Does B3LYP correctly describe magnetism of manganese complexes with various oxidation numbers and various structural motifs?

We assessed the applicability and basis set dependency of the B3LYP functional to investigate magnetic interactions of Mn complexes. For the purpose, we constructed a test set consisting of 16 Mn complexes with various oxidation states and structural motifs.The B3LYP results correctly reproduced magnetism and magneto–redox correlation of the standard μ-oxo motifs with superexchange paths, while it does not work for weak magnetic complexes. We also showed that a modest basis set yields results similar to those of triple-zeta plus diffuse-and-polarization functions. This basis set is expected to be a standard basis set for investigating magnetism of manganese complexes.     

N-tert-Butylbenzenesulfenamide-catalyzed oxidation of alcohols to the corresponding carbonyl compounds with N-chlorosuccinimide

N-tert-Butylbenzenesulfenamide (1)-catalyzed oxidation of various primary and secondary alcohols to the corresponding aldehydes and ketones was efficiently carried out by using N-chlorosuccinimide (NCS) in the coexistence of potassium carbonate and molecular sieves 4 Å at easy-to-control temperatures ranging from 0°C to room temperature. The present catalytic oxidation was performed without giving any damage to the functional groups in alcohols, and was particularly effective in the oxidation of alcohols that formed labile aldehydes because of its mild reaction conditions. Further, selective oxidation of primary hydroxy groups took place in 1-catalyzed oxidation of several diols. Mechanistic investigation suggested that the chlorination of the sulfenamide 1 by NCS led to the formation of a key species, N-tert-butylbenzenesulfinimidoyl chloride (2), which in turn oxidized alcohols in the presence of potassium carbonate to afford carbonyl products by accompanying regeneration of the catalyst 1.     

Fractional occupation numbers and spin density functional calculations of degenerate systems

We implemented ab initio self‐consistent field (SCF) fractional occupation numbers (FON) calculation with Dunlap's interpolation scheme for the twisted ethylene, which is a prototype molecule of a σ–π biradical system. The calculational results are compared with those of complete‐active‐space (CAS) SCF and spin‐unrestricted Kohn–Sham (UKS) calculations on potential surfaces, occupation numbers of natural orbitals, and correlation entropies. It was found that the UKS methods gave similar results to CASSCF, while the FON solutions appeared in only the nearly complete degenerate region. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 317–323, 2003     

Synthesis of o-LiMnO2 by Microwave Irradiation and StudyIts Heat Treatment and Lithium Exchange

Microwave irradiation of a suspension of γ-MnOOH in a 4 mol dm⁻³ LiOH solution brought about a rapid formation of semicrystalline orthorhombic LiMnO₂ (o-LiMnO₂) within 30 min at 120°C. Cubic Li_1.6Mn_1.6O₄ was obtained by heating o-LiMnO₂ at 400°C; lithium could be topotactically extracted from Li_1.6Mn_1.6O₄ with acid to form cubic H_1.6Mn_1.6O₄.     

Metal-induced regulation of fullerene complexation with double-calix[5]arene

The metal-induced regulation of fullerene complexation with double-calix[5]arene is described. The receptor shows strong binding to C70 only in the presence of Cu+.     

The influence of correlation on the interpretation of Hund's multiplicity rule: A quantum Monte Carlo study

A systematic quantum Monte Carlo study of 2p atoms (C, N, O) and 3p atoms (Si, P, S) is performed to investigate the influence of correlation on the interpretation of Hund's multiplicity rule, which is an extension of our previous study of the carbon atom [J. Chem. Phys. 121, 7144 (2004)] to heavier atoms. The accuracy in the present study is significantly improved as compared with the previous study. A detailed analysis of the correlation contribution to individual energy components of the total energy is given beyond the self-consistent Hartree-Fock calculation. The stability of the highest spin-multiplicity state of all the atoms is ascribed to the greater electron-nucleus attraction energy that is gained at the cost of increasing the electron-electron repulsion energy as well as the kinetic energy. The present study demonstrates that correlation does not change the above conclusion due to the Hartree-Fock theory to support Boyd's less screening mechanism.     

Open-loop and closed-loop control of dissociative ionization of ethanol in intense laser fields

The relative yield of the C-O bond breaking with respect to the C-C bond breaking in ethanol cation C2H5OH+ is maximized in intense laser fields (10(13)-10(15) Wcm2) by open-loop and closed-loop optimization procedures. In the open-loop optimization, a train of intense laser pulses are synthesized so that the temporal separation between the first and last pulses becomes 800 fs, and the number and width of the pulses within a train are systematically varied. When the duration of 800 fs is filled with laser fields by increasing the number of pulses or by stretching all pulses in a triple pulse train, the relative yield of the C-O bond breaking becomes significantly large. In the closed-loop optimization using a self-learning algorithm, the four dispersion coefficients or the phases of 128 frequency components of an intense laser pulse are adopted as optimized parameters. From these optimization experiments it is revealed that the yield ratio of the C-O bond breaking is maximized as far as the total duration of the intense laser field reaches as long as approximately 1 ps and that the intermittent disappearance of the laser field within a pulse does not affect the relative yields of the bond breaking pathways.     

Shimalactone Biosynthesis Involves Spontaneous Double Bicyclo-Ring Formation with 8π-6π Electrocyclization

Shimalactones A and B are neuritogenic polyketides possessing characteristic oxabicyclo[2.2.1]heptane and bicyclo[4.2.0]octadiene ring systems that are produced by the marine fungus Emericella variecolor GF10. We identified a candidate biosynthetic gene cluster and conducted heterologous expression analysis. Expression of ShmA polyketide synthase in Aspergillus oryzae resulted in the production of preshimalactone. Aspergillus oryzae and Saccharomyces cerevisiae transformants expressing ShmA and ShmB produced shimalactones A and B, thus suggesting that the double bicyclo-ring formation reactions proceed non-enzymatically from preshimalactone epoxide. DFT calculations strongly support the idea that oxabicyclo-ring formation and 8π-6π electrocyclization proceed spontaneously after opening of the preshimalactone epoxide ring through protonation. We confirmed the formation of preshimalactone epoxide in vitro, followed by its non-enzymatic conversion to shimalactones in the dark.     

Enhanced Operational Durability of Thermally Activated Delayed Fluorescence-Based Organic Light-Emitting Diodes with a Triazine Electron Transporter

In organic light-emitting diodes (OLEDs) based on materials that show thermally activated delayed fluorescence (TADF), the internal quantum efficiency of 100 % can be obtained without using phosphorescence-based organometallics that contain rare metals. Therefore, with TADF-based emitters, it is possible to fabricate high-performing OLEDs at a lower cost. However, compared with fluorescence- and phosphorescence-based OLEDs, an understanding of degradation mechanisms in TADF-based OLEDs is still insufficient for future commercialization. In particular, it is widely recognized that the development of electron transport materials is crucial for improving OLED characteristics, especially driving voltages and operational durability. In this study, it was demonstrated that the operational durability of TADF-based OLEDs was greatly improved by introducing a triazine-based material of 2,4,6-tris(1,1′-biphenyl-4-yl)-[1,3,5]triazine (pT2T) as a hole-blocking layer (HBL) compared with a conventional HBL material of 2,4,6-tris(biphenyl-3-yl)-[1,3,5]triazine (T2T). Several experiments were carried out to make the reasons of the improved durability clearer, and attributed the improved durability to the shift of a carrier recombination zone from the emitting layer/HBL interface and the suppressed formation of excited-state quenchers in the pT2T HBL, because of the higher electron mobility of pT2T and the better stability of its radical anion state.