Ruthenium(II) bipyridine complexes bearing new keto–enol azoimine ligands: Synthesis, structure, electrochemistry and DFT calculations
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Original research
  • Mousa Al-Noaimia, , , Firas F. Awwadib, Ahmad Mansia, Obadah S. Abdel-Rahmanc, Ayman Hammoudehd, Ismail Warade
The novel azoimine ligand, Phsingle bondNHsingle bondNdouble bond; length as m-dashC(COCH3)single bondNHPh(Ctriple bond; length of mdashCH) (H2L), was synthesized and its molecular structure was determined by X-ray crystallography. Catalytic hydration of the terminal acetylene of H2L in the presence of RuCl3·3H2O in ethanol at reflux temperature yielded a ketone (L1 = Phsingle bondNdouble bond; length as m-dashNsingle bondC(COCH3)double bond; length as m-dashNsingle bondPh(COCH3) and an enol (L2 = Phsingle bondNdouble bond; length as m-dashNsingle bondC(COCH3)double bond; length as m-dashNsingle bondPhC(OH)double bond; length as m-dashCH2) by Markovnikov addition of water. Two mixed-ligand ruthenium complexes having general formula, trans-[Ru(bpy)(Y)Cl2] (1–2) (where Y = L1 (1) and Y = L2 (2), bpy is 2.2′-bipyrdine) were achieved by the stepwise addition of equimolar amounts of (H2L) and bpy ligands to RuCl3·3H2O in absolute ethanol. Theses complexes were characterized by elemental analyses and spectroscopic (IR, UV–Vis, and NMR (1D 1H NMR, 13C NMR, (DEPT-135), (DEPT-90), 2D 1H–1H and 13C–1H correlation (HMQC) spectroscopy)). The two complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 604 mV vs. ferrocene/ferrocenium (Cp2Fe0/+) couple along with one electron ligand reduction at −1010 mV. The crystal structure of complex 1 showed that the bidentate ligand L1 coordinates to Ru(II) by the azo- and imine-nitrogen donor atoms. The complex adopts a distorted trans octahedral coordination geometry of chloride ligands. The electronic spectra of 1 and 1+ in dichloromethane have been modeled by time-dependent density functional theory (TD-DFT).
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy Volume 135, 25 January 2015, Pages 828–839
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