Hexaphenylbenzene Derivative Research Articles

Chiral Adaptive Induction of an Achiral Cucurbit[8]uril-Based Supramolecular Organic Framework by Dipeptides in Water.

Chiral induction by natural biomolecules can reveal the indispensable role of chiral structures in life and can be used to develop the chirality-sensing biomolecular recognition. Here, we present the synthesis and characterization of an achiral supramolecular organic framework (SOF-1) constructed from cucurbit[8]uril (CB[8]) and hexaphenylbenzene (HPB) derivative (1) in water. Due to the propeller-like rotational chiral conformation of HPB units and the specific recognition properties of CB[8], SOF-1 demonstrates chiral adaptive induction in water when interacting with the N-terminal Trp-/Phe-containing dipeptides including L-TrpX and L-PheX (X is an amino acid residue), respectively, exhibiting contrasting circular dichroism (CD) and circularly polarized luminescence (CPL) spectra. Consequently, SOF-1 has been developed as a supramolecular host and chiroptical sensor capable of recognizing and distinguishing the sequence-opposite Trp-/Phe-containing dipeptide pairs including L-TrpX/L-XTrp and L-PheX/L-XPhe based on the sequence-selective CD responses.

Chiral Adaptive Induction of an Achiral Cucurbit[8]uril‐Based Supramolecular Organic Framework by Dipeptides in Water

AbstractChiral induction by natural biomolecules can reveal the indispensable role of chiral structures in life and can be used to develop the chirality‐sensing biomolecular recognition. Here, we present the synthesis and characterization of an achiral supramolecular organic framework (SOF‐1) constructed from cucurbit[8]uril (CB[8]) and hexaphenylbenzene (HPB) derivative (1) in water. Due to the propeller‐like rotational chiral conformation of HPB units and the specific recognition properties of CB[8], SOF‐1 demonstrates chiral adaptive induction in water when interacting with the N‐terminal Trp‐/Phe‐containing dipeptides including L‐TrpX and L‐PheX (X is an amino acid residue), respectively, exhibiting contrasting circular dichroism (CD) and circularly polarized luminescence (CPL) spectra. Consequently, SOF‐1 has been developed as a supramolecular host and chiroptical sensor capable of recognizing and distinguishing the sequence‐opposite Trp‐/Phe‐containing dipeptide pairs including L‐TrpX/L‐XTrp and L‐PheX/L‐XPhe based on the sequence‐selective CD responses.

Hexaphenylbenzene‐Based Deep Blue‐Emissive Metallacages as Donors for Light‐Harvesting Systems

AbstractWe herein report the preparation of a series of hexaphenylbenzene (HPB)‐based deep blue‐emissive metallacages via multicomponent coordination‐driven self‐assembly. These metallacages feature prismatic structures with HPB derivatives as the faces and tetracarboxylic ligands as the pillars, as evidenced by NMR, mass spectrometry and X‐ray diffraction analysis. Light‐harvesting systems were further constructed by employing the metallacages as the donor and a naphthalimide derivative (NAP) as the acceptor, owing to their good spectral overlap. The judiciously chosen metallacage serves as the antenna, providing the suitable energy to excite the non‐emissive NAP, and thus resulting in bright emission for NAP in the solid state. This study provides a type of HPB‐based multicomponent emissive metallacage and explores their applications as energy donors to light up non‐emissive fluorophores in the solid state, which will advance the development of emissive metallacages as useful luminescent materials.

Hexaphenylbenzene-Based Deep Blue-Emissive Metallacages as Donors for Light-Harvesting Systems.

We herein report the preparation of a series of hexaphenylbenzene (HPB)-based deep blue-emissive metallacages via multicomponent coordination-driven self-assembly. These metallacages feature prismatic structures with HPB derivatives as the faces and tetracarboxylic ligands as the pillars, as evidenced by NMR, mass spectrometry and X-ray diffraction analysis. Light-harvesting systems were further constructed by employing the metallacages as the donor and a naphthalimide derivative (NAP) as the acceptor, owing to their good spectral overlap. The judiciously chosen metallacage serves as the antenna, providing the suitable energy to excite the non-emissive NAP, and thus resulting in bright emission for NAP in the solid state. This study provides a type of HPB-based multicomponent emissive metallacage and explores their applications as energy donors to light up non-emissive fluorophores in the solid state, which will advance the development of emissive metallacages as useful luminescent materials.

Hexaphenylbenzene-based fluorescent probes for the detection of fluoride ions

Novel hexaphenylbenzene derivatives (HPB-1 and HPB-2) were synthesized and their sensing abilities were investigated.

