Antimicrobial metal-based thiophene derived compounds

Figures & data

Scheme 1: Preparation of Schiff bases.

Scheme 2: Co(II), Ni(II), Cu(II) and Zn(II) metal complexes (1)–(12) with (L¹)–(L³).

Figure 1. Comparison of antibacterial activity of Schiff bases versus metal(II) complexes.

Table 1. Physical measurements and analytical data of metal(II) complexes (1)–(12).

					Elemental analysis (%) Calc. (found)
No.	Structure	Yield (%)	MW/formula	M.P. (°C)	C	H	N	M
(1)	[Co(L^1)2]	75	[466.36] C16H24N4S2Cl2Co	311–312	41.21 (41.14)	5.19 (5.16)	12.01 (11.96)	12.64 (12.60)
(2)	[Ni(L^1)2]	72	[466.12] C16H24N4S2Cl2Ni	315–316	41.23 (41.17)	5.19 (5.15)	12.01 (11.97)	12.59 (12.55)
(3)	[Cu(L^1)2]	68	[470.97] C16H24N4S2Cl2Cu	300–301	40.80 (40.74)	5.14 (5.11)	11.90 (11.85)	13.49 (13.44)
(4)	[Zn(L^1)2]	65	[472.81] C16H24N4S2Cl2Zn	305–306	40.64 (40.58)	5.12 (5.09)	11.85 (11.81)	13.56 (13.50)
(5)	[Co(L^2)2]	69	[494.41] C18H28N4S2Cl2Co	309–311	43.73 (43.66)	5.71 (5.68)	11.33 (11.27)	11.92 (11.88)
(6)	[Ni(L^2)2]	70	[494.17] C18H28N4S2Cl2Ni	305–307	43.75 (43.70)	5.71 (5.66)	11.34 (11.30)	11.88 (11.82)
(7)	[Cu(L^2)2]	75	[499.02] C18H28N4S2Cl2Cu	321–322	43.32 (43.28)	5.66 (5.63)	11.23 (11.19)	12.73 (12.68)
(8)	[Zn(L^2)2]	72	[500.87] C18H28N4S2Cl2Zn	319–321	43.16 (43.08)	5.63 (5.60)	11.19 (11.15)	12.80 (11.75)
(9)	[Co(L^3)2]	78	[522.46] C20H32N4S2Cl2Co	305–306	45.98 (45.91)	6.17 (6.13)	10.72 (10.68)	11.28 (11.23)
(10)	[Ni(L^3)2]	68	[522.22] C20H32N4S2Cl2Ni	325–326	46.00 (46.94)	6.18 (6.15)	10.73 (10.68)	11.24 (11.18)
(11)	[Cu(L^3)2]	65	[527.08] C20H32N4S2Cl2Cu	329–331	45.57 (45.51)	6.12 (6.08)	10.63 (10.58)	12.06 (12.02)
(12)	[Zn(L^3)2]	71	[528.92] C20H32N4S2Cl2Zn	327–329	45.42 (45.35)	6.10 (6.06)	10.59 (10.55)	12.36 (12.30)

Table 2. Conductivity, magnetic and spectral data of metal(II) complexes (1)–(12).

No.	ΩM (Ω^−1cm^2mol^−1)	B.M. μeff	λm (cm^−1)	IR (cm^−1)
(1)	88.3	4.2	7622, 17 490, 23 134, 29 858	3348 (NH2), 1663 (C=N), 1045 (C–N), 868 (C–S), 574 (M–N), 462 (M–S)
(2)	88.9	3.1	9875, 15 263, 25 743, 29 586	3350 (N–H), 1665 (C=N), 1044 (C–N), 870 (C–S), 565 (M–N), 460 (M–S)
(3)	92.7	2.2	15 713, 19 415, 29 967	3352 (NH2), 1666 (C=N), 1045 (C–N), 869 (C–S), 547 (M–N), 468 (M–S)
(4)	87.4	Dia	29 926	3355 (NH2),1668 (C=N), 1043 (C–N), 872 (C–S), 548 (M–N), 470 (M–S)
(5)	93.1	4.3	7590, 17 587, 23 252, 30 030	3330 (NH2),1645 (C=N), 1043 (C–N), 875 (C–S), 576 (M–N), 466 (M–S)
(6)	86.8	3.2	9939, 15 379, 25 865, 29 690	3336 (NH2),1642 (C=N), 1045 (C–N), 874 (C–S),561 (M–N), 465 (M–S)
(7)	92.3	2.4	15 681, 19 617, 29 935	3332 (NH2),1638 (C=N), 1044 (C–N), 873 (C–S), 573 (M–N), 463 (M–S)
(8)	87.0	Dia	29 898	3335 (NH2),1640 (C=N), 1045 (C–N), 871 (C–S), 546 (M–N), 470 (M–S)
(9)	91.2	4.5	7645, 17 642, 23 162, 29 961	3374 (NH2), 1649 (C=N), 1040 (C–N), 877 (C–S), 580 (M–N), 469 (M–S)
(10)	95.2	3.4	9914, 15 290, 25 812, 29 635	3375 (NH2), 1656 (C=N), 1041 (C–N), 876 (C–S), 568 (M–N), 463 (M–S)
(11)	90.5	2.5	15 802, 19 585, 29 892	3370 (NH2), 1652 (C=N), 1042 (C–N), 875 (C–S), 548 (M–N), 468 (M–S)
(12)	94.8	Dia	29 902	3372 (NH2), 1654 (C=N), 1043 (C–N), 874 (C–S), 543 (M–N), 471 (M–S)

