two aromatic hydrazide haptamers have been prepared,with both consisting of two hydrogen bonded folded segments. Compared to their fully hydrogen bonded analogues,the flexibility of their backbones increases due to lack of one or two intramolecular hydrogen bonds at the middle aromatic unit. (2D) 1H NMR,circular dichroism and fluorescent studies revealed that both oligomers moderately complex n-octyl-α-L-glucopyranoside in chloroform.展开更多
Previously we have shown that POCl3-mediated H-bonding-directed one-pot macrocyclization allows for the highly selective preparation of five-residue macrocycles as the predominant product with low yields of hexamers a...Previously we have shown that POCl3-mediated H-bonding-directed one-pot macrocyclization allows for the highly selective preparation of five-residue macrocycles as the predominant product with low yields of hexamers and an undetectable occurrence of both tetramers and heptamers.Replacing the interiorly arrayed methyl groups with ethyl groups in these 4-7 residue macrocycles alters the relative stability order among them.Specifically,ethoxy-substituted six-residue macrocycle,rather than pentamer,turns out to be computationally the most stable,suggesting that ethoxy-containing hexamer possibly can be formed as the major product under suitable conditions.We have investigated this possibility by varying reaction temperatures and concentrations,invariably affording pentamer as the major macrocycle with strained circular hexamers and highly strained circular heptamers produced in substantial amounts.This discrepancy can be reasonably explained on the basis of bimolecular reactions between two oligomers higher than monomers via kinetic simulations.In this scenario,the acyclic pentamer is kinetically "trapped" to undergo an intramolecular cyclization to yield circular pentamer,rather than to produce acyclic hexamer.As a result,acyclic hexamer precursor is generated largely from sterically demanding bimolecular reactions between a dimer and a tetramer,or between two trimers that are kinetically slower than the pentamer-producing chain-growth reactions.We additionally found that one-pot macrocyclization proceeds to the largest extent at 40 ℃,an intriguing finding that highlights the low reactivities of acid chloride and amine groups in these H-bond-enforced acyclic oligomeric intermediates.展开更多
基金financial supports from the 973 Program(No.2015CB856502)the National Natural Science Foundation of China(No.21672026)。
文摘Absolute one-handed chiral quinoline tetramers andoctamers containing different oxazolylanilines at the C-terminus have been synthesized.The absolute one-handed sense and diastereomeric excess values were valued by^1H NMR.X-ray crystal diffractionand CD studies reveal that the S-oxazolylaniline always induces a P-handed helicity and the absolute helicity is driven by the stable three-center hydrogen bonding between protons in the amide and N atoms in oxazolylaniline and adjacent quinoline ring.CPL investigations demonstrated that S-CQn-a-d are CPL active and its g(lum)values are dependent on its length.Interestingly,the sizes of the substituents in the chiral centers are different,howeve r,they exert no effect on the dissymmetric factors g(abs)and g(lum)of quinoline oligoamide foldamers.
基金supported by The Ministry of Science and Technology of China (No. 2013CB834501)The Science and Technology Commission of Shanghai Municipality (No. 13M1400200)+1 种基金The Ministry of Education of China research fund for the doctoral programthe National Natural Science Foundation of China (Nos. 21432004 and 21472023)
文摘Two naphthalene（NP） and bipyridinium（BIPY^2＋） alternately incorporated polymers P1 and P2 have been prepared through the formation of dynamic hydrazone bonds. The polymers formed NP–BIPY^2＋donor–acceptor interaction-induced pleated secondary structure. Upon reducing the BIPY^2＋units to radical cation BIPY＋, intramolecular dimerization of the BIPY＋units induced the backbones to afford another pleated secondary structure. Adding electron-rich macrocyclic polyether bis-1,5-dinaphtho[38]crown-10 or electron-deficient cyclobis（paraquat-p-phenylene） cyclophane did not break the first foldamer by complexing the BIPY^2＋or NP units of the polymers, whereas the di（radical cationic）ring of the second cyclophane could break the second foldamer by forming threading complexes with the BIPY＋units of the polymers.
