Aromaticity Relocation in Perylene Derivatives upon Two‐Electron Oxidation To Form Anthracene and Phenanthrene

We prepared perylene dications 1 ²⁺ and 2 ²⁺ by using “capped” perylene derivatives, and for the first time, successfully obtained single crystals of a perylene dication 1 ²⁺ that enabled us to perform its structural analysis. We realized that the substituted aryl groups on perylene control the positions of positive charges, thus the remaining electronic system satisfies Clar's sextet rule toward the highest number of localized sextets. Experimental and theoretical evidence proved that Clar's aromatic π‐sextet rule could be applied even for the dicationic perylenes in a very simple way.     

Visible-Light-Induced Heptacene Generation under Ambient Conditions: Utilization of Single-crystal Interior as an Isolated Reaction Site

The photo-induced generation of unstable molecules generally requires stringent conditions to prevent oxidation and the concomitant decomposition of the products. The visible-light-induced conversion of two heptacene precursors to heptacene was studied. Single crystals of bis- and mono-α-diketone-type heptacene precursors ( 7-DK2 and 7-DK1 , respectively), were prepared to investigate the effect of precursor structure on reactivity. The photoirradiation of a 7-DK2 single crystal cleaved only one α-diketone group, forming an intermediate bearing a pentacene subunit, while that of a 7-DK1 single crystal gave rise to characteristic absorption peaks of heptacene and their increase in intensity with photoirradiation time, indicating the generation of heptacene without decomposition. Heptacene production was not observed when the precursors were photoirradiated in solution, implying that the single crystal interior provided isolation from the external environment, thus preventing heptacene oxidation.     

Synthesis and Metalation of Doubly o‐Phenylene‐Bridged Cyclic Bis(dipyrrin)s with Highly Bent Skeleton of Dibenzoporphyrin(2.1.2.1)

Facile synthesis of dibenzoporphyrins(2.1.2.1) has been successfully reported by the simple condensation reaction of o‐dipyrrolylbenzene with various aldehydes in the presence of a Lewis acid. This reaction enables the preparation of various dibenzoporphyrin(2.1.2.1) derivatives with p‐substituted phenyl groups, five‐membered heterocycles, and ethynyl groups at the meso‐positions. Dibenzoporphyrins(2.1.2.1) consist of two dipyrrin units that are connected by o‐phenylene bridges, which adopt highly bent saddle‐shaped structures; this was confirmed by X‐ray diffraction analysis. We found that dibenzoporphyrin(2.1.2.1) can be described as a 20π antiaromatic conjugated system, but practically, it is not an antiaromatic macrocycle, which we revealed by ¹H NMR spectroscopy. The redox potentials had good correlations with Hammett substituent constant (σ_p) of the substituents at the meso‐positions. The free‐base dibenzoporphyrin(2.1.2.1) was able to form the metal complexes with nickel(II), copper(II), palladium(II), platinum(II), and tin(IV) ions. These results suggested that dibenzoporphyrin(2.1.2.1) derivatives can be utilized as novel macrocyclic dianionic tetradentate ligands for various metal ions to give complexes with varying optical and electrochemical properties.     

Regioselective protection of sugars catalyzed by dimethyltin dichloride

The first catalytic process for protection of hydroxyl groups in sugars has been developed. Highly regioselective protection was accomplished along with high chemical yield. The regioselectivity of the benzoylation was realized as an intrinsic character of sugars based on a stereorelationship among their hydroxyl groups. Furthermore, complete protection of alpha-methyl glucoside and beta-methyl xyloside was accomplished.     

Enhanced Four-Electron Oxygen Reduction Selectivity of Clamp-Shaped Cobalt(II) Porphyrin(2.1.2.1) Complexes

The molecular structure, electrochemistry, spectroelectrochemistry and electrocatalytic oxygen reduction reaction (ORR) features of two Co^II porphyrin(2.1.2.1) complexes bearing Ph or F₅Ph groups at the two meso-positions of the macrocycle are examined. Single crystal X-ray analysis reveal a highly bent, nonplanar macrocyclic conformation of the complex resulting in clamp-shaped molecular structures. Cyclic voltammetry paired with UV/Vis spectroelectrochemistry in PhCN/0.1 M TBAP suggest that the first electron addition corresponds to a macrocyclic-centered reduction while spectral changes observed during the first oxidation are consistent with a metal-centered Co^II/Co^III process. The activity of the clamp-shaped complexes towards heterogeneous ORR in 0.1 M KOH show selectivity towards the 4e⁻ ORR pathway giving H₂O. DFT first-principle calculations on the porphyrin catalyst indicates a lower overpotential for 4e⁻ ORR as compared to the 2e⁻ pathway, consistent with experimental data.     

