Redox and luminescent properties of robust and air-stable N-heterocyclic carbene group 4 metal complexes

Inorg Chem. 2014 Jul 21;53(14):7371-6. doi: 10.1021/ic500718y. Epub 2014 Jun 24.

Abstract

Robust and air-stable homoleptic group 4 complexes of the type M(L)2 [1-3; M = Ti, Zr, Hf; L = dianionic bis(aryloxide) N-heterocyclic carbene (NHC) ligand] were readily synthesized from the NHC proligand 1,3-bis(3,5-di-tert-butyl-2-hydroxyphenyl)imidazolinium chloride (H3L,Cl) and appropriate group 4 precursors. As deduced from cyclic voltammetry studies, the homoleptic bis-adduct zirconium and hafnium complexes 2 and 3 can also be oxidized, with up to four one-electron-oxidation signals for the zirconium derivative 2 (three reversible signals). Electron paramagnetic resonance data for the one-electron oxidation of complexes 1-3 agree with the formation of ligand-centered species. Compounds 2 and 3 are luminescent upon excitation in the absorption band at 362 nm with emissions at 485 and 534 nm with good quantum yields (ϕ = 0.08 and 0.12) for 2 and 3, respectively. In contrast, the titanium complex 1 does not exhibit luminescent properties upon excitation in the absorption band at 310 and 395 nm. Complexes 2 and 3 constitute the first examples of emissive nonmetallocene group 4 metal complexes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Electron Spin Resonance Spectroscopy
  • Heterocyclic Compounds / chemistry*
  • Luminescence
  • Magnetic Resonance Spectroscopy
  • Metals / chemistry*
  • Methane / analogs & derivatives*
  • Methane / chemistry
  • Oxidation-Reduction

Substances

  • Heterocyclic Compounds
  • Metals
  • carbene
  • Methane