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Helical architectures with controllable helical sense bias have recently attracted considerable interest for mimicking biological helices and developing novel chiral materials. Coordination polymers (CPs), composed of metal ion nodes and organic linkers, are intriguing systems showing tunable structures and functions. However, CPs with helical morphologies have rarely been explored so far. Particularly, chirality inversion through external stimulus has not been achieved in helical CPs. In this work, we carried out an in‐depth investigation on the self‐assembly of 1D gadolinium(III) phosphonate CPs using GdX3 (X=Cl, Br, I) and Gd(RSO3) (R=CH3, C6H5, CF3) as metal sources and R‐(1‐phenylethylamino)methyl phosphonic acid (R‐pempH2) as ligand. Superhelices were formed by precise control of the interchain interactions through different intercalated anions. Furthermore, the twisting direction of superhelices could be controlled by synergistic effect of anions and pH. This study may provide a new route to fabricate helical nanostructures of CPs with a desirable chiral sense and help understand the inner mechanism of the self‐assembly process of macroscopic helical structures of molecular systems. [ABSTRACT FROM AUTHOR]

Hydrogen bonds can efficiently guide the self‐assembly of organic materials, enabling to tune the properties of the aggregation processes. In the case of π‐conjugated materials, several parameters such as temperature, concentration and solvent can be used to modify the aggregation state while tuning the optoelectronic properties. Chirality can be included within the impacting parameters due to the differences in molecular packing. Here, chiral and achiral thiophene‐capped diketopyrrolopyrrole derivatives were designed and synthesized containing amide bonds, with the aim to study the interplay between chiral assemblies and their stabilization through hydrogen‐bonding. Differences in aggregation properties were observed with spectroscopy and microscopy, and a contactless microwave‐based technique was used to study their intrinsic charge carrier mobility. The positive role of hydrogen‐bonding has been highlighted and the differences between chiral and achiral compounds have been elucidated. [ABSTRACT FROM AUTHOR]

Coordination chemistry is a powerful method to synthesize supramolecular cages with distinct features that suit specific applications. This work demonstrates the synthesis of discrete, homochiral FeII2L3 cages via chirality‐driven self‐assembly. Specifically, the installation of chirality – at both the vertices and ligand backbones – allows the formation of discrete, homochiral FeII2L3 cages of different sizes via stereochemical control of the iron(II) centers. We observed that larger cages require multiple chiral centra (chiral ligands and vertices). In contrast, the formation of smaller cages is stereoselective with solely chiral ligands. The latter cages can also be formed from two chiral subcomponents, but only when they have matching chirality. Single‐crystal X‐ray diffraction of these smaller FeII2L3 cages revealed several non‐covalent interactions as a driving force for narcissistic chiral self‐sorting. This expected behavior was confirmed utilizing the shorter ligands in racemic form, yielding discrete, homochiral FeII2L3 cages formed in enantiomeric pairs. [ABSTRACT FROM AUTHOR]

Dynamically controlling the supramolecular chirality is of great significance in development of functional chiral materials, which is thus essential for the specific function implementation. As an external energy input, light is remote and accurate for modulating chiral assemblies. In non‐polarized light control, some photochemically reactive units (e. g. azobenzene, ɑ‐cyanostilbene, spiropyran, anthracene) or photo‐induced directionally rotating molecular motors were designed to drive chiral transfer or amplification. Besides, photoexcitation induced assembly based physical approach was also explored recently to regulate supramolecular chirality beyond photochemical reactions. In addition, circularly polarized light was applied to induce asymmetric arrangement of organic molecules and asymmetric photochemical synthesis of inorganic metallic nanostructures, in which both wavelength and handedness of circularly polarized light have effects on the induced supramolecular chirality. Although light‐triggered chiral assemblies have been widely applied in photoelectric materials, biomedical fields, soft actuator, chiral catalysis and chiral sensing, there is a lack of systematic review on this topic. In this review, we summarized the recent studies and perspectives in the constructions and applications of light‐responsive chiral assembled systems, aiming to provide better knowledge for the development of multifunctional chiral nanomaterials. [ABSTRACT FROM AUTHOR]

Supramolecular chirality in a binary mixture of achiral bent-core (BC) and achiral rodlike mesogens was observed. Three different nanosegregated mesophases were determined in the binary system, and meaningful changes in circular dichroism (CD) were detected near the phase-transition temperatures of the rodlike mesogens. The highest CD intensity in the binary system was noted in the nanosegregated mesophase, in which the BC mesogens were in the helical nanofilament (HNF) phase and the rodlike mesogens were in the smectic A phase. The supramolecular chirality in the binary mixture was attributed to the self-assembled hierarchical chiral superstructures. Based on the experimental results, plausible scenarios for the chiral superstructures of the rodlike molecules embedded in the HNF networks are suggested. In addition, a system comprising BC and rodlike molecules doped with a photoresponsive compound exhibited remarkable photoswitching of CD intensity. According to the isothermal photoinduced phase transition of the embedded molecules in BC molecular HNFs, the observed CD intensities can be dynamically and reversibly modulated. Such a material with easily controllable functionality is of considerable interest in the field of materials science. [ABSTRACT FROM AUTHOR]