Hexaphenylbenzene based push-pull fluorophores displaying intriguing polarity-dependent fluorescence behavior, AIE(E) characteristics and mega-large Stokes shifts

In general, most donor-acceptor type fluorophores are known to exhibit solvatochromic behavior and obey the energy gap law simultaneously, showing decreased emission with increasing solvent polarity. In this work, four push-pull hexaphenylbenzene (HPB) derivatives 1–4 have been designed and synthesized by introducing methoxy and dicyanovinyl groups at the tip of aromatic blades, which behave exceptionally polarity-dependent emission properties. In the low to medium solvent polarity region, the four dipole fluorophores display gradually enhanced fluorescence, whereas a reverse trend is observed with the further increase of solvent polarity. Meanwhile, 1–4 are found to exhibit the strongest emission at the same wavelength remarkably, which appears to be somewhat relevant to the intrinsic characteristics of dicyanovinyl-phenyl acceptor. A mechanistic scheme containing a conical intersection (CI) has been proposed to explain the up-down emission of 1–4 with increasing solvent polarity. Large Stokes shifts (up to 254 nm) and AIE(E) characteristics have also been achieved in these four HPB fluorophores. Besides, fluorophores 1–4 exhibit obvious freezing-solution induced chromism (FSIC), demonstrating an enhancement of the local matrix polarity upon freezing solutions.

Layered Hexaphenylbenzene (HPB) derivatives with pseudo-2D structure for high-performance Li ion batteries

Herein, we have synthesized a series of hexaphenylbenzene (HPB) derivatives: HPB-H, HPB-COOCH3 and HPB-COOH that differs in functional groups attached to the periphery of the outer benzene rings. Among them, the HPB with carboxyl functional group (HPB-COOH) as LIB anode shows a superior capacity of 997.4 mAh g−1 and better rate performance than HPB and HPB-COOCH3. Such superior anode properties can be attributed to the fact that HPB-COOH has a layered morphology, a pseudo-2D structure, lower LUMO energy, and higher electron conductivity, compared with that of HPB-COOCH3 and HPB-H, respectively. Moreover, low energy packing with transport channels is beneficial for Li ions diffusion during the lithiation and extraction processes. Furthermore, HPB-COOH shows excellent cycling stability presumably due to its layered molecular packing structures. Our work paves the way for the design synthesis of novel organic molecules with suitable electrochemical redox-active groups and layered hierarchical structure to achieve high capacity, good rate performance, and high cyclic stability for next generation Li ion batteries (LIBs).

A photocatalytic ensemble HP-T@Au-Fe3O4: synergistic and balanced operation in Kumada and Heck coupling reactions

A supramolecular catalytic ensemble HP-T@Au-Fe3O4 supported by highly branched assemblies of hexaphenylbenzene (HPB) derivative has been developed which serve as an efficient catalytic system for Kumada cross coupling and Heck coupling reactions.

One-pot synthesis of conjugated microporous polymers based on extended molecular graphenes for hydrogen storage

Incorporation of highly extended π-conjugated molecules into conjugated microporous polymers (CMPs) is one of the important aspects in material science. Herein we synthesize conjugated microporous polymers (CMP-Gs) with covalently linked molecular graphenes by an efficient tandem oxidative reaction in one-pot, which comprising Scholl-type cyclodehydrogenation and oxidative polymerization. Oxidation of m- or p-thienyl decorated hexaphenylbenzene derivatives with excess of FeCl3 allowing in situ generation of size-controlled graphitic segments form CMP-G1 and CMP-G2 in high yields, respectively. CMP-Gs possess large surface areas and micropore size from 0.5 to 1.5 nm. Gravimetric hydrogen adsorption isotherms show that the adsorption capacity for hydrogen is up to 2.69 wt% for CMP-G1 and 2.14 wt% for CMP-G2 at 20 bar and 77 K, respectively.

Cover Feature: Gram‐Scale Synthesis of a C2v‐Symmetric Hexaphenylbenzene with Three Different Types of Substituents (Asian J. Org. Chem. 10/2018)

C2v-symmetric hexaphenylbenzene (HPB) derivatives with three kinds of different substituents on the periphery of HPB coloured in red, blue, and yellow in the Cover Feature can be selectively synthesized by combining several types of building blocks. This type of C2v-symmetric HPB derivatives were synthesized using inexpensive reagents on gram scale. All the reactions were carried out at room temperature or by heating, and most materials along the synthetic route could be isolated without chromatographic purification. This method enables the preparation of novel HPB-based materials for a variety of purposes. More information can be found in the Communication by Shuichi Hiraoka et al. on page 2057 in Issue 10, 2018 (DOI: 10.1002/ajoc.201800448).

Nanotribological Study of Supramolecular Template Networks Induced by Hydrogen Bonds and van der Waals Forces.

