A Columnar Liquid‐Crystal Phase Formed by Hydrogen‐Bonded Perylene Bisimide J‐Aggregates

A new perylene bisimide (PBI) dye self‐assembles through hydrogen bonds and π–π interactions into J‐aggregates that in turn self‐organize into liquid‐crystalline (LC) columnar hexagonal domains. The PBI cores are organized with the transition dipole moments parallel to the columnar axis, which is an unprecedented structural organization in π‐conjugated columnar liquid crystals. Middle and wide‐angle X‐ray analyses reveal a helical structure consisting of three self‐assembled hydrogen‐bonded PBI strands that constitute a single column of the columnar hexagonal phase. This remarkable assembly mode for columnar liquid crystals may afford new anisotropic LC materials for applications in photonics.     

Photoconductive Core–Shell Liquid‐Crystals of a Perylene Bisimide J‐Aggregate Donor–Acceptor Dyad

A novel core–shell structured columnar liquid crystal composed of a donor‐acceptor dyad of tetraphenoxy perylene bisimide (PBI), decorated with four bithiophene units on the periphery, was synthesized. This molecule self‐assembles in solution into helical J‐aggregates guided by π–π interactions and hydrogen bonds which organize into a liquid‐crystalline (LC) columnar hexagonal domain in the solid state. Donor and acceptor moieties exhibit contrasting exciton coupling behavior with the PBIs’ (J‐type) transition dipole moment parallel and the bithiophene side arms’ (H‐type) perpendicular to the columnar axis. The dyad shows efficient energy and electron transfer in solution as well as in the solid state. The synergy of photoinduced electron transfer (PET) and charge transport along the narcissistically self‐assembled core–shell structure enables the implementation of the dye in two‐contact photoconductivity devices giving rise to a 20‐fold increased photoresponse compared to a reference dye without bithiophene donor moieties.     

Ferroelectrically Switching Helical Columnar Assembly Comprising Cisoid Conformers of a 1,2,3‐Triazole‐based Liquid Crystal

The 1,2,3‐triazole molecule, which is a product of click chemistry, possesses a high dipole moment and can be a useful polar motif for ferroelectric columnar liquid crystal (LC) materials—though it has not been used to date. Herein, we report the helical assembly and ferroelectric switching properties of a columnar liquid crystal comprising a naphthalene core and 1,2,3‐triazolyl linkages. The molecule assembles into a double‐stranded helical columnar LC structure (Col_hel). The X‐ray simulations of cisoid and transoid columnar models suggest that the helical assembly comprises cisoid conformers with a non‐zero dipole moment. The helical columns in the Col_hel phase are aligned homeotropically under an electric field. The ferroelectric switching of the axial polarization can be observed in the temperature range of 105–115 °C in the Col_hel phase, wherein the triazolyl hydrogen bonding along the column axis is weakened. The ferroelectric switching event is attributed to the rotation of the polar triazolyl units in response to the electric field.     

Hierarchical self-assembly,coassembly, and self-organization of novel liquid crystalline lattices and superlattices from a twin-tapered dendritic benzamide and its four-cylinder-bundle supramolecular polymer

The synthesis and structural analysis of the twin-dendritic benzamide 10, based on the first-generation, self-assembling, tapered dendrons 3,4,5-tris(4'-dodecyloxybenzyloxy)benzoic acid and 3,4,5-tris(4'-dodecyloxybenzyloxy)-1-aminobenzene, and the polymethacrylate, 20, which contains 10 as side groups, are presented. Benzamide 10 self-assembles into a supramolecular cylindrical dendrimer that self-organizes into a columnar hexagonal (Phi(h)) liquid crystalline (LC) phase. Polymer 20 self-assembles into an imperfect four-cylinder-bundle supramolecular dendrimer, and creates a giant vesicular supercylinder that self-organizes into a columnar nematic (N(c)) LC phase which displays short-range hexagonal order. In mixtures of 20 and 10, 10 acts as a guest and 20 as a host to create a perfect four-cylinder-bundle host-guest supramolecular dendrimer that coorganizes with 10. A diversity of Phi(h), simple rectangular columnar (Phi(r-s)) and centered rectangular columnar (Phi(r-c)), superlattices are produced at different ratios between 20 and 10. This diversity of LC lattices and superlattices is facilitated by the architecture of the twin-dendritic building block, polymethacrylate, the host-guest supramolecular assembly, and by hydrogen bonding along the center of the supramolecular cylinders generated from 10 and 20.     

