The synthesis of a series of 4-​(un)​substituted thiosemicarbazones of 6-​methyl-​5-​nitropyridine-​2-​carboxaldehyde, I (R = H, n-​Bu, 4-​ClC₆H₄, etc.)​, is reported by two different routes.  The prepd. compds. were tested for their binding ability against Cu(II)​, Hg(II) and Zn(II)​.  Four derivs. were tested for their complexing potentials in vivo.  These compds. showed promising antidotal activities against Cu(II) relative to D-​penicillamine.  I (R = Ph) exhibited marked and significant increase in the mean threshold LD of CuSO₄ in dose level (5 mg​/kg) equal to the effect of D-​penicillamine at dose level (30 mg​/kg)​.  The copper chelate and zinc chelate showed good activity against both Gram-​pos. and Gram-​neg. bacteria while the ligands showed activity against Gram-​pos. bacteria only.