Quinoxaline-based U-shaped septuple-bridged [7,7]orthocyclophanes: synthesis, solid-state structure, and self-assembly

We report a three-step synthesis of 12 septuple-bridged [7,7]orthocyclophanes 11 comprising (i) two quinoxaline-based sidewalls and (ii) a linker built-in with a succinimide ring that carries phenyl, p-methoxyphenyl, p-hydroxyphenyl, or p-methoxybenzyl appendants. The synthesis began from the Diels-Alder adduct of 1,2,3,4-tetrachloro-5,5-dimethoxycyclopentadiene (1) and succinimide ring-fused dioxatetracyclodecadiene 9, followed by ruthenium-promoted oxidation of dichloroetheno-bridges in the adduct to generate a bis-α-diketone, which was then condensed with an arene-1,2-diamine to construct sidewalls (phane parts), furnishing U-shaped septuple-bridged [7,7]orthocyclophanes 11 embedding quinoxaline, dimethylquinoxaline, or benzoquinoxaline rings. Concentration-variant ¹H NMR spectra of N-p-methoxybenzyl substituted orthocyclophanes (11zd, 11xd, and 11yd) and single-crystal structures of four orthocyclophanes (11xa, 11yd, 11zb, and 11zd) revealed that the U-shaped septuple-bridged [7,7]orthocyclophanes 11 have a tendency of self-assembly, forming V-shaped dimeric entities driven chiefly by intermolecular π-π stacking interaction in both solid state and solution of high concentration.     

Self-assembly and proton conductance of organic nanotubes from pillar[5]arenes

Organic nanotubes have been assembled from pillar[5]arenes 1 and 2. Compound 1 gelates organic solvents through the formation of tubular fibers which are evidenced by TEM and XRD experiments, while 2 assembles into two different channels under the template effect of water wires. In addition, the water wires in the nanotubes of 2 can be under selective proton conductance. The results described herein represent a new strategy for building tubular structures.     

Wide- and narrow-rim functionalised calix[4]arenes: synthesis and characterisation

Functionalisation of calix[4]arene at both the wide and narrow rims leads to the formation of compounds containing bipyridyl, via an amide linkage, at the wide rim and having either a butyl chain, a benzyl group or an alkyl ester functionality at the narrow rim. All compounds were characterised using ¹H and ¹³C NMR spectroscopies. Initial binding studies with Ru(bipy)₂Cl₂ are reported.     

Design and synthesis of self-included pillar[5]arene-based bis-[1]rotaxanes

Two strategies for the design of new pillar[5]arene-based mechanically self-interlocked molecules (MSMs) are reported here. The first strategy is based on the construction of an intermediate pseudo[1]rotaxane followed by the desired bis-[1]rotaxane. The other one is based on the construction of the desired bis-[1]-rotaxane directly via a condensation reaction through host-guest interactions between a mono-functionalized pillar[5]arene and the axle. This compound has interesting self-assembly properties in methanol and some extended applications of this compound will be reported in the near future.     

Amphiphilic dipyrrinones: methoxylated [6]-semirubins

Replacing the typical β-alkyl substituents of [6]-semirubin and [6]-oxosemirubin, two intramolecularly hydrogen-bonded bilirubin analogs, with methoxy groups produces amphiphilic dipyrrinones. Synthesized from the respective 9H-dipyrrinones prepared by base-catalyzed condensation of 3,4-dimethoxypyrrolin-2-one with the appropriate pyrrole α-aldehyde, the 2,3-dimethoxy and 2,3,7,8-tetramethoxy analogs of [6]-semirubin are yellow-colored dipyrrinones that form intramolecularly hydrogen-bonded monomers in CDCl₃, as deduced from ¹H NMR NH chemical shifts. They are monomeric in CHCl₃, as determined by vapor pressure osmometry. In contrast, in the solid, X-ray crystallography reveals supramolecular ribbons of intermolecularly hydrogen-bonded (dipyrrinone to dipyrrinone and acid to acid) 2,3,7,8-tetramethoxy-[6]-semirubin. The latter is approximately 20 times more soluble in water than the parent [6]-semirubin with four β-methyl groups.     

