Effect of Fullerene Volume Fraction on Two‐Dimensional Crystal‐Constructed Supramolecular Liquid Crystals

The volume fraction plays an important role in phase segregated soft matters. We demonstrate here that at high fullerene volume fraction in soft chain‐tethered‐fullerene dyads, different two‐dimensional (2D) crystal‐constructed smectic‐like lamella liquid crystalline (LC) phases can be formed with triple‐layer (S_T phase) or quadruple‐layer (S_Q phase) stacking of fullerenes in 2D crystals. The combination of 2D crystal and LC properties in one system affords these fullerene dyads controlled electron mobility in the range of 10^?5–10^?3 cm² V^?1 s^?1 at room temperature (S_T phase), by regulating the insulated soft layer thickness between 2D crystals via the manipulation of fullerene volume fraction.     

Supramolecular [60]Fullerene Liquid Crystals Formed By Self‐Organized Two‐Dimensional Crystals

Fullerene‐based liquid crystalline materials have both the excellent optical and electrical properties of fullerene and the self‐organization and external‐field‐responsive properties of liquid crystals (LCs). Herein, we demonstrate a new family of thermotropic [60]fullerene supramolecular LCs with hierarchical structures. The [60]fullerene dyads undergo self‐organization driven by π–π interactions to form triple‐layer two‐dimensional (2D) fullerene crystals sandwiched between layers of alkyl chains. The lamellar packing of 2D crystals gives rise to the formation of supramolecular LCs. This design strategy should be applicable to other molecules and lead to an enlarged family of 2D crystals and supramolecular liquid crystals.     

Large‐Area,Free‐Standing,Two‐Dimensional Supramolecular Polymer Single‐Layer Sheets for Highly Efficient Electrocatalytic Hydrogen Evolution

The rational construction of covalent or noncovalent organic two‐dimensional nanosheets is a fascinating target because of their promising applications in electronics, membrane technology, catalysis, sensing, and energy technologies. Herein, a large‐area (square millimeters) and free‐standing 2D supramolecular polymer (2DSP) single‐layer sheet (0.7–0.9 nm in thickness), comprising triphenylene‐fused nickel bis(dithiolene) complexes has been readily prepared by using the Langmuir–Blodgett method. Such 2DSPs exhibit excellent electrocatalytic activities for hydrogen generation from water with a Tafel slope of 80.5 mV decade⁻¹ and an overpotential of 333 mV at 10 mA cm⁻², which are superior to that of recently reported carbon nanotube supported molecular catalysts and heteroatom‐doped graphene catalysts. This work is promising for the development of novel free‐standing organic 2D materials for energy technologies.     

Spontaneous Single‐Crystal‐to‐Single‐Crystal Evolution of Two Cross‐Laminated Polymers

Two cases of spontaneous evolution of monomers to linear polymers having novel cross‐laminated topology are reported. We synthesized two peptide monomers N₃‐Gly‐Gly‐NH‐CH₂‐CCH and N₃‐Gly‐Gly‐Gly‐CH₂‐CCH and solved their crystal structures by single‐crystal X‐ray diffraction. They adopt H‐bonded crisscrossed layered packing in their crystals such that: (a) the monomers are aligned head‐to‐tail in 1D‐chain‐like arrays and parallel arrangement of such arrays forms a layer; (b) the proximally placed azide and alkyne motifs are in an orientation apt for their regiospecific cycloaddition; (c) each monomer having x peptide bonds is H‐bonded with 2x monomers disposed in intersecting arrangement, which pre‐organize 1D‐chain‐like arrays in adjacent layers in perpendicular orientation. These crystals underwent spontaneous single‐crystal‐to‐single‐crystal (SCSC) polymerization via azide–alkyne cycloaddition reaction to form triazolyl‐polyglycines, at room temperature. The crisscrossed arrangement of monomers in adjacent layers ensured the formation of cross‐laminated polymers.     

