Guest-induced assembly of tetracarboxyl-cavitand and tetra(3-pyridyl)-cavitand into a heterodimeric capsule via hydrogen bonds and CH-halogen and/or CH-pi interaction: control of the orientation of the encapsulated guest

The guest- or solvent-induced assembly of a tetracarboxyl-cavitand 1 and a tetra(3-pyridyl)-cavitand 2 into a heterodimeric capsule 1.2 in a rim-to-rim fashion via four intermolecular CO(2)H.N hydrogen bonds has been investigated both in solution and in the solid state. In the (1)H NMR study, a 1:1 mixture of1a and 2a (R = (CH(2))(6)CH(3)) in CDCl(3) gave a mixture of various complicated aggregates, whereas this mixture in CDCl(2)CDCl(2) or p-xylene-d(10) exclusively produced the heterodimeric capsule 1a.2a. It was found that an appropriate 1,4-disubstituted-benzene is a suitable guest for inducing the exclusive formation of 1a.2a in CDCl(3). The ability of a guest to induce the formation of guest-encapsulating heterodimeric capsule, guest@(1a.2a), increased in the order p-ethyltoluene < 1-ethyl-4-methoxybenzene < or = 1-ethyl-4-iodobenzene < or = 1,4-dibromobenzene < 1-iodo-4-methoxybenzene < or= 1,4-dimethoxybenzene < or = 1,4-diiodobenzene. The (1)H NMR study revealed that a CH-halogen interaction between the inner protons of the methylene-bridge rims (-O-H(out)CH(in)-O-) of the 1a and 2a units and the halogen atoms of 1,4-dihalobenzenes and a CH-pi interaction between the methoxy protons of 1,4-dimethoxybenzene and the aromatic cavities of the 1a and 2a units play important roles in the formation of 1,4-dihalobenzene@(1a.2a) and 1,4-dimethoxybenzene@(1a.2a), respectively. A preliminary single-crystal X-ray diffraction analysis of guest@(1b.2b) (R = (CH(2))(2)Ph; guest = 1-iodo-4-methoxybenzene or p-xylene) confirmed that the guest encapsulated in 1b.2b is oriented with the long axis of the guest along the long axis of 1b.2b and that the iodo and the methoxy groups of the encapsulated 1-iodo-4-methoxybenzene are specifically oriented with respect to the cavities of the 2b and 1b units, respectively.     

Facile Synthesis and Palladium‐Catalyzed Cross‐Coupling Reactions of 2,3‐Bis(pinacolatoboryl)‐1,3‐butadiene

Treatment of 1,1‐bis(pinacolatoboryl)ethene with an excess of 1‐bromo‐1‐lithioethene gave 2,3‐bis(pinacolatoboryl)‐1,3‐butadiene in high yield. Palladium‐catalyzed cross‐coupling of the resulting diborylbutadiene with aryl iodides took place smoothly in the presence of a catalytic amount of Pd(OAc)₂/PPh₃ and aqueous KOH to give 2,3‐diaryl‐1,3‐butadienes in good yields. The coupling reaction with commercially available 4‐acetoxyphenylmethyl chloride under the same conditions followed by hydrolysis of the acetyl groups gave anolignan B in a one‐pot manner. A variety of [3]‐ to [6]dendralenes were synthesized by palladium‐catalyzed coupling of the diene or 1,1‐bis(pinacolato)borylethene with alkenyl or dienyl halides, respectively, in good yields.     

Distorted Porphyrins with High Stability: Synthesis and Characteristic Electronic Properties of Mono- and Di-Nuclear Tricarbonyl Rhenium Tetraazaporphyrin Complexes

Mono- and di-nuclear tricarbonyl Re(I) tetraazaporphyrin complexes ( Re₁TAP and Re₂TAP ) are investigated and compared with Re(I) phthalocyanine complexes ( Re₁Pc and Re₂Pc ). Although Re₂Pc is unstable in polar solvents, and easily undergoes demetallation reaction, the coordination of the TAP ligand significantly improves the tolerance toward polar solvents, affording more stability to Re₂TAP . Additionally, the incorporation of [Re(CO)₃]⁺ unit(s) and the TAP ligand results in remarkable positive shifts in both oxidation and reduction potentials. Consequently, the more positive oxidation potentials of the ReTAP complexes significantly increase the tolerance toward oxidation, while the reduction potential indicates that Re₂TAP is suitable for a soluble electron acceptor. In contrast to Re₁Pc and Re₂Pc , Re₁TAP and Re₂TAP show unique broad Q bands, which can be attributed to the admixture of the π-π* and metal-to-ligand charge transfer characters, owing to the lowered π orbital energy in the TAP complexes. This study is useful for controlling electronic properties and realizing high stability in Pc analogues.     

Construction of Helical Structures with Multiple Fused Anthracenes: Structures and Properties of Long Expanded Helicenes

Polycyclic aromatic compounds consisting of four or five fused anthracene units were synthesized by PtCl₂-catalyzed cycloisomerization as novel long expanded helicenes. These compounds have helical structures with significant stacking of the terminal anthracene moieties at 0.33 nm interlayer distance. In the UV-vis and fluorescence spectra, the absorption and emission bands were red-shifted as the number of fused anthracene units was increased. The characteristic broad and long-lived emission bands of the long analogues are explained by the excimer-like stabilization of the excited state. These photophysical data as well as their cyclic voltammetric data are discussed on the basis of the π-conjugation and interlayer π⋅⋅⋅π interactions in the molecular structures and the molecular orbitals. The barrier and mechanism of helical inversion are also reported.     

Quarkonia at Finite T: An Approach Based On QCD Sum Rules and the Maximum Entropy Method

Quarkonium spectral functions at finite temperature are studied, making use of a recently developed method of analyzing QCD sum rules by the maximum entropy method. This approach enables us to directly obtain the spectral function from the sum rules, without having to introduce any specific assumption about its functional form. QCD sum rules for heavy quarkonia incorporate finite temperature effects in form of changing values of the various gluonic condensates that appear in the operator product expansion. These changes depend on the energy density and pressure at finite temperature, which we extract from quenched lattice QCD calculations. As a result, it is found that the charmonium ground states of both S-wave and P-wave channels dissolve into the continuum already at temperatures around or slightly above the critical temperature T _c , while the bottomonium states are less influenced by temperature effects, surviving up to about 2.5 T _c or higher for S-wave and about 2.0 T _c for P-wave states.     

Statistics of reaction progress variable and mixture fraction gradients of a pulverised coal jet flame using Direct Numerical Simulation data

The statistical behaviour of the variances, covariance and gradients of the reaction progress variable (c), and the mixture fraction (ξ) have been analysed in a pulverised coal jet flame using a three-dimensional carrier phase direct numerical simulation (DNS) dataset. It has been observed that the Favre-probability density functions (PDFs) of c and ξ can be parametrised by the standard β function. Furthermore, the log-normal distribution has been found to accurately represent |?c| and |?ξ|. It is also found that ?c and ?ξ remain aligned throughout the flame brush. Finally the joint PDF of |?c| and |?ξ| has been compared with the product of the PDF of |?c| and PDF of |?ξ| extracted from carrier phase DNS, and it has been found that |?c| and |?ξ| are not statistically independent in the case investigated.The bivariate log-normal distributions with and without correlation have also been considered, and the former is found to be in better agreement with the carrier phase DNS data.