Enantiomerically pure C16-alkyl amides derived from cis and trans cycloalkane-1,2-dicarboxylic acids, respectively, have been synthesized and their behavior as organogelators has been investigated. These compounds include cis/trans diastereomeric cyclobutane and cyclohexane derivatives with the aim to explore the influence of the ring size as well as the relative configuration in their hierarchical self-assembly to form gels. High resolution 1H NMR spectroscopy studies allowed the determination of the dynamics of the gelation process in [D8]toluene and the sol-gel transition temperature. The morphology and size of the aggregates have been investigated and results have shown that, in the case of cyclobutane derivatives, the cis/trans stereochemistry is not relevant for the gelation behavior and the properties of the soft-materials obtained, but it is remarkable for cyclohexane diamides, which are better organogelators. The four compounds produce chiral aggregates despite that two of them are meso achiral molecules. We show herein that this fact is an example of stochastic symmetry breaking induced by sonication. The self-assembly of these molecules has been modelled providing information and support about the structure and the chirality of the aggregates. [ABSTRACT FROM AUTHOR]

A highly accurate and reliable screening method for enantiomeric excess of amine derivatives in the presence of water is reported. The fluorescence-based screening system has been realized by self-assembly of chiral diol-type dyes (BINOL, VANOL and VAPOL), 2-formylphenylboronic acid, and chiral amines forming iminoboronate esters. The structure and chirality of the amine analytes determine the stability of the diastereomeric iminoboronate esters, which in turn display differential fluorescence. The fluorescence signal reflects the enantiomeric purity of the chiral amines and was utilized in high-throughput arrays. The arrays were able to recognize enantiomeric excess of amines, amino esters, and amino alcohols. In addition to qualitative analysis, quantitative experiments were successfully performed. Studies of the role of additives such as water or citrate were carried out to gain insight into the stability of the iminoboronate esters. It is shown that the above additives destabilize less stable esters while the stable esters remain unchanged. Thus, the presence of water and citrate leads to increased difference between the diastereomeric iminoboronates and contributes to the enantiodiscrimination of the chiral amines. [ABSTRACT FROM AUTHOR]

Both experiments and molecular dynamics simulations point to the fact that racemic assemblies are more stable than enantiopure ones. B Helicene rafts on water b : Amphiphilic derivatives of dibenzo[6]helicene form stable Langmuir layers at the air-water interface. Both experiments and molecular dynamics simulations point to the fact that racemic assemblies are more stable than enantiopure ones. [Extracted from the article]

We synthesized two bichromophoric difluoroboron‐β‐diketonates (DFB) connected in para and meta positions by using cyclohexane diamine as a chiral bridge (para and meta (R/S)‐CyDFB). TD‐DFT calculations revealed that the variation in connectivity of the DFB units leads to different spatial arrangements and a chirality inversion of the bichromophoric DFB. Higher gabs values were obtained in (R/S)‐CyDFB connected in para as compared to meta position. Aggregation of para (R/S)‐CyDFB in mixture of solvents increase the glum values as compared to its monomeric form. Ultrasonication and heating induced the formation of highly ordered nano‐helical wires of para (R/S)‐CyDFB that increased the glum values to 0.015. On the other hand, meta (R/S)‐CyDFB failed to form highly ordered self‐assembled wires due to hindered H‐binding sites. These observations indicate that the chiroptical properties of DFB bi‐chromophore system can be modulated with self‐assembly and spatial arrangement of the chromophores. [ABSTRACT FROM AUTHOR]

Chiral head groups have been introduced into water-soluble hydroxyl-terminated nonionic amphiphiles and the impact of the head group stereochemistry on the supramolecular ultrastructures has been studied. Enantiomeric isomers were compared with the achiral meso form and the racemic mixture by means of cryogenic transmission electron microscopy and circular dichroism spectroscopy. Structurally, all amphiphiles are composed of the first-generation hydrophilic polyglycerol head group coupled to a single hydrophobic hexadecyl chain through an amide linkage and diaromatic spacer. The enantiomers aggregate to form twisted ribbons with uniform handedness, whereas the meso stereoisomer and racemic mixture produce elongated assemblies, namely, tubules and platelets, but without a chiral ultrastructure. Simulations on the molecular packing geometries of the stereoisomers indicate different preferential assembly routes that explain the individual supramolecular aggregation behavior. [ABSTRACT FROM AUTHOR]

New advances into the chirality effect in the self-assembly of block copolymers (BCPs) have been achieved by tuning the helicity of the chiral-core-forming blocks. The chiral BCPs {[NP( R)-O2C20H12]200− x[NP(OC5H4N)2] x}- b- [NPMePh]50 (( R)-O2C20H12=( R)-1,1′-binaphthyl-2,2′-dioxy, OC5H4N=4-pyridinoxy (OPy); x=10, 30, 60, 100 for 3 a- d, respectively), in which the [NP(OPy)2] units are randomly distributed within the chiral block, have been synthesised. The chiroptical properties of the BCPs ([ α]D vs. T and CD) demonstrated that the helicity of the BCP chains may be simply controlled by the relative proportion of the chiral and achiral (i.e., [NP( R)-O2C20H12] and [NP(OPy)2], respectively) units. Thus, although 3 a only contained only 5 % [NP(OPy)2] units and exhibited a preferential helical sense, 3 d with 50 % of this unit adopted non-preferred helical conformations. This gradual variation of the helicity allowed us to examine the chirality effect on the self-assembly of chiral and helical BCPs (i.e., 3 a- c) and chiral but non-helical BCPs (i.e., 3 d). The very significant influence of the helicity on the self-assembly of these materials resulted in a variety of morphologies that extend from helical nanostructures to pearl-necklace aggregates and nanospheres (i.e., 3 b and 3 d, respectively). We also demonstrate that the presence of pyridine moieties in BCPs 3 a- d allows specific decoration with gold nanoparticles. [ABSTRACT FROM AUTHOR]