基金financially supported by the National Natural Science Foundation of China (Nos.21871154,21772099,21861132001,and 21873051)the Fundamental Research Funds for the Central Universities,Nankai University。
文摘A phosphorescent supramolecular foldamer is conveniently constructed by the 1:1 host-vip complexation with cucurbit[8]uril and 1,2-diaminocyclohexane-bridged 4-(4-bromophenyl)-pyridinium salt. The tightly compact host-vip complexation in molecular foldamer can greatly suppress the fluorescence emissive channel and promote the intersystem crossing from singlet to triplet states, thus leading to the green phosphorescence at ambient temperature in aqueous solution. More intriguingly, the phosphorescence emission shows very rapid and sensitive responsiveness to different antibiotics in both inanimate milieu and living cells. Remarkably, the limit of detection of such binary inclusion complex toward sulfamethazine can reach as low as 1.86 × 10^(-7) mol/L. Thus, it is envisaged that this supramolecular nanoplatform featuring unique complexation-enhanced phosphorescence emission may hold great promise in sensing and detecting many other biological targets under physiological environment.
基金supported by the National Natural Science Foundation of China(22471093,92156012,22071078)。
文摘π-conjugated polymers(CPs)hold great promise for optoelectronics,energy,and biomedicine,yet bioinspired folded architectures remain underexplored due to limited coupling strategies.Here,we report a scalable synthesis of helical polymer nanotubes via homogeneous Suzuki-Miyaura cross-coupling.Their helical conformation is stabilized by electrostatic repulsion between heteroatoms or intramolecular hydrogen bonding,confirmed by AFM,single-crystal X-ray diffraction,CD spectroscopy,and theoretical modeling.The nanotubes(~5 nm in length)feature hydrophilic,electron-rich lumens and hydrophobic alkyl exteriors,enabling spontaneous insertion into lipid bilayers.They display distinct,pore-size-dependent transport:wider pores facilitate glucose permeation,while narrower channels with defined coordination sites show selective K^(+)transport.K^(+)selectivity was validated through vesicle-based kinetics and symmetric/asymmetric bilayer lipid membrane(BLM)assays.Notably,the F3 system achieved a K^(+)/Na^(+)selectivity ratio of 26.8 in asymmetric BLMs.This work introduces a new class of aromatic helical polymers and highlights the role of coordination site density in ion selectivity.π-conjugated helical polymers are demonstrated for the first time to exhibit both ion selectivity and small-molecule transport,offering a blueprint for designing artificial K^(+)-specific nanopores with bio-medical potential,especially for treating channelopathies.
基金supported by the National Natural Science Foundation of China(Nos.22471093,92156012 and 22071078).
文摘Inspired by natural Ca^(2+)channels,we design and synthesize a type of artificial Ca^(2+)carriers using o-phenanthroline-oxadiazole-based foldamers.Through the incorporation of negative charges into cavity-containing foldamers,highly selective calcium ion transmembrane transport can be achieved,leading to the identification of two highly efficient Ca^(2+)carriers.Systematic investigation revealed a positive correlation between the number of negative charges on the foldamers and the foldamers‘cation-binding affinity.Furthermore,the size-selective effect,achieved through precise matching between the foldamer cavity dimensions and Ca^(2+)ion size,resulted in an unprecedented Ca^(2+)/Mg^(2+)selectivity ratio(S_(Ca/Mg)),reaching record S_(Ca/Mg) values greater than 100–the highest of all artificial Ca^(2+)carriers reported to date.Moreover,artificial Ca^(2+)carriers show high Ca^(2+)transport activity(EC_(50)=190 nM).This simple and modular approach enables tailored design of divalent cation transporters,thus providing promising applications for artificial divalent cation transporters in the fields of biochemistry and material chemistry.
基金This work is financially supported by the National Natural Science Foundation of China
文摘By introducing two and three zinc porphyrin units to one side of hydrogen bonding-induced aromatic amide foldamers, two new molecular tweezers 1 and 2 have been prepared. To explore new possible binding patterns, a leucine-based pyridine ligand 3 that bears a pentafluorophenyl group has been prepared. UV-Vis and IH NMR ex- periments reveal that 1 and 2 favorably complex one or two molecules of 3. UV-Vis titration experiments show that the apparent association constants of the complexes of the zinc porphyrin units of the two receptors and 3 are con- siderably higher than that of the complex between a simple control zinc porphyrin and 3. In the presence of excess of 3, the left zinc porphyrin unit of 1 and 2 can bind one more molecule of 3, which is, however, stabilized only by the single Zn-N coordination.
