Metal based drugs: design, synthesis and in-vitro antimicrobial screening of Co(II), Ni(II), Cu(II) and Zn(II) complexes with some new carboxamide derived compounds: crystal structures of N-[ethyl(propan-2-yl)carbamothioyl]thiophene-2-carboxamide and its copper(II) complex

Figures & data

Scheme 1. Preparation of ligands (L¹–L³) and their metal(II) complexes.

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

No.	ΩM (Ω^−1 cm^2 mol^−1)	B.M. (μeff)	λm cm^−1 (nm)	IR (cm^−1)
Co(L^1)2	15.1	3.82	18 140 (551)	3070-3030(CH), 1670(C = O), 1220(C = S), 885(C–S), 530(M–O), 455(M–S)
Ni(L^1)2	12.3	Dia	13 430 (744), 19 230 (520)	3070-3030(CH), 1665(C = O),1221(C = S), 885(C–S), 535(M–O), 460(M–S)
Cu(L^1)2	16.2	1.86	15 190 (658), 21 160 (472)	3070-3030(CH), 1667(C = O), 1222(C = S), 885(C–S), 525(M–O), 450(M–S)
Zn(L^1)2	18.2	Dia	27 360 (365)	3070-3030(CH), 1670(C = O), 1222(C = S), 885(C–S), 532(M–O), 458(M–S)
Co(L^2)2	15.4	3.78	18 380 (544)	3065-3025(CH), 1661(C = O), 1225(C = S), 880(C–S), 530(M–O), 460(M–S)
Ni(L^2)2	14.1	Dia	13 515 (739), 18 770 (532)	3065-3025(CH), 1662(C = O), 1226(C = S), 880(C–S), 535(M–O), 458(M–S)
Cu(L^2)2	10.9	1.90	15 220 (657), 21 450 (466)	3065-3025(CH), 1662(C = O), 1225(C = S), 880(C–S), 532(M–O), 450(M–S)
Zn(L^2)2	11.2	Dia	27 190 (367)	3065-3025(CH), 1660(C = O), 1227(C = S), 880(C–S), 534(M–O), 455(M–S)
Co(L^3)2	13.9	3.94	17 995 (555)	3075-3030(CH), 1665(C = O), 1237(C = S), 1160(C–O), 690(C–Br), 535(M–O), 460(M–S)
Ni(L^3)2	15.2	Dia	13 390 (746), 19 120 (523)	3075-3030(CH), 1665(C = O), 1235(C = S), 1160(C–O), 690(C–Br), 536(M–O), 455(M–S)
Cu(L^3)2	15.2	1.83	15 660 (638), 21 640 (462)	3075-3030(CH), 1667(C = O), 1236(C = S), 1160(C–O), 690(C–Br), 530(M–O), 458(M–S)
Zn(L^3)2	16.6	Dia	27 280 (366)	3075-3030(CH), 1665(C = O), 1235(C = S), 1160(C–O), 690(C–Br), 530(M–O), 455(M–S)

Figure 1. Molecular structure of ligand (L¹).

Figure 2. Molecular structure of Cu(L¹)₂ complex.

Figure 3. Comparison of antibacterial activity of (L¹–L³) and their complexes.

Figure 4. Comparison of antifungal activity of (L¹–L³) and their metal(II) complexes.

Table 2. Antibacterial bioassay (concentration used 1 mg/mL of DMSO) of ligands (L¹–L³) and their metal(II) complexes.

	Zone of inhibition (mm)
	Gram-negative				Gram-positive
Compounds	(a)	(b)	(c)	(d)	(e)	(f)	(SA)	Average
(L^1)	11	08	15	13	13	12	2.04	12.2
(L^2)	10	12	13	11	07	14	2.48	11.2
(L^3)	11	11	12	05	13	15	3.40	11.0
Co(L^1)2	12	11	17	17	12	14	2.64	13.8
Ni(L^1)2	13	12	19	14	16	14	2.50	14.6
Cu(L^1)2	11	12	15	12	17	17	2.79	14.2
Zn(L^1)2	13	11	20	16	13	16	3.19	14.8
Co(L^2)2	13	12	18	11	11	19	3.98	13.6
Ni(L^2)2	12	16	15	14	11	16	2.09	14.0
Cu(L^2)2	13	11	18	13	12	17	2.83	14.5
Zn(L^2)2	11	17	19	12	11	18	3.94	13.3
Co(L^3)2	11	12	18	14	16	17	3.93	14.7
Ni(L^3)2	13	11	17	12	18	18	4.17	14.8
Cu(L^3)2	12	11	18	13	16	17	4.23	14.5
Zn(L^3)2	13	12	19	12	17	19	4.91	15.3
SD	26	24	32	28	27	29	2.73	27.7

Activity of ligand (L¹–L³) = 11.5 mm; Average activity of metal complexes = 14.0 mm; (a) = E. coli; (b) = S. sonnei; (c) = P. aeruginosa; (d) = S. typhi; (e) = S. aureus; (f) = B. subtilis. Activity  < 10 = weak; > 10 = moderate; > 16 = Significant: SD = Standard Drug (Ampicillin). SA = Statistical analysis.

Table 3. Antifungal bioassay (concentration used 200 µg/mL) of ligands (L¹–L³) and metal(II) complexes.

	% Inhibition (mm)
Compounds	(a)	(b)	(c)	(d)	(e)	(f)	(SA)	Average
(L^1)	37	53	30	46	30	40	9.5	39.3
(L^2)	44	15	57	42	36	48	14.2	40.3
(L^3)	44	13	50	48	39	62	16.4	42.7
Co(L^1)2	42	54	31	48	33	43	8.8	41.8
Ni(L^1)2	41	57	36	49	36	41	8.2	43.3
Cu(L^1)2	40	56	35	47	34	46	9.9	44.7
Zn(L^1)2	36	59	34	50	30	44	10.9	42.1
Co(L^2)2	40	18	62	44	41	53	14.8	43.0
Ni(L^2)2	45	14	63	45	39	50	16.2	42.7
Cu(L^2)2	46	20	59	40	42	45	12.7	42.0
Zn(L^2)2	47	17	60	44	37	52	14.8	42.8
Co(L^3)2	50	10	54	52	39	67	19.5	45.3
Ni(L^3)2	47	15	55	46	44	59	15.5	44.3
Cu(L^3)2	49	17	56	47	42	65	16.3	46.0
Zn(L^3)2	40	20	57	50	40	64	15.5	45.1
SD	A	B	C	D	E	F	–	–

Activity of ligands (L¹–L³) = 40.8%; Average activity of metal complexes = 43.6%; (a) = T. longifusus; (b) = C. albicans; (c) = A. flavus; (d) = M. canis; (e) = F. solani; (f) = C. glabrata. SD = Standard drugs, MIC µg/mL; A = Miconazole (70 µg/mL: 1.6822 × 10⁻⁷M/mL), B = Miconazole (110.8 µg/mL: 2.6626 × 10⁻⁷M/mL), C = Amphotericin B (20 µg/mL: 2.1642 × 10⁻⁸M/mL), D = Miconazole (98.4 µg/mL: 2.3647 × 10⁻⁷M/mL), E = Miconazole (73.25 µg/mL: 1.7603 × 10⁻⁷M/mL), F = Miconazole (110.8 µg/mL: 2.66266 × 10⁻⁷M/mL). SA = Statistical analysis.