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Studies of the Translational and Reorientational Motions of Planar Nickel Complex Ions

1997; American Chemical Society; Volume: 101; Issue: 43 Linguagem: Inglês

10.1021/jp9712866

1520-6106

Bruce A. Kowert, Timothy L. Stemmler, Michael J. Fehr, Pamela J. Sheaff, Timothy J. Gillum, Nhan C. Dang, Angela M. Hughes, Bethany A. Staggemeier, David V. Zavich,

Thermodynamic properties of mixtures

The translational diffusion constants, DT, of the bis(maleonitriledithiolato)nickel anion and dianion, Ni(mnt)2- and Ni(mnt)22-, respectively, have been measured in acetone and ethyl alcohol solutions drawn through a microcapillary by reduced pressure at 25 °C. The translational radius, rt, obtained from DT is larger for Ni(mnt)22- than for Ni(mnt)2- in both solvents. The larger rt for Ni(mnt)22- is attributed to ion pairing with (n-Bu)4N+, while Ni(mnt)2- does not appear to be ion paired. rt for Ni(mnt)2- has been used to determine the rotational radius, ro, of this paramagnetic ion; ro has been used with ESR results to determine κ⊥, the solvent interaction parameter for Ni(mnt)2- in several solvents. ESR studies of Ni(mnt)2- in dimethyl phthalate (DMPT) and tris(2-ethylhexyl) phosphate (TEHP) have also been made. The analysis of the widths shows the reorientation of Ni(mnt)2- is fastest about its long in-plane axis by a factor of ≈3 in both solvents. The temperature dependence of the widths is discussed using the modified Stokes−Einstein−Debye (SED) model and the Vogel−Tammann−Fulcher (VTF) equation. The SED results indicate that Ni(mnt)2- has relatively weak interactions with both DMPT and TEHP. The ESR VTF parameters are consistent with those from viscosities and produce calculated values of the glass transition temperatures, Tg, that are also in general agreement with experiment.