Temperature-Responsive Chiral (A)6B Supramolecular Cages Based on Conformational Preferences.

Two chiral (A)6B-typed supramolecular cages were constructed from hydrogen-bonded C6 -symmetric zinc porphyrin hexamers and chiral C3-symmetric pyridyl hexadentates with a core of 1,3,5-triphenylbenzene. Circular dichroism and molecular simulations revealed that the symmetry of the supramolecular cages switched from pseudo-C3v to C3 with the rotational confinement of the biphenyl backbones at low temperatures, which generated conformationally chiral transfer and amplification. This unique phenomenon suggests a new strategy to develop smart materials with high sensitivity and excellent reversibility.

Redox-responsive reverse vesicles self-assembled by pseudo[2]rotaxanes for tunable dye release.

Reverse vesicles exhibiting functions similar to those of normal vesicles have been constructed through the self-assembly of TTF/CBPQT(4+)-based pseudo[2]rotaxanes in a nonpolar solvent. The ends of the threads of the pseudo[2]rotaxanes are attached with a Fréchet-type G-3 dendron and a hydrogen-bonded arylamide foldamer. These vesicles exhibit a response to redox.

A 1,4-diphenyl-1,2,3-triazole-based β-turn mimic constructed by click chemistry.

A series of 1,4-diphenyl-1,2,3-triazole-incorporated amide derivatives have been designed and prepared. X-ray crystallographic and (1D and 2D) (1)H NMR studies reveal that these compounds fold into stable U-shaped conformations driven by three-center intramolecular C-H···O hydrogen-bonding formed between the triazole C-5 H atom and the two ether O atoms. Such folded structures make this 1,4-diphenyl-1,2,3-triazole skeleton a good candidate to be used as β-turn mimic.

meta-Substituted benzamide oligomers that complex mono-, di- and tricarboxylates: folding-induced selectivity and chirality.

meta-Substituted arylamide trimer, pentamer and heptamer have been prepared from simple benzene-1,3-diamine, benzene-1,3-dicarboxylic acid, and 3-aminobenzoic acid units. 2D NOESY (1)H NMR experiments reveal that these flexible oligomers form folded conformations to complex di- and tricarboxylate anions of varying sizes and shapes in DMSO of high polarity, which is driven by multiple intermolecular N-H···O=C and C-H···O=C hydrogen-bonds between the amide and aromatic hydrogens of the oligomers and the carboxylate oxygens of the anions. Generally, tricarboxylate anions display an increased binding affinity compared with the dicarboxylate anions and the complexes formed by 1,3-benzenedicarboxylate anion are more stable than those formed by 1,2- or 1,4-benzenedicarboxylate anions.

Foldamer-tuned switching kinetics and metastability of [2]rotaxanes.

Slip sliding away: foldamers can function as modular stoppers to regulate the slippage and de-slippage of pseudorotaxanes and the switching kinetics and metastability of bistable rotaxanes. By simply changing the solvent or the length of the hydrogen-bonded foldamer, the lifetime of the metastable co-conformation state can be increased dramatically, from several minutes to as long as several days.

Highly stable chiral (A)6-B supramolecular copolymers: a multivalency-based self-assembly process.

A novel type of chiral layered supramolecular copolymer with high molecular weight has been assembled from a hydrogen bonded C(6)-symmetric zinc porphyrin hexamer and chiral C(3)-symmetric pyridine hexadentate linkers driven by multivalent zinc porphyrin-pyridine coordination. UV-vis, circular dichroism, and static light scattering experiments revealed that the formation of the layered supramolecular copolymers is at first dynamically controlled and then becomes thermodynamically controlled.

Hydrogen bonding-directed quantitative self-assembly of cyclotriveratrylene capsules and their encapsulation of C60 and C70.

Under the direction of intramolecular three-center hydrogen bonding, two cyclotriveratrylene (CTV)-based capsules are assembled quantitatively from C(3)-symmetric CTV precursors by forming three imine bonds from arylamide-derived foldamer segments. (1)H and (13)C NMR and UV/vis experiments reveal that the capsules strongly encapsulate C(60) and C(70) in discrete solvents.

Oligo(quinoxalineethynylene)s: synthesis, properties, and Ag+-mediated complanation.

A series of oligo(quinoxalineethylene)s which exhibit n-type semi-conducting features were synthesized, and adding Ag(+) to their solutions induced the backbones to adopt coplanar conformations due to Ag(+)-N coordination.

Construction of microbelts through the coassembly of a disclike molecule and primary alkyl ammoniums: a noncovalent strategy to mimic covalently bonded pi-core alkyl chain structure.

