We investigate the relationships between the diradical character (y) and nonlinear optical (NLO) properties of open-shell 1,3-diradical compounds using the broken-symmetry density functional theory method. The 2,2-substituent effects on the structure-property relationship are clarified for several 1,3-diphenylcyclopentane-1,3-diyl derivatives, which are known as the systems with weak or intermediate ?-single-bonding characters. The parent 1,3-diphenylcyclopentane-1,3-diyl (1a: X = H) is found to be almost pure diradical (y ? 1) owing to the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The energy gap is determined by the balance of the through-space coupling with the through bond coupling effect. On the other hand, the introduction of the electron-withdrawing substituents X at the C2 position of cyclopentane-1,3-diyls (1b: X = OH, 1c: X = F) is found to decrease the y-value owing to the effects of additional through-bond interactions. As a result, 1b and 1c are found to have intermediate y. Static second hyperpolarizabilities (?) of 1b and 1c are found to be enhanced by a factor of ?4.5 and ?6.4, respectively, compared with those of the pure singlet diradical 1a and those of the triplet 1a-1c. From the analysis of the third-order responses of electron density, the introduction of the 2,2-substituents is found to enhance the field-induced third-order polarizations over the whole system. We also investigate the effects of asymmetric donor/acceptor substitutions at the para positions of phenyl rings on the response properties. Although the asymmetric donor/acceptor substitutions have no significant impact on y in the present systems, they are found to provide the increase of ? from the corresponding nonsubstituted analogues. The present results have revealed strong correlation between the ?-bonding character (diradical character) and third-order NLO properties in the real 1,3-diradical compounds. On the basis of the theoretically predicted correlation in the real systems, NLO measurements are speculated to be utilized as a new probe of the unique chemical bonding nature in such localized diradical compounds, which is one of the fundamental subjects in chemistry.
Copper oxide clusters, Cu(n)O(m)(+) (n = 5-12), were prepared in the gas phase by laser ablation of a copper metal rod in the presence of oxygen diluted in He as the carrier gas. The stoichiometry of the cluster ions was investigated using mass spectrometry. The number ratio of copper atoms and oxygen atoms in Cu(n)O(m)(+) was distributed from n:m = 1:1-3:2, which was not affected significantly by the concentration of oxygen in the carrier gas as long as it exceeded 2%. When the cluster ions were heated up to 573 K downstream of the cluster source (post heating), Cu(n)O(m)(+) (n:m ? 3:2) clusters were selectively and dominantly formed as a result of thermal dissociation. No further changes in the ratio were observed when the clusters were heated up to 623 K. From the stoichiometry, Cu(n)O(m)(+) is considered to comprise both Cu(I) and Cu(II). Hence, the mixed valence states are found to be thermally stable for the small clusters in the gas phase, but they are not stable in the bulk phase. In addition to the thermal stability, we observed reactivity of Cu(n)O(m)(+) with CO molecules. It was found that Cu12O8(+) hardly binds to CO and that Cu9O6(+) and Cu6O4(+) along with other clusters with n:m ? 3:2 bind to CO very weakly, whereas CO attaches strongly to oxygen-rich clusters with release of an oxygen molecule.
To evaluate the superiority of using a task-specific onium salt (TSOS), a novel TSOS reagent 1-methyl-3-[2-(8-quinolinylaminosulfonyl)ethyl]imidazolium chloride (HmimesqCl) was synthesized, and its performance in extraction of different divalent metal cations was investigated. This TSOS reagent has both a cationic imidazolium unit and an anionic (proton-dissociable) complexation unit for the extraction of metal cations into an ionic liquid. In the use of HmimesqCl, relatively high extraction of metals resulted in comparison with the use of its non-imidazolium analogs, without changing the extraction selectivity.
The following unusual tRNAs have recently been discovered in the genomes of Archaea and primitive Eukaryota: multiple-intron-containing tRNAs, which have more than one intron; split tRNAs, which are produced from two pieces of RNA transcribed from separate genes; tri-split tRNAs, which are produced from three separate genes; and permuted tRNA, in which the 5 and 3 halves are encoded with permuted orientations within a single gene. All these disrupted tRNA genes can form mature contiguous tRNA, which is aminoacylated after processing by cis or trans splicing. The discovery of such tRNA disruptions has raised the question of when and why these complex tRNA processing pathways emerged during the evolution of life. Many previous reports have noted that tRNA genes contain a single intron in the anticodon loop region, a feature common throughout all three domains of life, suggesting an ancient trait of the last universal common ancestor. In this context, these unique tRNA disruptions recently found only in Archaea and primitive Eukaryota provide new insight into the origin and evolution of tRNA genes, encouraging further research in this field. In this paper, we summarize the phylogeny, structure, and processing machinery of all known types of disrupted tRNAs and discuss possible evolutionary scenarios for these tRNA genes.
Novel salicyl alcohol derivatives (H(2)X(n)sal), 5-bromo-, 3,5-dibromo-, and 3,5-diiodosalicyl alcohol which were abbreviated to H(2)Brsal, H(2)Br(2)sal, and H(2)I(2)sal, respectively, were synthesized and used for the selective extraction of boric acid. Boric acid was extracted with each H(2)X(n)sal into chlorobenzene containing trioctylmethylammonium chloride (TOMACl) as an ion-pair complex, TOMA·B(X(n)sal)(2), at a different pH range. The extraction constant (K(ex)) of boric acid was determined by the equilibrium analyses including the formation of hydrogen-bonded complex of each H(2)X(n)sal with TOMACl in the organic phase. The K(ex) values obtained by salicyl alcohol (H(2)sal) and its derivatives were decreased in the order of H(2)I(2)sal ? H(2)Br(2)sal > H(2)Brsal > H(2)sal. The most powerful extractant, H(2)I(2)sal, was employed for the substoichiometric extraction of boric acid, which was extracted at pH 5 - 9 with a substoichiometric amount of TOMACl in the presence of an excess of H(2)I(2)sal. The present substoichiometric separation method combined with the stable isotope dilution analysis using inductively coupled plasma mass spectrometry (ICP-MS) could be successfully applied to the determination of boron in a reference material of high-analysis compound fertilizer (FAMIC-A-08) without any correction as to the isotopic abundance.
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