Synthesis and Computational Investigations of Ruthenium(II) Complexes Containing Hydrazine Schiff Base Ligands

Pages

S. Kamalesu, K. Swarnalatha and R. Subramanian

DOI:

Published:

Abstract: Three new heteroleptic ruthenium(II) complexes containing hydrazine schiff base as ligands were synthesized and characterized by using elemental analysis, FT-IR, ¹H, ¹³C NMR, and mass spectroscopic techniques. FT-IR study showed that the substituted phenylhydrazine ligands behave as a monoanionic bidentate O and N donors (L) coordinate to ruthenium via the deprotonated phenolic oxygen and the azomethine nitrogen. They possess excellent thermal stabilities, evident from the thermal decomposition temperatures. Absorption, emission and electrochemical measurements were carried out and the structures of the synthesized complex were optimized using density functional theory (DFT). The molecular geometry, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) energies, Mulliken atomic charges and molecular electrostatic potential (MEP) of the molecules are determined using B3LYP method and standard 6-311++G (d, p) basis set.

Analysis of Thermodynamic Properties forRare Earth Complexes in Ionic Liquids by Raman Spectroscopy andDFT Calculation
Pages 157-167
Masahiko Matsumiya, Ryo Kazama and Katsuhiko Tsunashima

DOI: http://dx.doi.org/10.6000/1929-5030.2016.05.04.1

Published: 09 December 2016

Abstract: The coordination states of the divalent and trivalent rare earth complexes in ionic liquid, triethyl-pentyl-phosphonium bis(trifluoromethyl-sulfonyl) amide [P₂₂₂₅][TFSA] were investigated by Raman spectroscopy and DFT calculation. The concentration dependences of the deconvoluted Raman spectra were investigated for 0.23–0.45 mol kg^-1 RE(III), RE=Nd and Dy, and the mixed sample of RE(II)/RE(III)=1/3 at the molar ratio in [P₂₂₂₅][TFSA]. According to the conventional analysis, the solvation number; n of rare earth complexes in [P₂₂₂₅][TFSA] were determined to be n=4.06 for Nd(II), 5.01 for Nd(III), 4.12 for Dy(II) and 5.00 for Dy(III).

Thermodynamic properties such as Δ_isoG, Δ_isoH and Δ_isoS for the isomerism of [TFSA]^- from trans- to cis-isomer in bulk and the first solvation sphere of the centered [RE³⁺] cation in [P₂₂₂₅][TFSA] were evaluated from the temperature dependence in the range of 298-398K. Δ_isoG(bulk), Δ_isoH(bulk) and TΔ_isoS(bulk) at 298 K were -1.06, 6.86, and 7.92 kJ mol^-1, respectively. The trans-[TFSA]^-was dominant in the enthalpy due to the positive value of Δ_isoH(bulk) and TΔ_isoS(bulk) was slightly larger than Δ_isoH(bulk), so that cis-[TFSA]^-was revealed to be an entropy-controlled in [P₂₂₂₅][TFSA]. On the other hand, in the first solvation sphere of [RE³⁺] cation, Δ_isoH (Nd)(-47.39 kJ mol^-1) increased to the negative value remarkably and implied that the cis-[TFSA]^- isomers were stabilized for enthalpy. Δ_isoH(Nd) contributed to the remarkable decrease in the Δ_isoG(Nd) and this result clearly indicated that the cis-[TFSA]^- bound to Nd³⁺ cation was preferred and the coordination state of [Dy^(III)(cis-TFSA)₅]^2- was stable in [P₂₂₂₅][TFSA]

The optimized geometries and the bonding energies of [RE^(II)(cis-TFSA)₄]^2- and [RE^(III)(cis-TFSA)₅]^2- clusters were also investigated from DFT calculation with ADF package. The bonding energy; ΔE_b was calculated from ΔE_b= E_tot(cluster) –E_tot(RE^2,3+) –nE_tot([TFSA]^-). ΔE_b([Nd^(II)(cis-TFSA)₄]^2-), ΔE_b([Nd^(III)(cis-TFSA)₅]^2-), ΔE_b([Dy^(II)(cis-TFSA)₄]^2-) and ΔE_b([Dy^(III)(cis-TFSA)₅]^2-) were -2241.6, -4362.3, -2135.4 and -4284.2 kJmol^-1, respectively. This result was revealed that [RE^(III)(cis-TFSA)₅]^2-cluster formed stronger coordination bonds than [Dy^(II)(cis-TFSA)₄]^2- cluster. The average atomic charges and the bond distances of these clusters were consistent with the thermodynamic properties.