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The self-assembling of tetrakis(4-hydroxyphenyl)-cavitand and terta(4-pyridyl) cavitand into a heterodimeric capsule by the four ArOH...pyridyl hydrogen bonds in CD[Cl.sub.3] with high thermodynamic stability is described. The balance among electrostatic potential repulsion, CH-[pi] interaction, in tetrakis(4-hydroxyphenyl)-cavitand and terta(4-pyridyl) cavitand-guest assembly has affected the orientational isomeric selectivity of unsymmetrical guests within tetrakis(4-hydroxyphenyl)-cavitand and terta(4-pyridyl) cavitand.

A study is conducted to present the formation of a homo or hetero cavitand cage comprising of two kinds of ligands with different coordination ability as donors on metal and as an acceptor like tetra (4-pytidyl)-cavitand and Pt (dppp)(OTF)(sub 2). The results prove that the selectivity for the self-assembly of the homo or hetero cavitand cage is controlled by the balance between kinetic and thermodynamic stabilities of cages depending on factors like coordination ability and steric demand of the cavitands.

Cyclic and linear conjugated molecules featuring 9,10-dithienylanthracene linked with vinylene were synthesized by McMurry coupling, ring-opening metathesis polymerization (ROMP), and dehydration. The cyclic and linear dimers displayed strained ring and planar structures by single-crystal X-ray crystallography, respectively. UV-Vis and photoluminescence (PL) spectra of the cyclic dimer in benzene solution exhibited reversible changes in absorbance and PL intensity by UV irradiation and reversion by heating. The reversion followed the first-order equation, giving a kinetic constant of 0.75 min−1 at 35 °C and an activation energy of 70.9 kJ mol−1. Computational studies based on density functional theory supported the explanation of the experimental results. These spectral changes were attributed to unique conformational changes, particularly the flipping of the alkylated thienyl group. Furthermore, a single crystal of the cyclic dimer showed photoinduced bending. Contrarily, a free-standing film of polyvinylene synthesized via ROMP and polyimine synthesized via dehydration exhibited photoinduced elongation and bending, respectively. [ABSTRACT FROM AUTHOR]

A 2 : 4 mixture of tetrakis[4‐(4‐pyridyl)phenyl]cavitand (1) or tetrakis[4‐(4‐pyridyl)phenylethynyl]cavitand (2) and Pd(dppp)(OTf)2 self‐assembles into a homocapsule {12 ⋅ [Pd(dppp)]4}8+ ⋅ (TfO−)8 (C1) or {22 ⋅ [Pd(dppp)]4}8+ ⋅ (TfO−)8 (C2), respectively, through Pd−Npy coordination bonds. A 1 : 1 : 4 mixture of 1, 2, and Pd(dppp)(OTf)2 produced a mixture of homocapsules C1, C2, and a heterocapsule {1 ⋅ 2 ⋅ [Pd(dppp)]4}8+ ⋅ (TfO−)8 (C3) in a 1 : 1 : 0.98 mole ratio. Selective formation (self‐sorting) of homocapsules C1 and C2 or heterocapsule C3 was controlled by guest‐induced encapsulation under thermodynamic control. Applications of Pd−Npy coordination capsules with the use of 1 were demonstrated. Capsule C1 serves as a guard nanocontainer for trans‐4,4′‐diacetoxyazobenzene to protect against the trans‐to‐cis photoisomerization by encapsulation. A chiral capsule {12 ⋅ [Pd((R)‐BINAP)]4}8+ ⋅ (TfO−)8 (C5) was also constructed. Capsule C5 induces supramolecular chirality with respect to prochiral 2,2′‐bis(alkoxycarbonyl)‐4,4′‐bis(1‐propynyl)biphenyls by diastereomeric encapsulation through the asymmetric suppression of rotation around the axis of the prochiral biphenyl moiety. [ABSTRACT FROM AUTHOR]

New chiral sulfoxides ([R.sub.S],S)-3, ([S.sub.S],S)-3, ([R.sub.S],S)-4, and ([S.sub.S],S)-4 and known chiral sulfoxides ([R.sub.S])-5, ([R.sub.S])-6 and ([R.sub.S])-7 are synthesized based on the concept of intermolecular and intramolecular nonbonded S...O interactions. The mechanistic studies on the facile stereoselective Pummerer reactions have revealed the necessity for the amide/trimethylsilyl triflate complex to be an efficient activation reagent for [Ac.sub.2]O and a trapping reagent for the released acetate ion.

