Hybrid molecular orbitals for interacting systems. elucidation of catalytic activities

A method of orbital trasformations is applied to show the role of transition metal catalysis in nucleophilic additions to carbon:carbon double bonds.     

Combustion synthesis of high-quality diamond film suitable for application in electronic devices

The purpose of this research is to elucidate the electrical characteristics of a diamond film synthesized by combustion flame and synthesize a diamond film suitable for application in electronic devices. When the film contains amorphous carbon, the dielectric loss increases, i.e., the electrical characteristics of the diamond film are degraded. We employed three methods to decrease the amorphous carbon in the diamond film—the detection of the optimal equivalence ratio, addition of hydrogen into synthesizing gas, and heat treatment (annealing) of the diamond film. All these methods can decrease the amount of amorphous carbon effectively, thus systematically changing the factors influencing the optimal synthesis for improving the electric characteristics of the film. We have successfully developed a method for preparing a high-quality diamond film with excellent electrical characteristics that has no dielectric loss in the wide frequency range (10²–10⁸ Hz).     

Spectroscopic study of neutron shell closures via nucleon transfer in the near-dripline nucleus 23O

Neutron single particle energies have been measured in 23O using the 22O(d,p)23O*-->22O+n process. The energies of the resonant states have been deduced to be 4.00(2) MeV and 5.30(4) MeV. The first excited state can be assigned to the nu d3/2 single particle state from a comparison with shell model calculations. The measured 4.0 MeV energy difference between the nu s1/2 and nu d3/2 states gives the size of the N=16 shell gap which is in agreement with the recent USD05 ("universal" sd from 2005) shell model calculation, and is large enough to explain the unbound nature of the oxygen isotopes heavier than A=24. The resonance detected at 5.3 MeV can be assigned to a state out of the sd shell model space. Its energy corresponds to a approximately 1.3 MeV sized N=20 shell gap, therefore, the N=20 shell closure disappears at Z=8 in agreement with Monte Carlo shell model calculations using SDPF-M interaction.     

Square-wave Anodic Stripping Voltammetric Method for Novelty Detection of Bismuth Extracted by Aqueous Two-phase Systems

In this work, a voltammetric sensor was used to monitor the concentration of bismuth extracted from an eutectic alloy of BiSn by aqueous two-phase system. This strategy is a sustainable and economically viable way of recovering bismuth from secondary sources. In the aqueous two-phase system (ATPS), biodegradable and non-toxic constituents dispersed in water (major constituent) are used. For monitoring the extraction, bismuth was determined in the upper phase of the aqueous two-phase system, which is rich in L35 copolymer, that causes attenuation of the electrochemical signal (anodic peak current). The electrode and operational parameters of the square-wave anodic stripping voltammetry (SWASV) were evaluated according to the deposition and stripping processes of the bismuth on the surface of the carbon paste electrode (CPE). It was observed a similarity between the electrochemical response of the bismuth extracted by ATPS and with the standard solution of bismuth. The proposed method shows a linear range of 1.29–8.94 μmol L⁻¹, limit of detection (1.07 μmol L⁻¹) and limit of quantification (3.57 μmol L⁻¹) and good precision (RSD%=2.27 %). This method was validated by comparing the results with Flame Atomic Absorption Spectroscopy (FAAS), using statistical tests to verify precision and accuracy. In conclusion, using a voltammetric sensor to monitor the concentration of bismuth extracted by ATPS proved to be an efficient method, in agreement with the concentrations of the referenced method.     

Copper(I)-catalyzed highly efficient synthesis of benzoselenazoles and benzotellurazoles

A simple and practical useful synthetic method of 1,3-benzoselenazoles having a heteroatom substituent such as NRR', OR, and SR groups at the 2-position was developed by the copper(I)-catalyzed reaction of 2-bromophenyl (1) or 2-iodophenyl (2) isocyanides with selenium and heteroatom nucleophiles. In addition, the synthesis of 2-amino-1,3-benzotellurazoles is also described.     

Stereochemical studies of sialic acid derivatives by vibrational circular dichroism

Systematic VCD studies of N-acetylneuraminic acid (Neu5Ac), a recognition-related unique carbohydrate, were performed for the first time. Two pairs of anomeric isomers regarding a quaternary C2 asymmetric carbon of Neu5Ac derivatives were synthesized. VCD spectral patterns around the ester carbonyl region, as well as other Mid-IR regions, would be practical markers to distinguish the C2 stereochemistry.     

