A new method to reconstruct three-dimensional spatial distribution function from radial distribution function in solvation structure

Three-dimensional spatial distribution function (SDF) of solvent is a fundamental quantity for analysis of solvation. However, its calculation has been very limited because long computational time is required. We here developed a novel and robust method to construct approximated SDFs of solvent sites from radial distribution functions. In this method, the expansion of SDFs in real solid harmonics around atoms of solute leads to a linear equation, from which SDFs are evaluated with reasonable computational time. This method is applied to the analysis of the solvation structure of liquid water, as an example. The successful results clearly show that this method is very powerful to investigate solvation structure.     

A new analysis of molecular orbital wave functions based on resonance theory

A new method to evaluate the weights of resonance structures from molecular orbital wave function is proposed, which is based on the second quantization of singlet-coupling. The present method is useful to analyze molecules of which the electronic structures are well localizable. The evaluation is carried out through localization of molecular orbitals followed by algebraic calculation of density matrices. This method is applied to H(2)O, H(3)O(+), and BH(3). The calculated weights of covalent and ionic structures are in excellent agreement with those of the previous works and our chemical intuition.     

Numerical Verification Methods for Solutions of the Free Boundary Problem

We propose two methods to enclose the solution of an ordinary free boundary problem. The problem is reformulated as a nonlinear boundary value problem on a fixed interval including an unknown parameter. By appropriately setting a functional space that depends on the finite element approximation, the solution is represented as a fixed point of a compact map. Then, by using the finite element projection with constructive error estimates, a Newton-type verification procedure is derived. In addition, numerical examples confirming the effectiveness of current methods are given.     

Transition‐Metal‐Mediated Cleavage of Fluoro‐Silanes under Mild Conditions

Si?F bond cleavage of fluoro‐silanes was achieved by transition‐metal complexes under mild and neutral conditions. The Iridium‐hydride complex [Ir(H)(CO)(PPh₃)₃] was found to readily break the Si?F bond of the diphosphine‐ difluorosilane {(o‐Ph₂P)C₆H₄}₂Si(F)₂ to afford a silyl complex [{[o‐(iPh₂P)C₆H₄]₂(F)Si}Ir(CO)(PPh₃)] and HF. Density functional theory calculations disclose a reaction mechanism in which a hypervalent silicon species with a dative Ir→Si interaction plays a crucial role. The Ir→Si interaction changes the character of the H on the Ir from hydridic to protic, and makes the F on Si more anionic, leading to the formation of H^δ+???F^δ? interaction. Then the Si?F and Ir?H bonds are readily broken to afford the silyl complex and HF through σ‐bond metathesis. Furthermore, the analogous rhodium complex [Rh(H)(CO)(PPh₃)₃] was found to promote the cleavage of the Si?F bond of the triphosphine‐monofluorosilane {(o‐Ph₂P)C₆H₄}₃Si(F) even at ambient temperature.     

Structural-Deformation-Energy-Modulation Strategy in a Soft Porous Coordination Polymer with an Interpenetrated Framework

To achieve unique molecular-recognition patterns, a rational control of the flexibility of porous coordination polymers (PCPs) is highly sought, but it remains elusive. From a thermodynamic perspective, the competitive relationship between the structural deformation energy (E_def) of soft PCPs and the guest interaction is key for selective a guest-triggered structural-transformation behavior. Therefore, it is vital to investigate and control E_def to regulate this competition for flexibility control. Driven by these theoretical insights, we demonstrate an E_def-modulation strategy via encoding inter-framework hydrogen bonds into a soft PCP with an interpenetrated structure. As a proof of this concept, the enhanced E_def of PCP enables a selective gate-opening behavior toward CHCl₃ over CH₂Cl₂ by changing the adsorption-energy landscape of the compounds. This study provides a new direction for the design of functional soft porous materials.     

Reactions of a Silylyne Complex with Aldehydes: Formation of W−Si−O−C Four-Membered Metallacycles and Their Metathesis-Like Fragmentation

A tungsten silylyne complex having a W≡Si triple bond reacted with two molecules of aldehydes at room temperature to give W−Si−O−C four-membered metallacycles by [2+2] cycloaddition and subsequent formyl hydrogen transfer from one aldehyde molecule to another. Upon heating to 70 °C, the four-membered metallacycles underwent metathesis-like fragmentation cleanly to afford carbyne complexes and “silanoic esters,” in a manner similar to that of metallacyclobutadiene, an intermediate of alkyne metathesis reactions, and dimerization of the latter products gave 1,3-cyclodisiloxanes. The “silanoic ester” was also trapped by pivalaldehyde to give a [2+2] cycloaddition product in high yield.     

Fine-tuning of boron complexes with cage-shaped ligand geometry: rational design of triphenolic ligand as a template for structure control

Boron complexes surrounded with organic cages were controlled precisely by a remote atom placed at the bottom of the cage. A replacement of the bottom tether atom (carbon or silicon) changed the characteristics (kinetic and thermodynamic factors) of boron complexes by geometric effects. A theoretical study shows that the bottom atoms also control eigenvalues of MO. This cage complex will provide a systematic template for fine-tuning of metal complexes to create various properties.     

Towards single biomolecule handling and characterization by MEMS

Applications of microelectromechanical systems (MEMS) technology are widespread in both industrial and research fields providing miniaturized smart tools. In this review, we focus on MEMS applications aiming at manipulations and characterization of biomaterials at the single molecule level. Four topics are discussed in detail to show the advantages and impact of MEMS tools for biomolecular manipulations. They include the microthermodevice for rapid temperature alternation in real-time microscopic observation, a microchannel with microelectrodes for isolating and immobilizing a DNA molecule, and microtweezers to manipulate a bundle of DNA molecules directly for analyzing its conductivity. The feasibilities of each device have been shown by conducting specific biological experiments. Therefore, the development of MEMS devices for single molecule analysis holds promise to overcome the disadvantages of the conventional technique for biological experiments and acts as a powerful strategy in molecular biology. Figure Towards single bio molecular handling and characterization by MEMS