A complete selection of a self-assembling homo- or hetero-cavitand cage via metal coordination based on ligand tuning is described. The coordination ability and steric demand of cavitand ligands play an important role in the self-assembling process.

Synthesis of molecular containers capable of incorporating multiple fullerenes remains challenging. Reported here is that room‐temperature mixing of metal ions with W‐shaped bispyridine ligands featuring polyaromatic panels results in the quantitative formation of a peanut‐shaped M2L4 capsule. The capsule reversibly converts into two molecules of an ML2 double tube in response to changes in the solvent. Notably, the capsule allows the incorporation of two fullerene molecules into the connected two spherical cavities at room temperature. The close proximity yet non‐contact of the encapsulated C60 molecules, with a separation of 6.4 Å, was revealed by X‐ray crystallographic analysis. The resultant, unusual fullerene dimer undergoes sequential reduction within the capsule to generate (C60.−)2, C60.−⋅C602−, and (C602−)2 species. Furthermore, temperature‐controlled stepwise incorporation of two C60 molecules into the capsule is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: A polyaromatic tube with a subnanometer‐sized cavity was efficiently prepared on a gram‐scale through the stereo‐controlled cyclotrimerization of a diphenylanthracene derivative as a key step. The facile exterior alkylation of the polyaromatic framework leads to a moderately fluorescent tube (R=‐OC10H21; ΦF=20 %) in the solid state. The emission intensity of the solid‐state alkyl‐substituted tube is remarkably enhanced upon heating (up to 1.6 times, ΦF=31 %) as well as doping with fluorescent dyes (up to 4.2 times, ΦF=83 %) through efficient energy transfer. [ABSTRACT FROM AUTHOR]

The three-dimensional (3D) structural characterization of two catalyst complexes, one (crystal A) producing the opposite enantiomer with excellent selectivity compared to that obtained by the catalyst prepared in situ, and the other (crystal B) containing a 2:3 complex as a subunit and thus reflecting the optimized Gd catalyst in solution, is presented. The results have shown that enantioselectivity of an artificial asymmetric catalyst is tunable, depending on the assembly mode of the chiral modules.

For the development of novel nanospace with unique electrostatic character, we prepared new capsular and tubular nanostructures by the quantitative assembly of metal ions and bent bisacridinium ligands. The capsule and tube have closed spherical and open cylindrical cavities, respectively, with diameters of around 1 nm surrounded by cationic polyaromatic panels. Thanks to the facile synthetic protocol (three steps), another polycationic capsule with an elliptical nanocavity was also prepared by using an elongated ligand. In spite of the absence of pendant hydrophilic groups, the spherical polyaromatic capsule shows sufficient water solubility due to the polycationic shell. Moreover, the highly cationic cavity (12+) can selectively encapsulate anionic organic compounds in water. [ABSTRACT FROM AUTHOR]

Preparation of molecular nanostructures with polyradical frameworks remains a significant challenge because of the limited synthetic accessibility which is entirely different from that of neutral and ionic ones. Herein we report the quantitative formation of a new M2L4 molecular capsule from metal ions and dihydrophenazine-based ligands. The capsule has a spherical nanocavity (ca. 1 nm in diameter) enclosed by eight redox-active, dihydrophenazine panels. Electrochemical oxidation of the capsule leads to the generation of multiple radical cations on the shell framework. Moreover, a stable tetra(radical cation) capsule can be reversibly obtained by chemical as well as electrochemical oxidation. [ABSTRACT FROM AUTHOR]

