Synthesis and Biological Evaluation of Novel Zn(II) and Cd(II) Schiff Base Complexes as Antimicrobial, Antifungal, and Antioxidant Agents

Table 7

Stepwise stability for the complexes of DMPTHP with Zn(II) and Cd(II) metal ions in 50% DMSO-H₂O (V/V) solution at I = 0.1 mol·dm⁻³ NaNO₃.

Temperature (°C)	log K1 (±σ)^a		log K2 (±σ)		log K1 − log K2
	ZnL	CdL	ZnL2	CdL2	Zn(II) complex	Cd(II) complex
15	8.82 (0.06)	10.19 (0.05)	2.42 (0.08)	3.22 (0.05)	6.40	6.97
25	8.73 (0.07)	10.03 (0.03)	2.36 (0.05)	3.15 (0.04)	6.37	6.88
35	8.63 (0.04)	9.92 (0.06)	2.31 (0.07)	3.09 (0.06)	6.32	6.83

^a(σ) is the standard deviation; definitions of stability constants: K₁ = [ML]/[M][L]; K₂ = [ML₂]/[ML][L]; L = DMPTHP. Charges are omitted for simplicity.