A DFT-D study on the electrochromic mechanism of ruthenium sulfoxide complexes

Abstract

In this work, redox stimulated S → O and O → S isomerization of the bound sulfoxide in [Ru(bpy)(tpy)(dmso)]²⁺ (bpy = 2,2′-bipyridine; tpy = 2,2′:6′,2′′-terpyridine; dmso = dimethyl sulfoxide) was explored theoretically with dispersion corrected density functional theory to gain an understanding of the electrochromic mechanism of polypyridine ruthenium sulfoxide complexes. It is interesting to note that oxidation and reduction play different roles in the intramolecular isomerization of ruthenium(II) sulfoxide complexes. Potential energy surface (PES) results demonstrate that Ru–S to Ru–O linkage isomerization is more thermodynamically favored in the oxidized state of the Ru²⁺(S) complex. Differently, reduction of Ru³⁺(O) or Ru²⁺(O) complexes makes the Ru–O bond-breaking and Ru–S bond-making reaction much easier. These can be explained by different effects of oxidation and reduction on the energy gap (ΔE) between S, O donors and Ru acceptors, by which Ru–S and Ru–O bond-strengths were determined.