Heteroleptic [Bis(oxazoline)](dipyrrinato)zinc(II) Complexes: Bright and Circularly Polarized Luminescence from an Originally Achiral Dipyrrinato Ligand

Heteroleptic zinc(II) complexes synthesized using achiral dipyrrinato and chiral bis(oxazoline) ligands show bright fluorescence with quantum efficiencies of up to 0.70. The fluorescence originates from the ¹π–π^* photoexcited state localized exclusively on the dipyrrinato ligand. Furthermore, the luminescence is circularly polarized despite the achirality of the dipyrrinato ligand. Single‐crystal X‐ray structure analysis discloses that the chiral bis(oxazoline) ligand undergoes intramolecular π–π stacking with the dipyrrinato ligand, inducing axial chirality in the dipyrrinato moiety.     

Crystallization-induced diastereomer transformation of 2-quinolone-4-carboxamide followed by stereoselective intermolecular photocycloaddition reaction

2-Quinolone-4-carboxamide derived from (S)-proline, which exists as a mixture of two diastereomers before crystallization, converged to a single diastereomer by crystallization (CIDT), and the homochirality was transferred by a intermolecular 2 + 2 photocycloaddition reaction with high optical activity.     

Structural order in perfluoropentacene thin films and heterostructures with pentacene

Synchrotron x-ray diffraction reciprocal space mapping was performed on perfluoropentacene (PFP) thin films on SiO2 in order to determine the crystal structure of a novel, substrate-induced thin film phase to be monoclinic with unit cell parameters of a = 15.76 +/- 0.02 A, b = 4.51 +/- 0.02 A, c = 11.48 +/- 0.02 A, and beta = 90.4 +/- 0.1 degrees . Moreover, layered and co-deposited heterostructures of PFP and pentacene (P) were investigated by specular and grazing-incidence x-ray diffraction, atomic force microscopy, and Fourier-transform infrared spectroscopy. For a ca. three-monolayers-thick PFP film grown on a P underlayer, slightly increased lattice spacing was found. In contrast, co-deposited P/PFP films form a new mixed-crystal structure with no detectable degree of phase separation. These results highlight the structural complexity of these technically relevant molecular heterojunctions for use in organic electronics.     

Electrically driven motion of an air bubble on hemispherical oil/water interface by three-phase boundary reactions

Our electrochemical cell consisted of a ferrocene-included hemispherical nitrobenzene (NB) droplet on the glassy carbon (GC) electrode which was immersed in the aqueous solution including sodium sulfate and sodium dodecyl sulfate (SDS). When an air bubble was injected near the boundary between the oil and the aqueous phase, it stayed at the top of the hemisphere on the boundary so that the lower half of the bubble was put in oil and the other half was in water. From the force balance of surface tension and buoyancy of the bubble, the bubble took an energetic minimum at the interface. It sank into the oil phase when ferrocene in the oil was electrochemically oxidized through the GC electrode by the three-phase boundary reaction. The electrochemical reduction caused the bubble to move back toward the aqueous phase. The motion of the bubble was synchronized with the redox reaction of ferrocene. The potential step oxidation showed such a rapid response that the motion could not be attributed to diffusion of ferricenium ion from the three-phase boundary to the bubble. Our idea of explaining the rapidity was the translational motion of the SDS layer along the boundary, which was driven by the difference in the surface concentration of SDS caused by the electrochemical generation of the ferricenium ion. The motion of the SDS layer was demonstrated by the shrinkage of the oil layer spread on the water surface when SDS solution was dropped on the oil layer. The spreading velocity was close to the velocity of propagating the oxidation of ferrocene to the bubble.     

Effects of preparation conditions on the synthesis of nano-sized Ag metal particles by the wet-process using 3-mercapto-propionic acid

By the addition of sodium borohydride as a reducing agent into an aqueous solution of AgNO₃ mixed with 3-mercapto-propionic acid as a protective agent, nano-sized Ag metal particles could be synthesized. Using this advanced wet-process the synthesis of an aqueous Ag colloid system with a high density became possible, because the surfaces of the synthesized nano-sized Ag metal particles were covered and protected by the adsorbed 3-mercapto-propionic acid. By changing the mix ratio of AgNO₃ to 3-mercapto-propionic acid, the particle size of synthesized nano-sized Ag metal particles could be controlled; a higher 3-mercapto-propionic acid/AgNO₃ ratio was preferable in the synthesis of smaller Ag metal particles. From the relationship between the Ag metal particle size and the residual S content adsorbed on the metal particles, the mechanism of dispersion of Ag particles can be proposed as that the 3-mercapto-propionic acid having a thiol group adsorbs on Ag particles by forming Ag-S bonds as a protective agent.     

