Liquid‐Crystalline Mixed [5 : 1]Hexa‐adducts of [60]Fullerene. Preliminary Communication

A liquid‐crystalline mixed [5 : 1]hexa‐adduct of [60]fullerene was synthesized by addition of two different malonate derivatives onto C₆₀. The hexa‐adduct derivative 2 was prepared by a stepwise synthetic procedure (fullerene→mono‐adduct of C₆₀→hexa‐adduct of C₆₀). Cyanobiphenyl and octyloxybiphenyl derivatives were selected as mesogens. The malonate derivatives showed either a monotropic nematic phase or a monotropic smectic A phase, and the hexa‐adduct derivative gave rise to an enantiotropic smectic A phase.     

A mixed fullerene-ferrocene thermotropic liquid crystal: synthesis, liquid-crystalline properties, supramolecular organization and photoinduced electron transfer

Grafting of a ferrocene-containing liquid-crystalline malonate derivative to C60 led to the mixed fullerene-ferrocene material 1 which gave rise to a smectic A phase. Cholesterol was used as liquid-crystalline promoter. X-ray diffraction experiments and volumetric measurements indicated that 1 is organized in double layered structures. The corresponding supramolecular organization within the mesomorphic lamellar phase is characterized by a microsegregation of the different units (ferrocene, fullerene, and cholesterol) in distinct sublayers. In such a smectic A phase, C60 imposes the arrangement of the other molecular moieties. Photophysical studies revealed that electron transfer occurs from the donor ferrocene to the electron accepting fullerene. The formation of a long-lived radical pair, with lifetimes of the order of several hundred nanoseconds, was confirmed by time-resolved spectrometry, especially in the near infrared region, in which the radical anion of the fullerene moiety displays its characteristic fingerprint absorption.     

Liquid-crystalline bisadducts of [60]fullerene

A second-generation cyanobiphenyl-based dendrimer was used as a liquid-crystalline promoter to synthesize mesomorphic bisadducts of [60]fullerene. Liquid-crystalline trans-2, trans-3, and equatorial bisadducts were obtained by condensation of the liquid-crystalline promoter, which carries a carboxylic acid function, with the corresponding bisaminofullerene derivatives. A monoadduct of fullerene was also prepared for comparative purposes. All the compounds gave rise to smectic A phases. An additional mesophase, which could not be identified, was observed for the trans-2 derivative. The supramolecular organization of the monoadduct derivative is governed by steric constraints. Indeed, for efficient space filling, adequacy between the cross-sectional areas of fullerene (approximately 100 A(2)) and of the mesogenic groups (approximately 22-25 A(2) per mesogenic group) is required. As a consequence, the monoadduct forms a bilayered smectic A phase. The supramolecular organization of the bisadducts is essentially governed by the nature and structure of the mesogenic groups and dendritic core. Therefore, the bisadducts form monolayered smectic A phases. The title compounds are promising supramolecular materials as they combine the self-organizing behavior of liquid crystals with the properties of fullerene.     

Pseudocryptand-type [3]pseudorotaxane and "hook-ring" polypseudo[2]catenane based on a bis(m-phenylene)-32-crown-10 derivative and bisparaquat derivatives

The first pseudocryptand-type supramolecular [3]pseudorotaxane was designed and prepared via the self-assembly of a bispicolinate BMP32C10 derivative and a bisparaquat. The complexation behavior was cooperative. In addition, the complex comprised of the BMP32C10 derivative and a cyclic bisparaquat demonstrated strong binding; interestingly, a poly[2]pseudocatenane structure was formed in the solid state for the first time.     

Synthesis and structures of malonate derivative-calix[4]arene conjugates

A series of novel malonate derivatives-calix[4]arene conjugates were synthesized through Knoevenagel condensation reaction, and the structures of these functionalized calix[4]arenes have been determined     

Solvent-free reactions of C60 with active methylene compounds, either with or without carbon tetrabromide, in the presence of bases under high-speed vibration milling conditions