The methyl group is a small substituent, usually showing relatively weak or no interactions with other functional groups and metal ions. Herein, we present the recognition of the number of methyl groups on synthetic and natural aromatic compounds (i.e., benzene and xanthine derivatives, respectively) by the 1 nm-sized polyaromatic cavity of a coordination capsule in water. Detailed competitive encapsulation experiments as well as X-ray crystallographic analysis revealed that multiple guest-host CH3-polyaromatic interactions in the confined nanospace are key driving forces for the high selectivity. [ABSTRACT FROM AUTHOR]

A V-shaped bisanthracene derivative with three butyl groups formed two types of emissive solids that display bluish green and blue fluorescence (ΦF=72 and 32 %, respectively), depending on the preparation conditions. The crystal and powder X-ray analyses reveal that the highly emissive solid adopts a head-to-head arrangement with discrete stacks of the anthracene moieties, whereas the moderately emissive solid adopts a head-to-tail arrangement without the stacks. The obtained molecular arrangements are transformed by thermal stimuli accompanying the change in fluorescence. Furthermore, large enhancements of dye emissions (12-45-fold) through highly efficient host-guest energy transfer were achieved in the solid state by adding minute amounts of various fluorescent dyes (e.g. rubrene and Nile red) to the V-shaped compound. [ABSTRACT FROM AUTHOR]

A new molecular capsule with a flexible fluorescent shell was formed by the quantitative self-complementary assembly of amphiphilic, U-shaped polyaromatic subunits in water. The capsule can fully encapsulate a variety of non-fluorescent monoterpene compounds (e.g., menthone, menthol, and p-menthane) in the hydrophobic cavity and act as a fluorescent supramolecular probe for recognizing the structural identity of the analytes by emissive signals in water at room temperature. [ABSTRACT FROM AUTHOR]

Anisotropic expansion of a spherical M2L4 coordination capsule through the elongation of the ligand led to a new M2L'4 capsule. The expanded capsule provides an elliptical cavity encircled by polyaromatic frameworks with large openings and thereby can encapsulate elliptical fullerene C70 and monofunctionalized fullerene C60 in high yields. In addition, selective formation of a new M2L2L'2 capsule occurs by mixing the original M2L4 and expanded M2L'4 capsules in a 1:1 ratio upon addition of C60 or monofunctionalized C60 as a template molecule. [ABSTRACT FROM AUTHOR]

A fluorescent macrocycle containing four anthracene panels linked by meta-phenylene spacers and amino hinges was synthesized. The macrocycle adopts a twisted, compressed conformation that places embedded anthracene fluorophores in close contact. Emission from the convoluted macrocycle is highly solvatochromic and significantly enhanced as compared with that of the partial structures. [ABSTRACT FROM AUTHOR]

This article reports that an M2L4 molecular capsule is capable of encapsulating various neutral molecules in quantitative yields. The capsule was obtained as a single product by mixing a small number of components; two PdII ions and four bent bispyridine ligands containing two anthracene panels. Detailed studies of the host capability of the PdII-linked capsule revealed that spherical (e.g., paracyclophane, adamantanes, and fullerene C60), planar (e.g., pyrenes and triphenylene), and bowl-shaped molecules (e.g., corannulene) were encapsulated in the large spherical cavity, giving rise to 1:1 and 1:2 host-guest complexes, respectively. The volume of the encapsulated guest molecules ranged from 190 to 490 Å3. Within the capsule, the planar guests adopt a stacked-dimer structure and the bowl-shaped guests formed an unprecedented concave-to-concave capsular structure, which are fully shielded by the anthracene shell. Competitive binding experiments of the capsule with a set of the planar guests established a preferential binding series for pyrenes≈phenanthrene>triphenylene. Furthermore, the capsule showed the selective formation of an unusual ternary complex in the case of triphenylene and corannulene. [ABSTRACT FROM AUTHOR]