The controlled crystallization of enantiomers of an organic compound (a cyclic phosphoric acid derivative) on templated micro-patterned functionalised surfaces is demonstrated. Areas where a complementary chiral thiol has been located were effective heterogeneous nucleation centres when a solution of the compound is evaporated slowly. Various organic solvents were employed, which present a challenge with respect to other examples when water is used. The solvent and the crystallization method have an important influence on the crystal growth of these compounds. When chloroform was employed, well-defined crystals grow away from the surface, whereas crystals grow in the plane from solutions in isopropanol. In both cases, nucleation is confined to the polar patterned regions of the surface, and for isopropanol growth is largely limited within the pattern, which shows the importance of surface chemistry for nucleation and growth. The apparent dependence on the enantiomer used in the latter case could imply stereo-differentiation as a result of short-range interactions (the templating monolayer is disordered, even at the nanometre scale). The size of the pattern of chiral monolayer also determines the outcome of the crystallization; 5 μm dots are most effective. Despite the low surface tension of the samples (relative to the high surface tension of water), differential solvation of the polar and hydrophobic layers of the solvents allows crystallization in the polar regions of the monolayer, therefore the polarity of the regions in which heterogeneous nucleation takes place is indeed very important. Despite the complex nature of the crystallization process, these results are an important step towards to the use of patterned surfaces for heterogeneous selective nucleation of enantiomers. [ABSTRACT FROM AUTHOR]

Although chiral nanostructures have been fabricated at various structural levels, the transfer and amplification of chirality from molecules to supramolecular self‐assemblies are still puzzling, especially for heterochiral molecules. Herein, four series of C2‐symmetrical dipeptide‐based derivatives bearing various amino acid sequences and different chiralities are designed and synthesized. The transcription and amplification of molecular chirality to supramolecular assemblies are achieved. The results show that supramolecular chirality is only determined by the amino acid adjacent to the benzene core, irrespective of the absolute configuration of the C‐terminal amino acid. In addition, molecular chirality also has a significant influence on the gelation behavior. For the diphenylalanine‐based gelators, the homochiral gelators can be gelled through a conventional heating–cooling process, whereas heterochiral gelators form translucent stable gels under sonication. The racemic gels possess higher mechanical properties than those of the pure enantiomers. All of these results contribute to an increasing knowledge over control of the generation of specific chiral supramolecular structures and the development of new optimized strategies to achieve functional supramolecular organogels through heterochiral and racemic systems. [ABSTRACT FROM AUTHOR]

The chiral stereoisomers of new non‐ionic dendritic amphiphiles self‐assemble in aqueous solution towards helical ribbons with opposite handedness. However, in the case of the meso‐compound, cylindrical assemblies are observed, as illustrated. Modelling suggests that they consist of right‐ or left‐handed helical molecular strands in equal distribution. The hydrophobic core of such a cylinder is sized to accommodate the hydrophobic tails. Only the head groups and the aromatic platforms, which contribute high density in transmission electron microscopy (TEM), are shown for clarity. The paper discusses stereochemical aspects upon supramolecular assembly of these new dendritic amphiphiles. More information can be found in the Full Paper by C. Böttcher, et al. on page 5629 ff. [ABSTRACT FROM AUTHOR]

The ability of a star‐shaped tris(triazolyl)triazine derivative to hierarchically build supramolecular chiral columnar organizations through the formation of H‐bonded complexes with benzoic acids was studied from a theoretical and experimental point of view. The combined study has been done at three different levels including the study of the structure of the triazine core, the association with benzoic acids in stoichiometry 1:3, and the assembly of 1:3 complexes in helical aggregates. Although the star‐shaped triazine core crystallizes in a non‐C3 conformation, the C3‐symmetric conformation is theoretically predicted to be more stable and gives rise to a favorable C3 supramolecular 1:3 complex upon the interaction with three benzoic acids in their voids. In addition, calculations at different levels (DFT, PM7, and MM3) for the 1:3 host‐guest complex predict the formation of large stable columnar helical aggregates stabilized by the compact packing of the interstitial acids by π–π and CH⋅⋅⋅π interactions. The acids restrict the movement of the the star‐shaped triazine cores along the stacking axis causing a template effect in the self‐assembly of the complex. Theoretical predictions correlate with experimental results, since the interaction with achiral or chiral 3,4,5‐(4‐alkoxybenzyloxy)benzoic acids gives rise to supramolecular complexes that organize in bulk hexagonal columnar mesophases stable at room temperature with intracolumnar order. The existence of supramolecular chirality in the mesophase was determined for complexes formed by acids derived from (S)‐2‐octanol. Chiral aggregation was also evidenced for complexes formed in dodecane. [ABSTRACT FROM AUTHOR]