A surface plasmon resonance sensor on a compact disk-type microfluidic device

A surface plasmon resonance (SPR) sensor on a compact disk (CD)-type microfluidic device was developed to miniaturize the elements of a complete analytical system, pump and valves. The CD-type microfluidic device was fabricated by attaching a polydimethylsiloxane disk plate that contained microchannels and reservoirs to a flat polycarbonate disk plate that contained grating films with a thin layer of Au. The optical system of the SPR sensor and the theory for its operation are based on the principle of a grating coupled-type SPR. The sample and reagent solutions in the reservoirs on the CD-type microfluidic device were sequentially introduced into the detection chamber by centrifugal force generated by the rotation of the microfluidic device. The variation of resonance wavelength was dependent on the refractive index of the sample solution. This CD-type SPR sensor was successfully used in an immunoassay of immunoglobulin A (IgA). The anti-IgA, blocking reagent, sample and washing solution in the reservoirs were sequentially introduced into the detection chamber by changing the frequency of rotation of the microfluidic device. IgA in the sample solution was adsorbed to the anti-IgA immobilized on the Au thin layer in the detection chamber and was then detected by the SPR sensor.     

Singlet�Ctriplet energy gap for trimethylenemethane, oxyallyl diradical, and related species: single- and multireference computational results

We have investigated the through-bond exchange interactions in three non-Kekulé hydrocarbon diradicals on the basis of single- and multireference coupled cluster and related broken-symmetry (BS) methods. The singlet?Ctriplet energy gap (S-T gap) and diradical characters for these species are evaluated. It is found that the spin contamination involved in the BS solutions is non-negligible and the approximate spin-projection method greatly improves the usual BS solutions. As for Mukherjee??s state-specific multireference coupled cluster (MkMRCC) computations, the size-consistent correction with the UHF localized natural orbitals (ULO) is useful to obtain the qualitatively correct 2J values.     

Symmetry and broken symmetry in molecular orbital description of unstable molecules IV: comparison between single- and multi-reference computational results for antiaromtic molecules

First principle calculations of the effective exchange integrals (J) in the Heisenberg model for diradical species are presented for both symmetry-adapted multi-reference (MR) and single-reference broken-symmetry (BS) methods. The Mukherjee-type state-specific MR coupled cluster singles and doubles (MkCCSD) method with several different reference orbitals including BS natural orbitals is used to calculate the singlet?Ctriplet energy gaps (S?CT energy gap or 2J) and diradical characters for the antiaromatic molecules [a cyclopropenyl anion (CPA), b cyclobutadiene (CBD), and c cyclopentadienyl cation (CPC)], the cyclobutadiene derivatives with polar substitutents [d aminocyclobutadiene (ACBD), e formylcyclobutadiene (FCBD), and f 1-amino-2-formyl-cyclobutadiene (AFCBD)] and finally the cyclobutadine derivatives with radical substitutents [g 1,2-bis(methylene)cyclobutadiene (1,2-BMCBD) and h 1,3-bis(methylene)cyclobutadiene (1,3-BMCBD)]. For the BS methods, the spin-unrestricted Hartree?CFock based CCSD (UHF-CCSD), the CCD with the spin-unrestricted Brueckner determinant (UBD), and BS density functional theory (UDFT) computations are performed. Comparison between MkCCSD and the UHF-CCSD results indicates that spin-contamination of UHF-CCSD solutions still remains. In comparison with UHF-CCSD, the UBD results show that spin-contamination involved in BS solutions is greatly suppressed. To eliminate the spin contamination, an approximate spin-projection (AP) scheme is applied to the BS solutions. The AP procedure with the use of the expectation value of the total-spin operator corresponding to UHF-CCSD and UBD results yields good agreement with the MkCCSD results. As for the AP correction of the UDFT methods, three different computational schemes for predicting the expectation value of the total-spin operator are examined. Systematic comparisons between these methods are presented for the S?CT energy gaps (2J). Implications of the present computational results have been discussed in relation to the design of magnetic oligomers and polymers.     

Fe(z+) (z = 1-6) generation from ferrocene

Multiply charged iron atoms up to Fe(6+) with few carbon ions were produced from ferrocene under intense femtosecond laser fields. The production of Fe(4+) and Fe(5+) from ferrocene requires much less laser intensity than theoretically expected for iron atoms. The dissociation of ferrocene and the generation mechanism of multiply charged iron atoms are discussed.