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Issue 6, 2019
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Effects of the long octyl chain on complex formation of nickel(ii) with dimethyl sulfoxide, methanol, and acetonitrile in ionic liquid of [C8mim][TFSA]

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Abstract

In the room-temperature ionic liquid (IL) of 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)amide ([C8mim][TFSA]), the complex formation of Ni2+ with molecular liquids (MLs), dimethyl sulfoxide (DMSO), methanol (MeOH), and acetonitrile (AN), has been examined using ultraviolet (UV)-visible spectroscopy. The overall stability constants log βn, enthalpies Image ID:c8cp06345a-t1.gif, and entropies Image ID:c8cp06345a-t2.gif of the equilibria have been determined to elucidate the mechanism of complex formation. From a comparison of such thermodynamic parameters of the present [C8mim][TFSA] systems with those of the previous systems of 1-ethyl-3-methylimidazolium-based IL, [C2mim][TFSA], the effects of the octyl chain of the imidazolium cation, [C8mim]+, on the complex formation of Ni2+ with MLs have been demonstrated. In [C8mim][TFSA]–ML systems, more stable complexes are formed with MLs in the sequence of AN > DMSO ≫ MeOH. This sequence differs from that of DMSO ≫ AN > MeOH in [C2mim][TFSA]. For the AN systems, the stabilities of [Ni(an)n] in [C8mim][TFSA] are higher as compared to those in [C2mim][TFSA]. In contrast, for the DMSO systems, [Ni(dmso)n] is less stable in the IL with the longer alkyl chain than that in the IL with the shorter chain. The dependence of the alkyl chain length on the stabilities of [Ni(meoh)n] is the least significant among the three MLs. These varieties of the stabilities of Ni2+ complexes with the MLs have been interpreted from the thermodynamic parameters, together with the static interactions in the [C8mim][TFSA]–ML and [C2mim][TFSA]–ML solvents observed by means of 1H and 13C NMR, small-angle neutron scattering (SANS), and infrared (IR) with an ATR diamond prism.

Graphical abstract: Effects of the long octyl chain on complex formation of nickel(ii) with dimethyl sulfoxide, methanol, and acetonitrile in ionic liquid of [C8mim][TFSA]

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Publication details

The article was received on 11 Oct 2018, accepted on 07 Jan 2019 and first published on 08 Jan 2019


Article type: Paper
DOI: 10.1039/C8CP06345A
Phys. Chem. Chem. Phys., 2019,21, 3154-3163

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    Effects of the long octyl chain on complex formation of nickel(II) with dimethyl sulfoxide, methanol, and acetonitrile in ionic liquid of [C8mim][TFSA]

    T. Takamuku, H. Sakurai, A. Ogawa, A. Tashiro, M. Kawano, Y. Kawazu, K. Sadakane, H. Iwase and K. Ozutsumi, Phys. Chem. Chem. Phys., 2019, 21, 3154
    DOI: 10.1039/C8CP06345A

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