A Pseudorotaxane System Containing γ-Cyclodextrin Formed via Chiral Recognition with an AuI6AgI3CuII3 Molecular Cap

Solvent-mediated crystal-to-crystal transformations of [Au₆Ag₃Cu₃(H₂O)₃(d -pen)₆(tdme)₂]³⁺ (d -[ 1 (H₂O)₃]³⁺; pen²⁻= penicillaminate, tdme=1,1,1-tris(diphenylphosphinomethyl)ethane) to form unique supramolecular species are reported. Soaking crystals of d -[ 1 (H₂O)₃]³⁺ in aqueous Na₂bdc (bdc²⁻=1,4-benzenedicarboxylate) yielded crystals containing d -[ 1 (bdc)(H₂O)₂]⁺ due to the replacement of a terminal aqua ligand in d -[ 1 (H₂O)₃]³⁺ by a monodentate bdc²⁻ ligand. When γ-cyclodextrin (γ-CD) was added to aqueous Na₂bdc, d -[ 1 (H₂O)₃]³⁺ was transformed to d -[ 1 (bdc@γ-CD)(H₂O)₂]⁺, where a γ-CD ring was threaded by a bdc²⁻ molecule to construct a pseudorotaxane structure. While the use of dicarboxylates with an aliphatic carbon chain instead of bdc²⁻ afforded analogous pseudorotaxanes, such pseudorotaxane species were not formed when crystals of [Au₆Ag₃Cu₃(H₂O)₃(l -pen)₆(tdme)₂]³⁺ (l -[ 1 (H₂O)₃]³⁺) enantiomeric to d -[ 1 (H₂O)₃]³⁺ were soaked in aqueous Na₂bdc and γ-CD, affording only crystals containing l -[ 1 (bdc)(H₂O)₂]⁺.     

Synthesis of Tetra-Substituted Trifluoromethyl-3,1-Benzoxazines by Transition-Metal-Catalyzed Decarboxylative Cyclization of N-Benzoyl Benzoxazinones

Efficient synthesis of N,O-heterocyclic tetra-substituted trifluoromethyl-3,1-benzoxazines via a transition-metal-catalyzed decarboxylative intramolecular cyclization was achieved. The decarboxylation of N-benzoyl trifluoromethyl-benzoxazinones generated the amide oxygen nucleophile, allowing a selective internal C₁-attack on Pd- or Cu-coordinated zwitterions, affording medicinally attractive tetra-substituted vinyl- or ethynyl-trifluoromethyl-3,1-benzoxazines. This protocol can be applied to the synthesis of perfluoroalkyl- and non-fluorinated 3,1-benzoxazines.     

Catalytic reactions of oxetanes with protonic reagents and aprotic reagents leading to novel polymers

This paper reports new addition reactions of oxetanes with certain protonic reagents such as carboxylic acid, phenol, and thiol, and with certain aprotic reagents such as acyl chloride, thioester, phosphonyl dichloride, silyl chloride, and chloroformate using quaternary onium salts as catalysts. The kinetic study of the addition reactions of oxetanes was also investigated. These new addition reactions were applicable to the synthesis of new polymers. These polyaddition systems could also construct both polymer main chains and reactive side chains. The alternating copolymerization of oxetanes with carboxylic anhydride was performed. Furthermore, it was found that anionic ring‐opening polymerization of oxetanes containing hydroxy groups proceeded to afford the hyperbranched polymer (HBP) with an oxetanyl group and many hydroxy groups at the ends of the polymer chains. Alkali developable photofunctional HBPs were synthesized by the polyaddition of bis(oxetane)s or tris(oxetane)s, and their patterning properties were examined, too. The photo‐induced cationic polymerization of the polymers with pendant oxetanyl groups and the thermal curing reactions of polyfunctional oxetanes (oxetane resins) were also examined to give the crosslinking materials quantitatively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 709–726, 2007     

Photocontrolled Translational Motion of a Microscale Solid Object on Azobenzene‐Doped Liquid‐Crystalline Films

On the move : Irradiation of azobenzene‐doped liquid crystalline films with UV/Vis light results in the photocontrolled translational motion of microscale solid object on the surface, which occurs through cis–trans isomerization of the azobenzene unit. Irradiation with an Ar⁺ laser (488 nm) resulted in precise control of the translational motion so that the particle always moved away from the irradiation position (see picture).

     

New Pseudostationary Phases for Electrokinetic Chromatography: A High-Molecular Surfactant and Proteins

To extend the applicability of electrokinetic chromatography (EKC), two new types of pseudostationary phases have been introduced. A high-molecular surfactant, butyl acrylate/butyl methacrylate/methacrylic acid copolymer (BBMA) is employed as a micellar forming surfactant for miccllar electrokinetic chromatography (MEKC). The critical micelle concentration of BBMA is essentially zero, which means the micellar concentration is constant irrespective of temperature and buffer. Some characteristic features of BBMA as the pseudostationary phase for MEKC is investigated in comparison with conventional ionic surfactants. Ovomucoid and avidin, which are proteins isolated from egg white, have been found to be useful chiral selectors in affinity EKC. A few examples of the separation of enantiomers with these proteins are shown.     

