Solvation structure and thermodynamics for lanthanide complexes in phosphonium-based ionic liquid evaluated by Raman spectroscopy and density functional theory
Solvation structure and thermodynamics for lanthanide complexes in phosphonium-based ionic liquid evaluated by Raman spectroscopy and density functional theory
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DOI：
10.1016/j.molliq.2020.114008
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发表时间：
2020-11
影响因子：
6
通讯作者：
Daiki Nomizu;Yusuke Tsuchida;M. Matsumiya;K. Tsunashima
中科院分区：
文献类型：
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作者：
Daiki Nomizu;Yusuke Tsuchida;M. Matsumiya;K. Tsunashima
采用拉曼光谱和密度泛函理论（DFT）研究了二价和三价稀土配合物在离子液体（IL）三乙基正戊基膦双（三氟甲基磺酰基）酰胺[P2225][NTf 2]中的配位状态.在298-398 K温度范围内，计算了[NTf 2]的反式-顺式异构和[Ln 3 +]在离子液体中的第一溶剂化球的热力学性质（ΔisoG，ΔisoH和ΔisoS）. 298 K时的ΔisoG（体）、ΔisoH（体）和T ΔisoS（体）值分别为−0.71、7.63和8.34 kJ mol−1。由于ΔisoH（本体）的正值，反式-[NTf 2]异构体具有最高的焓;TΔisoS（本体）略高于ΔisoH（本体），因此，顺式-[NTf 2]在IL中是熵控制的。在[Nd 3 +]阳离子的第一溶剂化层中，ΔisoH（Nd）（-47.79 kJ mol−1）的负值显著增大，表明顺式[NTf 2]异构体的焓趋于稳定。这一结果表明，顺式-[NTf 2]与[Ln 3 +]（Ln=Nd或Dy）阳离子的结合是优选的，并且[Ln（III）（cis-NTf 2）5]2-在IL中的配位状态是稳定的。利用ADF对[Ln（II）（cis-NTf 2）4]2-和[Ln（III）（cis-NTf 2）5]2-簇合物的几何构型和键能进行了优化。键能ΔEb的计算公式为ΔEb=Etot（cluster）−Etot（Ln 2，3+）−nEtot（[NTf 2]−）。ΔEb（[Nd（II）（cis-NTf 2）4]2−）、ΔEb（[Nd（III）（cis-NTf 2）5]2−）、ΔEb（[Dy（II）（cis-NTf 2）4]2−）和ΔEb（[Dy（III）（cis-NTf 2）5]2−）值分别为−2219.2、−4340.5、−2118.3和−4258.5 kJ mol−1。该结果表明，[Ln（III）（cis-NTf 2）5]2−簇形成的配位键比[Ln（II）（cis-NTf 2）4]2−簇更强。
Coordination states of the divalent and trivalent lanthanide complexes in an ionic liquid (IL), triethyl-n-pentylphosphonium bis(trifluoromethyl-sulfonyl) amide [P2225][NTf2], were investigated by Raman spectroscopy and density functional theory (DFT) with the Amsterdam density functional package (ADF). Thermodynamic properties (ΔisoG, ΔisoH, and ΔisoS) for thetrans-to-cisisomerism of [NTf2] in bulk and the first solvation sphere of the [Ln3+] cation in the IL were evaluated from their temperature dependence in the range 298–398 K. The ΔisoG(bulk), ΔisoH(bulk), andTΔisoS(bulk) values at 298 K were −0.71, 7.63, and 8.34 kJ mol−1, respectively. Thetrans-[NTf2] isomer had the highest enthalpy due to the positive value of ΔisoH(bulk);TΔisoS(bulk) was slightly higher than ΔisoH(bulk), and hence,cis-[NTf2] was entropy-controlled in the IL. In the first solvation sphere of the [Nd3+] cation, the negative value of ΔisoH(Nd) (−47.79 kJ mol−1) remarkably increased, which implied that thecis-[NTf2] isomers were stabilized for enthalpy. This result revealed thatcis-[NTf2] bound to the [Ln3+] (Ln=Nd or Dy) cation was preferred and the coordination state of [Ln(III)(cis-NTf2)5]2−was stable in the IL. The optimized geometries and the bonding energies of the [Ln(II)(cis-NTf2)4]2−and [Ln(III)(cis-NTf2)5]2−clusters were also investigated using the ADF. The bonding energy, ΔEb, was calculated from ΔEb=Etot(cluster) −Etot(Ln2,3+) −nEtot([NTf2]−). The ΔEb([Nd(II)(cis-NTf2)4]2−), ΔEb([Nd(III)(cis-NTf2)5]2−), ΔEb([Dy(II)(cis-NTf2)4]2−), and ΔEb([Dy(III)(cis-NTf2)5]2−) values were −2219.2, −4340.5, −2118.3, and −4258.5 kJ mol−1, respectively. This result showed that the [Ln(III)(cis-NTf2)5]2−cluster formed stronger coordination bonds than the [Ln(II)(cis-NTf2)4]2−cluster.