Amphiphilic poly(ethylene glycol)-b-poly(ethylene brassylate) copolymers: One-pot synthesis,self-assembly,and controlled drug release

A set of amphiphilic poly(ethylene glycol)-b-poly(ethylene brassylate) (PEG-b-PEB) copolymers based on the PEB hydrophobic block was first synthesized by ring-opening polymerization of ethylene brassylate with an organic catalyst. The EB/PEGmolar ratios and reaction times were adjusted to achieve different chain lengths of PEB. Block copolymers that were characterized by ¹H NMR and GPC could selfassemble into multimorphological aggregates in aqueous solution, which were characterized by DLS and TEM. The hydrophobic doxorubicin (DOX) was chosen as a drug model and successfully encapsulated into the nanoparticles. The release kinetics of DOX were investigated.     

Metal-metal bond formation between [n]metallocenophanes: synthesis and characterisation of a dicarba[2]ruthenocenophanium dimer

Feeling the strain: The first example of metal-metal bonding between strained [n]metallocenophanes is reported. A dicarba[2]ruthenocenophanium dimer has been synthesised through the oxidation of a dicarba[2]ruthenocenophane (see figure). The structural and electrochemical characterisation of the dimer is also discussed.     

Anionic water-soluble sulfonated phthalocyanines: microwave-assisted synthesis,aggregation behaviours,electrochemical and in-situ spectroelectrochemical characterisation

In this work, a phthalonitrile derivative bearing p-sulfonylphenoxy group at the 3-position has been synthesised. The water-soluble non-peripherally tetrasubstituted zinc (3) and cobalt (4) phthalocyanines were obtained by cyclotetramerisation of this phthalonitrile derivative in the presence of anhydrous metal salts by microwave irradiation. The compounds have been characterised by using FT-IR, ¹H NMR, UV–Vis and Mass spectrometry (MS) data. The aggregation behaviours of these compounds were investigated in methanol, DMSO, DMF, and water. We have also studied the aggregation behaviours of the phthalocyanine complex 3 in various DMSO/water mixtures. Additionally, the redox properties of the phthalocyanine complexes were examined in dimethylsulfoxide by voltammetry and in situ spectroelectrochemistry. Redox behaviours of the complexes supported the structures of the complexes. Metal and ring-based reductions were observed for 4 and only ring-based electron transfer processes were observed with 3.     

Preparation of nitrogen-doped anatase TiO2 nanoworm/nanotube hierarchical structures and its photocatalytic effect

As-anodized amorphous TiO₂ nanotube arrays (TNAs) are immersed in hot ammonia solution (90 °C), which can both spontaneously reconstruct the amorphous TNAs to be anatase nanoworm/nanotube hierarchical structures in situ and simultaneously implant nitrogen into them. These hierarchical structures, having larger surface area, higher electrical conductivity and broader light absorption range than the original TNAs, possess dramatically enhanced photocatalytic activity for degradation of methyl orange (MO) under visible light irradiation. The optimized nitrogen doped hierarchical structures exhibit a best photodegradation rate (K) of 0.722 h⁻¹, which greatly exceeds the degradation rate of the original TNAs annealed in ambient air at 500 °C for 2.5 h. This simple technique would enable us conveniently to design and fabricate highly photoactive one-dimensional TNAs-based functional materials applicable to photocatalysis and solar energy conversion.     

