The structure of water in the vicinity of complex ions of transition elements in their aqueous solutions as revealed by the shift of the temperature of maximum density of water.
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概要
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The temperature of the maximum density (TMD) of aqueous solutions was measured for twenty complex ions of transition metals. From the degrees of depression of TMD, Despretz's constant <I>k</I><SUP>ion</SUP><SUB>D</SUB> and the constant of excess depression of mixing Δ<I>k</I><SUP>ion</SUP> were determined. These constants along with <I>B</I><SUP>ion</SUP> coefficient of viscosity give us information on the structure of water in the vicinity of ions. [Co(H<SUB>2</SUB>O)<SUB>6</SUB>]<SUP>2+</SUP>, [Ni(H<SUB>2</SUB>O)<SUB>6</SUB>]<SUP>2+</SUP>, [Cu(H<SUB>2</SUB>O)<SUB>6</SUB>]<SUP>2+</SUP>, and [Zn(H<SUB>2</SUB>O)<SUB>6</SUB>]<SUP>2+</SUP> are electrostrictive structure-breakers in the natural order of Irving-Williams, Co(II)<Ni(II)<Cu(II)>Zn(II). Of the complexes [Co(NH<SUB>3</SUB>)<SUB>6</SUB>]<SUP>3+</SUP>, [Co(en)<SUB>3</SUB>]<SUP>3+</SUP>, and [Co(pn)<SUB>3</SUB>]<SUP>3+</SUP>, the pn-complex is the strongest hydrophobic structure-maker due to the hydrophobic nature of its aliphatic constituent. Both [Fe(CN)<SUB>6</SUB>]<SUP>3−</SUP> and [Co(CN)<SUB>6</SUB>]<SUP>3−</SUP> are fairly strong electrostrictive structure-breakers, while [Fe(phen)<SUB>3</SUB>]<SUP>2+</SUP>, [Co(phen)<SUB>3</SUB>]<SUP>2+</SUP>, and [Co (phen)<SUB>3</SUB>]<SUP>3+</SUP> are clathrate-like structure-makers. The EDTA and CyDTA complex ions of Co(II), Ni(II), Cu(II), and Zn(II) show no significant difference in <I>k</I><SUP>ion</SUP><SUB>D</SUB>, the situation being complicated by the hydrophobicity of the ligands and the radius effect of the complex ion. The actions of ions as structure-makers should be classified into three categories; electrostrictive, hydrophobic (iceberg formation), and hydrophobic (clathrate-like structure formation). The characteristic influence of the structure-making nature on <I>k</I><SUP>ion</SUP><SUB>D</SUB>, Δ<I>k</I><SUP>ion</SUP>, and <I>B</I><SUP>ion</SUP> is discussed.
- 公益社団法人 日本化学会の論文
著者
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Wada Goro
Department of Chemistry, Faculty of Science, Nara Women's University
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Wada Goro
Department of Chemistry, Faculty of Science, Nara Women s University
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Nagao Emiko
Department of Chemistry, Faculty of Science, Nara Women's University
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Kawamura Nagako
Department of Chemistry, Faculty of Science, Nara Women's University
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Kinumoto Kyoko
Department of Chemistry, Faculty of Science, Nara Women's University
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