Theoretical study on the β−-decay effect in mono-tritiated two hydrogen bonded systems: proton transfer along the hydrogen bond direction

The effect of tritium β^?-decay on the “two” hydrogen bonds in mono-tritiated formamide dimer (A), formic acid dimer (B), and acetic acid-formic acid (C) was studied with ab initio MO calculations. The tritium β^?-decay in (A) and (B) is expected to result in spontaneous transfer of one proton along the hydrogen bond direction: no proton transfer takes place in (C).     

Anisotropic optical spectra of PrBa2Cu4O8: possible Tomonaga-Luttinger liquid response of the quasi-one-dimensional metallic CuO double chains

The optical spectra of PrBa2Cu4O8 show large in-plane anisotropy. For the a polarization (E perpendicular chain), the spectrum is characterized by a gap of 1.4 eV, indicating the charge-transfer insulating nature of the CuO2 planes. For the metallic chain direction (E // b), the spectrum deviates from a simple Drude response; reflectivity R(b)(omega) shows a sharp edge at approximately 1 eV but it also shows a dip at approximately 15 meV, which splits the conductivity spectrum into two parts--a zero-energy mode with small weight and a pronounced 40 meV mode. These features are discussed in terms of a Tomonaga-Luttinger liquid in a doped 1D Mott insulator and compared with 1D Bechgaard salts.     

Oxidation of 4-Oxo-4H-1-Benzopyran-3-Carboxaldehydes with N-Bromosuccinimide

4-Oxo-4-H-1-benzopyran-3-carboxylic acids and their derivatives (esters and amides), 2, are known to possess interesting pharmacological activities.¹ As part of our synthetic studies of biologically active compounds, we needed to prepare a variety of 2 (carboxylic acids, esters, amides, etc.). An elegant method for the preparation of 4-oxo-4H-1-benzopyran-3-carboxaldehydes, 1, was reported independently by Nohara et al. ² and Harnish.³ However, despite a rather extensive effort by Nohara et al., the oxidation of 1 to 2 (Y=OH) has not been realized in good yield; thus the yields by Jones oxidation, the best reported method, ranged only from 9.5 to 39%.⁴     

Ab initio molecular orbital study on structures and energetics of CH3O−(H2O)n and CH3S−(H2O)n in gas phase

The purpose of this article was to calculate the structures and energetics of CH₃O⁻(H₂O)_n and CH₃S⁻(H₂O)_n in the gas phase; the maximum number of water molecules that can directly interact with the O of CH₃O⁻; and when n is larger, we asked how the CH₃O⁻ and CH₃S⁻ moiety of CH₃O⁻(H₂O)_n and CH₃S⁻(H₂O)_n changes and how we can reproduce experimental ΔH ⁰_{n−1, n}. Using the ab initio closed-shell self-consistent field method with the energy gradient technique, we carried out full geometry optimizations with the MP2/aug-cc-pVDZ for CH₃O⁻(H₂O)_n (n=0, 1, 2, 3) and the MP2/6–31+G(d,p) (for n=5, 6). The structures of CH₃S⁻(H₂O)_n (n=0, 1, 2, 3) were fully optimized using MP2/6–31++G(2d,2p). It is predicted that the CH₃O⁻(H₂O)₆ does not exist. We also performed vibrational analysis for all clusters [except CH₃O⁻(H₂O)₆] at the optimized structures to confirm that all vibrational frequencies are real. Those clusters have all real vibrational frequencies and correspond to equilibrium structures. The results show that the above maximum number of water molecules for CH₃O⁻ is five in the gas phase. For CH₃O⁻(H₂O)_n, when n becomes larger, the C—O bond length becomes longer, the C—H bond lengths become smaller, the HCO bond angles become smaller, the charge on the hydrogen of CH₃ becomes more positive, and these values of CH₃O⁻(H₂O)_n approach the corresponding values of CH₃OH with the n increment. The C—O bond length of CH₃O⁻(H₂O)₃ is longer than the C—O bond length of CH₃O⁻ in the gas phase by 0.044 Å at the MP2/aug-cc-pVDZ level of theory. The structure of the CH₃S⁻ moiety in CH₃S⁻(H₂O)_n does not change with the n increment. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 1138–1144, 1999