A chiral, octahedral M12L12 cage, which is charge neutral and contains an internal void of about 2000 Å3, is reported. The cage was synthesised as an enantiopure complex by virtue of amino‐acid‐based dicarboxylate ligands, which assemble around copper paddlewheels at the vertices of the octahedron. The cage persists in solution with retention of the fluorescence properties of the parent acid. The solid‐state structure contains large pores both within and between the cages, and displays permanent porosity for the sorption of gases with retention of crystallinity. Initial tests show some enantioselectivity of the cage towards guests in solution. [ABSTRACT FROM AUTHOR]

Directional self‐assembly of uncharged molecules in water is a major challenge in supramolecular chemistry. Herein, it is demonstrated that peptide‐based cavitands wrap around a hydrophobic core (fullerene C60) by a combination of the hydrophobic effect and hydrogen‐bonding interactions to form highly ordered three‐component complexes in water that resemble the molten‐globule stage of protein folding. The complexes were characterized by DOSY NMR spectroscopy, small‐angle X‐ray scattering, and circular dichroism, and their structures were confirmed by X‐ray crystallography. Enhancement of the CD signals by nearly one order of magnitude and increased hydrolytic stability of hydrazone bonds of the complexes relative to the nonassembled species were observed. In contrast, DMSO and DMSO/water mixtures were found to be highly disintegrative for these complexes. Interestingly, some cavitands can only be synthesized in the presence of the hydrophobic template followed by disassembly of the complexes. Highly competitive: Directional self‐assembly of uncharged molecules in water is a major challenge in supramolecular chemistry. In this work, a combination of hydrogen bonding and the hydrophobic effect allows peptide‐based cavitands to wrap around a C60 fullerene core to form well‐ordered noncovalent chiral assemblies in a highly competitive environment involving intermolecular and intramolecular interactions with water and charged substituents, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Herein, the self‐assembly of a few 1,3‐dihydroxyl functionalized naphthalene diimide (NDI) derivatives has been reported with particular emphasis on the impact of chirality on gelation and the effect of self‐assembly on charge‐carrier mobility. A nonconventional gelator (R)‐NDI, devoid of any long alkyl chains, exhibited spontaneous gelation in tetra‐chloroethylene (TCE). Based on X‐ray crystallography and powder X‐ray diffraction studies, it was established that a ladder‐like hydrogen‐bonded chain formation between the 1,3‐dihydroxyl group leads to the fibrillar structures with preferential helicity. Likewise the (S)‐isomer also exhibited identical gelation and mesoscopic structure but produced fibrils with the opposite handedness. Intriguingly, an equimolar mixture of the (R)‐ and (S)‐isomers did not show any gelation ability, rather a macroscopic precipitation was observed and, in sharp contrast to the individual isomers, the morphology of the mixture showed ill‐defined near spherical agglomerates. Differential scanning calorimetry (DSC) studies revealed an identical crystallization peak for the supramolecular polymer produced from the enantiopure gelators ((R)‐ or (S)‐isomer), which was absent in their equimolar mixture. However, mixtures of the two isomers with enantiomeric excess retrieved the gelation ability and preferential helicity demonstrating that chiral amplification is operative in the present system through the so‐called “majority rule” effect. Chirality induction was also realized by the “sergeant and soldier” principle in the supramolecular assembly of an achiral NDI gelator in the presence of either the (R)‐ or (S)‐isomer as the chiral dopant. However, the strong helical bias induced by the chiral gelator was found to be opposite in nature compared to that found in the self‐assembly of the pure chiral gelator that has been rarely reported in the literature. Flash‐photolysis time‐resolved microwave conductivity (FP‐TRMC) measurements indicated the strong positive impact of the gelation on the electrical conductivity. [ABSTRACT FROM AUTHOR]

Controlling helical chirality and creating protein secondary structures in cyclic/acyclic ferrocene-dipeptide bioorganometallic conjugates were achieved by adjusting the conformational flexibility of the dipeptide chains. In systems reported to date, the helical chirality of a conjugate was determined by the absolute configuration of the adjacent amino acid reside. In contrast, it was possible to induce both M- and P-helical chirality, even when the configuration of the adjacent amino acid was the same. It is particularly interesting to note that M-helical chirality was produced in a cyclic ferrocene-dipeptide conjugate composed of the l-Ala- d-Pro-cystamine- d-Pro- l-Ala dipeptide sequence ( 1), in which a type II β-turn-like secondary structure was established. [ABSTRACT FROM AUTHOR]

Recognition of enantiomers of chiral acids by anion-π or lone pair-π interactions has not yet been investigated but is a significant and attractive challenge. This study reports an optically active polymer-based supramolecular system with capabilities of discriminating enantiomers of various chiral acids. The polymer featuring alternate π-acidic naphthalenediimides (NDIs) and methyl l-phenylalaninates in the backbone exhibits an unprecedented slow self-assembly process that is susceptible to perturbation by various chiral acids. Thus, the combination of anion-π or lone pair-π interactions and sensitivity of the polymeric self-assembly process to external chiral species endows the system with recognition capabilities. This is the first time that anion-π or lone pair-π interactions have been applied in the recognition of enantiomers of various chiral acids with a single system. The results shed light on new strategies for material design by integrating π-acidic aromatic systems and chiral building blocks to afford relevant advanced functions. [ABSTRACT FROM AUTHOR]

