Ligand modification effects on the electrochromic character of ruthenium sulfoxide complexes: a theoretical perspective

Here, we use dispersion-corrected density functional theory methods to illustrate how it is possible to control the electronic and photophysical properties of [Ru(bpy)2(OSO)]+ (bpy = 2,2′-bipyridine; OSO = methylsulfinylbenzoate) isomers with the type and positions of the substituents on coordinated ligand. It is found that the frontier MOs of the ruthenium sulfoxide complexes can be substantially modulated as a function of different substitution patterns. Correspondingly, the first absorption and phosphorescence emission transitions can be tuned because both of them are dominated by one-electron transitions between frontier MOs. More importantly, the relative thermodynamic stabilities of two linkage isomers also can be changed with ligand modification. It is proposed that the Ru–S → Ru–O1 isomerization is more thermodynamically favored by electron-withdrawing group substitution on coordinated ligands. Understanding the variation of electronic and photophysical properties induced by ligand modification can be used for developing a rational design process for such electrochromic materials.