A Geminal Method Based on the Generalized Electron Pairing Applied to the Heisenberg Model of Hydrocarbons

In the approximate valence bond (VB) description of molecular electronic structures, the resonating VB effect might be incorporated in an efficient manner by mixing the triplet component into conventional singlet geminals. We developed a variational optimization scheme for this generalized pairing type wave function in the framework of the spin Hamiltonian model. With numerical verifications, we found the resonance stabilization is partially described through the contamination of higher spin states for molecules such as non-Kekulé hydrocarbons

〔論文〕募金広告におけるエージェントの存在が寄付行動に及ぼす影響

　　Anthropomorphic agents are utilized to support people in their day-to-day lives. For instance, studies suggest that anthropomorphic agents serve to enhance purchase intent and prosocial behavior in advertising and on ecommerce websites (Kimura et al. 2012, etc.). The current study investigates whether anthropomorphic agents promote donations, a kind of prosocial behavior, in an advertising context. In Experiment 1, we used two advertisements that differ in context － one asserting the necessity for aid and the other asserting the effectiveness of aid － to examine whether congruence with the agent’s facial expression (smiling/crying) and the ad description (context) promotes donation behavior. Here, the agent’s presence did not exert an influence. When comparing two types of agents with different attributes (people calling for donations/children needing donations) in Experiment 2, donation amounts increased when children needing donations, rather than people calling for donations, served as anthropomorphic agents

A geminal theory based on the generalized electron pairing

As in the hierarchy of the Hartree–Fock theory in terms of spin symmetry, the extension of spin functions in a theory of two-electron units or geminal, was developed in this study. A trial wave function is constructed as an antisymmetrized product of geminals, in which singlet and triplet two-electron functions are fully mixed. We present a variational optimization method for this generalized pairing wave function in the strong orthogonality condition. The present method is considered an extension of the antisymmetrized product of strongly orthogonal geminals or perfect pairing generalized valence bond methods, maintaining the compactness of the trial wave function. The obtained broken-symmetry solutions were similar to the unrestricted Hartree–Fock wave functions in terms of spin contamination while giving lower energy due to the inclusion of the electron correlation effect in geminals. The degeneracy of the obtained broken-symmetry solutions in the Sz space is reported for the tested four-electron systems

Cobalt(I)-Catalyzed Reductive Cyclization of Enynes and Diynes Using Hydrogen Gas as a Reductant

Reductive cyclization of enynes and diynes by using H2 gas as a reductant was realized, and the corresponding cyclized products were obtained in good yields without olefin isomerization and over-reduction of the products. By an experiment using D2 instead of H2, it was confirmed that H2 unambiguously operates as a reductant in this reaction. The protocol of the reaction is very economical and user-friendly, using air- and moisture-stable CoBr2·6H2O and 1 atm of pressure of H2

Extraction of local spin-coupled states by second quantized operators

We present a methodology for analyzing chemical bonds embedded in the electronic wave function of molecules, especially in terms of spin correlations or so-called “local spin.” In this paper, based on biorthogonal second quantization, the spin correlation functions of molecules are naturally introduced, which enables us to extract local singlet and local triplet elements from the wave function. We also clarify the relationship between these spin correlations and traditional chemical concepts, i.e., resonance structures. Several chemical reactions, including the intramolecular radical cyclization and the formation of preoxetane, are demonstrated to verify the analysis method numerically

A catalyzed E/Z isomerization mechanism of stilbene using para-benzoquinone as a triplet sensitizer

Sensitizer molecules affect not only the quantum yield but also the selectivity of photochemical reactions. For an appropriate design of sensitized photochemical processes, we need to elucidate the reaction mechanism in detail. Here we investigated the mechanism of photoisomerization of stilbene via the triplet state with a para-benzoquinone sensitizer using density functional theory. In general, the isomerization of stilbene via the triplet state exhibits (Z)-selectivity (cis-selectivity); however, the para-benzoquinone sensitizer changes it to (E)-selectivity (trans-selectivity). The calculations showed that stilbene and para-benzoquinone form stable exciplexes having a preoxetane structure. The E/Z isomerization occurred via this exciplex, in which para-benzoquinone acted as a photocatalyst rather than a sensitizer only providing excitation energy. The spin-density distribution of the exciplex differed from the isolated stilbene in the triplet state. Therefore, the stilbene moiety could take (E)-conformation in the exciplex. The intermolecular charge-transfer drove the exciplex formation. This specific reaction mechanism originated from the electron-accepting ability of para-benzoquinone in the triplet state

