Possibilities of Density Functional Theory in Standardless Quantitative Spectral Analysis

Density functional theory can be used in the quantitative analysis of substances by their IR spectra in cases when high precision is not necessary or certified reference samples are principally unavailable or are difficult to obtain. IR spectra of 30 complex organic molecules including different heteroatoms (Br, Cl, F, N, O) were calculated using the Gaussian98w program (6-31G) basis set. The calculated spectra were compared with experimental ones, and quantitative inverse spectral problems (calculation of concentrations) were solved for all of the molecules studied. It was shown that the found concentrations for the majority of the studied substances differ from their true concentrations by no more than 30%, which is acceptable, for example, for ecological monitoring.     

Statement of quantum problems for “hot” molecules and solution of the Schrödinger equation for electron states in the field of distributed nuclear charges

The issue concerning the basics of statement of the problem of determining the energy levels and wave functions of the “hot” (vibrationally excited) molecule and the states of electrons in the field of spatially distributed nuclear charges has been considered. It has been shown that such a problem in which nonadiabaticity is taken into accounted in part from the very beginning can be reduced to the conventional problem by changing the AO type.     

Variational Approach to the General Problem Of Vibrational-Rotational States of Molecules

A new method is proposed to calculate energy levels and wave functions of vibrational-rotational molecular states without the necessity to separate the types of motion. The procedure is described to find the corresponding energy matrix which is diagonalized to obtain the final solution. The simplicity of computing matrix elements makes it possible to analyze very large molecules.     

An F. and M. Riesz Theorem on the Complex Sphere

Let μ be a measure on the complex sphere. Denote by μ_pq the projection of μ on H(p, q), the space of complex spherical harmonics. Assume that μ_pq = 0 if (p − 1)q ≠ 0, and ∥μ_1q∥_∞ → 0 as q → ∞. Then μ is absolutely continuous with respect to Lebesgue measure on the sphere.     

Standardless Analysis of Multicomponent Mixtures of Substances by Time-Resolved Vibronic Spectroscopy

A new approach to the quantitative and qualitative standardless analysis of complex substances based on experimental time-dependent vibronic luminescence spectra (in the UV and visible regions) is proposed. The approach requires no preliminary calculation of absolute intensities for molecular models. It is shown that this analysis can be carried out for both individual substances and multicomponent mixtures, including unknown substances and mixtures of unknown composition. The concentration ranges of mixture components available for the analysis are evaluated, depending on the optical properties of mixtures.     

Ruthenium-Catalyzed Coupling Reactions of CO2 with C2H4 and Hydrosilanes towards Silyl Esters

A series of in situ-prepared catalytic systems incorporating Ru^II precursors and bidentate phosphine ligands has been probed in the reductive carboxylation of ethylene in the presence of triethylsilane as reductant. The catalytic production of propionate and acrylate silyl esters was evidenced by high-throughput screening (HTS) and implemented in batch reactor techniques. The most promising catalyst systems identified were made of Ru(H)(Cl)(CO)(PPh₃)₃ and 1,4-bis(dicyclohexylphosphino)butane (DCPB) or 1,1’-ferrocene-diyl-bis(cyclohexylphosphine) (DCPF). A marked influence of water on the acrylate/propionate selectivity was noted. Turnover numbers [mol mol(Ru)⁻¹] up to 16 for acrylate and up to 68 for propionate were reached under relatively mild conditions (20 bar, 100 °C, 0.5 mol % Ru, 40 mol % H₂O vs. HSiEt₃). Possible mechanisms are discussed.     

Pluriharmonic Clark measures and analogs of model spaces

Let $B_d$ denote the unit ball of ${\mathbb{C}}^d$, $d\ge 1$. Given an inner function $I:B_d\to B_1$, we study the corresponding family ${\sigma }_{\alpha }[I]$, $\alpha \in ?B_1$, of pluriharmonic Clark measures on the complex sphere. We introduce and investigate related unitary operators $U_{\alpha }$ mapping analogs of model spaces onto $L^2({\sigma }_{\alpha })$, $\alpha \in ?B_1$. In particular, we explicitly characterize the set of $U_{\alpha }^{?}f$ such that $f{\sigma }_{\alpha }$ is a pluriharmonic measure.     

Scanning tunneling microscopy/spectroscopy study of atomic and electronic structures of In2O on InAs and In0.53Ga0.47As(001)-(4×2) surfaces

Interfacial bonding geometry and electronic structures of In(2)O on InAs and In(0.53)Ga(0.47)As(001)-(4×2) have been investigated by scanning tunneling microscopy/scanning tunneling spectroscopy (STM/STS). STM images show that the In(2)O forms an ordered monolayer on both InAs and InGaAs surfaces. In(2)O deposition on the InAs(001)-(4×2) surface does not displace any surface atoms during both room temperature deposition and postdeposition annealing. Oxygen atoms from In(2)O molecules bond with trough In/Ga atoms on the surface to form a new layer of O-In/Ga bonds, which restore many of the strained trough In/Ga atoms into more bulklike tetrahedral sp(3) bonding environments. STS reveals that for both p-type and n-type clean In(0.53)Ga(0.47)As(001)-(4×2) surfaces, the Fermi level resides near the valence band maximum (VBM); however, after In(2)O deposition and postdeposition annealings, the Fermi level position is close to the VBM for p-type samples and close to the conduction band minimum for n-type samples. This result indicates that In(2)O bonding eliminates surface states within the bandgap and forms an unpinned interface when bonding with In(0.53)Ga(0.47)As/InP(001)-(4×2). Density function theory is used to confirm the experimental finding.     

Transport properties of Nafion membranes modified with tetrapropylammonium ions for direct methanol fuel cell application

This work presents a study of transport properties (proton conductivity, methanol permeability, and water uptake) and acid-base properties of commercial Nafion-112, -115, and -117 membranes modified with tetrapropylammonium (TPA) cations. In the interaction between TPA hydroxide and protons of sulfonate groups in the Nafion matrix, some of the protons are shown to be bound to sulfonate groups and do not participate in transport processes. These findings are confirmed by IR spectroscopy, acid-base titration, and data on proton conductivity of the modified membranes. Proton conductivity of the modified membranes is shown to be effectively described by a percolation model with parameters that agree with published data for commercial Nafion membranes. Based on these results, a model is proposed for the interaction of TPA cations with the sulfonate groups in Nafion membranes. According to this model, TPA cations form hydrophobic clusters in hydrophilic regions of the polymer matrix, thus preventing some of the protonated sulfonate groups from participating in transport processes.