Downregulation of two isoforms of ubiquitin carboxyl-terminal hydrolase isozyme L1 correlates with high metastatic potentials of human SN12C renal cell carcinoma cell clones

Proteomic differential display analysis was performed on human renal cell carcinoma cell SN12C clones having different metastatic potentials by using 2-DE and LC-MS/MS. The SN12C cell clones were SN12C parent cell line, SN12C-clone 2, SN12C-clone 4, and SN12C-PM6. The SN12C parent cell line was established from an HRCC surgical specimen. SN12C-clone 4 has lower, and SN12C-clone 2 and SN12C-PM6 have higher metastatic potential than SN12C parent cells. We found eight protein spots whose expression level was different between low metastatic clones and high metastatic clones. The protein expression of three appeared to be higher in high metastatic clones than low metastatic clones, and that of other five protein spots appeared to be lower in high metastatic clones than low metastatic clones. These spots were selected, digested and analyzed by LC-MS/MS analysis, and they were identified by peptide sequencing tag. In high metastatic potential clones, two isoforms of ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCH-L1) were downregulated. These results suggest that UCH-L1 expression seems to be associated with the metastatic potential of HRCC SN12C cell clones.     

Ruthenium(II) pyridylamine complexes with diimine ligands showing reversible photochemical and thermal structural change

Ruthenium(II)-TPA-diimine complexes, [Ru(TPA)(diimine)]2+ (TPA=tris(2-pyridylmethyl)amine; diimine=2,2'-bipyridine (bpy), 2,2'-bipyrimidine (bpm), 1,10-phenanthroline (phen)) were synthesized and characterized by spectroscopic and crystallographic methods. Their crystal structures demonstrate severe steric hindrance between the TPA and diimine ligands. They exhibit drastic structural changes on heating and photoirradiation at their MLCT bands, which involve partial dissociation of the tetradentate TPA ligand to exhibit a facially tridentate mode accompanied by structural change and solvent coordination to give [Ru(TPA)(diimine)(solvent)]2+ (solvent=acetonitrile, pyridine). The incoming solvent molecules are required to have pi-acceptor character, since sigma-donating solvent molecules do not coordinate. The thermal process is irreversible dissociation to give the solvent-bound complexes, which takes place by an interchange associative mechanism with large negative activation entropies. The photochemical process is a reversible reaction reaching a photostationary state, probably by a dissociative mechanism involving a five-coordinate intermediate to afford the same product as obtained in the thermal reaction. Quantum yields of the forward reactions to give dissociated products were lower than those of the backward reactions to recover the starting complexes. In the photochemical process, the conversions of the forward and backward reactions depend on the absorption coefficients of the starting materials and those of the products at certain wavelength, as well as the quantum yields of those reactions. The reversibility of the motions can be regulated by heating and by photoirradiation at certain wavelength for the recovery process. In the bpm system, we could achieve about 90 % recovery in thermal/photochemical structural interconversion.     

Simultaneous analytical optimization of variational parameters in Gaussian-type functions with full configuration interaction of multicomponent molecular orbital method by elimination of translational and rotational motions: application to isotopomers of the hydrogen molecule

We have extended the multicomponent molecular orbital (MCMO) method to the full-configuration interaction (full-CI) fully variational molecular orbital method by elimination of translational and rotational motion components from total Hamiltonian. In the MCMO scheme, the quantum effects of protons and deuterons as well as electrons can be directly taken into account. All variational parameters in the full-CI scheme, i.e., exponents and centers (alpha and R) in the Gaussian-type function (GTF) basis set as well as the CI coefficients, are simultaneously optimized by using their analytical gradients. The total energy of the H(2) molecule calculated using the electronic [6s3p2d1f] and nuclear [1s1p1d1f] GTFs is -1.161 726 hartree, which can be compared to the energy of -1.164 025 hartree reported using a 512 term-explicitly correlated GTF calculation. Although the d- and f-type nuclear GTFs contribute to the improvement of energy convergence, the convergence of electron-nucleus correlation energy is slower than that of electron-electron one. The nuclear wave functions are delocalized due to the electron-nucleus correlation effect compared to the result of Hartree-Fock level of MCMO method. In addition, the average internuclear distances of all diatomic molecules are within 0.001 A of the previously reported experimental results. The dipole moment of the HD molecule estimated by our method is 8.4 x 10(-4) D, which is in excellent agreement with the experimental result of (8-10) x 10(-4) D.     

Imaging of conformational changes of biotinylated triamide molecules covalently bonded to a carbon nanotube surface

A diamide molecule bearing a biotin terminus was bonded via an amide linkage to the surface of an aminated single-walled carbon nanotube and examined by a high-resolution transmission electron microscope. The still and movie images allowed us to study not only the conformation of the molecule but also its time evolution. An iterative sequence of modeling and simulation allowed us to assign one plausible conformation out of >10(8) possibilities. The images also provide direct support for the accepted wisdom that the curved regions of pristine carbon nanotubes are chemically reactive.     

Reversible heterolysis of H2 mediated by an M-S(thiolate) bond (M = Ir, Rh): a mechanistic implication for [NiFe] hydrogenase

Facile H2 heterolysis was found to be mediated by coordinatively unsaturated Cp*Ir and Cp*Rh thiolate complexes. The reaction of iridium complex is reversible, and the formation of an intermediary Ir-H/thiol complex was detected. The reversible conversion between thiolate complex+H2 and hydride complex+thiol provides an intriguing functional model of [NiFe] hydrogenase.