Three Dicyanidometallate(I)‐based Complexes Incorporating Hydrogen‐bonding, π–π Packing and d10–d10 Interactions with Auxiliary 2,2′‐Bipyridyl‐like Ligands

To investigate the influence of the non‐covalent interactions, such as hydrogen‐bonding, π–π packing and d¹⁰–d¹⁰ interactions in the supramolecular motifs, three cyanido‐bridged heterobimetallic discrete complexes {Mn(bipy)₂(H₂O)[Ag(CN)₂]}[Ag(CN)₂] ( 1 ), {Mn(phen)₂(H₂O)[Au(CN)₂]}₂[Au(CN)₂]₂ · 4H₂O ( 2 ), and {Cd(bipy)₂(H₂O)[Au(CN)₂]}[Au(CN)₂] ( 3 ) (bipy = 2,2′‐bipyridine, and phen = 1,10‐phenanthroline), which are based on dicyanidometallate(I) groups with 1:2 stoichiometry of metal ions and 2,2′‐bipyridyl‐like co‐ligands were synthesized and structurally characterized. In compound 1 , hydrogen bonding and π–π interactions governed the supramolecular contacts. In compound 2 , the incorporation of aurophilic, hydrogen bonding and π–π interactions result in a 3D supramolecular network. In compound 3 , hydrogen bonding and π–π stacking interactions result in a 2D supramolecular layer. In the three complexes, hydrogen‐bonding, π–π packing and/or d¹⁰–d¹⁰ interactions can play important roles in increasing the dimensionality of supramolecular assemblies.     

Hydrogen‐bonded assemblies in the molecular crystals of 2,2′‐thiodiacetic acid with ethylenediamine and o‐phenylenediamine

Carboxylate molecular crystals have been of interest due to the presence of hydrogen bonding, which plays a significant role in chemical and crystal engineering, as well as in supramolecular chemistry. Acid–base adducts possess hydrogen bonds which increase the thermal and mechanical stability of the crystal. 2,2′‐Thiodiacetic acid (Tda) is a versatile ligand that has been widely explored, employing its multidendate and chelating coordination abilities with many metals; however, charge‐transfer complexes of thiodiacetic acid have not been reported. Two salts, namely ethylenediaminium 2,2′‐thiodiacetate, C₂H₁₀N₂²⁺·C₄H₄O₄S₂²⁻, denoted Tdaen, and 2‐aminoanilinium 2‐(carboxymethylsulfanyl)acetate, C₆H₉N₂⁺·C₄H₅O₄S⁻, denoted Tdaophen, were synthesized and characterized by IR, ¹H and ¹³C NMR spectroscopies, and single‐crystal X‐ray diffraction. In these salts, Tda reacts with the aliphatic (ethylenediamine) and aromatic (o‐phenylenediamine) diamines, and deprotonates them to form anions with different valencies and different supramolecular networks. In Tdaen, the divalent Tda²⁻ anions form one‐dimensional linear supramolecular chains and these are extended into a three‐dimensional sandwich‐type supramolecular network by interaction with the ethylenediaminium cations. However, in Tdaophen, the monovalent Tda⁻ anions form one‐dimensional zigzag supramolecular chains, which are extended into a three‐dimensional supramolecular network by interaction with the 2‐aminoanilinium cations. Thus, both three‐dimensional structures display different ring motifs. The structures of these diamines, which are influenced by hydrogen‐bonded assemblies in the molecular crystals, are discussed in detail.     

Head‐to‐Tail Zig‐Zag Packing of Dipolar Merocyanine Dyes Affords High‐Performance Organic Thin‐Film Transistors

Attachment of bulky substituents at both thiophene donor (D) and thiazole acceptor (A) heterocycles of a dipolar (μ_g=10.4 D) D‐π‐A merocyanine dye affords a more than 1 Å expansion of the common antiparallel supramolecular dimer motif in the solid state, enabling very close π‐contacts (3.36 Å) to two other neighbor molecules on each of the two remaining π‐faces. This unusual packing motif leads to three‐dimensional percolation pathways for hole transport and affords thin‐film transistors with mobility up to 0.64 cm² V^?1 s^?1.     