Chiral helical structures have attracted increasing attention in the field of supramolecular assembly because of their critical roles in life and material sciences. In this research, the achiral amphiphile 1-[11-(2-anthracenylmethoxy)-11-oxoundecyl]pyridinium bromide ( 2-APB), in which the hydrophobic anthracene and the hydrophilic pyridinium units are linked by alkyl chains, was found to form chiral supramolecular assemblies in a cooperative manner in the presence of iodide anion. Moreover, these assemblies show left (L)- or right (R)-handedness randomly, independent of the assembly conditions. By using the same method, 2-APB could assemble together with other pseudo-halogen anions (OCN−, SCN−, SeCN−) that have similar anionic radius as iodide to form chiral structures. This work illustrates a simple and rational design that can be used to fabricate supramolecular chiral structures from achiral molecules. [ABSTRACT FROM AUTHOR]

Racemic mixtures of aminomethylenehelicene ( P)- and ( M)-pentamers exhibited deterministic and stochastic chiral symmetry breaking during hetero-double-helix formation and self-assembly in solution. Heating a 50:50 mixture of ( P)- and ( M)-pentamers at 90 °C, and then cooling the mixture to 70 °C resulted in hetero-double-helix formation; a Cotton effect with negative Δ ε at λ=315 nm appeared. Chiral self-assembly occurred when the mixture was cooled to 25 °C. A strong tendency of deterministic chiral symmetry breaking appeared at the molecular and self-assembled levels, which was indicated by the negative Δ ε at λ=315 nm that appeared in most cases in repeated experiments. Mixtures containing 60:40 and 40:60 ( P)-/( M)-pentamers also self-assembled with the same chirality. When a homo-double-helix ( P)-/( M)-pentamer and a random coil ( M)-/( P)-pentamer were mixed, the chiral self-assembly formed stochastically, and heating and cooling resulted in deterministic chiral symmetry breaking. [ABSTRACT FROM AUTHOR]

When mixtures of D2O/DCl are used to foster the self-assembly formation of TPPS4 porphyrin J-aggregates in aqueous solutions, an inverse kinetic isotope effect of 0.4 and an inverse equilibrium isotope effect of 0.6 are clearly detected. Most importantly, the addition of at least 10 % D2O causes an inversion in the handedness of the final chiral J-aggregates, thus evidencing an important role of deuterium in driving the enantiomeric excess in the scalemic mixture of such supramolecular assemblies. [ABSTRACT FROM AUTHOR]

Two isomeric achiral bent-core liquid crystals involving a 4-cyanoresorcinol core and containing a carbosilane unit as nanosegregating segment were synthesized and were shown to form ferroelectric liquid-crystalline phases. Inversion of the direction of one of the COO groups in these molecules leads to a distinct distribution of the electrostatic potential along the surface of the molecule and to a strong change of the molecular dipole moments. Thus, a distinct degree of segregation of the carbosilane units and consequent modification of the phase structure and coherence length of polar order result. For the compound with larger dipole moment ( CN1) segregation of the carbosilane units is suppressed, and this compound forms paraelectric SmA and SmC phases; polar order is only achieved after transition to a new LC phase, namely, the ferroelectric leaning phase (SmCLsPS) with the unique feature that tilt direction and polar direction coincide. The isomeric compound CN2 with a smaller dipole moment forms separate layers of the carbosilane groups and shows a randomized polar SmA phase (SmAPAR) and ferroelectric polydomain SmCsPS phases with orthogonal combination of tilt and polar direction and much higher polarizations. Thus, surprisingly, the compound with the smaller molecular dipole moment shows increased polar order in the LC phases. Besides ferroelectricity, mirror-symmetry breaking with formation of a conglomerate of macroscopic chiral domains was observed in one of the SmC phases of CN1. These investigations contribute to the general understanding of the development of polar order and chirality in soft matter. [ABSTRACT FROM AUTHOR]

Spontaneous generation of macroscopic homochirality in soft matter systems by self-assembly of exclusively achiral molecules under achiral conditions is a challenging task with relevance for fundamental scientific research and technological applications. Dark conglomerate phases (DC phases), being optically isotropic mesophases composed of conglomerates of macroscopic chiral domains and formed by some non-chiral bent-core mesogens, represent such a case. Here we report two new series of non-symmetric bent-core molecules capable of forming a new type of mirror symmetry broken DC phases. In the synthesized molecules, a bent 4-bromoresorcinol core is connected to a phenyl benzoate wing and an azobenzene wing with or without additional peripheral fluorine substitution. The self-assembly was investigated by DSC, polarizing microscopy, electro-optical studies and XRD. Chiral and apparently achiral DC phases were observed besides distinct types of lamellar liquid crystalline phases with different degree of polar order, allowing the investigation of the transition from smectic to DC phases. This indicates a process in which increased packing density at first gives rise to restricted rotation and thus to growing polar order, which then leads to chirality synchronization, layer frustration and nano-scale crystallization. Topological constraints arising from the twisted packing of helical conformers in lamellar crystals is proposed to lead to amorphous solids composed of helical nano-crystallites with short coherence length (HNC phases). This is considered as a third major type of DC phases, distinct from the previously known liquid crystalline sponge phases and the helical nano-filament phases (HNF phases). Guidelines for the molecular design of new materials capable of self-assembly into these three types of DC phases are proposed. [ABSTRACT FROM AUTHOR]