Alkyl chain self ordering,induction and suppression of mesophase by Cu(II) containing [1,2,3]-triazole-based bidentate salicylaldimine ligands: synthesis,characterisation and X-ray diffraction studies

Some new Cu(II) complexes containing [1,2,3]-triazole-based bidentate salicylaldimine and its analogues with terminal substituent (F, Cl, Br and I) have been synthesieed. All the target complexes and their uncoordinated ligands were elucidated by elemental analysis and spectroscopic techniques (UV-visible, FT-IR, 1D, 2D ¹H and ¹³C-NMR). The polarising optical microscope and differential scanning calorimetry (DSC) have disclosed all complexes and ligands are mesomorphic except the complex without any terminal substituent. The fluoro-substituted complexes with even parity C₁₄H₂₉ and C₁₆H₃₃ exhibit new enantiotropic nematic phase which was absent in their corresponding ligands, whereas the suppression of SmC phase occurred for all complexes with longer C₁₆H₃₃ and C₁₈H₃₇. X-ray diffraction confirmed the existence of SmA, SmC and N phases for complexes and ligands. The other notable feature is that the self-ordering of terminal alkyl chain occurred in SmA and SmC phases of complexes with even terminal alkyl chain ranging from C₁₄H₂₉ to C₁₈H₃₃. Their corresponding ligands exhibit intercalated structure of SmA and SmC phases. The thermal behaviour studies show that the fluoro-substituted triazole-based complexes possess lowest phase transition temperature and more stable as compared to other substituent which decomposed during the isotropisation.     

Wire-type ruthenium(II) complexes with terpyridine-containing [2]rotaxanes as ligands: Synthesis, characterization, and photophysical properties

[2]Rotaxanes based on the 1,2-bis(pyridinium)ethane subset[24]crown-8 ether motif were prepared that contain a terminal terpyridine group for coordination to a transition-metal ion. These rotaxane ligands were utilized in the preparation of a series of heteroleptic [Ru(terpy)(terpy-rotaxane)]2+ complexes. The compounds were characterized by 1D and 2D 1H NMR spectroscopy, X-ray crystallography, and high-resolution electrospray ionization mass spectrometry. The effect of using a rotaxane as a ligand was probed by UV/Vis/NIR absorption and emission spectroscopy of the Ru(II) complexes. In contrast with the parent [Ru(terpy)(2)]2+ complex, at room temperature the examined complexes exhibit a luminescence band in the near infrared region and a relatively long lived triplet metal-to-ligand charge-transfer (3MLCT) excited state, owing to the presence of strong-electron-acceptor pyridinium substituents on one of the two terpy ligands. Visible-light excitation of the Ru-based chromophore in acetonitrile at room temperature causes an electron transfer to the covalently linked 4,4'-bipyridinium unit and the quenching of the MLCT luminescence. The 3MLCT excited state, however, is not quenched at all in rigid matrix at 77 K. The rotaxane structure was found to affect the absorption and luminescence properties of the complexes. In particular, when a crown ether surrounds the cationic axle, the photoinduced electron-transfer process is slowed down by a factor from 2 to 3. Such features, together with the synthetic and structural advantages offered by [Ru(terpy)2]2+-type complexes compared to, for example, [Ru(bpy)3]2+-type compounds, render these rotaxane-metal complexes promising candidates for the construction of photochemical molecular devices with a wire-type structure.     

Comparison of Hydrogen and Gold Bonding in [XHX]−, [XAuX]−, and Isoelectronic [NgHNg]+, [NgAuNg]+ (X=Halogen,Ng=Noble Gas)

