Antibacterial cobalt (II), copper (II), nickel (II) and zinc (II) complexes of mercaptothiadiazole—derived furanyl, thienyl, pyrrolyl, salicylyl and pyridinyl Schiff bases

Figures & data

Scheme 1 Synthesis and structures of (L¹)–(L⁶).

Figure 1 Proposed structural formulae of the metal (II) complexes.

Table I.  Preliminary screening of the schiff bases (L¹)–(L⁶) and their metal (II) complexes (1)–(24) for antibacterial activity (zone of inhibition in mm).

	Microbial species
	Gram-negative				Gram-positive
Schiff base/Complex	E. coli	P. aeruginosa	S. typhi	S. flexneri	B. subtilis	S. aureus
L^1	12	11	10	11	13	12
L^2	10	10	10	11	11	13
L^3	11	11	09	13	12	11
L^4	13	10	10	10	11	13
L^5	11	11	12	13	12	12
L^6	12	12	13	13	14	14
1	18	16	17	18	21	16
2	18	14	15	16	19	20
3	18	16	15	16	17	20
4	19	13	13	17	19	21
5	20	16	21	23	27	27
6	21	17	21	23	28	28
7	20	17	17	18	23	22
8	21	16	17	18	22	24
9	22	18	22	23	28	28
10	23	19	23	24	30	30
11	21	18	19	20	25	23
12	23	17	20	22	26	26
13	19	14	17	17	22	19
14	20	16	21	22	28	27
15	16	16	16	19	18	19
16	20	15	16	16	19	21
17	18	15	16	16	20	22
18	20	14	15	17	20	19
19	18	14	14	17	16	22
20	16	13	17	15	21	21
21	18	16	20	22	25	26
22	20	17	21	22	27	27
23	15	16	16	15	22	19
24	17	15	16	18	17	20
Imipenum	30	24	25	27	33	33

< 9: weak; 9–16: moderate; >16: significant.

Table II.  Minimum inhibitory concentration (mM/ml) of compounds (5)–(6), (9)–(10), (14) and (22) against selected bacteria.

Compound no.	5	6	9	10	14	22
Gram-negative
S. typhi	0.017	0.042	0.013	0.013	0.021	0.017
S. flexneri	0.017	0.017	0.013	0.013	>0.207	>0.173
Gram-positive
B. subtilis	>0.171	0.042	0.034	0.013	>0.207	>0.173
S. aureus	>0.171	>0.170	0.135	0.033	0.052	0.086