Combining meta-triphenylamine or triphenylphosphine with three anthracene fluorophores gives rise to fluorescent non-planar triskelions 1 and 2. The emissive properties of 1 are highly solvatochromic, yielding blue to pale green and even pale yellow fluorescence, whereas the blue emission of 2 is solvent-insensitive. Anthracene trimers 1 and 2 are both emissive in the solid state, displaying yellow and pale green fluorescence, respectively, with moderate quantum yields. [ABSTRACT FROM AUTHOR]

Transesterification reactions of acyclic oligoether esters E3-E10 with metal alkoxides were accelerated upon noncovalent complexation of the esters with metal ions. In the reaction of monovalent alkaline metal alkoxides, CH3ONa and CH3OK, plots of the observed rate constants kobs with respect to the chain length of E3-E10 showed selective acceleration of the transesterification. Compared with the shortest E3, which can hardly bind metal ion, 4.3- and 6.6-fold accelerations in the maxima were achieved in the combinations of E5/CH3ONa and E6/CH3OK, respectively. Supramolecular intermediate complex could be spectrometrically visualized by ESI-FT-ICR-MS in the course of reaction. Kinetic experiments, together with structural analyses by means of NMR, mass spectrometry, and DFT calculations of the intermediate complexes, indicate that a size-fit complex of host substitute with alkali metal ion allows strong electron withdrawing due to the close contact of the carbonyl oxygen to the metal ion, resulting in the selective rate enhancement of the reaction, while in the reaction of E3-E10 with a divalent alkaline earth metal alkoxide, (CH3CH2O)2Ba, the kobs values increased stepwise with elongation of the side arm to attain an dramatic large acceleration. In comparison with the kobs of E3, 4610-fold acceleration was achieved in the reaction of E10. The double activation of the host substrate and guest counter nucleophile at once brings about this extraordinary rate acceleration. The strong wrapping complexation of long oligoether ester with barium ethoxide allows for the effective electron withdrawal from the ester carbonyl group (host activation) as well as separation of the accompanying guest alkoxide anions (guest activation). [ABSTRACT FROM AUTHOR]

The self-assembly of 2,4,6-tris(pyridin-4-yl)-1,3,5-triazine (tpt) triangular panels with p-cymene (p-PriC6H4Me) ruthenium building blocks and 2,5-dioxydo-1,4-benzoquinonato (dobq) bridges, in the presence of a functionalised pyrenyl derivative (pyrene–R), affords the triangular prismatic host–guest compounds [(pyrene–R) ⊂ Ru6(p-PriC6H4Me)6(tpt)2(dobq)3]6+([(pyrene–R) ⊂ 1]6+). The inclusion of eight mono-substituted pyrenyl derivatives including biologically relevant structures (a= 1-pyrenebutyric acid, b= 1-pyrenebutanol, c= 1-pyrenemethylamine, d= 1-pyrenemethylbutanoate, e= 1-(4,6-dichloro-1,3,5-triazin-2-yl)pyrene, f= N-hexadecylpyrene-1-sulfonamide, g= pyrenyl ethacrynic amide and h= 2-(pyren-1-ylmethylcarbamoyl) phenyl acetate), and a di-substituted pyrenyl derivative (i= 1,8-bis(3-methyl-butyn-1-yl-3-ol)pyrene), has been accomplished. The carceplex nature of these systems with the pyrenyl moiety being firmly encapsulated in the hydrophobic cavity of the cage with the functional groups pointing outwards was confirmed by NMR (1H, 2D, DOSY) spectroscopy and electrospray ionization mass spectrometry (ESI-MS). The cytotoxicities of these water-soluble compounds have been established using human ovarian A2780 cancer cells. All the host–guest systems are more cytotoxic than the empty cage itself [1][CF3SO3]6(IC50= 23 μM), the most active carceplex [f⊂ 1][CF3SO3]6is an order of magnitude more cytotoxic. [ABSTRACT FROM AUTHOR]

Enantioselective alcoholysis of σ-symmetric cyclic dicarboxylic anhydrides with benzyl alcohol catalyzed by a chiral bifunctional sulfonamide was achieved in up to 98% ee at 5 mol% loading. [ABSTRACT FROM AUTHOR]