Synthesis, spectroscopy and electrochemistry in relation to DFT computed energies of ferrocene- and ruthenocene-containing β-diketonato iridium(III) heteroleptic complexes. Structure of [(2-pyridylphenyl)2Ir(RCCOCHCOCH3]

Blenerhassitt E. Buitendach, Jeanet Conradie, Frederick P. Malan, J. W. Niemantsverdriet, Jannie C. Swarts (Corresponding author)

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Abstract

A series of new ferrocene- and ruthenocene-containing iridium(III) heteroleptic complexes of the type [(ppy)2Ir(RCOCHCOR′)], with ppy = 2-pyridylphenyl, R = Fc = FeII5-C5H4)(η5-C5H5) and R′ = CH3 (1) or Fc (2), as well as R = Rc = RuII5-C5H4)(η5-C5H5) and R′ = CH3 (3), Rc (4) or Fc (5) was synthesized via the reaction of appropriate metallocene-containing β-diketonato ligands with [(ppy)2(μ-Cl)Ir]2. The single crystal structure of 3 (monoclinic, P21/n, Z = 4) is described. Complexes 1–5 absorb light strongly in the region 280−480 nm the metallocenyl β-diketonato substituents quench phosphorescence in 1–5. Cyclic and square wave voltammetric studies in CH2Cl2/[N(nBu)4][B(C6F5)4] allowed observation of a reversible IrIII/IV redox couple as well as well-resolved ferrocenyl (Fc) and ruthenocenyl (Rc) one-electron transfer steps in 1−5. The sequence of redox events is in the order Fc oxidation, then IrIII oxidation and finally ruthenocene oxidation, all in one-electron transfer steps. Generation of IrIV quenched phosphorescence in 6, [(ppy)2Ir(H3CCOCHCOCH3)]. This study made it possible to predict the IrIII/IV formal reduction potential from Gordy scale group electronegativities, χR and/or ΣχR′ of β-diketonato pendent side groups as well as from DFT-calculated energies of the highest occupied molecular orbital of the species involved in the IrIII/IV oxidation at a 98 % accuracy level.

Original languageEnglish
Article number3923
Number of pages20
JournalMolecules
Volume24
Issue number21
DOIs
Publication statusPublished - 30 Oct 2019

Keywords

  • Betadiketone
  • Crystal structure
  • Electrochemistry
  • Electronic spectrum
  • Ferrocene
  • Iridium
  • Phosphorescence
  • Ruthenocene
  • Spectroelectrochemistry
  • Substituent effects
  • Oxidation-Reduction
  • Iridium/chemistry
  • Models, Molecular
  • Crystallography, X-Ray
  • Thermodynamics
  • Density Functional Theory
  • Spectrum Analysis
  • Organometallic Compounds/chemical synthesis

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