Solvent-free reactions of C(60) with active methylene compounds, either with or without carbon tetrabromide (CBr(4)), in the presence of a base under high-speed vibration milling (HSVM) conditions were investigated. The reaction of C(60) with diethyl bromomalonate was conducted under HSVM conditions in the presence of piperidine, triethylamine or Na(2)CO(3) to afford cyclopropane derivative. In the presence of CBr(4), methanofullerenes, and could be obtained by the direct reaction of C(60) with diethyl malonate, dimethyl malonate, ethyl acetoacetate and ethyl cyanoacetate, respectively, with the aid of 1,8-diazabicyclo[5,4,0]undec-7-ene, piperidine, triethylamine or Na(2)CO(3). More interestingly, 1,4-bisadducts and were produced by the reaction of C(60) with diethyl malonate and dimethyl malonate in the presence of piperidine, triethylamine or Na(2)CO(3) under HSVM conditions. On the other hand, dihydrofuran-fused C(60) derivatives, and were obtained from the reaction of C(60) with ethyl acetoacetate, 2,4-pentanedione and 5,5-dimethyl-1,3-cyclohexanedione with the aid of a base. Under the same conditions, less activated aryl methyl ketones such as 2-acetylpyridine, 2-acetylpyrazine and acetophenone provided monocarbonylated methanofullerene derivatives, and. Except for the Bingel reactions, all other reactions under the HSVM conditions are considered to proceed according to a single-electron-transfer mechanism.     

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.     

Reaction of [60]fullerene with free radicals generated from active methylene compounds by manganese(III) acetate dihydrate

The reaction of [60]fullerene with dimethyl malonate and diethyl malonate in the presence of manganese(III) acetate dihydrate (Mn(OAc)3.2H2O) for 20 min afforded singly bonded [60]fullerene dimers 1a and 1b in a 1,4-addition pattern. When the reaction time was extended to 1 h, 1,4-bisadducts 2a and 2b were obtained. Unsymmetrical 1,4-adduct 5 and C2 symmetrical 1,16-bisadduct 6 were obtained when diethyl bromomalonate was used as the active methylene compound. Reaction of [60]fullerene with malononitrile and ethyl cyanoacetate with the aid of Mn(OAc)3.2H2O produced methanofullerenes 7 and 8. It is proposed that all these products were formed the addition of free radicals from the active methylene compounds generated by Mn(OAc)3.2H2O.     

5‐Unsubstituted Pyrido[3,2,1‐jk]carbazol‐6‐ones: Syntheses,Substitution, and Cyclization Reactions

The synthesis of the 5‐unsubstituted pyrido[3,2,1‐jk]carbazol‐6‐one 4 can be achieved by the reaction of carbazole ( 1 ) and malonate derivatives, either in a three‐step synthesis via 5‐acetyl‐pyridocarbazolone 3 or in a one‐step reaction from 1 and malonic acid/phosphoryl chloride. The 5‐acetyl derivative 5 can be transformed via a tosylate intermediate to 4‐azido‐pyridocarbazolone 11 , which cyclizes by thermal decomposition to the isoxazolo‐pyrido[3,2,1‐jk]carbazolone 12 . The thermolysis conditions were investigated by DSC. Nitration of pyridocarbazolone 4 and subsequent introduction of azide leads to azido derivative 23 , which cyclizes on thermolysis to furazan‐oxide derivative 24 . Again, the thermolysis conditions were investigated by DSC. 5‐Chloro‐5‐nitro‐pyrido[3,2,1‐jk]carbazole‐4,6‐dione, obtained from 4 by subsequent nitration and chlorination, forms by exchange of both 5‐substituents 5,5‐dihydroxy‐pyridocarbazoledione 17 , which acylates phenol to give 5‐hydroxy‐5‐(p‐hydroxyphenyl)‐pyridocarbazoledione 20 . Acid‐catalyzed cyclodehydration of 20 forms a highly fused benzofuro‐pyridocarbazole 21 . Another C–C coupling at position 5 starts from 4‐chloro‐5‐nitro‐pyridocarbazolone 22 and diethyl malonate 2a , which forms the diethyl (nitrocarbazolyl)malonate 25 . With dimethyl malonate 2c , the intermediate dimethyl (nitrocarbazolyl)malonate gives on thermolysis the (nitrocarbazolyl)acetate 27 by loss of one ester group.     

Synthesis and characterization of water-soluble amino fullerene derivatives

[formula: see text] A series of amino-substituted methanofullerene derivatives were prepared by mono-, tris-, and hexa-Bingel-Hirsch reactions using an N-protected malonate derivative. Upon scission of the protecting groups, the e,e,e-tris- and octahedral Th hexa-methano amino fullerenes were found to be among the most water-soluble fullerene derivatives yet prepared. 3He NMR data on corresponding adducts of 3He/C60 helped verify the assigned structures. UV spectral studies confirmed the influence of aggregation on solubility of these adducts in water.     

