Lithium Ion Solvation in Room-Temperature Ionic Liquids Involving Bis(trifluoromethanesulfonyl) Imide Anion Studied by Raman Spectroscopy and DFT Calculations

Abstract

The solvation structure of the lithium ion in room-temperature ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (EMI(+)TFSI(-)) and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (BMP(+0TFSI(-)) has been studied by Raman spectroscopy and DFT calculations. Raman spectra of EMI(+)TFSI(-) and BMP(+)TFSI(-) containing Li(+)TFSI(-) over the range 0.144-0.589 and 0.076-0.633 mol dm(-3), respectively, were measured at 298 K. A strong 744 cm-1 band of the free TFSI(-) ion in the bulk weakens with increasing concentration of the lithium ion, and it revealed by analyzing the intensity decrease that the two TFSI(-) ions bind to the metal ion. The lithium ion may be four-coordinated through the O atoms of two bidentate TFSI(-) ions. It has been established in our previous work that the TFSI(-) ion involves two conformers of C(1) (cis) and C(2) (trans) symmetries in equilibrium, and the dipole moment of the C(1) conformer is significantly larger than that of the C(2) conformer. On the basis of these facts, the geometries and SCF energies of possible solvate ion clusters [Li(C(1)-TFSI(-))(2)](-), [Li(C(1)-TFSI(-))(C(2)-TFSI(-))](-), and [Li(C(2)-TFSI(-))(2)](-) were examined using the theoretical DFT calculations. It is concluded that the C(1) conformer is more preferred to the C(2) conformer in the vicinity of the lithium ion.

Solvation of Lithium Ion in N,N-Diethyl-N-methyl-N-(2-methoxyethyl)ammonium Bis(trifluoromethanesulfonyl)-amide Using Raman and Multinuclear NMR Spectroscopy

“…As a result, it has been clarified that Li + ion is solvated by two TFSA -anions in these RTILs. 16 However, little information is available on the solvation structure of the Li(I) species in DEMETFSA solutions containing LiTFSA. From this viewpoint, we have studied the solvation structure of the Li(I) species in DEMETFSA solutions by using Raman and multinuclear NMR spectroscopy over a relatively wide concentration range of LiTFSA.…”

“…In addition, the weak band observed at around 764 cm -1 may be due to the DEME + cation and the TFSA -anion in analogy with the Raman spectra for EMImTFSA and P14TFSA solutions containing LiTFSA. 16 Based on the above assignment, the Raman bands in the range of 720 -770 cm -1 observed in DEMETFSA solutions containing LiTFSA were deconvoluted into three components at around 741, 747, and 764 cm -1 , as shown in Fig. 3.…”

Communication: Collective dynamics of room-temperature ionic liquids and their Li ion solutions studied by high-resolution inelastic X-ray scattering

“…According to our previous work though including unpublished data, the solvation structure of Li + ion is essentially different in between TFSA and FSA-based ILs. The Li ion in the TFSA-based IL is solvated by two TFSA anions to form [Li(TFSA) 2 ] cluster, 32,33 while that in the FSA-based IL is by three FSA anions to form [Li(FSA) 3 ]. 34 The difference in the solvation structure may affect the collective dynamics at t < 15 ps to lead to the difference in the F(Q, t)/F(Q, 0)s in the Li + ion solutions.…”

Estudos espectroscópicos de misturas líquido iônico/sal de lítio

“…O valor encontrado diverge novamente em relação aos líquidos previamente estudados e proporciona mais evidências de que a inserção de grupos funcionais no lugar dos carbonos presentes na molécula gera interações mais fortes capazes de dificultar a formação de agregados. É importante notar que a formação de estruturas ainda é substancial e causa um grande aumento nas viscosidades e, portanto, redução das propriedades de transporte da mesma maneira que nos líquidos iônicos previamente estudados 33,48,58,59 . Os resultados obtidos para os dois líquidos iônicos estudados nesta etapa do trabalho se encontram representados no diagrama à seguir (figura 21).…”

“…Por final, a utilização de uma curva mestra, e o modelo esquemático MCT para a descrição do espectro OHD-OKE será demonstrada na seção 4.3. As bandas foram analisadas por meio de um ajuste de curva considerando-se dois picos com caráter amalgamado Gaussiano e Lorentziano (a escolha do perfil das bandas foi largamente estudada 48,58 e o perfil amalgamado mostra-se o ideal para a obtenção do melhor ajuste). Os resultados obtidos para as áreas integradas dos picos nos sistemas, com diferentes concentrações de sal, foram então comparadas utilizando as equações 3.1 e 3.8 para a obtenção da porcentagem dos ânions livres e pertencentes a agregados presentes na amostra.…”