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

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

doi:10.1021/jp9712866

Cited by 8 publications

(56 citation statements)

References 29 publications

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“…The r t values for [Ni(mnt) 2 ] − are essentially the same in acetonitrile (ACN), EtOH, acetone, and BuOH (≈3.60 Å) and are smaller than those for [Ni(mnt) 2 ] 2− in EtOH, acetone, and ACN (≈4.50 Å). 16,31 These results are in agreement with electrochemical, 32 conductivity, 33,34 and vapor phase osmometry 32 data in ACN that showed [Ni(mnt) 2 ] 2− but not [Ni(mnt) 2 ] − was ion-paired with Et 4 N + (we used Bu 4 N + ). The absence of ion pairing between [Ni(mnt) 2 ] − and Bu 4 N + in diglyme is consistent with infrared studies that indicated a lack of association between Bu 4 N + and CF 3 SO 3 − in both diglyme 35 and triglyme 36 (triethylene glycol dimethyl ether).…”

Section: Discussionsupporting

confidence: 88%

“…Simulation of the trianion’s glassy spectrum in diglyme gave g x = 2.0824, g y = 2.0660, and g z = 2.2053 (with relative uncertainties of ±0.0010); details of their determination, the spectrometer, and other aspects of the ESR methods are given in refs 15 and 16. The assignment of the g factors to molecular axes (Figure 1) is by analogy with single crystal results 8 for [Cu(mnt) 2 ] 2− , which like [Ni(mnt) 2 ] 3− , has a formally d 9 metal ion.…”

Section: Methodsmentioning

confidence: 99%

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Molecular Motion of the Bis(maleonitriledithiolato)nickel Trianion in Solution

Kowert

Stemmler

et al. 2012

J. Phys. Chem. B

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Electron spin resonance (ESR) has been used to study the reorientational motion of the bis(maleonitriledithiolato)nickel trianion, [Ni(mnt)2]3−, in diethylene glycol dimethyl ether (diglyme). [Ni(mnt)2]3− has one unpaired electron and was prepared by reducing the dianion, [Ni(mnt)2]2−, with potassium metal. The trianion and dianion are members of the redox series [Ni(mnt)2]n− with n = 0, 1, 2, 3. The monoanion, [Ni(mnt)2]−, also has S = ½ and its rotational diffusion in diglyme was the subject of previous ESR studies. This made possible the comparison of the reorientational data for two different oxidation states of the same planar complex in the same solvent. Differences were found; isotropic rotational diffusion produced agreement between the trianion’s experimental and calculated spectra while the monoanion’s simulations required axially symmetric reorientation with diffusion about the long in-plane axis three times faster than that about the two perpendicular axes. At a given temperature, the monoanion’s reorientation rates about the long in-plane axis and two perpendicular axes were faster than the trianion’s isotropic rate by factors of ~27 and ~9, respectively. These differences suggest that [Ni(mnt)2]− and [Ni(mnt)2]3− have different shapes and sizes in solution; the monoanion is approximately a prolate ellipsoid while the trianion is larger and more spherical. [Ni(mnt)2]3− appears to be ion-paired while, in accord with results from other techniques, [Ni(mnt)2]− is not.

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Section: Discussionsupporting

confidence: 88%

Section: Methodsmentioning

confidence: 99%

Molecular Motion of the Bis(maleonitriledithiolato)nickel Trianion in Solution

Kowert

Stemmler

et al. 2012

J. Phys. Chem. B

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“…Analyses of the spectra show that, as in our previous solvents, 8,9 Ni(mnt) 2 − is reorienting with D || = D y and D || / D ⊥ ≈ 3.0. The values of τ 2 (0) can be fitted using eq 1, 11 and as discussed below, the values of C ⊥ and κ ⊥ indicate relatively strong solute–solvent interactions.…”

Section: Introductionsupporting

confidence: 74%

“…9 The values of C ⊥ and κ ⊥ in the above solvents 8,9 are given in Table 1 and differ by more than a factor of 3, showing that the viscosity is not the only solvent property determining the reorientation of Ni(mnt) 2 − .…”

Section: Introductionmentioning

confidence: 98%

Electron Spin Resonance Studies of the Reorientational Motion of Ni(mnt)₂⁻

et al. 2010

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Electron spin resonance studies of the planar bis(maleonitriledithiolato)nickel complex ion, Ni(mnt)2−, have been carried out from the motional narrowing region to the glassy limit in a series of ethers: 2-methyltet-rahydrofuran (MTHF), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), and tetraethylene glycol dimethyl ether (tetraglyme). Analyses of the spectra show that Ni(mnt)2− is reorienting a factor of 3 faster about its long in-plane axis in all of these solvents; i.e., axially symmetric rotational diffusion produces agreement between the experimental and calculated line widths with D||/D⊥= 3.0 ± 0.2; D|| and D⊥ are the diffusion constants for reorientation about the long in-plane (parallel) and perpendicular axes, respectively. The temperature dependence of the reorientational correlation time τ2(0) = (6D⊥)−1 determined from the widths is in agreement with the modified Stokes–Einstein–Debye model; the results indicate that Ni(mnt)2− has relatively strong (but not associative) interactions with the ethers. The experimental values of τ2(0) and the solvents’ viscosities, self-diffusion constants, and dielectric relaxation times are compared and found to have a common temperature dependence. The ESR data also are compared with values of 〈τ〉solv, the correlation time obtained when a fluorescent probe is excited and its emission is monitored as the nonequilibrium solvent distribution relaxes. 〈τ〉solv and τ2(0) are found to have a common temperature dependence in MTHF, tetraglyme, and two other solvents (ethyl alcohol and 1-butanol) in which Ni(mnt)2− has been studied. The factors determining these transport properties are discussed.

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“…A detection wavelength of 260 nm was used for toluene in hexane. Other aspects of the instrumentation and data gathering are described in ref 17.…”

Section: Methodsmentioning

confidence: 99%

Diffusion of Dioxygen in n-Alkanes

Kowert

Dang

1999

J. Phys. Chem. A

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The translational diffusion constant, D, of dioxygen, O 2 , has been measured in n-alkane solutions drawn through a microcapillary by reduced pressure. The passage of O 2 through the capillary has been monitored using its UV absorption at 190 nm. Data were taken in hexane, octane, decane, dodecane, tetradecane, and hexadecane. The diffusion constants decrease as the chain length increases and are not in agreement with the Stokes-Einstein relation. The data can be fitted to D/T ) A/η p with A ) 1.27 × 10 -8 and p ) 0.562 (p ) 1 for the Stokes-Einstein relation); T is the absolute temperature, and η is the viscosity in P.

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

Cited by 8 publications

References 29 publications

Molecular Motion of the Bis(maleonitriledithiolato)nickel Trianion in Solution

Molecular Motion of the Bis(maleonitriledithiolato)nickel Trianion in Solution

Electron Spin Resonance Studies of the Reorientational Motion of Ni(mnt)₂⁻

Diffusion of Dioxygen in n-Alkanes

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

Cited by 8 publications

References 29 publications

Molecular Motion of the Bis(maleonitriledithiolato)nickel Trianion in Solution

Molecular Motion of the Bis(maleonitriledithiolato)nickel Trianion in Solution

Electron Spin Resonance Studies of the Reorientational Motion of Ni(mnt)2−

Diffusion of Dioxygen in n-Alkanes

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Electron Spin Resonance Studies of the Reorientational Motion of Ni(mnt)₂⁻