Ordered nanostructures at two different length scales mediated by temperature: A triphenylene‐containing mesogen‐jacketed liquid crystalline polymer with a long spacer

A mesogen‐jacketed liquid crystalline polymer (MJLCP) containing triphenylene (Tp) moieties in the side chains with 12 methylene units as spacers (denoted as PP12V) was synthesized. Its liquid crystalline (LC) phase behavior was studied with a combination of solution ¹H NMR, solid‐state NMR, gel permeation chromatography, thermogravimetric analysis, polarized light microscopy, differential scanning calorimetry, and one‐ and two‐dimensional wide‐angle X‐ray diffraction. By simply varying the temperature, two ordered nanostructures at sub‐10‐nm length scales originating from two LC building blocks were obtained in one polymer. The low‐temperature phase of the polymer is a hexagonal columnar phase (Φ_H, a = 2.06 nm) self‐organized by Tp discotic mesogens. The high‐temperature phase is a nematic columnar phase with a larger dimension (a′ = 4.07 nm) developed by the rod‐like supramolecular mesogen—the MJLCP chain as a whole. A re‐entrant isotropic phase is found in the medium temperature range. Partially homeotropic alignment of the polymer can be achieved when treated with an electric field, with the polymer in the Φ_H phase developed by the Tp moieties. The incorporation of Tp moieties through relatively long spacers (12 methylene units) disrupts the ordered packing of the MJLCP at low temperatures, which is the first case for main‐chain/side‐chain combined LC polymers with MJLCPs as the main‐chain LC building block to the best of our knowledge. The relationship of the molecular structure and the novel phase behavior of PP12V has implications in the design of LC polymers containing nanobuilding blocks toward constructing ordered nanostructures at different length scales. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 295–304     

Metallic and Mott Insulating Spin‐Frustrated Antiferromagnetic States in Ionic Fullerene Complexes with a Two‐Dimensional Hexagonal C60.− Packing Motif

(MDABCO⁺)(C₆₀^.?)(TPC) ( 1 ), in which MDABCO⁺ is N‐methyldiazabicyclooctanium, TPC is triptycene, and both have threefold symmetry, is a rare example of a fullerene‐based quasi‐2D metal and contains closely packed hexagonal fullerene layers with interfullerene center‐to‐center distances of 10.07 Å at 300 K. Evidence for the metallic nature of 1 was obtained by optical and microwave conductivity measurements on single crystals. The metal is characterized by a nontypical Drude response and relatively large optical mass (m*/m₀=6.7). The latter indicates a narrow‐band nature, which is consistent with the calculated bandwidth of 0.10–0.15 eV. The coexistence of metallic and antiferromagnetic nonmetallic 2D layers was observed in 1 above 200–230 K. It was assumed that the nonmetallic layers undergo a transition to the metallic state below 200 K due to ordering of the fullerene and cationic sublattices. New layered complex (MQ⁺)(C₆₀^.?)(TPC) ( 2 ) with a hexagonal arrangement of C₆₀^.? was obtained by increasing the interfullerene distance with the bulkier N‐methylquinuclidinium cations (MQ⁺) having threefold symmetry. The structure of 2 is characterized by increased interfullerene center‐to‐center distances in the layers (10.124, 10.155, and 10.177 Å at 250 K). Unit‐cell doubling parallel to the 2D layer (along the b axis) was observed at low temperatures. In contrast to metallic 1 , 2 exhibits a nonmetallic spin‐frustrated state with an antiferromagnetic interaction of spins (the Weiss temperature is ?27 K) and no magnetic ordering down to 1.9 K. It was supposed that the expanded interfullerene distances in the triangular arrangement decrease the bandwidth and suppress metallic conductivity in 2 , and thus a Mott–Hubbard insulating state with antiferromagnetically frustrated spins results.     

