**4. Antioxidant activities**

The scavenging activity of the synthesized of the NHC precursors [27–31] is in **Figure 3** and Ag(I) complexes with DPPH (1,1-diphenyl- 2-picrylhydrazyl) is represented in **Figure 4**.

**Figure 3.** *DPPH radicals scavenging activity of benzimidazoles salts 2a, 2d, 2g.*

*Novel N-Heterocyclic Carbene Silver (I) Complexes: Synthesis, Structural Characterization… DOI: http://dx.doi.org/10.5772/intechopen.101950*

**Figure 4.** *DPPH radicals scavenging activity of (Ag-NHC) complexes 3d, 3g.*

The antioxidant activities for compounds **2a**, **2d**, **2g**, **3g**, and **3d** are summarized in **Figures 3** and **4**. The results analysis indicated that the antiradical activity profiles obtained from the tested synthetic products **3g** and **3d** had improved and demonstrated antioxidant activity compared to the other products. At a concentration used (0.0625 mg/ml), **2d** showed the lowest free radical activity when compared to both gallic acid and BHT (butylated hydroxytoluene). Similarly, compounds **2a**, **2g** and **3d**, at a concentration of 0.0625 mg/ml, had lower radical activity than gallic acid as well as BHT (butylated hydroxytoluene). **2a**, **2d**, **2g**, **3g** and **3d** revealed significant DPPH activity over synthetic antioxidants at the concentration of 1 mg/ ml.