Shear flow and magnetic field effects on smectic C,C*, CM and C*M liquid crystals

Abstract

The continuum equations of Leslie et al. [1] for smectic C, and the extension of this theory for chiral smectic C* [2], are applied to problems involving simple planar layer configurations which accommodate uniform layer thickness constraints. The chiral smectic C*_M and non-chiral smectic C_M [3] are considered as either biaxial smectic A phases or antiferroelectric smectic C phases and are therefore included as interesting degenerate cases of the smectic C* and C phases, respectively. The effects of static and time dependent magnetic fields on these materials are compared with related deformations occurring in nematics [4] and cholesterics [5,6]. Their reaction to applied shears is also investigated yielding examples of flow alignment, induced secondary flows and unwinding of the chiral helix and testing the validity of enforcing a constant layer thickness.     

Atomistic simulations of liquid crystal mixtures of alkoxy substituted phenylpyrimidines 2PhP and PhP14

We study liquid crystal mixtures of alkoxy substituted phenylpyrimidines 2-[4-(butyloxy)phenyl]-5-(octyloxy)pyrimidine (2PhP) and 2-[4-(tetradecyloxy)phenyl]-5-(tetradecyloxy)pyrimidine (PhP14) using molecular dynamics simulations at the all atom level. The molecular length of PhP14 is 1.8 times that of 2PhP, resulting in an interesting binary mixture phase diagram. Our simulations are composed of 1000-1600 molecules for a total of 80,000-130,000 atomic sites, with total simulation times of 60-100 ns. We first show that a pure 2PhP system self-assembles into isotropic, nematic, smectic A and smectic C phases, and a pure PhP14 system self-assembles into isotropic and smectic C phases. Binary mixtures of PhP14 and 2PhP display a stabilization of the smectic A phase at the expense of the smectic C and nematic phases. We determine that the concentration-induced phase transition from the smectic C to the smectic A phase in the mixture is driven by an out-of-layer fluctuation arrangement of the molecules. We also observe that the tilt angle in the smectic C phases formed in the mixtures is concentration dependent. The results of our simulations are in good agreement with the experimental findings of Kapernaum et al. [J. Org. Chem. 5, 65 (2009)], thus showing that atomistic simulations are capable of reproducing the phase behavior of liquid crystal mixtures and can also provide microscopic details regarding the mechanisms that govern phase stability.     

Design and characterization of novel supramolecular liquid crystals involving multiple hydrogen bonds

A novel type of liquid crystalline system, namely 5-[4-(4-methoxyphenylazo)phenyloxyalkyloxy]isophthalic acidhydrazides (Dn, n = 3, 6, 10) was designed and synthesized. The FTIR spectra of the Dn compounds were examined in the range 4000-1000 cm^-1 at different temperatures. The results showed that the stretching vibration frequencies of the NH and C=O groups, and the NH₂ deformation shifted to lower frequencies with decrease of temperature, while out-of-plane NH bending shifted slightly to higher frequency. Intermolecular hydrogen bonding between NH, NH₂ and C=O groups is proposed and the schematic supramolecular Dn structure is given. This may explain the higher Dn transitional temperatures and their smectic phase behaviour compared with that of 5-[4-(4-methoxyphenylazo)phenyloxyalkyloxy]isophthalic acid diethyl esters.     

Tetra-benzothiadiazole-based [12]Cycloparaphenylene with Bright Emission and Its Supramolecular Assembly

The radial conjugated π-system of cycloparaphenylenes (CPPs) makes them intriguing fluorophores and unique supramolecular hosts. However, the bright photoluminescence (PL) of CPPs was limited to the blue light and the supramolecular assembly behavior of large CPPs was rarely investigated. Here we present the synthesis of tetra-benzothiadiazole-based [12]cycloparaphenylene (TB[12]CPP), which exhibits a lime to orange PL with an excellent quantum yield up to 82 % in solution. The PL quantum yield of TB[12]CPP can be further improved to 98 % in polymer matrix. Benefiting from its enlarged size, TB[12]CPP can accommodate a fullerene derivative or concave–convex complexes of fullerene and buckybowl through the combined π–π and C−H⋅⋅⋅π interactions. The latter demonstrates the first case of a ternary supramolecule of CPPs.     