Quantum chemical calculations at the MP2/aug‐cc‐pVTZ and CCSD(T)/aug‐cc‐pVTZ levels have been carried out for the title compounds. The electronic structures were analyzed with a variety of charge and energy partitioning methods. All molecules possess linear equilibrium structures with D_∞h symmetry. The total bond dissociation energies (BDEs) of the strongly bonded halogen anions [XHX]^? and [XAuX]^? decrease from [FHF]^? to [IHI]^? and from [FAuF]^? to [IAuI]^?. The BDEs of the noble gas compounds [NgHNg]⁺ and [NgAuNg]⁺ become larger for the heavier atoms. The central hydrogen and gold atoms carry partial positive charges in the cations and even in the anions, except for [IAuI]^?, in which case the gold atom has a small negative charge of ?0.03 e. The molecular electrostatic potentials reveal that the regions of the most positive or negative charges may not agree with the partial charges of the atoms, because the spatial distribution of the electronic charge needs to be considered. The bonding analysis with the QTAIM method suggests a significant covalent character for the hydrogen bonds to the noble gas atoms in [NgHNg]⁺ and to the halogen atoms in [XHX]^?. The covalent character of the bonding in the gold systems [NgAuNg]⁺ and [XAuX]^? is smaller than in the hydrogen compound. The energy decomposition analysis suggests that the lighter hydrogen systems possess dative bonds X^?→H⁺←X^? or Ng→H⁺←Ng while the heavier homologues exhibit electron sharing through two‐electron, three‐center bonds. Dative bonds X^?→Au⁺←X^? and Ng→Au⁺←Ng are also diagnosed for the lighter gold systems, but the heavier compounds possess electron‐shared bonds.     

Titanosilicate beads with hierarchical porosity: synthesis and application as epoxidation catalysts

Porous titanosilicate beads with a diameter of 0.5-1.5 mm (TiSil-HPB-60) were synthesized from a preformed titanosilicate solution with a porous anion-exchange resin as template. The bead format of this material enables its straightforward separation from the reaction mixture in its application as a liquid-phase heterogeneous catalyst. The material displays hierarchical porosity (micro/mesopores) and incipient TS-1 structure building units. The titanium species are predominantly located in tetrahedral framework positions. TiSil-HPB-60 is a highly active catalyst for the epoxidation of cyclohexene with t-butyl hydroperoxide (TBHP) and aqueous H(2)O(2). With both oxidants, TiSil-HPB-60 gave higher epoxide yields than Ti-MCM-41 and TS-1. The improved catalytic performance of TiSil-HPB-60 is mainly ascribed to the large mesopores favoring the diffusion of reagents and products to and from the titanium active sites. The epoxide yield and selectivity could be further improved by silylation of the titanosilicate beads. Importantly, TiSil-HPB-60 is a stable catalyst immune to titanium leaching, and can be easily recovered and reused in successive catalytic cycles without significant loss of activity. Moreover, TiSil-HPB-60 is active and selective in the epoxidation of a wide range of bulky alkenes.     

Synthesis and self-assembly of novel calix[4]arenocrowns: formation of calix[4]areno[2]catenanes

A series of novel calix[4]arenocrowns 1a-c were efficiently synthesized by a one-pot reaction of calix[4]monohydroquinone diacetate 5 with ditosylate 6 and its analogues in the presence of sodium hydroxide. It was found that the calix[4]arenocrowns could form stable pseudorotaxane-type complexes 2a-c with paraquat, and further self-assemble into calix[4]areno[2]catenanes 3a-c with dicationic salt 8 and p-bis(bromomethyl)benzene.     

Isolation, characterisation and synthesis of an insecticidal tetramethyltetrahydrochromenedione-spiro-bicyclo[3.1.1]cycloheptane from two species of Myrtaceae

A new moderately insecticidal compound, named ficifolidione, has been isolated from the hexane extract of the aerial parts of two species of Myrtaceae, Eucalyptus ficifolia and Kunzea ericoides. Its structure, (1′R,2′R,4R)-4-isobutyl- 6,6,8,8-tetramethyl-2,3,4,8-tetrahydrochromene-5,7-dione-2-spiro-2′-6,6-dimethyl-bicyclo[3.1.1]heptane (1), was confirmed by synthesis from syncarpic acid, isovaleraldehyde and (1S)-β-pinene.     

