Electron withdrawing and electron donating effects of 4,4′-bipyridine substituents on ruthenium mono(bipyridine) complexes

Abstract

Monobipyridine complexes of ruthenium (4,4′-L₂-2,2′-bpy)Ru(CO)₂Cl₂ (L = H, Me, t-Bu, Cl, Br, H₂PO₃, NO₂) were synthesised and structurally characterised. The electronic effects of the substituents L on vibration and absorption spectra were studied using both experimental and theoretical methods, calculations were carried out with the density functional hybrid B3PW91 and Hartree–Fock ab initio methods. The energy differences between the HOMO and LUMO orbitals of the complexes depended on the electron withdrawing properties of the bipyridine substituents. The electronic effects of the substituents were observed as a correlation between the spectra (λ_max and ν_CO bands) and the electronic character of the substituents.