Synthesis, characterization and biological studies of sulfonamide Schiff’s bases and some of their metal derivatives

Figures & data

Table 1.  Physical measurements and analytical data of metal(II) complexes, (1)–(8).

No.	Complexes	Molecular mass	M.P. (dec.)	Colour	Yield	Calculation (found) (%)
	Molecular formula		(°C)		(%)	C	H	N
(1)	[Co(L^1-H)2(H2O)2] C34H30N6O10S2Br2Co	[965.53]	240–242	Red-brown	79	42.26 (42.38)	3.11 (3.10)	8.70 (8.62)
(2)	[Ni(L^1-H)2(H2O)2] C34H30N6O10S2Br2 Ni	[965.26]	234–236	Brown	82	42.27 (42.38)	3.11 (3.1)	8.71 (8.63)
(3)	[Cu(L^1-H)2(H2O)2] C34H30N6O10S2Br2Cu	[970.14]	223–225	Brick red	80	42.06 (42.15)	3.10 (3.04)	8.66 (8.72)
(4)	[Zn(L^1-H)2(H2O)2] C34H30N6O10S2Br2 Zn	[971.98]	235–237	Brick red	79	41.98 (42.11)	3.09 (3.06)	6.65 (6.74)
(5)	[Co(L^2-H)2(H2O)2] C30H32N4O8S2Br2 Co	[859.47]	208–210	Green-brown	83	41.88 (42.01)	3.73 (3.66)	6.52 (6.6)
(6)	[Ni(L^2-H)2(H2O)2] C30H32N4O8S2Br2 Ni	[859.23]	202–204	Light green	79	41.90 (41.89)	3.73 (3.72)	6.52 (6.75)
(7)	[Cu(L^2-H)2(H2O)2] C30H32N4O8S2Br2 Cu	[864.08]	220–222	Green-yellow	82	41.67 (41.78)	3.70 (3.78)	6.48 (6.42)
(8)	[Zn(L^2-H)2(H2O)2] C30H32N4O8S2Br2 Zn	[865.93]	212–214	Brown	80	41.57 (41.64)	3.70 (3.76)	6.47 (6.44)

Table 2.  Conductivity, magnetic and spectral data of metal(II) complexes, (1)–(8).

No.	ωM	B.M.	λmax	IR
	(ω^−1 cm^2 mol^−1)	(μeff)	(cm^−1)	(cm^−1)
(1)	16.7	4.91	7361, 17519, 20626, 29353	1569 (C=N), 1393 (C-O), 1345, 1110 (SO2), 954 (S-N), 841 (C-S), 441 (M-N), 534 (M-O)
(2)	15.6	3.36	10434, 15789, 26494, 30955	1566 (C=N), 1393 (C-O), 1345, 1110 (SO2), 954 (S-N), 842 (C-S), 439 (M-N), 534 (M-O)
(3)	13.9	1.85	15156, 19210, 30356	1565 (C=N), 1394 (C-O), 1345, 1110 (SO2), 954 (S-N), 841 (C-S), 441 (M-N), 529 (M-O)
(4)	15.9	Dia	29134	1567 (C=N), 1393 (C-O), 1345, 1110 (SO2), 953 (S-N), 841 (C-S), 439 (M-N), 533 (M-O)
(5)	17.6	4.94	7297, 17492, 20485, 29362	1569 (C=N), 1395 (C-O), 1345, 1110 (SO2), 954 (S-N), 841 (C-S), 441 (M-N), 529 (M-O)
(6)	18.1	3.32	10410, 15689, 26538, 29991	1565 (C=N), 1394 (C-O), 1345, 1110 (SO2), 954 (S-N), 841 (C-S), 440 (M-N), 531 (M-O)
(7)	15.2	1.88	14981, 19188, 30382	1567 (C=N), 1395 (C-O), 1345, 1110 (SO2), 954 (S-N), 841 (C-S), 441 (M-N), 535 (M-O)
(8)	15.7	Dia	28984	1569 (C=N), 1395 (C-O), 1345, 1110 (SO2), 954 (S-N), 841 (C-S), 439 (M-N), 529 (M-O)

IR, infrared.

Scheme 1.  Preparation of Schiff’s bases (L¹) and (L²).

Scheme 2.  Proposed structure of the metal(II) complexes (1)–(8).

Table 3.  Antibacterial study (concentration used 1 mg/mL of DMSO) of ligands (L¹) and (L²) and metal(II) complexes (1)–(8).