Supramolecular framework in catena‐poly[[(nitrato‐κO)silver(I)]‐μ‐(R,S)‐2‐(pyridin‐4‐ylsulfinyl)pyrimidine‐κ3N,O:N′]

In the title complex, [Ag(NO₃)(C₉H₇N₃OS)]_n, η¹:η¹:η¹:μ₂‐bridging 2‐(pyridin‐4‐ylsulfinyl)pyrimidine (pypmSO) ligands with opposite chiralities are alternately arranged to link the Ag^I cations through two N atoms and one sulfinyl O atom of each ligand, leading to an extended zigzag coordination chain structure along the [01] direction. An FT–IR spectroscopic study shows a decreased stretching frequency for the η¹‐O‐bonded S=O group compared with that of the free ligand. The parallel chains are arranged and interconnected via O(S=O)...π(pyridine/pyrimidine) and C—H(pyridine)...O(NO₃⁻) interactions to furnish a layer almost parallel to the ac plane. Along the b axis, the layers are stacked and stabilized through anion(NO₃⁻)...π(pyrimidine) interactions to form a three‐dimensional supramolecular framework. The ligand behaviour of the new diheterocyclic sulfoxide and the unconventional O(S=O)...π(pyridine/pyrimidine) and anion(NO₃⁻)...π(pyrimidine) interactions in the supramolecular assembly of the title complex are presented.     

Temperature‐Independent Hole Mobility of a Smectic Liquid‐Crystalline Semiconductor based on Band‐Like Conduction

A liquid‐crystalline (LC) phenylterthiophene derivative, which exhibited an ordered smectic phase at room temperature, was purified by vacuum sublimation under a flow of nitrogen. During the sublimation process, thin plates with sizes of 1 mm grew on the surface of the vacuum tube. The crystals exhibited the same X‐ray diffraction patterns as the ordered smectic phase of the LC state that was formed through a conventional recrystallization process by using organic solvents. Because of the removal of chemical impurities, the hole mobility in the ordered smectic phase of the vacuum‐grown thin plates increased to 1.2×10^?1 cm² V^?1 s^?1 at room temperature, whereas that of the LC precipitates was 7×10^?2 cm² V^?1 s^?1. The hole mobility in the ordered smectic phase of the vacuum‐sublimated sample was temperature‐independent between 400 and 220 K. The electric‐field dependence of the hole mobility was also very small within this temperature range. The temperature dependence of hole mobility was well‐described by the Hoesterey–Letson model. The hole‐transport characteristics indicate that band‐like conduction affected by the localized states, rather than a charge‐carrier‐hopping mechanism, is a valid mechanism for hole transport in an ordered smectic phase.     

Superfluorinated Ionic Liquid Crystals Based on Supramolecular,Halogen‐Bonded Anions

Unconventional ionic liquid crystals in which the liquid crystallinity is enabled by halogen‐bonded supramolecular anions [C_nF_{2 n+1}‐I⋅⋅⋅I⋅⋅⋅I‐C_nF_{2 n+1}]⁻ are reported. The material system is unique in many ways, demonstrating for the first time 1) ionic, halogen‐bonded liquid crystals, and 2) imidazolium‐based ionic liquid crystals in which the occurrence of liquid crystallinity is not driven by the alkyl chains of the cation.     

2D Organic Photonics: An Asymmetric Optical Waveguide in Self‐Assembled Halogen‐Bonded Cocrystals

Anisotropic organic molecular construction and packing are crucial for the optoelectronic properties of organic crystals. Two‐dimensional (2D) organic crystals with regular morphology and good photon confinement are potentially suitable for a chip‐scale planar photonics system. Herein, through the bottom‐up process, 2D halogen‐bonded DPEpe‐F₄DIB cocrystals were fabricated that exhibit an asymmetric optical waveguide with the optical‐loss coefficients of R_Backward=0.0346 dB μm^?1 and R_Forward=0.0894 dB μm^?1 along the [010] crystal direction, which can be attributed to the unidirectional total internal reflection caused by the anisotropic molecular packing mode. Based on this crystal direction‐oriented asymmetric photon transport, these as‐prepared 2D cocrystals have been demonstrated as a microscale optical logic gate with multiple input/out channels, which will offer potential applications as the 2D optical component for the integrated organic photonics.     