基金This research was made possible as a result of a generous grant from the National Natural Science Foundation of China(nos.21788102 and 21673082)the Natural Science Foundation of Guangdong Province(no.2019B030301003)the Fundamental Research Funds for the Central Universities.
文摘Conjugation,as an essential chemical term used to describe electron delocalization,can be roughly grouped into two categories,through-bond conjugation(TBC)and through-space conjugation(TSC).A hybrid conjugation system integrating both TBC and TSC is rarely studied and utilized,for lack of a well-established model and difficulty of structure modification and property tuning,despite its theoretical significance and potential applications.Herein,various foldamers with a tetraphenylethene(TPE)core are employed as hybrid conjugation models to investigate structure–property correlation by introducing heterocycles of furan/thiophene into theπ-stacking TSC component.For comparison,two kinds of TPE-cored foldamers with different stacking models,a benzene–heterocycle stacking model and a benzene–benzene stacking model,are designed.Combining experimental measurements and theoretical calculations,the impact of benzene–heterocycle interaction on the hybrid conjugation natures and photophysical properties has been studied systematically.The results reveal that the benzene–heterocycle stacking model can fabricate a hybrid conjugation nature with an improved TSC component to make a more dominant contribution to the electronic transition natures than the benzene–benzene stacking model,leading to the distinguishing photophysical behavior.This work provides valuable guidance for the design of new functional materials with hybrid conjugation systems.
基金supported by the Changjiang Scholar Programthe Cultivation Fund of the Key Scientific and Technical Innovation Project+1 种基金Ministry of Education of China (Grant No. 706009)the US National Science Foundation (CHE-0314577)
文摘Recent studies have started to provide initial insights into the aggregation and assembly of two classes of back-rigidified foldamers with flat,curved backbones consisting of aromatic residues.With their persistent shape that presents large,well-defined aromatic surface areas,these crescent foldamers were found to undergo size-dependent aggregation in solution and pack into 1D assemblies in the solid state.Crescent aromatic oligoamides undergo stacking interactions not only in polar solvents but also in nonpolar ones,a unique property that is not associated with many other molecules that associate via π-π stacking interaction.The stacking of oligo(m-phenylene ethynylenes) is similar to aromatic hydrocarbons,being promoted in polar solvents such as methanol while being discouraged in nonpolar solvents such as halohydrocarbons.The ready synthetic availability of crescent foldamers makes it possible to directly control the intermolecular interaction by tuning surface areas.Besides,the columnar assembly of these cavity-containing molecules provides a new strategy for constructing supramolecular nanotubular structures.
基金We thank the National Natural Science Foundation of China，the National Basic Research Program of China (Grant No.2009CB930802)for financial support
文摘A series of aromatic oligoamide foldamers based on 8-fluoro amino-quinoline carboxyl acid have been synthe- sized and characterized. Studies show that these foldamers self-assemble to form well-defined twisted helical mi- crofibers in chloroform-methanol （1 ： 1, V/V） binary solvent due to the intermolecular π-π stacking and van der Waals forces of aliphatic chains, which are supported by SEM, TEM and XRD. It is also revealed that the assembly morphologies show strong dependence on the length of alkyl chains.
基金the National Natural Science Foundation of China(Nos.21772026 and 21432004)for financial support
文摘The crystal structures of three intramolecularly hydrogen bonded rigid aromatic amide derivatives,which all bear one iodine atom at one end as the donor and one pyridine unit at the other end as the acceptor,have been described to reveal the utility of halogen bonding in inducing the formation of supramolecular macrocycles.All the three compounds formed intermolecular I···N halogen bonding.For short compound 1,halogen bonding induced the formation of an extended supramolecular array.For longer folded compounds 2 and 3,halogen bonding could hold two molecules to form supramolecular macrocycles even by adopting a highly distorted,energetically less favorable conformation(for 3).Depending on the solvent for the growth of crystals,compound 3 could also gave rise to a halogen bonded supramolecular double helix.
基金the Science and Technology Commission of Shanghai Munic- ipality （No. 13M1400200）, the Ministry of Science and Technology （No. 2013CB834501） and the Ministry of Education （Research Fund for the Doctoral Program） of China, and the National Science Foundation of China （Nos. 21432004 and 21272042）.