Stereodynamic optical probes are becoming very popular for their capability to act as molecular sensors for the determination of the enantiomeric excess ( ee) of chiral compounds. Herein, we describe a new molecular architecture formed by the self-assembly of three zinc metal ions, two modified tris(2-pyridylmethyl)amine ligands, and two amino acids. This system is the structural and functional serendipitous evolution of our previous probe for the determination of amino acids ee. In the new system, one of the metals templates in close proximity two chromophores enhancing their exciton coupling. [ABSTRACT FROM AUTHOR]

The twisting of supramolecular aggregates formed from simple linear bis(benzamides) has been investigated. The antiparallel arrangement of the amide functional groups controls the generation of twisted supramolecular structures. The results presented herein could contribute to elaborate predictive tools applicable in the generation of chiral supramolecular structures. [ABSTRACT FROM AUTHOR]

The C3-symmetric chiral propylated host-type ligands (±)- tris(isonicotinoyl)- tris(propyl)-cyclotricatechylene ( L1) and (±)- tris(4-pyridyl-4-benzoxy)- tris(propyl)-cyclotricatechylene ( L2) self-assemble with PdII into [Pd6L8]12+ metallo-cages that resemble a stella octangula. The self-assembly of the [Pd6( L1)8]12+ cage is solvent-dependent; broad NMR resonances and a disordered crystal structure indicate no chiral self-sorting of the ligand enantiomers in DMSO solution, but sharp NMR resonances occur in MeCN or MeNO2. The [Pd6( L1)8]12+ cage is observed to be less favourable in the presence of additional ligand, than is its counterpart, where L=(±)- tris(isonicotinoyl)cyclotriguaiacylene ( L1 a). The stoichiometry of reactant mixtures and chemical triggers can be used to control formation of mixtures of homoleptic or heteroleptic [Pd6L8]12+ metallo-cages where L= L1 and L1 a. [ABSTRACT FROM AUTHOR]

D-Glucaric acid ( D-Glc) associates with linear poly(ethyleneimine) (PEI) through hydrogen bonding and electrostatic interactions in aqueous media to form nanostructured crystalline PEI/ D-Glc/H2O complexes with PEI/ D-Glc/H2O ratios of 2:1:2. These complexes can serve as templates for silica depositions from hydrolytic condensation of tetramethoxysilane to guide morphologically duplicated silica under very mild conditions. Their microscale morphologies are tunable by use of the crystalline complexes regulated in the different pH of the PEI/ D-Glc solutions. It was also found that some metal ions added in the PEI/ D-Glc complexation process could have a synergistic effect under a certain pH regimes, bringing about remarkable changes in the hierarchy of the resulting complexes. Especially, the complexes formed through fine-tuning of the complexation conditions could direct torsionally stacked silica nanosheets, in which the nanosheets are composed of orderly-bundled nanofibrils. Final elimination of organic components of the templates afforded chiral inorganic silica while retaining the morphologically higher-order structures. The chirality of the silica, which was obtained after calcination at 600 °C, was characterized by means of diffused reflectance circular dichroism (DRCD) spectroscopy with a remote confirmation of the appearance of induced-CD (ICD) signals of achiral or racemic chromophores covalently linked on the silica frames. Interestingly, the shapes and signs of these ICD signals are dramatically changed depending on the pH-tuned templates used in silicification and are strongly correlated to that of the CD signals of the complex templates, indicating that the chiral transcription proceeds accurately with imprinting the higher-order chirality of the complexes on the morphologically structured silica networks. [ABSTRACT FROM AUTHOR]

Chirality is widely found in nature and is expressed hierarchically in many organic-inorganic hybrid materials. Optical activity (OA) is the most fundamental attribute of these chiral materials. In this study, we found that the OA of impeller-like chiral DNA-silica assemblies (CDSAs) was inverted with the addition of water. The state of DNA under dry and wet conditions, and the dual chirality of chiral DNA layers and twisted helical arrays of opposite handedness in CDSAs were considered to exert predominant effects on the OAs. The circular dichroism (CD) responses for the dry CDSAs were mostly attributed to the chiral arrangement of DNA layers, whereas the opposite CD responses for the wet CDSAs primarily originated from twisted helical arrays of DNA molecules. The observed CD signals were a super-position of the two opposing OA responses. The increase in the longitudinal relation of DNA molecules due to the recovery of a double-helical structure of DNA in the presence of water was considered to be the reason for the increase in intensity of the CD signals that originated from the twisted helical array, which led to the inversion of OA of the CDSAs. The inversion of the plasmon-resonance-based OAs for the chiral-arranged achiral Ag nanoparticles (NPs) located in the channels of the CDSAs in dry and wet states further confirmed the dual chirality of DNA packing. Such research on DNA assemblies and metal NPs with dual, opposite chirality assists in the understanding of DNA hierarchical chirality in living systems and the creation of macroscopic ordered helical materials and biosensors. [ABSTRACT FROM AUTHOR]

