The ionic partial molar volumes at infinite dilution, V∞(ion), were determined for several dicarboxylate ions, disulfonate ions, tartrate ions, and [Co(gly)(en)2]2+ (gly=glycinate ion and en=ethylenediamine) from density measurements at 25°C. The values of V∞(ion) obtained for the divalent anions generally increased with their van der Waals volumes. Significant differences in V∞(ion) were observed between geometrical isomers with dicarboxylate and disulfonate ions and were attributed to those in both of electrostriction volume and the void space volume around the anions. The former volume was decreased and the latter was increased with increasing distance between two negatively charged groups in the anions. A relatively strong electrostriction behavior of the tartrate ions, compared to the dicarboxylate ions, suggested the presence of an extra electrostriction caused by hydroxyl groups. The electrostriction strength of [Co(gly)(en)2]2+ was significantly large compared to that of [Ni(en)3]2+, rather close to those of [Cr(en)3]3+ and [Co(en)3]3+, and was attributed to the dissymmetrically localized charge distribution in the [Co(gly)(en)2]2+ ion. The effective ionic radii and apparent van der Waals volumes were estimated by using Glueckauf’s equation from the ionic partial molar volume and were discussed in comparison with those calculated from the van der Waals increments of atoms.
在25°C下通过密度测量,确定了若干种二
羧酸盐离子、二
磺酸盐离子、
酒石酸盐离子以及[Co(gly)(en)2]2+(gly=甘
氨酸盐离子,en=
乙二胺)在无限稀释条件下的离子偏摩尔体积V∞(ion)。获得的二价阴离子的V∞(ion)值通常随着其范德华体积的增大而增大。在几何异构体之间,二
羧酸盐和二
磺酸盐离子的V∞(ion)存在显著差异,这归因于它们在电紧缩体积和阴离子周围空隙体积上的差异。随着阴离子中两个负电荷基团间距的增加,前者体积减小,后者体积增大。与二
羧酸盐离子相比,
酒石酸盐离子表现出相对较强的电紧缩行为,这表明羟基的存在带来了额外的电紧缩效应。[Co(gly)(en)2]2+的电紧缩强度显著大于[Ni(en)3]2+,与[Cr(en)3]3+和[Co(en)3]3+相当,这归因于[Co(gly)(en)2]2+离子中电荷分布的不对称性。通过Glueckauf方程从离子偏摩尔体积估算出有效离子半径和表观范德华体积,并与根据原子范德华增量计算的值进行了比较讨论。