Helical arrangement of a hydrogen‐bonded columnar liquid crystal induced by a centered triphenylene derivative bearing chiral side‐chains

A hydrogen‐bonded helical columnar liquid crystal was synthesized, in which the helical structure is induced by a centered triphenylene derivative bearing chiral side‐chains. The triphenylene derivative, 2,6,10‐tris(carboxymethoxy)‐3,7,11‐tris((S)‐(‐)‐2‐methyl‐1‐butanoxy)triphenylene ( TPC4(S) ), and a dendric amphiphile, 3,5‐bis‐(3,4‐bis‐dodecyloxy‐benzyloxy)‐N‐pyridine‐4‐yl‐benzamide ( DenC12 ), were mixed in a 1:3 ratio to obtain a complex, TPC4(S)‐DenC12 . Analyses by ¹H‐NMR spectroscopy, diffusion ordered spectroscopy (DOSY), CD spectroscopy, infrared (IR) spectroscopy, polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X‐ray diffractometry revealed that TPC4(S)‐DenC12 self‐assembles to form helical columnar stacks in solution and a helical columnar liquid crystal in bulk. The hydrogen bonding between TPC4(S) and DenC12 is essential for the helical columnar organization, and the preference for a one‐handed helical conformation is likely derived from the steric interaction between the chiral side‐chains and the dendric amphiphiles in the packing of the hydrogen‐bonded columnar assemblies. Copyright © 2008 John Wiley & Sons, Ltd.     

Ultrafast Vibrational Dynamics of Membrane‐Bound Peptides at the Lipid Bilayer/Water Interface

Vibrational energy transfer (VET) of proteins at cell membrane plays critical roles in controlling the protein functionalities, but its detection is very challenging. By using a surface‐sensitive femtosecond time‐resolved sum‐frequency generation vibrational spectroscopy with infrared pump, the detection of the ultrafast VET in proteins at cell membrane has finally become possible. The vibrational relaxation time of the N−H groups is determined to be 1.70(±0.05) ps for the α‐helix located in the hydrophobic core of the lipid bilayer and 0.9(±0.05) ps for the membrane‐bound β‐sheet structure. The N−H groups with strong hydrogen bonding gain faster relaxation time. By pumping the amide A band and probing amide I band, the vibrational relaxation from N−H mode to C=O mode through two pathways (direct coupling and through intermediate states) is revealed. The ratio of the pathways depends on the NH⋅⋅⋅O=C hydrogen‐bonding strength. Strong hydrogen bonding favors the coupling through intermediate states.     

Designing Hydrogen‐Bonded Organic Frameworks (HOFs) with Permanent Porosity

Designing organic components that can be used to construct porous materials enables the preparation of tailored functionalized materials. Research into porous materials has seen a resurgence in the past decade as a result of finding of self‐standing porous molecular crystals (PMCs). Particularly, a number of crystalline systems with permanent porosity that are formed by self‐assembly through hydrogen bonding (H‐bonding) have been developed. Such systems are called hydrogen‐bonded organic frameworks (HOFs). Herein we systematically describe H‐bonding patterns (supramolecular synthons) and molecular structures (tectons) that have been used to achieve thermal and chemical durability, a large surface area, and functions, such as selective gas sorption and separation, which can provide design principles for constructing HOFs with permanent porosity.     

Hydrogen Bonding Between Ions of Like Charge in Ionic Liquids Characterized by NMR Deuteron Quadrupole Coupling Constants—Comparison with Salt Bridges and Molecular Systems

We present deuteron quadrupole coupling constants (DQCC) for hydroxyl‐functionalized ionic liquids (ILs) in the crystalline or glassy states characterizing two types of hydrogen bonding: The regular Coulomb‐enhanced hydrogen bonds between cation and anion (c–a), and the unusual hydrogen bonds between cation and cation (c–c), which are present despite repulsive Coulomb forces. We measure these sensitive probes of hydrogen bonding by means of solid‐state NMR spectroscopy. The DQCCs of (c–a) ion pairs and (c–c) H‐bonds are compared to those of salt bridges in supramolecular complexes and those present in molecular liquids. At low temperatures, the (c–c) species successfully compete with the (c–a) ion pairs and dominate the cluster populations. Equilibrium constants obtained from molecular‐dynamics (MD) simulations show van't Hoff behavior with small transition enthalpies between the differently H‐bonded species. We show that cationic‐cluster formation prevents these ILs from crystallizing. With cooling, the (c–c) hydrogen bonds persist, resulting in supercooling and glass formation.     