A 1,1′-binaphthyl-based bis(pyridine) ligand ( 1) was prepared in racemic and enantiomerically pure form to study the formation of [Pd2( 1)4] complexes upon coordination to palladium(II) ions with regard to the degree of chiral self-sorting. The self-assembly process proceeds in a highly selective narcissistic self-recognition manner to give only homochiral supramolecular M2L4 cages, which were characterized by ESI-MS, NMR, and electronic circular dichroism (ECD) spectroscopy, as well as by single-crystal XRD analysis. [ABSTRACT FROM AUTHOR]

Chiral amino acid- and amino alcohol-oxalamides are well-known as versatile and efficient gelators of various lipophilic and polar organic solvents and water. To further explore the capacity of the amino acid/oxalamide structural fragment as a gelation-generating motif, the dioxalamide dimethyl esters 16Me and 19Me, and dicarboxylic acid 26OH/ 29OH derivatives containing flexible methylene bridges with odd ( 9; n=7) and even ( 6; n=4) numbers of methylene groups were prepared. Their self-assembly motifs and gelation properties were studied by using a number of methods (FTIR, 1H NMR spectroscopy, CD, TEM, DSC, XRPD, molecular modeling, MMFF94, and DFT). In contrast to the previously studied chiral bis(amino acid or amino alcohol) oxalamide gelators, in which no chiral morphology was ever observed in the gels, the conformationally more flexible 16Me, 19Me, 26OH, and 29OH provide gelators that are capable of forming diverse aggregates of achiral and chiral morphologies, such as helical fibers, twisted tapes, nanotubules, straight fibers, and tapes, in some cases coexisting in the same gel sample. It is shown that the differential scanning calorimetry (DSC)-determined gelation enthalpies could not be correlated with gelator and solvent clogP values. Spectroscopic results show that intermolecular hydrogen-bonding between the oxalamide units provides the major and self-assembly directing intermolecular interaction in the aggregates. Molecular modeling studies reveal that molecular flexibility of gelators due to the presence of the polymethylene bridges gives three conformations ( zz, p1, and p2) close in energy, which could form oxalamide hydrogen-bonded layers. The aggregates of the p1 and p2 conformations tend to twist due to steric repulsion between neighboring iBu groups at chiral centers. The X-ray powder diffraction (XRPD) results of 16Me and 19Me xerogels prove the formation of p1 and p2 gel aggregates, respectively. The latter results explain the formation of gel aggregates with chiral morphology and also the simultaneous presence of aggregates of diverse morphology in the same gel system. [ABSTRACT FROM AUTHOR]

A series of optically active helical polyphosphazene block copolymers of general formula R[NP(O2C20H12)] n- b-[NPMePh] m ( R- 7 a- c) was synthesized and characterized. The polymers were prepared by sequential living cationic polycondensation of N-silylphosphoranimines using the mono-end-capped initiator [Ph3PNPCl3][PCl6] ( 5) and exhibit a low polydispersity index (ca. 1.3). The temperature dependence of the specific optical activity ([ α]D) of R- 7 a, b relative to that for the homopolymers R-[NP(O2C20H12)] n ( R- 8 a) and the R/ S analogues ( R/ S- 7 a, b), revealed that the binaphthoxy-phosphazene segments induce a preferential helical conformation in the [NPMePh] blocks through a 'sergeant-and-soldiers' mechanism, an effect that is unprecedented in polyphosphazenes. The self-assembly of drop-cast thin films of the chiral block copolymer R- 7 b (bearing a long chiral and rigid R[NP(O2C20H12)] segment) evidenced a transfer of helicity mechanism, leading to the formation of twisted morphologies (twisted 'pearl necklace'), not observed in the nonchiral R/ S- 7 b. The chiral R- 7 a and the nonchiral R/ S- 7 a, self-assemble by a nondirected morphology reconstruction process into regular-shaped macroporous films with chiral-rich areas close to edge of the pore. This is the first nontemplate self-assembly route to chiral macroporous polymeric films with pore size larger than 50 nm. The solvent annealing (THF) of these films leads to the formation of regular spherical nanostructures (ca. 50 nm), a rare example of nanospheres exclusively formed by synthetic helical polymers. [ABSTRACT FROM AUTHOR]

The self-assembly behavior of an achiral perylene bisimide (PBI) organogelator that bears two 3,4,5-tridodecyloxybenzoylaminoethyl substituents at the imide positions has been investigated in chiral solvents ( R)- and ( S)-limonene in great detail by circular dichroism (CD) spectroscopy and atomic force microscopy (AFM). CD spectroscopic studies on dilute solutions revealed a preferential population of one-handed helical assemblies in chiral solvent with an enantiomeric excess close to 100 %, whereas AFM images of more than 100 nanofibers of the organogel obtained from more concentrated solutions were found to consist of both handed helices with an enantiomeric excess of only 20 %. This discrepancy is attributed to the fast gelation process at high dye concentration that evidently proceeds through non-equilibrated nuclei in a kinetic rather than thermodynamic self-assembly process. Under these conditions the chiral induction from the homochiral solvent may not be adequate in effectively populating only one-handed helices. [ABSTRACT FROM AUTHOR]