Bacteria	Compound [zone of inhibition (mm)]
	(L^1)	(L^2)	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	SD
Gram-negative
(a)	14	16	16	19	20	22	15	19	18	24	25
(b)	08	07	08	12	10	11	09	10	11	12	17
(c)	12	14	16	22	20	22	17	17	17	23	25
(d)	13	10	17	19	18	21	18	19	16	22	23
Gram-positive
(e)	16	17	14	21	19	23	14	18	17	25	26
(f)	15	19	18	20	17	20	16	17	19	23	25
Average	13	13.83	14.83	18.83	17.33	19.83	14.83	16.67	16.33	21.5	23.5

(a) = Escherichia coli, (b) = Shigella flexneri, (c) = Pseudomonas aeruginosa, (d) = Salmonella typhi, (e) = Staphylococcus aureus, (f) = Bacillus subtilis; <10 = weak, >10 = moderate, >16 = significant; SD = standard drug (imipenum).

DMSO, dimethyl sulfoxide.

Figure 1.  Comparison of antibacterial activity of ligands (L¹) and (L²) and metal(II) complexes (1)–(8).

Figure 2.  Average antibacterial activity of ligands (L¹) and (L²) and metal(II) complexes (1)–(8).

Table 4.  Antifungal study (concentration used 200 µg/mL) of ligands (L¹) and (L²) and metal(II) complexes (1)–(8).

Organism	Compounds
	(L^1)	(L^2)	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	SD
(a)	68	00	75	68	38	69	53	51	46	72	A
(b)	00	55	00	00	45	45	34	00	00	65	B
(c)	82	86	52	65	61	88	75	62	68	00	C
(d)	44	32	76	85	84	72	38	54	76	84	D
(e)	32	00	44	23	56	00	69	82	81	80	E
(f)	20	44	00	57	00	65	00	42	00	45	F
Average	41	36.16	41.16	49.67	47.33	56.5	44.83	48.5	45.16	57.67

(a) = Trichophyton longifusus; (b) = Candida albicans; (c) = Aspergillus flavus; (d) = Microsporum canis; (e) = Fusarium solani; (f) = Candida glabrata; SD, standard drugs MIC µg/mL; A = miconazole (70 µg/mL:1.6822 × 10⁻⁷ M/mL), B = miconazole (110.8 µg/mL:2.6626 × 10⁻⁷ M/mL), C = amphotericin B (20 µg/mL:2.1642 × 10⁻⁸ M/mL), D = miconazole (98.4 µg/mL:2.3647 × 10⁻⁷ M/mL), E = miconazole (73.25 µg/mL: 1.7603 × 10⁻⁷ M/mL), F = miconazole (110.8 µg/mL: 2.66266 × 10⁻⁷ M/mL).

MIC, minimum inhibitory concentration.

Figure 3.  Comparison of antifungal activity of ligands (L¹) and (L²) and metal(II) complexes (1)–(8).

Figure 4.  Average antifungal activity of ligands (L¹) and (L²) and metal(II) complexes (1)–(8).

Table 5.  Minimum inhibitory concentration (M/mL) of the selected compounds (2), (4) and (8) against selected bacterial strains.

Bacterial strains	(2)	(4)	(8)
Gram-negative
Escherichia coli	–	4.168 × 10^−8	2.215 × 10^−7
Pseudomonas aeruginosa	–	–	3.294 × 10^−8
Salmonella typhi	1.341 × 10^−7	3.394 × 10^−8	3.714 × 10^−8
Gram-positive
Staphylococcus aureus	6.743 × 10^−8	5.338 × 10^−7	6.439 × 10^−8
Bacillus subtilis	2.891 × 10^−7	1.677 × 10^−8	3.252 × 10^−8

Table 6.  Brine shrimp study of the ligands (L¹)–(L²) and their metal(II) complexes (1)–(8).

Compounds	LD50 (M/mL)
(L^1)	>3.284 × 10^−3
(L^2)	>3.284 × 10^−3
(1)	>3.284 × 10^−3
(2)	>3.284 × 10^−3
(3)	6.342 × 10^v4
(4)	>3.284 × 10^−3
(5)	>3.284 × 10^−3
(6)	>3.284 × 10^−3
(7)	6.173 × 10^−4
(8)	>3.284 × 10^−3

Figure 5.  The proposed fragmentation pattern of ligand (L²).

Figure 6.  The proposed fragmentation pattern of complex [Cu(L²-H)₂(H₂O)₂].