Tightly Bound Double‐Caged [60]Fullerene Derivatives with Enhanced Solubility: Structural Features and Application in Solar Cells

A series of novel highly soluble double‐caged [60]fullerene derivatives were prepared by means of lithium‐salt‐assisted [2+3] cycloaddition. The bispheric molecules feature rigid linking of the fullerene spheres through a four‐membered cycle and a pyrrolizidine bridge with an ester function CO₂R (R=n ‐decyl, n ‐octadecyl, benzyl, and n ‐butyl; compounds 1 a – d , respectively), as demonstrated by NMR spectroscopy and X‐ray diffraction. Cyclic voltammetry studies revealed three closely overlapping pairs of reversible peaks owing to consecutive one‐electron reductions of fullerene cages, as well as an irreversible oxidation peak attributed to abstraction of an electron from the nitrogen lone‐electron pair. Owing to charge delocalization over both carbon cages, compounds 1 a – d are characterized by upshifted energies of frontier molecular orbitals, a narrowed bandgap, and reduced electron‐transfer reorganization energy relative to pristine C₆₀. Neat thin films of the n ‐decyl compound 1 a demonstrated electron mobility of (1.3±0.4)×10⁻³ cm² V⁻¹ s⁻¹, which was comparable to phenyl‐C₆₁‐butyric acid methyl ester (PCBM) and thus potentially advantageous for organic solar cells (OSC). Application of 1 in OSC allowed a twofold increase in the power conversion efficiencies of as‐cast poly(3‐hexylthiophene‐2,5‐diyl) (P3HT)/ 1 devices relative to the as‐cast P3HT/PCBM ones. This is attributed to the good solubility of 1 and their enhanced charge‐transport properties — both intramolecular, owing to tightly linked fullerene cages, and intermolecular, owing to the large number of close contacts between the neighboring double‐caged molecules. Test P3HT/ 1 OSCs demonstrated power‐conversion efficiencies up to 2.6 % ( 1 a ). Surprisingly low optimal content of double‐caged fullerene acceptor 1 in the photoactive layer (≈30 wt %) favored better light harvesting and carrier transport owing to the greater content of P3HT and its higher degree of crystallinity.     

Syntheses and Characterization of Two Coordination Polymers Constructed by the Ligand 3,5‐Bis(pyridin‐4‐ylmethoxy)benzoic Acid

Two coordination polymers, namely [Zn(L1)(OAc)]·H₂O ( 1 ) and [Cd(L1)₂] ( 2 ), where L1 = 3,5‐bis(pyridin‐4‐ylmethoxy)benzoic acid, have been synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction analysis. Complex 1 has a 2D layer structure in which the hydrogen bonds between lattice water molecules and uncoordinated carboxylate oxygen atoms of the ligand L1 in the adjacent layers extend the 2D layer into a 3D supramolecular architecture. The structure of 2 is a 2D (3,5)‐connected net with (3·5²)(3²·5³·6⁴·7) topology. In addition, the luminescent properties of complexes 1 and 2 have been studied in the solid state at room temperature.     

Large‐Area,Free‐Standing,Two‐Dimensional Supramolecular Polymer Single‐Layer Sheets for Highly Efficient Electrocatalytic Hydrogen Evolution

The rational construction of covalent or noncovalent organic two‐dimensional nanosheets is a fascinating target because of their promising applications in electronics, membrane technology, catalysis, sensing, and energy technologies. Herein, a large‐area (square millimeters) and free‐standing 2D supramolecular polymer (2DSP) single‐layer sheet (0.7–0.9 nm in thickness), comprising triphenylene‐fused nickel bis(dithiolene) complexes has been readily prepared by using the Langmuir–Blodgett method. Such 2DSPs exhibit excellent electrocatalytic activities for hydrogen generation from water with a Tafel slope of 80.5 mV decade^?1 and an overpotential of 333 mV at 10 mA cm^?2, which are superior to that of recently reported carbon nanotube supported molecular catalysts and heteroatom‐doped graphene catalysts. This work is promising for the development of novel free‐standing organic 2D materials for energy technologies.     