DNA Dangling‐End‐Induced Colloidal Stabilization of Gold Nanoparticles for Colorimetric Single‐Nucleotide Polymorphism Genotyping

A single‐nucleotide polymorphism (SNP) detection method was developed by combining single‐base primer extension and salt‐induced aggregation of gold nanoparticles densely functionalized with double‐stranded DNA (dsDNA‐AuNP). The dsDNA‐AuNPs undergo rapid aggregation in a medium of high ionic strength, whereas particles having a single‐base protrusion at the outermost surface disperse stably, allowing detection of a single‐base difference in length by color changes. When SNP typing primers are used as analytes to hybridize to the single‐stranded DNA on the AuNP surface, the resulting dsDNA‐AuNP works as a visual indicator of single‐base extension. A set of four extension reaction mixtures is prepared using each of ddNTPs and subsequently subjected to the aggregation assay. Three mixtures involving ddNTP that is not complementary to the SNP site in the target produce the aggregates that exhibit a purple color. In contrast, one mixture with the complementary ddNTP generates the single‐base protrusion and appears red. This method could potentially be used in clinical diagnostics for personalized medicine.     

Intramolecular SN2 reaction caused by photoionization of benzene chloride-NH3 complex: direct ab initio molecular dynamics study

Ionization processes of chlorobenzene-ammonia 1:1 complex (PhCl-NH3) have been investigated by means of full dimensional direct ab initio molecular dynamics (MD) method, static ab initio calculations, and density functional theory (DFT) calculations. The static ab initio and DFT calculations of neutral PhCl-NH3 complex showed that one of the hydrogen atoms of NH3 orients toward a carbon atom in the para-position of PhCl. The dynamics calculation for ionization of PhCl-NH3 indicated that two reaction channels are competitive with each other as product channels: one is an intramolecular SN2 reaction expressed by a reaction scheme [PhCl-NH3]+-->SN2 intermediate complex-->PhNH3++Cl, and the other is ortho-NH3 addition complex (ortho complex) in which NH3 attacks the ortho-carbon of PhCl+ and the trajectory leads to a bound complex expressed by (PhCl-NH3)+. The mechanism of the ionization of PhCl-NH3 is discussed on the basis of the theoretical results.     

Electron hydration dynamics in water clusters: A direct ab initio molecular dynamics approach

Electron attachment dynamics of excess electron in water cluster (H2O)n (n = 2 and 3) have been investigated by means of full-dimensional direct ab initio molecular dynamics (MD) method at the MP26-311++G(d,p) level. It was found that the hydrogen bond breaking due to the excess electron is an important process in the first stage of electron capture in water trimer. Time scale of electron localization and hydrogen bond breaking were determined by the direct ab initio MD simulation. The initial process of hydration in water cluster is clearly visualized in the present study. In n = 3, an excess electron is first trapped around the cyclic water trimer with a triangular form, where the excess electron is equivalently distributed on the three water molecules at time zero. After 50 fs, the excess electron is concentrated into two water molecules, while the potential energy of the system decreases by -1.5 kcal/mol from the vertical point. After 100 fs, the excess electron is localized in one of the water molecules and the potential energy decreases by -5.3 kcal/mol, but the triangular form still remained. After that, one of the hydrogen bonds in the triangular form is gradually broken by the excess electron, while the structure becomes linear at 100-300 fs after electron capture. The time scale of hydrogen bond breaking due to the excess electron is calculated to be about 300 fs. Finally, a dipole bound state is formed by the linear form of three water molecules. In the case of n = 2, the dipole bound anion is formed directly. The mechanism of electron hydration dynamics was discussed on the basis of theoretical results.     

Ozone-water 1:1 complexes O3-H2O: an ab initio study

Ab initio MO calculations have been carried out for the ozone-water 1:1 complexes in order to elucidate the structures and electronic state of the complexes. The QCISD calculations indicated that three structures are obtained as stable forms of O(3)-H(2)O. The most stable structure of O(3)-H(2)O has C(s) symmetry where the central oxygen of O(3) and all atoms of H(2)O are located on the molecular C(s) plane. The dipole of H(2)O orients toward the central oxygen atom of O(3) (i.e., dipole orientation form). The other two forms are cis and trans forms of O(3)-H(2)O where all atoms are located on the molecular plane, and a hydrogen of H(2)O binds to one of the terminal oxygen atoms of O(3) by a hydrogen bond. The binding energies of O(3) to H(2)O for dipole, cis, and trans forms are calculated to be 2.39, 2.27, and 2.30 kcal/mol, respectively, at the QCISD(T)/6-311++G(3df,3pd)//QCISD/6-311++G((d,p) level. The dipole orientation form is more stable in energy than the cis and trans forms. Rotational constants for the dipole orientation form are calculated to be A = 11.897, B = 4.177, and C = 3.318 GHz which are in good agreement with the experimental values (A = 11.961, B = 4.174, and C = 3.265 GHz). The electronic states of O(3)-H(2)O were discussed on the basis of theoretical results.