Influence of Ester versus Amide Linkers on the Supramolecular Polymerization Mechanisms of Planar BODIPY Dyes

We report the H‐type supramolecular polymerization of two new hydrophobic BODIPY derivatives equipped with ester and amide linkages. Whereas the ester‐containing BODIPY derivative undergoes an isodesmic supramolecular polymerization in which the monomers are parallel‐oriented, the replacement of the ester by amide groups leads to a highly cooperative self‐assembly process into H‐type aggregates with a rotational displacement of the dye molecules within the stack. The dye organization imposed by simultaneous π–π and hydrogen bonding interactions is the driving force for the cooperative supramolecular polymerization, whereas the absence of additional hydrogen bonds for the ester‐containing moiety does not suffice to induce cooperative phenomena.     

A new urea gelator: incorporation of intra- and intermolecular hydrogen bonding for stable 1D self-assembly

A new bisurea gelator derived from 2,6-diaminopyridine has been developed. It efficiently gelates common organic and liquid crystalline (LC) solvents by forming elongated self-assembled fibres in solvents. X-Ray crystallography and 1H NMR measurements reveal that two urea groups in pyridine-based bisurea compounds form different hydrogen bonding patterns. One of two urea units is involved in intramolecular hydrogen bonding with the pyridyl nitrogen, while the other urea unit forms bifurcated intermolecular hydrogen bonding. This hydrogen-bonded structure is key for the fibrous self-assembly along with the efficient gelation. In addition, LC gels based on the pyridine-based gelator exhibit good electrooptic properties. These results indicate that the pyridine-based bisurea compound is a good gelator not only effective in gelation but also useful as a component of functional soft materials.     

A Competing Hydrogen Bonding Pattern to Yield a Thermo‐Thickening Supramolecular Polymer

Introduction of competing interactions in the design of a supramolecular polymer (SP) creates pathway complexity. Ester–bis‐ureas contain both a strong bis‐urea sticker that is responsible for the build‐up of long rod‐like objects by hydrogen bonding and ester groups that can interfere with this main pattern in a subtle way. Spectroscopic (FTIR and CD), calorimetric (DSC), and scattering (SANS) techniques show that such ester–bis‐ureas self‐assemble into three competing rod‐like SPs. The previously unreported low‐temperature SP is stabilized by hydrogen bonds between the interfering ester groups and the urea moieties. It also features a weak macroscopic alignment of the rods. The other structures form isotropic dispersions of rods stabilized by the more classical urea‐urea hydrogen bonding pattern. The transition from the low‐temperature structure to the next occurs reversibly by heating and is accompanied by an increase in viscosity, a rare feature for solutions in hydrocarbons.     

High‐Field NMR Spectroscopy Reveals Aromaticity‐Modulated Hydrogen Bonding in Heterocycles

From DNA base pairs to drug–receptor binding, hydrogen (H‐)bonding and aromaticity are common features of heterocycles. Herein, the interplay of these bonding aspects is explored. H‐bond strength modulation due to enhancement or disruption of aromaticity of heterocycles is experimentally revealed by comparing homodimer H‐bond energies of aromatic heterocycles with analogs that have the same H‐bonding moieties but lack cyclic π‐conjugation. NMR studies of dimerization in C₆D₆ find aromaticity‐modulated H‐bonding (AMHB) energy effects of approximately ±30 %, depending on whether they enhance or weaken aromatic delocalization. The attendant ring current perturbations expected from such modulation are confirmed by chemical shift changes in both observed ring C−H and calculated nucleus‐independent sites. In silico modeling confirms that AMHB effects outweigh those of hybridization or dipole–dipole interaction.     

Intermolecular H···O═C bonds induced 2D self‐assembly of thiophene based diketopyrrolopyrrole derivative

Compounds with diketopyrrolopyrrole (DPP) and thiophene moieties have attracted considerable attention because of their promising charge transport properties. The molecular conformation and self‐assembly of 2,5‐dihexadecyl‐3,6‐di(thiophen‐2‐yl)‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione (TDPP‐C16) molecule have been investigated by scanning tunneling microscopy and density functional theory alculation. The TDPP‐C16 molecules adsorb with their optimized S‐shaped conformation and form a zipper‐like pattern on highly oriented pyrolytic graphite surface. R and S rotated structures are observed. The nanostructure is dominated by intermolecular double hydrogen bonds between C═O of the DPP units and hydrogen atom of thiophene rings in the neighboring molecules in each row. Atomic force microscopy and density functional theory calculation also display the existence of strong intermolecular hydrogen bonding. The results provide molecular evidence for the intermolecular interactions of the surface structure, which could benefit to the design of the organic semiconducting materials and understanding of underlying principle of charge transfer process. Copyright © 2017 John Wiley & Sons, Ltd.     