In this letter, we report the fabrication of microbelts through the coassembly of hexa-2-pyridyl-hexaazatriphenylen (HPHAT), a disklike pi-conjugated molecule, with primary alkyl ammonium triflate. The strategy is first to construct hydrogen-bonded complexes between HPHAT and primary alkyl ammoniums to mimic covalently bonded pi-core alkyl chain structures, and then the complexes self-assemble into microbelts driven by pi-pi stacking in the pi core and van der Waals interactions between the peripheral alkyl chains. The morphology of as-prepared microbelts has been characterized with scanning electron microscopy (SEM), optical microscopy, polarizing microscopy, and transmission electron microscopy (TEM).

Vesicle self-assembly by tetrathiafulvalene derivatives in both polar and nonpolar solvents and pseudo-rotaxane mediated vesicle-to-microtube transformation.

This paper reports the self-assemblies of vesicles from two tetrathiafulvalene (TTF) derivatives (T1 and T2), that bear four or two amphiphilic side chains, in both polar and nonpolar solvents. The formation of vesicles is evidenced by scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and dynamic light scattering (DLS) experiments, while the microstructural aspects of the vesicles are investigated by UV-vis, (1)H NMR, and high resolution TEM, which support a monolayer model for the vesicles. It is revealed that the formation of vesicles is driven by the combination of multiple noncovalent interactions, including pi-pi stacking, hydrogen-bonding, van der Waals force, and S.

Folding of aromatic amide-based oligomers induced by benzene-1,3,5-tricarboxylate anion in DMSO.

In this paper, we describe the folding of a series of linear arylamide oligomers in DMSO that is induced by benzene-1,3,5-tricarboxylate anion. The oligomers are comprised of naphthalene-2,7-diamine and 1,3,5-benzenetricarboxylic acid segments with two (tert-butoxycarbonylamino) groups at the ends and two to four hydrophilic N,N-bis(2-(2-(2-methoxyethoxy)ethoxy)ethyl)amino groups at one side of the backbones. (2D NOESY) (1)H NMR, fluorescence and UV-vis studies indicate that the oligomers do not adopt defined conformations in DMSO but fold into compact structures in the presence of the anion.

Organic nanotubes assembled from isophthalamides and their application as templates to fabricate Pt nanotubes.

A new class of organic nanotubes have been assembled from simple isophthalamide derivatives and their surface can be conveniently coated with Pt, which form new Pt nanotubes after the inside organic materials are removed with hot methanol.

Self-assembly of porphyrin-azulene-porphyrin and porphyrin-azulene conjugates.

In this paper we report the synthesis and self-assembling behavior of new porphyrin-azulene-porphyrin and porphyrin-azulene conjugates. The porphyrin-azulene-porphyrin conjugate gelates a number of organic solvents, while the porphyrin-azulene conjugates form vesicles in a chloroform-methanol binary mixture. The structures of the organogels and vesicles have been characterized by SEM and AFM.

Self-assembly of vesicles from amphiphilic aromatic amide-based oligomers.

A novel class of linear arylamide oligomers has been designed and synthesized from naphthalene-2,7-diamine and benzene-1,3,5-tricarboxylic acid segments. The molecules carry two (tert-butoxycarbonylamino) groups at the ends and one to three hydrophilic N,N-bis(2-(2-(2-methoxyethoxy)ethoxy)ethyl)amino groups at one side of the backbone. The oligomers self-assembled into vesicular structures in methanol as a result of ordered stacking of the oligomeric amide backbones, which were evidenced by SEM, AFM, TEM, and fluorescent micrography experiments.

Hydrogen-bonding-mediated dynamic covalent synthesis of macrocycles and capsules: new receptors for aliphatic ammonium ions and the formation of pseudo[3]rotaxanes.

This paper describes a novel, highly efficient approach to the self-assembly of monomacrocycles and two-layered capsules by using dynamic covalent chemistry. Intramolecular hydrogen-bonding was used to preorganize aromatic amide-based monomers that contain aldehyde and tert-butoxycarbonylamino units. As a result, in the presence of an excess of trifluoroacetic acid (TFA), four monomers could self-couple to produce macrocycles selectively through the formation of three imine or hydrazone bonds.

Cholesterol-appended aromatic imine organogelators: a case study of gelation-driven component selection.

This letter describes a novel approach for developing organogelators through the formation of reversible imine bonds from two molecular components and the enriching behavior of the gelating imines. Cholesterol-appended aniline 1 and 4-substituted benzaldehydes 2a-d did not gelate any solvents. Their condensation products, imines 3a-d, however, could gelate alcohols because of the enhanced stacking interaction of the imine unit.

Hydrogen bonding-directed multicomponent dynamic covalent assembly of mono- and bimacrocycles. Self-sorting and macrocycle exchange.

This paper describes the multicomponent dynamic covalent assembly of macrocyclic structures by utilizing hydrogen bonding-driven zigzag anthranilamides as "leading" components. Two or three amino groups have been introduced to one side of hydrogen bonded anthranilamide oligomers. The preorganization of the frameworks enabled the amino groups to condense with structurally matched aldehydes to form mono- and bimacrocycles in good to quantitative yields.