Nanotribology has been given increasing attention by researchers in pursuing the nature of friction. In the present work, an approach that combines the supramolecular assembly and nanotribology is introduced. Herein, the nanotribological study was carried out on seven supramolecular template networks [namely, hydrogen bond induced tricarboxylic acids and van der Waals force induced hexaphenylbenzene (HPB) derivatives]. The template networks, as well as the host-guest assemblies of template molecules induced by different forces, were constructed on the highly oriented pyrolytic graphite (HOPG) surface and explicitly characterized using scanning tunneling microscopy (STM). Meanwhile, the nanotribological properties of the template networks were measured using atomic force microscopy (AFM). Together with the theoretical calculation using the density functional theory (DFT) method, it was revealed that the friction coefficients were positively correlated with the interaction strength. The frictional energy dissipation mainly derives from both the intermolecular interaction energy and the interaction energy between molecules and the substrate. The efforts not only help us gain insight into the competitive mechanisms of hydrogen bond and van der Waals force in supramolecular assembly but also shed light on the origin of friction and the relationship between the assembly structures and the nanotribological properties at the molecular level.

Selective Preparation of C 2v -Symmetric Hexaphenylbenzene Derivatives through Sequential Suzuki Coupling

We have developed effective reaction conditions for the ­Suzuki cross-coupling of chlorinated hexaphenylbenzene derivatives. A chloro group on a hexaphenylbenzene framework exhibits a low reactivity to Suzuki cross-coupling, and only nickel catalysts bearing alkyl-substituted phosphine ligands achieved the coupling. With this as a key step, we succeeded in the selective preparation of a C 2v -symmetric hexaphenylbenzene derivative containing two kinds of aryl group.

Importance of Molecular Meshing for the Stabilization of Solvophobic Assemblies.

The effect of the methyl groups in neutral gear-shaped amphiphiles (GSAs) on the stability of nanocubes was investigated using a novel C2 v-symmetric GSA, which was synthesized using selective alternate trilithiation of a pentabrominated hexaphenylbenzene derivative. The lack of only one methyl group in the GSA decreased the association constant for the assembly of the nanocube by 3 orders of magnitude. A surface analysis recently developed by the authors (SAVPR: surface analysis with varying probe radii) was carried out for characteristic isomers of the nanocube consisting of C2 v-symmetric GSAs. It was found that the methyl groups near the equator of the nanocube play a significant role in the stabilization of the nanocubes.

Synthesis and Characterization of Polycyclic Aromatic Hydrocarbons with Different Spatial Constructions Based on Hexaphenylbenzene Derivatives.

In recent years, low-bandgap polymers have attracted much attention in a wide range of fields. The synthesis of these compounds has been focused on three factors according to the Roncali bandgap theory: 1) the degree of bond-length alternation (Eδr ), 2) the aromatic resonance energy of the cycle (ERes ), and 3) the substituted groups (ESub ). Herein, we have designed and prepared low-bandgap polymers in a different way by using the factors Eθ (the deviation from planarity of the polymer chain) and EInt (the interaction of the molecular chains in the solid state). Thus, three polycyclic aromatic hydrocarbons with different spatial constructions, based on hexaphenylbenzene derivatives, were prepared in this work: linear (P1-OX), V (P2-OX), and zigzag (P3-OX) types. These well-defined polymers exhibited interesting optical and electrochemistry behavior due to their different extents of planarity. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry gave the incremental orderly molecular weight distributions of P1, P2, and P3, the weight-average molecular weights (M‾w ) of which were 9000, 5500, and 69 000, respectively. Their lamellar layer structures and π-π intermolecular stacking were demonstrated by using two-dimensional grazing-incidence X-ray diffraction, which revealed the edge-on chain conformation. Finally, the materials were perfectly adapted to fabricate high-performance organic field-effect transistor devices, which revealed that these compounds could have great prospects as semiconductors.

AIEE Active Donor-Acceptor-Donor-Based Hexaphenylbenzene Probe for Recognition of Aliphatic and Aromatic Amines.

In the present investigation, an intramolecular charge transfer (ICT) and aggregation induced emission enhancement (AIEE) active donor-acceptor-donor (D-A-D) system 5 having fumaronitrile as the acceptor and hexaphenylbenzene (HPB) as the donor moieties joined through rotatable phenyl rings has been designed and synthesized that is highly emissive in the solid state and exhibits stimuli-responsive reversible piezochromic behavior upon grinding and heating. Because of its AIEE characteristics, HPB derivative 5 undergoes aggregation to form fluorescent aggregates in mixed aqueous media that exhibit ratiometric fluorescence response toward aliphatic amines (primary/secondary/tertiary) and turn-off response toward aromatic amines and hence differentiates between them. Further, the solution-coated portable paper strips of derivative 5 showed pronounced and sensitive response toward aromatic and aliphatic amines with a detection limit in the range of picogram and nanogram level, respectively.

