Oxidative stress (OS) is a primary contributor to sperm DNA fragmentation (SDF) and impaired male reproductive function. Numerous studies have demonstrated the advantages of natural antioxidants; however, evidence supporting the efficacy of synthetic antioxidants is limited and inconclusive. This study aimed to assess the effectiveness of laboratory-synthesized synthetic compounds in the preservation of sperm DNA. This study aimed to evaluate the effectiveness of laboratory-synthesized synthetic compounds in maintaining the integrity of sperm DNA. The study a Schiff's base ligand [L] from L-asparagine and 4-dimethylaminobenzaldehyde, as well as its heavy metal complexes, utilizing FT-IR, UV–Vis, 1H/13C-NMR, conductivity tests, and magnetic susceptibility analysis. We used the DPPH method to test how well the synthesized compounds worked as antioxidants. The Comet test was used to see how well the chemical protected sperm DNA. Hydrogen peroxide made sperm DNA fragmentation a lot worse. Treatment with the free Schiff base ligand [L] reduced damage in a dose-dependent way, with the 50 µg/mL dose bringing head DNA (HD%) back to roughly 92% (P < 0.001), which is the same as ascorbic acid. Metal complexation greatly increased protection. [Mn₂(L).3Cl.H₂O] and [Co₂(L).3Cl.H₂O] kept more than 99.9% of head DNA (HD%) and reduced tail DNA (TD%) to less than 0.12% (P < 0.0001 compared to the H₂O₂ group). The Zn(II) compound only protected about 80% of the head DNA (HD%). The DPPH IC₅₀ values were in line with functional protection, which showed that Mn and Co complexes worked as antioxidants. Schiff-base metal complexes, specifically Mn(II) and Co(II), exhibit notable antioxidant capabilities that protect sperm DNA and may be utilized in in vitro sperm washing media. However, additional preclinical investigations are required to confirm their safety and efficacy.