CHEMISTRY OF 1,3-OXAZINE-6-THIONES. RING TRANSFORMATION

Abstract

Two 1,3-oxazine-6-thione derivatives obtained by “S,N-Double Rearrangement²” reacted with several nucleophiles to produce 1,3-diazin-6-ones, 6-imino-1,3-oxazines, 1,3,4-triazoles, 1,2,4-oxadiazoles, and 1,3-thiazol-6-ones. Their ring transformations are discussed.     

A minimal implementation of the AMBER-GAUSSIAN interface for ab initio QM/MM-MD simulation

For applying to a number of theoretical methodologies based on an ab initio quantum mechanical/molecular mechanical (QM/MM) molecular dynamics method connecting AMBER9 with GAUSSIAN03, we have developed an AMBER-GAUSSIAN interface (AG-IF), which can be one of the simplest architectures. In the AG-IF, only a few subroutines addition is necessary to retrieve the QM/MM energy and forces, obtained by GAUSSIAN, for solving a set of Newtonian equations of motion in AMBER. It is, therefore, easy to be modified for individual applications since AG-IF utilizes most of those functions originally equipped not only in AMBER but also in GAUSSIAN. In the present minimal implementation, only AMBER is modified, whereas GAUSSIAN is left unchanged. Moreover, a different method of calculating electrostatic forces of MM atoms interacting with QM region is proposed. Using the AG-IF, we also demonstrate three examples of application: (i) the QM versus MM comparison in the radial distribution function, (ii) the free energy gradient method, and (iii) the charge from interaction energy and forces.     

Colorimetric response of spiropyran derivative for anions in aqueous or organic media

We previously found that a simple spiropyran derivative (1:1′,3′,3′-trimethyl-6-nitro-spiro-[2H-1-benzopyran-2,2′-indoline]) behaves as a selective and sensitive cyanide anion (CN⁻) receptor in aqueous media under UV irradiation¹³. The receptor, when irradiated by UV light in a water/MeCN mixture, creates a CN⁻-selective absorption band via a nucleophilic addition of CN⁻ to 1 (formation of the 1-CN⁻ species) and allows quantitative determination of very low levels of CN⁻. In the present work, effects of pH and water content on the response of 1 to anions were studied to clarify the detailed properties of 1. In aqueous media, 1 reacts selectively with CN⁻regardless of pH and water content, but the reaction is suppressed by a decrease in pH and an increase in water content due to the protonation of CN⁻. In contrast, in pure MeCN, addition of F⁻ also creates a new absorption band, as does CN⁻. This is promoted via a nucleophilic interaction between 1 and F⁻ in a 1:2 stoichiometry (formation of the 1-2F⁻ species). The 1-CN⁻ and 1-2F⁻ species have different photochemical properties; the 1-CN⁻ species is stable upon UV irradiation, while the UV irradiation of the 1-2F⁻ species leads to a decomposition of the spiropyran platform.     

Solid polymer electrolytes based on squaric acid structure

Poly(squarate)s (PPS-1 and PPS-2) were synthesized by the reaction of squaryl dichloride with hydroquinone for PPS-1 and with 2,5-diethoxy-1,4-bis(trimethylsilyloxy)benzene for PPS-2, and the ionic conductivities, thermal properties, and electrochemical and thermal properties of their polymer electrolytes with LiN(CF₃SO₂)₂ were investigated. The ionic conductivity increased with increasing the lithium salt concentration for the PPS-1–LiN(CF₃SO₂)₂ electrolyte, and the highest ionic conductivities of 8.60 × 10⁻⁵ S/cm at 100 °C and 9.57 × 10⁻⁸ S/cm at 30 °C were found at the [Li] to [O] ratio of 2:1. And also, the ionic conductivity for the PPS-1–LiN(CF₃SO₂)₂ electrolyte increased with an increase in the lithium salt concentration, reached a maximum value at the [Li] to [O] ratio of 1:2, and then decreased. The highest ionic conductivity was to be 1.04 × 10⁻⁵ S/cm at 100 °C and 1.71 × 10⁻⁸ S/cm at 30 °C, respectively. Both polymer electrolytes exhibited relatively better electrochemical and thermal stabilities. Addition of the PPS-1 as a plasticizer into the poly(ethylene oxide) (PEO)–LiN(CF₃SO₂)₂ electrolyte system suppressed the crystallization of PEO, and improved the ionic conductivity at room temperature. Invited paper dedicated to Professor W. Weppner on his 65th birthday.     

Scheme for independently stabilizing the repetition rate and optical frequency of a laser using a regenerative mode-locking technique

We have succeeded in achieving independent control of the repetition rate and optical frequency of a pulse laser by employing a regenerative mode-locking technique. By adopting a voltage-controlled microwave phase shifter or an optical delay line in a regenerative feedback loop we can control the repetition rate of the laser without directly disturbing the optical frequencies. We experimentally show how this independent control can be realized by employing a 40 GHz harmonically and regeneratively mode-locked fiber laser.     

Thermal and electrochemical properties of poly(butylene sulfite)-based polymer electrolyte

Poly(butylene sulfite) (poly-1) was synthesized by cationic ring-opening polymerization of butylene sulfite (1), which was prepared by the reaction of 1,4-butanediol and thionyl chloride, with trifluoromethanesulfonic acid (TfOH) in bulk. The polymer electrolytes composed of poly-1 with lithium salts such as bis(trifluoromethanesulfonyl)imide (LiN(SO₂CF₃)₂, LiTFSI) and bis(fluorosulfonyl)imide (LiN(SO₂F)₂, LiFSI) were prepared, and their ionic conductivities, thermal, and electrochemical properties were investigated. Ionic conductivities of the polymer electrolytes for the poly-1/LiTFSI system increased with lithium salt concentrations, reached maximum values at the [LiTFSI]/[repeating unit] ratio of 1/10, and then decreased in further more salt concentrations. The highest ionic conductivity values at the [LiTFSI]/[repeating unit] ratio of 1/10 were 2.36?×?10^?4 S/cm at 80 °C and 1.01?×?10^?5 S/cm at 20 °C. On the other hand, ionic conductivities of the polymer electrolytes for the poly-1/LiFSI system increased with an increase in lithium salt concentrations, and ionic conductivity values at the [LiFSI]/[repeating unit] ratio of 1/1 were 1.25?×?10^?3 S/cm at 80 °C and 5.93?×?10^?5 S/cm at 20 °C. Glass transition temperature (T _g) increased with lithium salt concentrations for the poly-1/LiTFSI system, but T _g for the poly-1/LiFSI system was almost constant regardless of lithium salt concentrations. Both polymer electrolytes showed high transference number of lithium ion: 0.57 for the poly-1/LiTFSI system and 0.56 for the poly-1/LiFSI system, respectively. The polymer electrolytes for the poly-1/LiTFSI system were thermally more stable than those for the poly-1/LiFSI system.