Mesomorphic behaviour of 1,3-phenylene bis[4-(4-alkoxyphenyliminomethyl)benzoates] and related compounds

DSC and X-ray diffraction studies on a series of 1,3-phenylene bis[4-(4-alkoxyphenyliminomethyl)benzoates] are presented. The only mesophase exhibited by the methoxy to hexadecyloxy homologues is of the smectic C type. The reversal of the iminomethyl linkage reduces drastically the incidence of a mesophase; that is, only the first five homologous members exhibit a smectic C phase in the series of 1,3-phenylene bis[4-(4-alkoxybenzylideneamino)benzoates]. Almost all the members in the second series become nematogenic by the chloro substitution at the 4-position of the 1,3-phenylene moiety. In addition, a smectic C phase is observable for the ethoxy to pentyloxy and also the tetradecyloxy and hexadecyloxy members. The second chloro-substituent introduced to the 6-position of the same central ring eliminates completely the smectic C phase and enhances the nematic thermal stability.     

Langmuir monolayers of an inclusion complex formed by a new calixarene derivative and fullerene

The design of new molecules with directed interactions to functional molecules as complementary building blocks is one of the main goals of supramolecular chemistry. A new p-tert-butylcalix[6]arene monosubstituted derivative bearing only one alkyl chain with an acid group (C6A3C) has been synthesized. The C6A3C has been successfully used for building Langmuir monolayers at the air-water interface. The C6A3C molecule adopts a flatlike orientation with respect to the air-water interface. The molecular structure gives the molecule amphiphilic character, while allowing the control of both the dissociation degree and the molecular conformation at the air-water interface. The C63AC has been combined with pristine fullerene (C60) to form the supramolecular complex C6A3C:C60 in 2:1 molar ratio (CFC). The CFC complex retains the ability of C6A3C to form Langmuir monolayers at the air/water interface. The interfacial molecular arrangement of the CFC complex has been convincingly described by in situ UV-vis reflection spectroscopy and synchrotron X-ray reflectivity measurements. Computer simulations complement the experimental data, confirming a perpendicular orientation of the calixarene units of CFC with respect to the air-water interface. This orientation is stabilized by the formation of intermolecular H-bonds. The interfacial monolayer of the CFC supramolecular complex is proposed as a useful model for the well-defined self-assembly of recognition and functional building blocks.     

Light‐Controlled Regioselective Synthesis of Fullerene Bis‐Adducts

Multi‐functionalization and isomer‐purity of fullerenes are crucial tasks for the development of their chemistry in various fields. In both current main approaches—tether‐directed covalent functionalization and supramolecular masks—the control of regioselectivity requires multi‐step synthetic procedures to prepare the desired tether or mask. Herein, we describe light‐responsive tethers, containing an azobenzene photoswitch and two malonate groups, in the double cyclopropanation of [60]fullerene. The formation of the bis‐adducts and their spectroscopic and photochemical properties, as well as the effect of azobenzene photoswitching on the regiochemistry of the bis‐addition, have been studied. The behavior of the tethers depends on the geometry of the connection between the photoactive core and the malonate moieties. One tether lead to a strikingly different adduct distribution for the E and Z isomers, indicating that the covalent bis‐functionalization of C₆₀ can be controlled by light.     

One-pot regioselective synthesis and X-ray crystal structure of a stable [60]fullerene trisadduct with the e(edge),e(face),trans-1 addition pattern

The Bingel functionalisation of C(60) with a structurally novel tether equipped with three reactive malonate groups afforded a C(2v)-symmetrical e(edge),e(face),trans-1 trisadduct in a complete regioselective manner and in an excellent yield of 65%. The [60]fullerene trisadduct showed pronounced ability to crystallise and gave X-ray quality single crystals for analysis.     

Self-assembly and characterization of a novel hydrogen-bonded nanostructure

A novel hydrogen-bonded supramolecular system of a [60]fullerene derivative with perylene bisimide was synthesized and characterized. 1H NMR spectra confirmed the existence of strong hydrogen-bonding interaction between compounds 1 and 5. Transmission electron microscopy images of 1.5 aggregates showed spherical particles having a mean diameter of 50 nm. The photocurrent response of the film was measured, and a steady and rapid anodic photocurrent response was obtained.     

C3v-symmetrical tribenzotriquinacenes as hosts for C60 and C70 in solution and in the solid state

Various tribenzotriquinacenes (TBTQs), most of which incorporate six functional groups at the periphery of their C3v-symmetrical, rigid and convex-concave molecular framework, have been studied with respect to their ability to form supramolecular complexes with the C60 and C70 fullerenes, either in the solid state or in solution. The hexabromo derivative Br6-TBTQ was cocrystallized with C60 as [Br6-TBTQ相似文献