An analysis of valence electronic structure from a viewpoint of resonance theory: Tautomerization of formamide and diazadiboretidine

The resonance theory is still very useful in understanding the valence electron structure. However, such a viewpoint is not usually obtained by general-purpose quantum chemical calculations, instead requires rather special treatment such as valence bond methods. In this study, we propose a method based on second quantization to analyze the results obtained by general-purpose quantum chemical calculations from the local point of view of electronic structure and analyze diazadiboretidine and the tautomerization of formamide. This method requires only the “PS”-matrix, consisting of the density matrix (P-matrix) and overlap matrix, and can be computed with a comparable load to that of Mulliken population analysis. A key feature of the method is that, unlike other methods proposed so far, it makes direct use of the results of general-purpose quantum chemical calculations

An analysis of valence electronic structure from a viewpoint of resonance theory: Tautomerization of formamide and diazadiboretidine

The resonance theory is still very useful in understanding the valence electron structure. However, such a viewpoint is not usually obtained by general-purpose quantum chemical calculations, instead requires rather special treatment such as valence bond methods. In this study, we propose a method based on second quantization to analyze the results obtained by general-purpose quantum chemical calculations from the local point of view of electronic structure and analyze diazadiboretidine and the tautomerization of formamide. This method requires only the “PS”-matrix, consisting of the density matrix (P-matrix) and overlap matrix, and can be computed with a comparable load to that of Mulliken population analysis. A key feature of the method is that, unlike other methods proposed so far, it makes direct use of the results of general-purpose quantum chemical calculations

Menstrual Cycle Modulates Motor Learning and Memory Consolidation in Humans

Numerous studies have noted that sex and/or menstrual phase influences cognitive performance (in particular, declarative memory), but the effects on motor learning (ML) and procedural memory/consolidation remain unclear. In order to test the hypothesis that ML differs across menstrual cycle phases, initial ML, overlearning, consolidation, and final performance were assessed in women in the follicular, preovulation and luteal phases. Primary motor cortex (M1) oscillations were assessed neuro-physiologically, and premenstrual syndrome and interoceptive awareness scores were assessed psychologically. We found not only poorer performance gain through initial ML but also lower final performance after overlearning a day and a week later in the luteal group than in the ovulation group. This behavioral difference could be explained by particular premenstrual syndrome symptoms and associated failure of normal M1 excitability in the luteal group. In contrast, the offline effects, i.e., early and late consolidation, did not differ across menstrual cycle phases. These results provide information regarding the best time in which to start learning new sensorimotor skills to achieve expected gains

Solvation in nitration of benzene and the valence electronic structure of the Wheland intermediate

Nitration of benzene is a representative aromatic substitution reaction related to the σ-complex (arenium ion or “Wheland” intermediate) concept. This reaction is typically carried out in a mixed acid solution to generate nitronium ions, and how solvent molecules play roles in the reaction has been of great interest. Here we will shed new light on the reaction, namely the electronic structure and the microscopic insights of the solvation, which have been rarely discussed so far. We studied this process using the reference interaction site model-self consistent field with constrained spatial electron density distribution (RISM-SCF-cSED) method, considering sulfuric acid or water molecules as a solvent. In this method, the electronic structure of the solute and the solvation structure are self-consistently determined based on quantum chemistry and statistical mechanics of molecular liquids. The solvation free energy surfaces in solution and solvation structures were verified. In the bond formation process of benzene and nitronium ions, the solvation structure by sulfuric acid molecules drastically changes and the solvation effect on the free energy is quite large. We revealed largely contributing resonance structures in the π-electron system of the σ-complex in gas and solution phases by analysing the valence electronic structures