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

Table 6

Protonation constants for the DMPTHP ligand and stability constants for the Zn(II) and Cd(II) complexes with the DMPTHP ligand at 0.1 mol·L⁻¹ NaNO₃ at different temperatures.

Reaction	p	q	r	log β (±σ)^a
				15°C	25°C	35°C
L + H = HL^a	0	1	1	8.51 (0.02)	8.31 (0.09)	8.11 (0.04)
L + 2H = H2L	0	1	2	11.88 (0.04)	11.58 (0.05)	11.31 (0.04)
L + 3H = H3L	0	1	3	15.65 (0.05)	15.24 (0.03)	14.88 (0.03)
Zn + L = ZnL	1	1	0	8.82 (0.06)	8.73 (0.07)	8.632 (0.04)
Zn + 2L = ZnL2	1	2	0	11.24 (0.06)	11.09 (0.04)	10.94 (0.09)
Cd + L = CdL2	1	1	0	10.19 (0.08)	10.03 (0.04)	9.92 (0.05)
Cd + 2L = CdL2	1	2	0	13.41 (0.05)	13.18 (0.04)	13.01 (0.06)

^a(σ) is the standard deviation; definitions of stability constants: ; ; L = thiosemicarbazone ligand. Charges are omitted for clarity.