Measurement of sugars using the laser spray technique with a gold capillary

A gold (Au) capillary has higher thermal conductivity than a stainless steel capillary and can withstand capillary over-heating induced by high CO(2) laser irradiation (over 2.5 W) better than a stainless steel capillary. For this study, a laser spray using an Au capillary was applied for the detection of sugars. The signal of cationized compounds [M+Na](+) can be detected with higher sensitivity than with conventional laser sprays using high laser power (over 2.7 W). Using 3.5 W of laser power, the signal intensity is 15 times higher than the maximum value with stainless steel (2.3 W) in a 10(-5) M maltose aqueous solution. It is considered that almost all the water molecules evaporate by laser irradiation, which is impossible to achieve using a stainless steel capillary.     

Nonlinear magneto-optical effects and photomagnetism of electrochemically synthesized molecule-based magnets

This article describes novel optical functionalities such as photomagnetic effects and magnetization-induced second harmonic generation (MSHG) in several cyano-bridged metal assemblies. Single crystal- and film-types of a cyano-bridged Cu–Mo bimetallic assembly, , were electrochemically prepared. When this compound was irradiated with light, spontaneous magnetization with a Curie temperature (T _C) of 23 K was observed. Electrochemically prepared Fe^II[Cr^III(CN)₆]_2/3·5H₂O thin film, which was a ferromagnet with T _C=21 K, showed photoreduced magnetization. This photomagnetism is due to the change of ferromagnetic coupling between Fe^II and Cr^III. MSHG was observed in Cs^ICo^II[Cr^III(CN)₆]·0.5H₂O. This -type Prussian blue analog-based magnet is proven to be a piezoelectric ferromagnet, i.e., condensed matter with both piezoelectric and ferromagnetism. This MSHG is due to the coupling between a piezoelectric structure of and ferromagnetism with a T _C of 46 K.

Ambient-pressure organic superconductors kappa-(DMEDO-TSeF)2[Au(CN)4](solv.): Tc tuning by modification of the solvent of crystallization

The unsymmetrical pi donor dimethyl(ethylenedioxy)tetraselenafulvalene (DMEDO-TSeF) has provided six new organic superconductors with a monovalent square-planar [Au(CN)(4)](-) ion and cyclic ethers as solvent of crystallization. The six new organic superconductors kappa-(DMEDO-TSeF)(2)[Au(CN)(4)](solv.) [solv.=1,3-dioxolane (DOL), 2,5-dihydrofuran (DHF), tetrahydropyran (THP), 1,3-dioxane (1,3-DOX), 3,4-dihydro-2H-pyran (DHP), or 1,4-dioxane (1,4-DOX)] are classified into two subphases kappa(L) and kappa' according to the differences in their space group symmetry. kappa(L)-(DMEDO-TSeF)(2)[Au(CN)(4)](solv.) (solv.=DOL, DHF, THP, 1,3-DOX or DHP) crystallizes in the orthorhombic space group Pnma, and T(c) of the kappa(L) phase varies by 1.7-5.3 K according to the size and shape of the solvent of crystallization. On the other hand, kappa'-(DMEDO-TSeF)(2)[Au(CN)(4)](solv.) (solv.=DOL or 1,4-DOX) crystallizes in the noncentrosymmetric monoclinic space group Cc. The kappa'-phase containing 1,4-DOX shows superconductivity at 4.2 K, but the kappa'-phase containing DOL does not show superconductivity down to 1.4 K. Systematic investigation of the six new organic superconductors, together with the two previously reported superconductors kappa(H)- and kappa(L)-(DMEDO-TSeF)(2)[Au(CN)(4)](THF), revealed that the T(c) of the present system is finely tunable by utilizing the effect of the solvent of crystallization.     

Analysis of antitumor active OSW-1 and its analogues by liquid chromatography coupled with electrospray and atmospheric pressure chemical ionization quadrupole mass spectrometry

Three cholestane glycosides including OSW-1 with antitumor activity and two new analogues with modified steroidal side chains, thienyl OSW-1 and silylated thienyl OSW-1, were synthesized. Analyses were performed using optimized, reversed-phase liquid chromatography (LC) with electrospray ionization and atmospheric pressure chemical ionization quadrupole mass spectrometry (MS). The ionization mode and polarity, cone voltage, and chromatographic conditions were evaluated. The optimum LC/MS conditions to obtain valuable ions, indispensable for identifying the structures, are described. The key fragmentation pathways, which will be useful for confirming the detailed structures of steroidal glycosides, are also proposed.