Supramolecular Self-Assembly of Hexaphenylbenzene Derivatives with Different Symmetry and Number of Carboxylic Acid at Liquid/Solid Interfaces

Functional molecules, especially with carboxyl groups are crucial in building supramolecular structures. It is great important to study the effect of the symmetry, number of carboxyl groups on the self-assembly behavior of corresponding molecules. A series of hexaphenylbenzene (HPB) derivatives (HPB-1,3,5-3A, HPB-1,2,4-3A, and HPB-1,4-2A) substituted with different number of carboxyl groups at different position have been synthesized and their self-assembled structures were investigated at both 1-phenyloctane/HOPG and heptanoic acid/HOPG interfaces by using scanning tunneling microscopy (STM) technique. The self-assembled mechanisms of these HPB-based compounds were further studied with the help of density functional theory (DFT) calculations. The results indicate that symmetry and number of carboxyl groups as well as solvent play a significant role on the tuning self-assemble process resulting in various structures.

Toroidal delocalization of a single electron through circularly-arrayed benzophenone chromophores in hexakis(4-benzoylphenyl)benzene

Abstract Molecules incorporating with multiple electro-active chromophores are actively sought owing to their potential to serve as energy- and charge-transport materials in the area of photovoltaics and energy storage devices. Herein we demonstrate that a hexaphenylbenzene derivative with six circularly-arrayed electroactive chromophores exhibits effective (toroidal) electronic coupling amongst the six benzophenone moieties. The hexaphenylbenzene-based monobenzoyl ppbBP and hexabenzoyl HBP afford the stabilization of triplet exciton by 4–5 kcal/mol, as compared to parent benzophenone, due to the formation of intramolecular exciplexes with the hexaphenylbenzene propeller. The HBP anion radical, generated by photoinduced electron transfer from a hindered tertiary amine, showed the presence of an intense charge-resonance transition, which was absent in the model compounds (such as ppbBP anion radical). The charge-resonance transition in HBP − evidences delocalization of an electron by hopping over six identical circularly-arrayed benzophenone moieties, which is highly reminiscent of the hole delocalization observed earlier in a number of hexaarylbenzene cation radicals.

Strong Physical Hydrogels from Fibrillar Supramolecular Assemblies of Poly(ethylene glycol) Functionalized Hexaphenylbenzenes

Gel formation without chemical cross-links requires strong physical bonds, as observed in diverse molecular and macromolecular systems or supramolecular assemblies above a critical concentration. Here, we present a new molecular amphiphile of propeller-like hexaphenylbenzene derivative bearing two short poly(ethylene glycol) (PEG) chains which forms reversible physical gels comprising long (∼2.2 μm) bundles of hydrogel fibrils in coexistence with spherical micelles. Combination of topological (entanglement-like) interactions between the fibers and specific hydrophobic interactions due to the helicity of the PEG chains is proposed to account for the hydrogelation in the semidilute regime. The present supramolecular hydrogels, which are based on small molecules, exhibit extraordinary properties with an exceptionally strong dependence of the shear modulus on concentration, akin to the behavior of ultrahigh molecular weight cellulose-based fibers.

Development of a supramolecular ensemble of an AIEE active hexaphenylbenzene derivative and Ag@Cu2O core-shell NPs: an efficient photocatalytic system for C-H activation.

A supramolecular ensemble having Ag@Cu2O core-shell nanoparticles stabilized by aggregates of a hexaphenylbenzene derivative has been developed which exhibits excellent photocatalytic efficiency in reactions involving preparation of imidazole and benzimidazole derivatives via C-H activation.

Formation of Ordered Coronene Clusters in Template Utilizing the Structural Transformation of Hexaphenylbenzene Derivative Networks on Graphite Surface.

In the present work, we report the fabrication of regular coronene (COR) clusters on surfaces in ambient conditions in the two-dimensional network formed by hexaphenylbenzene derivatives (HPB) via structural transformation. HPB could form a stable snowflake network structure on the highly oriented pyrolytic graphite surface at the air-solid interface. When COR molecules were introduced into the system, the HPB snowflake network could transform to honeycomb structures, and the COR heptamers were subsequently aggregated and entrapped into the cavity. Scanning tunneling microscopic was employed to monitor the assembly behavior of both HPB and HPB/COR at a submolecule scale level, and density functional theory calculations were utilized to reveal that the structural transformation and the entrapment are the energetically favorable. The pores formed from HPB might also give a clue to immobilizing some functional molecule clusters, like COR, to fabricate their ordered monolayer in ambient conditions, so as to obtain complex supramolecular surface structures.