A dihydrogen phosphate anionic network as a host lattice for cations in 1‐methylpiperazine‐1,4‐diium bis(dihydrogen phosphate) and 2‐(pyridin‐2‐yl)pyridinium dihydrogen phosphate–orthophosphoric acid (1/1)

In the salt 1‐methylpiperazine‐1,4‐diium bis(dihydrogen phosphate), C₅H₁₃N₂²⁺·2H₂PO₄⁻, (I), and the solvated salt 2‐(pyridin‐2‐yl)pyridinium dihydrogen phosphate–orthophosphoric acid (1/1), C₁₀H₉N₂⁺·H₂PO₄⁻·H₃PO₄, (II), the formation of O—H...O and N—H...O hydrogen bonds between the dihydrogen phosphate (H₂PO₄⁻) anions and the cations constructs a three‐ and two‐dimensional anionic–cationic network, respectively. In (I), the self‐assembly of H₂PO₄⁻ anions forms a two‐dimensional pseudo‐honeycomb‐like supramolecular architecture along the (010) plane. 1‐Methylpiperazine‐1,4‐diium cations are trapped between the (010) anionic layers through three N—H...O hydrogen bonds. In solvated salt (II), the self‐assembly of H₂PO₄⁻ anions forms a two‐dimensional supramolecular architecture with open channels projecting along the [001] direction. The 2‐(pyridin‐2‐yl)pyridinium cations are trapped between the open channels by N—H...O and C—H...O hydrogen bonds. From a study of previously reported structures, dihydrogen phosphate anions show a supramolecular flexibility depending on the nature of the cations. The dihydrogen phosphate anion may be suitable for the design of the host lattice for host–guest supramolecular systems.     

Dual Photo‐functionalized Amphiphile for Photo‐reversible Liquid Crystal Alignments

Without the conventional polymer‐based liquid crystal (LC) alignment process, a newly synthesized dual photo‐functionalized amphiphile (abbreviated as ADMA₁) was successfully applied as a robust photo‐reversible LC alignment layer by self‐assembly and photo‐polymerization. The LC alignment layer constructed by directly adding dual photo‐functionalized amphiphiles into LC media significantly cuts the manufacturing cost as well as opens new doors for the fabrication of novel electro‐optical devices.     

Crystal Structure,Solution and Solid‐state Photoluminescence of a 2D Zinc(II) Supramolecular Architecture

A new 2D zinc(II) supramolecular complex [Zn(2,4‐D)(o‐phen)(H₂O)₂](NO₃) ( 1 ) (2,4‐D = 2,4‐dichlorophenoxyacetic acid, o‐phen = 1,10‐phenanthroline), was synthesized and characterized by single‐crystal X‐ray diffraction, elemental analyses, TG analysis, IR, and luminescence spectroscopy. For complex 1 , each Zn^II ion lies in a pentacoordinate distorted quadrilateral pyramidal configuration. The 8‐member‐ring hydrogen bonds clusters result in 1D ladder‐like supramolecular chains, which further stack up by face‐to‐face π–π stacking interactions into 2D supramolecular layers. The TG analysis shows that complex 1 has high thermal stability. The solution and solid‐state photoluminescence of 1 are reported.     

Hydro­gen bonding in calcium–tri­fluoro­methane­sulfonate–1,3‐di‐4‐pyridyl­urea–methanol (1/2/2/4)

The structure of the supramolecular complex calcium–tri­fluoro­methane­sulfonate–1,3‐di‐4‐pyridyl­urea–methanol (1/2/2/4), Ca²⁺·2CF₃SO₃⁻·2C₁₁H₁₀N₄O·4CH₄O, is presented. The Ca²⁺ ion lies on an inversion centre and is octahedrally coordinated by four methanol mol­ecules and two tri­fluoro­methane­sulfonate counter‐ions. The molecular packing is dominated by hydrogen‐bonded sheets in the (110) plane which contain R(32) rings; in these rings, significant π–π interactions are observed between inversion‐related 1,3‐di‐4‐pyridyl­urea mol­ecules.