Unveiling the Role of Hydrogen Bonds in Luminescent N-Annulated Perylene Liquid Crystals

We report the liquid-crystalline (LC) and luminescent properties of a series of N-annulated perylenes ( 1 – 4 ) in whose molecular structures amide and ester groups alternate. We found that the LC properties of these compounds not only depend on the number of hydrogen-bonding units, but also on the relative position of the amide linkers in the molecule. The absence of amide groups in compound 1 leads to no LC properties, whereas four amide groups induce the formation of a wide temperature range columnar hexagonal phase in compound 4 . Remarkably, compound 3 , with two amide groups in the inner part of the structure, stabilizes the columnar LC phases better than its structural isomer 2 , with the amide groups in the outer part of the molecule. Similarly, we found that only compounds 1 and 2 , which have no hydrogen bonding units in the inner part of the molecule, exhibit luminescence vapochromism upon exposure to organic solvent vapors.     

Hydrogen‐Bonding‐Regulated Supramolecular Nanostructures and Impact on Multivalent Binding

Herein we describe the H‐bonding‐regulated nanostructure, thermodynamics, and multivalent binding of two bolaamphiphiles NDI‐1 and NDI‐2 consisting of a hydrophobic naphthalene diimide connected to a hydrophilic wedge by a H‐bonding group and a glucose moiety on its two arms. NDI‐1 and NDI‐2 differ by the single H‐bonding group, namely, hydrazide or amide, which triggers the formation of vesicles and cylindrical micelles, respectively. Although the extended H‐bonding ensures stacking with head‐to‐head orientation and the formation of an array of the appended glucose moieties in both systems, the adaptive cylindrical structure exhibited superior multivalent binding with concanavalin A (ConA) to that of the vesicle. A control amphiphile lacking a H‐bonding group assembled with a random lateral orientation to produce spherical micelles without any notable multivalent binding.     

Enclosure of a Keggin-type heteropolyoxometalate into a tubular π-space via hydrogen bonds with a nonplanar Mo(V)-porphyrin complex forming a supramolecular assembly

A 2:1 supramolecular assembly composed of a non-planar Mo(V)-porphyrin, [Mo(DPP)(O)(H(2)O)](+) (1) (DPP(2+); dodecaphenylporphyrin), and a Keggin-type heteropolyoxometalate (POM), α-[(n-butyl)(4)N](2)[SW(12)O(40)] (2), was formed via hydrogen bonds. The crystal structure was determined by X-ray crystallography to clarify that the POM was enclosed into a π-space of a supramolecular porphyrin nanotube by virtue of a hydrogen-bond network. In contrast to the formation of the 2:1 assembly ([{Mo(DPP)(O)(H(2)O)}(2)(SW(12)O(40))] (3)) between 1 and [SW(12)O(40)](2-) in the crystal, it was revealed that those two components form a 1:1 assembly in solution, in light of the results of MALDI-TOF-MS measurements in PhCN. Variable-temperature UV-vis spectroscopic titration allowed us to determine the thermodynamic parameters for the formation of the 1:1 supramolecular assembly in solution, the heat of formation (ΔH) and the entropy change (ΔS). These results provide the first thermodynamic data set to elucidate the formation process of supramolecuar structures emerged by hydrogen bonding between metalloporphyrin complexes and POMs, indicating that the formation of the assembly is an entropy-controlled process rather than an enthalpy-controlled one. Comparisons of the thermodynamic parameters with those of a planar Mo(V)-porphyrin complex also highlighted high Lewis acidity of the Mo(V) centre in the distorted porphyrin.     

(S,S)‐4′′‐Cyano‐7,7′′‐dimethoxy‐3′,6′‐dioxodispiro[indane‐2,2′‐piperazine‐5′,2′′‐indane]‐4‐carboxamide methanol solvate: interrupting the amide‐to‐amide hydrogen‐bonded tape

The title methanol solvate, C₂₄H₂₂N₄O₅·CH₃OH, forms an extended three‐dimensional hydrogen‐bonded structure, assisted by the presence of several good donor and acceptor sites. It shows none of the crystal packing features typically expected of piperazinediones, such as amide‐to‐amide R₂²(8) hydrogen bonding. In this structure the methanol solvent appears to play only a space‐filling role; it is not involved in any hydrogen bonding and instead is disordered over several sites. This study reports, to the best of our knowledge, the first crystal structure of an indane‐containing piperazinedione compound which exhibits a three‐dimensional hydrogen‐bonded structure formed by classical (N—H...O and N—H...N) hydrogen‐bonding interactions.     