A new chiral nonracemic thiol derived from a popular acidic resolving agent that incorporates a cyclic disubstituted phosphate group (phencyphos) has been prepared in enantiomerically pure form. The stereochemistry and absolute configuration were established by performing a single-crystal X-ray structural analysis of a synthetic intermediate. The thiol compound was used for the preparation of self-assembled monolayers (SAMs) on both monocrystalline and polycrystalline metallic gold, which have very different surface roughness. The monolayers were used to promote the nucleation and growth of crystals from nonaqueous solutions of an organic molecule (the parent phencyphos) of similar structure to the compound present in the monolayer. The template layers influence the nucleation and growth of the phencyphos crystals despite the lack of two-dimensional order in the surfaces. Heterogeneous nucleation of phencyphos takes place upon evaporation of either CHCl3 or isopropanol solutions of the compound on the SAM surfaces, where the evaporation rate merely influences the size and homogeneity of the crystals. The roughness of the surface also plays an important role; the polycrystalline gold produces more homogeneous samples because of the greater number of nucleation sites. Clear evidence for nucleation and growth on the surfaces is shown by scanning electron microscopy. The variation in crystal form achieved by using different surfaces and solvents suggests that the layers are applicable for the preparation of organic crystals from organic solutions. [ABSTRACT FROM AUTHOR]

A chiral bisurea-based superhydrogelator that is capable of forming supramolecular hydrogels at concentrations as low as 0.2 m M is reported. This soft material has been characterized by thermal studies, rheology, X-ray diffraction analysis, transmission electron microscopy (TEM), and by various spectroscopic techniques (electronic and vibrational circular dichroism and by FTIR and Raman spectroscopy). The expression of chirality on the molecular and supramolecular levels has been studied and a clear amplification of its chirality into the achiral analogue has been observed. Furthermore, thermal analysis showed that the hydrogelation of compound 1 has a high response to temperature, which corresponds to an enthalpy-driven self-assembly process. These particular thermal characteristics make these materials easy to handle for soft-application technologies. [ABSTRACT FROM AUTHOR]

Herein, two asymmetric chiral bent-core molecules, 3-[(4-{[4-(heptyloxy)benzoyl]oxy}benzoyl)oxy]-phenyl-4-[(4-{[(1 R)-1-methylheptyl]oxy}benzoyl)oxy] benzoate (BC7R) and 3-[(4-{[4-(heptyloxy)benzoyl]oxy}benzoyl)oxy]-phenyl-4-[(4-{[(1 S)-1-methylheptyl]oxy}benzoyl)oxy] benzoate (BC7S), were synthesized to demonstrate control of the helicity of their self-assembled hierarchical superstructures. Mirror-imaged CD spectra showed a split-type Cotton effect after the formation of self-assembled aggregates of BC7R and BC7S, thereby suggesting the formation of intermolecular exciton couplets with opposite optical activities. Both twisted and helical ribbons with preferential helicity that corresponded to the twisting character of the intermolecular exciton couplet were found in the aggregates. The formation of helical ribbons was attributed to the merging of twisted ribbons through an increase in width to improve morphological stability. As a result, control of the helicity of hierarchical superstructures from the self-assembly of bent-core molecules could be achieved by taking advantage of the transfer of chiral information from the molecular level onto the hierarchical scale. [ABSTRACT FROM AUTHOR]

The aggregation of achiral sulfonatophenyl- and phenyl- meso-substituted diprotonated porphyrins to chiral J-aggregates is a hierarchical noncovalent polymerization process preceded by a critical nucleation stage. This allows significant enantiomeric excesses by the formation of a few primary nuclei and the control of their growth by the effect that flows (imperfect mixing) have on the secondary nucleation of the J-aggregate particles. In addition, the results strongly suggest that when only one species of aggregate predominates, the CD signals of the three excitonic bands in the visible region (around 420, 490, and 700 nm) show the same sign. Thus, differences on their relative sign would be due to the presence of different species. [ABSTRACT FROM AUTHOR]

Herein we report on structural, morphological, and optical properties of homochiral and heterochiral J-aggregates that were created by nucleation-elongation assembly of atropo-enantiomerically pure and racemic perylene bisimides (PBIs), respectively. Our detailed studies with conformationally stable biphenoxy-bridged chiral PBIs by UV/Vis absorption, circular dichroism (CD) spectroscopy, and atomic force microscopy (AFM) revealed structurally as well as spectroscopically quite different kinds of J-aggregates for enantiomerically pure and racemic PBIs. AFM investigations showed that enantiopure PBIs form helical nanowires of unique diameter and large length-to-width ratio by self-recognition, while racemic PBIs provide irregular-sized particles by self-discrimination of the enantiomers at the stage of nucleation. Steady-state fluorescence spectroscopy studies revealed that the photoluminescence efficiency of homochiral J-aggregated nanowires (47±3 %) is significantly higher than that of heterochiral J-aggregated particle-like aggregates (12±3 %), which is explained in terms of highly ordered molecular stacking in one-dimensional nanowires of homochiral J-aggregates. Our present results demonstrate the high impact of homochirality on the construction of well-defined nanostructures with unique optical properties. [ABSTRACT FROM AUTHOR]