Amphiphilic cholesteryl-bearing carboxymethylcellulose derivatives: self-assembly and rheological behaviour in aqueous solution

The self-assembly of amphiphilic cholesteryl-bearing carboxymethylcellulose derivatives (CCMCs) from individual molecules to self-aggregates, in addition to their rheological behaviour in aqueous solution were investigated. The conformations of the individual CCMC individual molecules and self-aggregates, and the microstructures of CCMC self-aggregates were characterized using the static and dynamic light scattering analyses, and the steady fluorescence technology. The results showed that the individual CCMC chains became compact, and aqueous NaCl solution changed from an approximate θ solvent to a bad one when the number of hydrophobic cholesteryl groups increased. The CCMC self-aggregates exhibited as compact spheres. The microstructural characterization indicated that one CCMC self-aggregate consisted of multiple individual CCMC molecules and hydrophobic microdomains, and multiple cholesteryl groups self-associated into one hydrophobic microdomain. The atomic force microscopy images of CCMC self-aggregates in phase mode showed that the multiple interior hydrophobic phase separation regions were surrounded by hydrophilic polysaccharide chains, providing an evidence for multiple hydrophobic microdomains in one self-aggregate. The rheological analysis proved that the CCMC self-aggregates were a microgel, in which the associations of cholesteryl groups provided multiple cross-linking points in the polymer network. The microgel solutions displayed a unique thixotropy and a shear thinning behaviour.     

Investigation of Large Polychloride Anions: [Cl11]−, [Cl12]2−, and [Cl13]−

For decades the chemistry of polyhalides was dominated by polyiodides and more recently also by an increasing number of polybromides. However, apart from a few structures containing trichloride anions and a single report on an octachloride dianion, [Cl₈]^2?, polychlorine compounds such as polychloride anions are unknown. Herein, we report on the synthesis and investigation of large polychloride monoanions such as [Cl₁₁]^? found in [AsPh₄][Cl₁₁], [PPh₄][Cl₁₁], and [PNP][Cl₁₁]?Cl₂, and [Cl₁₃]^? obtained in [PNP][Cl₁₃]. The polychloride dianion [Cl₁₂]^2? has been obtained in [NMe₃Ph]₂[Cl₁₂]. The novel compounds have been thoroughly characterized by NMR spectroscopy, single‐crystal Raman spectroscopy, and single‐crystal X‐ray diffraction. The assignment of their spectra is supported by molecular and periodic solid‐state quantum‐chemical calculations.     

Synthesis of Amphiphilic [60]Fullerene [3:3]Hexakisadducts with Four Spherically Defined Addend Zones

New [3:3]hexakisadducts 3 , 6 , and 7 have been synthesized by a stepwise addition of two tripodal malonate tethers to pristine [60]fullerene. For the first time, [3:3]hexakisadducts of two sets of asymmetrically substituted malonate addends could be prepared as single in/out isomers by following this synthetic protocol. Thereby, four spherically defined addend zones I–IV were created with various similar degrees of latitude on the fullerene sphere. Four amphiphilic [3:3]hexakisadducts 12 , 14 , 18 , and 19 were prepared with different relative arrangements of both the hydrophilic and lipophilic moieties in the addend zones I / II and III / IV , respectively.     

Amphiphilic Fluorescence Resonance Energy-Transfer Dyes: Synthesis,Fluorescence, and Aggregation Behavior in Water

Amphiphilic pyrene/perylene bis-chromophore dyes were synthesized from unsymmetrically substituted perylene bisimide dyes, which were obtained through three synthetic methods. The optical and aggregation behaviors of these functional dyes were studied by means of UV/Vis absorption and fluorescence spectroscopy, dynamic light scattering, and TEM. These dyes are highly fluorescent and cover the whole visible-light region. A donor/acceptor dye displays intramolecular fluorescence resonance energy transfer (FRET), with a high efficiency of up to 96.4 % from pyrene to perylene bisimide chromophores, which leads to a high fluorescence color sensitivity to environmental polarity. Under a λ=365 nm UV lamp, the light-emitting colors of the donor/acceptor dye change from green to yellow with increasing solvent polarity, which demonstrates application potential as a new class of FERT probes. The donor/acceptor dye in water was assembled into hollow vesicles with a narrow size distribution. The bilayer structure of the vesicular wall was directly observed by means of TEM. These vesicular aggregates in water are fluorescent at λ=650–850 nm within the near-infrared region.