文摘Two benzene/2,2＇-bipyridine-alternately incorporated amide polymers have been prepared, which are driven by hydrophobicity to form two different helical conformations. Both helices exhibit twist sense bias in water induced by chiral valine side chains and the coordination of the 2,2＇-bipyridine unit to the Ni2＋ ions.
基金Project supported by the National Natural Science Foundation of China （Nos. 20321202, 20332040, 20672137, and 20425208） and the Major State Basic Research Development Program （No. 2007CB808000）.
文摘The complexing behaviour of two linear compounds 1 and 2 toward the trifluoroacetic acid （TFA） salts of n-dodecylamine, di-n-octylamine, n-dodecyl D- and L-phenylalaninates （3, 4, and D- and L-5） in chloroform has been described. Compounds 1 and 2 consist of two folded amide moieties with two pyridyls at the terminals which are connected directly or with an acetylene linker. The rigidified folded moieties are stabilized by intramolecular hydrogen bonding, while the whole molecules can adopt an ＂S＂- or a ＂C＂-styled conformation depending on the relative orientation of the two rigidified moieties. ^1H NMR, UV-Vis, fluorescent and circular dichroism investigations revealed that 1 and 2 could bind primary and secondary ammonium cations with their ＂C＂-styled conformation. In the presence of 1 equiv, of TFA, the binding stability was increased significantly as a result of promoted formation of the ＂C＂-styled conformation due to the monoprotonation of the peripheral pyridyl units in 1 and 2. In contrast, the addition of 2 equiv, of TFA substantially weakened the binding stability because the ＂S＂-styled conformation was favored as a result of protonation of both of their pyridyl units. Moreover, remarkable induced circular dichroisms were also displayed for the complexes of 1 and 2 with chiral D- and L-5.
基金Supported by the National Natural Science Foundation of China(Grant Nos. 20732007, 20621062, 20872167, and 20672137)the National Basic Research Project (Grant No. 2007CB808000)the Chinese Academy of Sciences (Grant No. KJCX2-YW-H13)
文摘Two aromatic hydrazide haptamers have been prepared,with both consisting of two hydrogen bonded folded segments. Compared to their fully hydrogen bonded analogues,the flexibility of their backbones increases due to lack of one or two intramolecular hydrogen bonds at the middle aromatic unit. (2D) 1H NMR,circular dichroism and fluorescent studies revealed that both oligomers moderately complex n-octyl-α-L-glucopyranoside in chloroform.
基金supports by A*STAR BMRC Research Consortia(R-143-000- 388-305 to H.Z.)Environment and Water Industry Development Council and Economic Development Board(SPORE,COY-15-EWI-RCFSA/N197-1 to H.Z.).
文摘Previously we have shown that POCl3-mediated H-bonding-directed one-pot macrocyclization allows for the highly selective preparation of five-residue macrocycles as the predominant product with low yields of hexamers and an undetectable occurrence of both tetramers and heptamers.Replacing the interiorly arrayed methyl groups with ethyl groups in these 4-7 residue macrocycles alters the relative stability order among them.Specifically,ethoxy-substituted six-residue macrocycle,rather than pentamer,turns out to be computationally the most stable,suggesting that ethoxy-containing hexamer possibly can be formed as the major product under suitable conditions.We have investigated this possibility by varying reaction temperatures and concentrations,invariably affording pentamer as the major macrocycle with strained circular hexamers and highly strained circular heptamers produced in substantial amounts.This discrepancy can be reasonably explained on the basis of bimolecular reactions between two oligomers higher than monomers via kinetic simulations.In this scenario,the acyclic pentamer is kinetically "trapped" to undergo an intramolecular cyclization to yield circular pentamer,rather than to produce acyclic hexamer.As a result,acyclic hexamer precursor is generated largely from sterically demanding bimolecular reactions between a dimer and a tetramer,or between two trimers that are kinetically slower than the pentamer-producing chain-growth reactions.We additionally found that one-pot macrocyclization proceeds to the largest extent at 40 ℃,an intriguing finding that highlights the low reactivities of acid chloride and amine groups in these H-bond-enforced acyclic oligomeric intermediates.
