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Reaction of Cu(ClO4 )2 ⋅6 H2 O with a tripodal 2N2O ligand, H2 Me2 NL, having a p-(dimethylamino)phenol moiety, in CH2 Cl2 /MeOH (1:1 v/v) under basic conditions under an inert gas atmosphere gave [Cu(Me2 NL)(H2 O)] (1). The same reaction carried out under aerobic conditions gave [Cu(Me2 NL)(MeOH)]ClO4 (2), which could be obtained also from the isolated complex 1 by reaction with O2 in CH2 Cl2 /MeOH. The X-ray crystal structures of 1 and 2 revealed similar square-pyramidal structures, but 2 showed the (dimethylamino)phenoxyl radical features. Complex 1 exhibits characteristic CuII EPR signals of the d x 2 - y 2 ground state in CH2 Cl2 /MeOH at 77 K, whereas 2 is EPR-silent. The EPR and X-ray absorption fine structure (XAFS) results suggest that 2 is assigned to the CuII -(dimethylamino)phenoxyl radical. However, complex 1 showed different features in the absence of MeOH. The EPR spectrum of the CH2 Cl2 solution of 1 exhibits distortion from the d x 2 - y 2 ground state and a temperature-dependent equilibrium between the CuII -(dimethylamino)phenolate and the CuI -(dimethylamino)phenoxyl radical. From these results, CuII -phenoxyl radical complex 2 is concluded to be formed by the reaction of 1 with O2 via the CuI -phenoxyl radical species.

In order to gain new insights into the effect of the π-π stacking interaction of the indole ring with the CuII -phenoxyl radical as seen in the active form of galactose oxidase, we have prepared a CuII complex of a methoxy-substituted salen-type ligand, containing a pendent indole ring on the dinitrogen chelate backbone, and characterized its one-electron-oxidized forms. The X-ray crystal structures of the oxidized CuII complex exhibited the π-π stacking interaction of the indole ring mainly with one of the two phenolate moieties. The phenolate moiety in close contact with the indole moiety showed the characteristic phenoxyl radical structural features, indicating that the indole ring favors the π-π stacking interaction with the phenoxyl radical. The UV/Vis/NIR spectra of the oxidized CuII complex with the pendent indole ring was significantly different from those of the complex without the side-chain indole ring, and the absorption and CD spectra exhibited a solvent dependence, which is in line with the phenoxyl radical-indole stacking interaction in solution. The other physicochemical results and theoretical calculations strongly support that the indole ring, as an electron donor, stabilizes the phenoxyl radical by the π-π stacking interaction.

Methylthiophenoxyl radical plays an important role as the active form of galactose oxidase (GO), which catalyzes oxidation of a primary alcohol to the corresponding aldehyde. Although many metal(II)-phenoxyl radical species have been reported, only a few studies have been reported on the properties of methylthiophenoxyl radical-metal complexes. We have prepared the group 10 metal (Ni, Pd and Pt) complexes of a salen-type ligand with a methylthio group at para-position of the two phenolate moieties and characterized them by X-ray crystal structure analyses and various spectroscopic methods in order to understand the role of the methylthio moiety in phenoxyl radical metal complexes. The corresponding p-methoxy substituted derivatives have been also characterized for comparison. All the one-electron oxidized group 10 metal methylthiophenolate complexes have a relatively localized radical site on one of the two phenolate moieties in comparison to the one-electron oxidized complexes of p-methoxy derivatives and exhibit different properties dependent on the central metal ions.

Adduct formations of Pt(II) complexes containing an aromatic diimine (DA) and an L-amino acid (A) with an aromatic carboxylate (AR) or a mononucleotide (NMP) has been studied by synthetic, structural, spectroscopic, and calorimetric methods. Several adducts between Pt(II) complexes, [Pt(DA)(L-A)] (charges are omitted; DA=2,2'-bipyrimidine (bpm); A=L-arginine (L-Arg), L-alaninate (L-Ala), and AR (=indole-3-acetate (IA), gentisate (GA)) or GMP were isolated as crystals and structurally characterized by the X-ray diffraction method. GMP in [Pt(bpm)(Arg)](GMP).5 H(2)O was revealed to be bound through the pi-pi stacking and guanidinium-phosphate hydrogen bonds. The [Pt(DA)(A)]-AR and -NMP systems in aqueous solution exhibited NMR upfield shifts of the aromatic ring proton signals due to stacking. The stability constants (K) for the adducts were determined by absorption and NMR spectra and calorimetric titrations. The log K values were found to be in the range 1.40-2.29 for AR and 1.8-3.3 for NMP, the order for NMP being GMP>AMP>CMP>UMP. The DeltaH degrees values were negative for all the systems studied, and the values for AR (=IA and GA) were more negative than those for NMP, indicating that ARs are stronger electron donors than NMPs. Comparison of the log K values for [Pt(bpm)(L-Arg)] and [Pt(bpm)(L-Ala)] (Ala=alaninate) indicated that the Arg moiety further stabilized the adducts by the guanidinium-carboxylate or -phosphate hydrogen bonds. The combined effects of weak interactions on the stability of the adducts in solution are discussed on the basis of the thermodynamic parameters and solid state structures.

3-Chloropyridazine-6-carboxylic acid hydrazide (5) was synthesized by employing hydrazine monohydrate and methyl levulinate as starting materials through five steps, including hydrozinolysis. Selective hydrazinolysis of 3, 6-substituted pyridazines was investigated.

著者らは,高温で良好なプロトン伝導性を示す酸化物を各種探索した結果, SrCeO3やBaCeO3を母体としたぺロブスカイト型酸化物固溶体が数10O～1000℃の高温で水素または水蒸気の存在下において安定で高いプ0トン伝導率を示すことを見いだした。また,同型のペロブスカイト型酸化物BaZrO3やCaZrO3,SrZrO3などを母体とした固溶体の焼結体も同様なプ群トン俵導性を示すことがわかってきた。これらのプロトン伝導体は,母体酸化物を構成するセリウムまたはジルコニウムの一部を三価のカチオンMで置換した組成の固溶体のセラミックスで,プロトン伝導性を発現させるためにはこのような三価カチオンによるドーピングが不可欠である。代表的なプロトン伝導体の例としてSrCe0.95Yb0.05O3-aやBaCe0.9Nd0.1O8-aなどが研究されてきた。そのプロトン伝導率は1000℃で10-2Scm-1,600℃で10-3Scm-1のオーダーで,高温でこれほど高いプロトン伝導率を示す固体はこれまでになかった。この種のプロトン伝導体は,その固体の本来の成分ではないプロトンが高温で雰囲気の水素源から取り込まれて,はじめてプロトン伝導性を示すという特異な性質を示す。本稿では,このようなぺ質ブスカイト型酸化物の高温におけるプロトン伝導性とその電気化学的性質に関して著者らが行ってきた研究について最新の成果を含めて概説し,その応用についても簡単に触れる。