Theoretical study on naphthobischalcogenadiazole conjugated polymer systems and C61 derivative as organic photovoltaic semiconductors

We investigated the charge-transfer reactions of solar cells including a quaterthiophene copolymer with naphtho-bis-thiadiazole (PNTz4T) and naphtho-bis-oxadiazole (PNOz4T) using constrained density functional theory (CDFT). According to our calculations, the high electron-transfer rate results in a highly efficient solar cell, and the stable charge-transfer state results in low energy loss. Our computations imply that the following three factors are crucial to improve the performance of semiconducting polymers: (i) large structural changes following charge-transfer, (ii) narrow band gap, and (iii) spatially delocalized lowest unoccupied molecular orbital (LUMO) of the ground state

Novel 1,8-Naphthalimide derivative with an open space for an anion: Unique fluorescence behaviour depending on the binding anion’s electrophilic property

We have designed a novel 1,8-naphthalimide derivative with an open space for an anion. Computational calculation has predicted that the space could trap various anion species and photo-induced charge transfer depending on the anion's electrophilic properties. Indeed, the fluorescence behaviour of the 1,8-naphthalimide derivative complexes with each anion is consistent with the computational prediction

Theoretical Study of Singlet Oxygen Molecule Generation via an Exciplex with Valence-Excited Thiophene

Singlet-oxygen [O₂(¹Δ_g)] generation by valence-excited thiophene (TPH) has been investigated using multireference Møller–Plesset second-order perturbation (MRMP2) theory of geometries optimized at the complete active space self-consistent field (CASSCF) theory level. Our results indicate that triplet TPH­(1³B₂) is produced via photoinduced singlet TPH­(2¹A₁) because 2¹A₁ TPH shows a large spin–orbit coupling constant with the first triplet excited state (1³B₂). The relaxed TPH in the 1³B₂ state can form an exciplex with O₂(³Σ_g^–) because this exciplex is energetically more stable than the relaxed TPH. The formation of the TPH­(1³B₂) exciplex with O₂(³Σ_g^–) whose total spin multiplicity is triplet (T₁ state) increases the likelihood of transition from the T₁ state to the singlet ground or first excited singlet state. After the transition, O₂(¹Δ_g) is emitted easily although the favorable product is that from a 2 + 4 cycloaddition reaction

新奇光機能ナフタルイミド誘導体の理論・実験融合型基盤研究

科学研究費助成事業 研究成果報告書：基盤研究(B)2017-2020課題番号 : 17H0303

Assessment of Methodology and Chemical Group Dependences in the Calculation of the p<i>K</i>_a for Several Chemical Groups

We have investigated the dependencies of various computational methods in the calculation of acid dissociation constants (p<i>K</i>_a values) of certain chemical groups found in protonatable amino acids based on our previous scheme [Matsui; Phys. Chem. Chem. Phys. 2012, 14, 4181−4187]. By changing the quantum chemical (QC) method (Hartree–Fock (HF) and perturbation theory, and composite methods, or exchange–correlation functionals in density functional theory (DFT)), basis sets, solvation models, and the cavities used in the solvent models, we have exhaustively tested about 2,200 combinations to find the best combination for p<i>K</i>_a estimation among them. Of the tested parameters, the choice of the basis set and cavity is the most crucial to reproduce experimental values compared to other factors. Concerning the basis set, the inclusion of diffuse functions is quite important for carboxyl, thiol, and phenol groups judging from the mean absolute errors (MAEs) measured from the experimental values. Of the cavity models, between the Pauling, Klamt, and the universal force field (UFF) definitions, the UFF defined cavity is the best choice, resulting in the smallest MAEs. Concerning the QC methods, hybrid DFTs and range-separated DFTs always provide better results than pure DFTs and HF. As a result, we found that LC-ϖPBE/6-31+G­(d) with PCM-SMD/UFF provides the best p<i>K</i>_a estimation with a MAE within 0.15 p<i>K</i>_a units

Machine Learning Analysis for Photo-Induced Phenomena of 1-Methyl-3-(N-(1,8- Naphthalimidyl)ethyl)imidazolium Salts

1-Methyl-3-(N-(1,8-naphthalimidyl)ethyl)imidazolium (MNEI) salts show various photochemical phenomena depending on the guest anion. We used machine learning techniques to extract decisive factors that dominate the fate of MNEI salts after UV irradiation and prepared a decision tree diagram to deduce their photochemical phenomena before experiments

Molecular Dynamics and Quantum Chemical Approach for the Estimation of an Intramolecular Hydrogen Bond Strength in Okadaic Acid

We have evaluated the strength of intramolecular hydrogen bond in a protein based on molecular dynamics and quantum chemical calculation. To estimate the intramolecular hydrogen bond strength in okadaic acid (OA), we analyzed the influence of solvent and protonation states on the hydrogen bond and the entire structure. We performed molecular dynamics calculation and analyzed the strength of the hydrogen bond by measuring bond length and bond angle. The stable structure differs depending on the kind of solvent used and the protonation state of OA. Using the mean interaction energy from the quantum chemical calculation, hydrogen bond length and angle were investigated against bond energy. Although dielectric constant slightly depends on bond energy, the estimation of the intramolecular hydrogen bond strength in OA is possible even in a protein environment. The Coulomb interaction between OA and surrounding arginine produced a more negatively charged O1 in OA. The hydrogen bond energy in the deprotonated state is larger than that in the protonated state