Controlled diffusion coefficient electrochromic materials for use in electrochromic mediums and associated electrochromic devices

An electrochromic medium for use in an electrochromic device comprising: at least one solvent; an anodic electroactive material; a cathodic electroactive material; wherein at least one of the anodic and cathodic electroactive materials is electrochromic; and wherein at least one of the anodic and cathodic electroactive materials is associated with a diffusion coefficient controlling moiety which serves to lower the diffusion coefficient of the associated material relative to the same without the diffusion coefficient controlling moiety.