Foldamer organogels: a circular dichroism study of glucose-mediated dynamic helicity induction and amplification.

This paper reports a systematic study of the dynamic process for the self-assembly of chiral organogels from achiral hydrogen bonded hydrazide foldamers by induction of chiral glucose. Six foldamers incorporated with six decyl chains and two benzene, naphthalene, anthracene, or pyrene units at the ends are revealed to strongly gelate apolar and polar solvents, including alkanes, arenes, esters, alcohols, and 1,4-dioxane. The gels are characterized by UV-vis, fluorescent, XRD, SEM, and AFM methods, based on which a dislocated "tail-to-tail" stacking pattern is proposed.

Vesicles and organogels from foldamers: a solvent-modulated self-assembling process.

Nonamphiphilic, hydrogen-bonded hydrazide foldamers appended with four or six long flexible chains were revealed to spontaneously assemble to form vesicles in methanol and organogels in aliphatic hydrocarbons. SEM, AFM, TEM, DLS, and fluorescence microscopy were all used to identify the structures of the vesicles. It was proposed that intermolecular pi stacking of the folded frameworks and hydrogen bonding of the amide units in the appended chains induced the molecules to produce cylindrical aggregates.

Hydrogen-bonded aryl amide macrocycles: synthesis, single-crystal structures, and stacking interactions with fullerenes and coronene.

Six hydrogen-bonded shape-persistent aryl amide macrocycles have been prepared by using one-step and (for some) step-by-step approaches. From the one-step reactions, 3 + 3, 2 + 2, or even 1 + 1 macrocycles were obtained in modest to good yields. The reaction selectivity was highly dependent on the structures of the precursors.

Strong stacking between FH--N hydrogen-bonded foldamers and fullerenes: formation of supramolecular nano networks.

The stacking interactions between FH--N hydrogen-bonded foldamers 1-3, bis-foldamer 4, and tris-foldamer 5 and C(60) and C(70) are described. Compound 4 contains two folded units, which are connected by an isophthalamide linker, whereas 5 has a C(3)-symmetrical discotic structure, in which three folded units are connected by a benzene-1,3,5-tricarboxamide unit. UV/Vis, fluorescence, and NMR experiments have revealed that the foldamers or folded units strongly stack with fullerenes in chloroform.

Diastereomeric recognition of chiral foldamer receptors for chiral glucoses.

[reaction: see text] Three chiral aromatic hydrazide foldamers have been designed and synthesized, in which two R- or S-proline units were incorporated at the terminals of their backbones. The 1H NMR, circular dichroism (CD), and fluorescent experiments and molecular dynamics simulations revealed that the foldamers adopted a chiral helical conformation and complexed alkylated glucoses in chloroform with a good diastereomeric selectivity.

Dynamic [2]catenanes based on a hydrogen bonding-mediated bis-zinc porphyrin foldamer tweezer: a case study.

This paper describes the self-assembly of a new class of three-component dynamic [2]catenanes, which are driven or stabilized by intramolecular hydrogen bonding, coordination, and electrostatic interaction. One of the component molecules 2, consisting of an aromatic oligoamide spacer and two peripheral zinc porphyrin units, was designed to adopt a folded preorganized conformation, which is stabilized by consecutive intramolecular three-centered hydrogen bonds. Component molecule 3 is a linear secondary ammonium bearing two peripheral pyridine units, which was designed to form a 1:1 complex with 24-crown-8 (5).

Hydrogen bonding-induced aromatic oligoamide foldamers as spherand analogues to accelerate the hydrolysis of nitro-substituted anisole in aqueous media.

Four intramolecular hydrogen bonding-driven aromatic amide foldamers 2-5 have been designed and synthesized in which a 2-methoxy-3-nitrobenzamide unit was incorporated at the end of the backbone. Kinetic studies in dioxane-water (4:1, v/v) at 60-90 degrees C have revealed that the folded backbone of the oligomers was, like the rigidified spherand, able to complex Li+, Na+, and K+ and, consequently, accelerated the hydrolysis of the nitro-appended anisole unit of the foldamers. Generally, longer foldamers displayed an increased accelerating effect, and LiOH displayed the highest reactivity probably due to the most efficient complexation by the folded oligomers.

Hydrogen-bonding-mediated anthranilamide homoduplexes. Increasing stability through preorganization and iterative arrangement of a simple amide binding site.

This paper describes the assembly of two new series of self-complementary duplexes by making use of amide units, the simplest assembling units of hydrogen bonding, as binding sites. All the new monomers possess a rigidified anthranilamide skeleton, which is stabilized by intramolecular hydrogen bonding. Amide units are iteratively introduced to one side of the preorganized skeletons to facilitate the formation of intermolecular hydrogen bonding.