Multiple Ionic-Covalent Couplings in Molecules and Clusters

The electronic states of molecules made of electropositive and electronegative components result from the interference between the covalent configurations and the ionic configurations. This work shows complex aspects of these ionic-covalent couplings in small molecules such as Li2H, Li2F, and Li4F. The extension of this type of analysis to the adsorption of the electrophilic molecules on the metal clusters or on the metal surfaces is supposed to lead to a radically new interpretation of the observed physical and chemical properties.     

Resonant Ionic,Covalent Bond,and Steric Characteristics Present in 1Σu+ States of Li2

The molecular bonding in the excited states of the alkali dimers involves the resonant ionic, covalent bond and steric interactions. We show here the case of the ¹Σ_u⁺ states of Li₂ by ab initio calculation. These interactions as functions of the internuclear distance lead to complex potential energy curves, providing an important application for high resolution laser spectroscopy. The spectroscopic constants for the 4 and 5 ¹Σ_u⁺ states are obtained for the first time.     

Heterogeneous photoredox catalysis using fluorescein polymer brush functionalized glass beads

Photocatalysis is a valuable and versatile method to perform a variety of chemical transformations under ambient temperatures and pressures using mild visible light. This work showcases an example of fluorescein-functionalized polymers grafted to micro-scale glass beads as heterogeneous photoredox catalysts. X-ray photoelectron spectroscopy and thermogravimetric analysis were used to analyze the resulting functional glass beads. Model reactions that are demonstrated include a cyclic condensation and a radical dehalogenation that can both be performed to high yields. Successful recyclability of the fluorescein polymer brush beads is demonstrated with detailed characterization confirming that photocatalytic polymer brushes remain tethered to the surface. As such, this allows for purification and reuse of the heterogeneous photocatalyst beads after simple filtration.     

Pancreatic lipase inhibition by C-glycosidic flavones Isolated from Eremochloa ophiuroides

Activity-guided fractionation of a methanolic extract of the leaves of Eremochloa ophiuroides (centipede grass) using a pancreatic lipase inhibitory assay led to the isolation and identification of a new C-glycosidic flavone, luteolin 6-C-?-D-boivinopyranoside (1), as well as eight known compounds. The structures of these compounds were established on the basis of interpretation of their spectroscopic data. Among these isolates, the C-glycosidic flavones 1-5 showed potent inhibitory effects on pancreatic lipase, with IC?? values ranging from 18.5 ± 2.6 to 50.5 ± 3.9 μM.     

Robust HLLC Riemann solver with weighted average flux scheme for strong shock

Many researchers have reported failures of the approximate Riemann solvers in the presence of strong shock. This is believed to be due to perturbation transfer in the transverse direction of shock waves. We propose a simple and clear method to prevent such problems for the Harten–Lax–van Leer contact (HLLC) scheme. By defining a sensing function in the transverse direction of strong shock, the HLLC flux is switched to the Harten–Lax–van Leer (HLL) flux in that direction locally, and the magnitude of the additional dissipation is automatically determined using the HLL scheme. We combine the HLLC and HLL schemes in a single framework using a switching function. High-order accuracy is achieved using a weighted average flux (WAF) scheme, and a method for v-shear treatment is presented. The modified HLLC scheme is named HLLC–HLL. It is tested against a steady normal shock instability problem and Quirk’s test problems, and spurious solutions in the strong shock regions are successfully controlled.     

Theoretical investigation of RbCs via two-component spin-orbit pseudopotentials: spectroscopic constants and permanent dipole moment functions

Potential energy curves for the 28 lowest LambdaSigma states and 49 Omega states of RbCs are obtained from large-scale multireference configuration interaction calculations using both spin-averaged and two-component spin-orbit energy-consistent effective core potentials. Spectroscopic properties of all states are compared across available data in literature to date. Variations of the permanent dipole moments on the internuclear separation (R) for the (1)Sigma(+), (3)Sigma(+), (1)Pi, and (3)Pi states are evaluated over a wide range of R. The most important effects of the spin-orbit interaction on the dipole moment distribution are discussed.     

Molecular properties and potential energy surfaces of the cyanides of the groups 1 and 11 metal atoms

Ab initio calculations on the metal (groups 1 and 11) cyanide complexes show two stable configurations for the ground state geometry, a linear cyanide (MCN) and a triangular (MNC) form with an obtuse M-N-C angle. Lithium complex may exist in a linear isocyanide (MNC) form, but it cannot be differentiated from the triangular configuration because of the flatness of the potential energy surface connecting the two isomers. The metal atom and cyano radical are bonded through a strongly ionic configuration (M+CN-) in both geometrical forms. The MNC triangular form is a very floppy structure having one low frequency for the bending mode, whereas the MCN linear form is more rigid. The CN complexes of the alkali atoms have a triangular geometry as the lowest energy conformer, while the noble metal atoms prefer the linear cyanide one. The relative stability of the two isomers, dipole moments, and effective charges are reported in this paper. The essential aspects of the potential energy surfaces for the ground and the first excited states exhibiting a closely avoided crossing are also explained.     

Synthesis and molecular structure analysis of nano‐sized methacryl‐grafted polysiloxane resin for fabrication of nano hybrid materials

The molecular structures of methacryl‐grafted polysiloxane resins from 3‐(trimethoxysilyl)propyl methacrylate (MPTS) and diphenylsilanediol (DPSD) were determined by theoretical computation and experimental measurement. The molecular structures obtained from theoretical computation coincided well with those from experimental measurement, and we found that the structural changes in the resins could be controlled by precursor compositions. While molecular weights and polysiloxane chain lengths of the resins increase with DPSD contents, their molecular sizes do not vary significantly. In the present study, molecular sizes and shapes of the resins with various compositions are hypothesized theoretically and proven experimentally. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 827–836, 2005