Table 3. Antibacterial activity of ligands (L¹)–(L³) and metal(II) complexes (1)–(12).

[Zone of inhibition (mm)]
	Gram-negative				Gram-positive
Compounds	(a)	(b)	(c)	(d)	(e)	(f)	(SA)	Average
(L^1)	10	13	12	16	10	16	2.71	12.83
(L^2)	11	10	13	09	09	12	1.63	10.67
(L^3)	13	16	15	19	08	09	3.66	13.33
(1)	23	18	19	18	20	17	2.14	19.17
(2)	20	21	11	18	19	21	3.78	18.33
(3)	18	16	20	21	19	17	1.87	18.50
(4)	19	21	18	23	17	16	2.61	19.00
(5)	10	20	24	21	18	17	4.35	18.33
(6)	19	20	24	17	23	16	3.19	19.83
(7)	20	19	12	16	18	19	2.94	17.33
(8)	12	16	20	21	24	18	4.18	18.50
(9)	21	18	13	20	14	19	3.28	17.50
(10)	16	21	18	17	25	19	3.27	19.33
(11)	13	16	19	20	23	24	4.17	19.17
(12)	18	24	17	20	21	17	2.74	19.50
SD	25	26	25	26	27	28	1.07	26.17

Average activity of ligand (L¹)–(L³) = 12.28 mm; average activity of complexes (1)–(12) =18.71 mm; (a) E. coli, (b) P. aeruginosa, (c) S. typhi, (d) S. flexneri, (e) S. aureus and (f) B. subtilis; SD: standard drug (imipenem); weaker = 0–09 mm; moderate = 10–15 mm; above 16 mm = significant; SA: statistical analysis.

Figure 2. Comparison of antifungal activity of Schiff bases versus metal(II) complexes.

Table 4. Antifungal activity of ligands (L¹)–(L³) and metal(II) complexes (1)–(12).

[% Inhibition (mm)]
Compounds	(a)	(b)	(c)	(d)	(e)	(f)	(SA)	Average
(L^1)	57	40	45	50	38	31	8.42	43.50
(L^2)	41	60	39	00	56	38	19.39	39.00
(L^3)	36	44	00	46	51	00	21.32	29.50
(1)	74	62	67	62	60	56	5.71	63.50
(2)	68	55	59	65	61	59	4.26	61.17
(3)	71	59	56	71	59	58	6.21	62.33
(4)	69	66	70	62	57	60	4.73	64.00
(5)	60	75	61	29	69	57	14.51	58.50
(6)	56	67	57	20	74	61	17.16	55.83
(7)	65	76	60	31	61	55	13.69	58.00
(8)	68	72	58	29	70	62	14.58	59.83
(9)	59	57	42	70	78	27	16.95	55.50
(10)	55	60	35	71	71	17	19.61	51.50
(11)	66	64	40	60	62	31	13.35	53.83
(12)	60	58	38	58	69	30	13.57	52.17
SD	A	B	C	D	E	F	–	–

Average activity of ligands (L¹)–(L³) = 37.33%; average activity of complexes (1)–(12) = 58.01%; (a) T. longifusus, (b) = C. albicans, (c) = A. flavus, (d) = M. canis, (e) = F. solani and (f) = C. 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) and F = miconazole (110.8 μg/mL: 2.66 266 × 10⁻⁷ M/mL); weaker = 0–33%; moderate = 34–54%; 55–100% = significant; SA: statistical analysis.

Table 5. Minimum inhibitory concentration (μg/mL) of the metal complexes (1)–(12).

Compounds	E. coli	P. aeruginosa	S. typhi	S. flexneri	S. aureus	B. subtilis
(1)	18.42	–	–	–	–	–
(2)	23.69	–	–	–	–	–
(3)	–	–	33.93	24.32	–	–
(4)	–	38.86	–	19.23	–	–
(5)	–	–	36.61	–	–	–
(6)	–	–	30.08	–	19.55	–
(7)	38.22	–	–	–	–	–
(8)	–	–	26.43	39.91	22.39	–
(9)	31.52	–	–	–	–	–
(10)	–	33.35	–	–	32.36	–
(11)	–	–	–	–	26.31	19.42
(12)	–	36.73	–	–	–	–