Gelation‐Induced Enhanced Fluorescence Emission from Organogels of Salicylanilide‐Containing Compounds Exhibiting Excited‐State Intramolecular Proton Transfer: Synthesis and Self‐Assembly

Self‐assembly structure, stability, hydrogen‐bonding interaction, and optical properties of a new class of low molecular weight organogelators (LMOGs) formed by salicylanilides 3 and 4 have been investigated by field‐emission scanning electron microscopy (FESEM), X‐ray diffraction (XRD), UV/Vis absorption and photoluminescence, as well as theoretical studies by DFT and semiempirical calculations with CI (AM1/PECI=8) methods. It was found that salicylanilides form gels in nonpolar solvents due to π‐stacking interaction complemented by the presence of both inter‐ and intramolecular hydrogen bonding. The supramolecular arrangement in these organogels predicted by XRD shows lamellar and hexagonal columnar structures for gelators 3 and 4 , respectively. Of particular interest is the observation of significant fluorescence enhancement accompanying gelation, which was ascribed to the formation of J‐aggregates and inhibition of intramolecular rotation in the gel state.     

Thermoresponsive Synergistic Hydrogen Bonding Switched by Several Guest Units in a Water‐Soluble Polymer

Thermoresponsive synergistic hydrogen bonding (H‐bonding) switched by several guest units in a water‐soluble polymer is reported. Adjusting the distribution of guest units can effectively change the synergistic H‐bonding inside polymer chains, thus widely switch the preorganization and thermoresponsive behavior of a water‐soluble polymer. The synergistic H‐bonding is also evidenced by converting less polar aldehyde groups into water‐soluble oxime groups, which bring about the lowering‐down of cloud point and an amplified hysteresis effect. This is a general approach toward the wide tunability of thermosensitivity of a water‐soluble polymer simply by adjusting the distribution of several guest H‐bonding units.     

Hydrogen bonding between aromatic H and F groups leading to a stripe structure with R‐ and S‐columns: the crystal structure of (2,7‐dimethoxynaphthalen‐1‐yl)(3‐fluorophenyl)methanone and comparison with its 1‐aroylnaphthalene analogues

In the molecule of (2,7‐dimethoxynaphthalen‐1‐yl)(3‐fluorophenyl)methanone, C₁₉H₁₅FO₃, (I), the dihedral angle between the plane of the naphthalene ring system and that of the benzene ring is 85.90 (5)°. The molecules exhibit axial chirality, with either an R‐ or an S‐stereogenic axis. In the crystal structure, each enantiomer is stacked into a columnar structure and the columns are arranged alternately to form a stripe structure. A pair of (methoxy)C—H...F hydrogen bonds and π–π interactions between the benzene rings of the aroyl groups link an R‐ and an S‐isomer to form a dimeric pair. These dimeric pairs are piled up in a columnar fashion through (benzene)C—H...O=C and (benzene)C—H...OCH₃ hydrogen bonds. The analogous 1‐benzoylated compound, namely (2,7‐dimethoxynaphthalen‐1‐yl)(phenyl)methanone [Kato et al. (2010). Acta Cryst. E 66 , o2659], (II), affords three independent molecules having slightly different dihedral angles between the benzene and naphthalene rings. The three independent molecules form separate columns and the three types of column are connected to each other via two C—H...OCH₃ hydrogen bonds and one C—H...O=C hydrogen bond. Two of the three columns are formed by the same enantiomeric isomer, whereas the remaining column consists of the counterpart isomer. In the case of the fluorinated 1‐benzoylated naphthalene analogue, namely (2,7‐dimethoxynaphthalen‐1‐yl)(4‐fluorophenyl)methanone [Watanabe et al. (2011). Acta Cryst. E 67 , o1466], (III), the molecular packing is similar to that of (I), i.e. it consists of stripes of R‐ and S‐enantiomeric columns. A pair of C—H...F hydrogen bonds between R‐ and S‐isomers, and C—H...O=C hydrogen bonds between R(or S)‐isomers, are also observed. Consequently, the stripe structure is apparently induced by the formation of R...S dimeric pairs stacked in a columnar fashion. The pair of C—H...F hydrogen bonds effectively stabilizes the dimeric pair of R‐ and S‐enantiomers. In addition, the co‐existence of C—H...F and C—H...O=C hydrogen bonds makes possible the formation of a structure with just one independent molecule.