fig4

Figure 4. Examples for improving electrochemical properties of small molecules: (A) OH-substituted DDQ^[32]; reproduced from Ref.^[32] with permission from Elsevier. (B) Fluorinated-contorted HBC^[33,34]; reproduced from Ref.^[33] with permission from Royal Society of Chemistry. Reproduced from Ref.^[34] with permission from John Wiley and Sons. (C) Metal oxide-coated PTCD^[36]; reproduced from Ref.^[36] with permission from John Wiley and Sons. (D) Heterogeneous Pzdc^[37]. Reproduced from Ref.^[37] with permission from Elsevier.