Solvation structure for Fe(II), Co(II) and Ni(II) complexes in [P2225][NTf2] ionic liquids investigated by Raman spectroscopy and DFT calculation

The optimized geometries and the binding energies of [Fe(II)(cis-NTf2)3]−, [Co(II)(cis-NTf2)3]−, and [Ni(II)(cis-NTf2)3]− clusters were calculated by ADF simulations. The bonding energy, ΔEb, was calculated as ΔEb = Etot(cluster) − Etot(M2+) − nEtot([NTf2]−), and ΔEb ([Fe(II)(cis-NTf2)3]−), ΔEb([Co(II)(cis-NTf2)3]−), and ΔEb([Ni(II)(cis-NTf2)3]−) were calculated to be −2132.1 ± 6.4, −2254.6 ± 6.1, and −2283.4 ± 7.2 kJ mol−1, respectively. Furthermore, the bond distances of these clusters were consistent with the thermodynamic properties.