Metal-based ethanolamine-derived compounds: a note on their synthesis, characterization and bioactivity

Figures & data

Scheme 1. Preparation of ligands.

Scheme 2. Metal(II) complexes.

Table 1. Physical measurements and analytical data of metal (II) complexes (1)–(16).

					Elemental analysis (%)Calc (Found)
No	Structure	Yield (%)	MW/Formula	M.P (°C)	C	H	N	M
1	[Co(L^1–H)2]	70	[487.41]C26H24N2O4Co	166–168	64.07(64.01)	4.96 (4.92)	5.75 (5.72)	12.09 (12.04)
2	[Ni(L^1–H)2]	70	[487.17] C26H24N2O4Ni	220–222	64.10 (64.01)	4.97 (4.92)	5.75 (5.71)	12.05 (12.01)
3	[Cu(L^1–H)2]	75	[492.02]C26H24N2O4Cu	185–187	64.77 (64.71)	4.92 (4.89)	5.69 (5.65)	12.92 (12.88)
4	[Zn(L^1–H)2]	83	[493.89]C26H24N2O4Zn	197–199	63.23 (63.18)	4.90 (4.86)	5.67 (5.62)	13.24 (13.20)
5	[Co(L^2–H)2]	71	[387.30]C18H20N2O4Co	175–176	55.82 (55.77)	5.21 (5.18)	7.23 (7.20)	15.22 (15.18)
6	[Ni(L^2–H)2]	74	[387.06]C18H20N2O4Ni	230–232	55.86 (55.80)	5.21 (5.17)	7.24 (7.20)	15.16 (15.12)
7	[Cu(L^2–H)2]	81	[391.91]C18H20N2O4Cu	194–196	55.16 (55.11)	5.14 (5.10)	7.15 (7.12)	16.21 (16.17)
8	[Zn(L^2–H)2]	82	[393.77]C18H20N2O4Zn	270–272	54.90 (54.85)	5.12 (5.09)	7.11 (7.06)	16.61 (16.56)
9	[Co(L^3–H)2]	85	[545.09]C18H18Br2N2O4Co	225–227	39.66 (39.61)	3.33 (3.29)	5.14 (5.11)	10.81 (10.77)
10	[Ni(L^3–H)2]	80	[544.85]C18H18Br2N2O4Ni	194–196	39.68 (39.64)	3.33 (3.29)	5.14 (5.10)	10.77 (10.73)
11	[Cu(L^3–H)2]	84	[549.70]C18H18Br2N2O4Cu	214–216	39.33 (39.29)	3.30 (3.27)	5.10 (5.07)	11.56 (11.52)
12	[Zn(L^3–H)2]	80	[551.56] C18H18Br2N2O4Zn	211–212	39.20 (39.15)	3.29 (3.26)	5.08 (5.04)	11.86 (11.82)
13	[Co(L^4)2]	74	[481.32]C18H22N4O8Co	176–177	44.92 (44.87)	4.61 (4.57)	11.64 (11.60)	12.24 (12.20)
14	[Ni(L^4)2]	82	[481.07]C18H22N4O8Ni	206–208	44.94 (44.89)	4.61 (4.58)	11.65 (11.60)	12.20 (12.16)
15	[Cu(L^4)2]	77	[485.84]C18H22N4O8Cu	190–191	44.49 (44.44)	4.56 (4.53)	11.53 (11.50)	13.08 (13.05)
16	[Zn(L^4)2]	78	[487.80] C18H22N4O8Zn	278–280	44.32 (44.27)	4.55 (4.51)	11.49 (11.45)	13.41 (13.37)

Table 2. Conductivity, magnetic and spectral data of metal(II) complexes (1)–(16).

No	ΩM (Ω^−1 cm^2 mol^−1)	B.M μeff	λm (cm^−1)	IR (cm^−1)
1	15.9	4.35	8723, 17 690, 29 820	3370 (OH), 1616 (HC = N), 1370 (C–O), 520 (M–N), 442 (M–O)
2	15.7	3.56	8635, 17 717, 25 817, 29 781	3372 (OH), 1615 (HC = N), 1372 (C–O), 535 (M–N), 450 (M–O)
3	14.6	1.66	8897, 17 783, 29 816	3371 (OH), 1620 (HC = N), 1373 (C–O), 529 (M–N), 448 (M–O)
4	14.9	Dia	28 915	3373 (OH), 1618 (HC = N), 1371 (C–O), 533 (M–N), 450 (M–O)
5	16.2	4.53	8650, 17 729, 29 841	3366 (OH), 1612 (HC = N), 1372 (C–O), 522 (M–N), 446 (M–O)
6	15.8	3.41	8712, 17 761, 25 778, 29 738	3365 (OH), 1610 (HC = N), 1370 (C–O), 536 (M–N), 445 (M–O)
7	15.6	1.71	8937, 17 892, 29 812	3365 (OH), 1615 (HC = N), 1371 (C–O), 526 (M–N), 443 (M–O)
8	15.1	Dia	28 928	3368 (OH), 1613 (HC = N), 1373 (C–O), 532 (M–N), 440 (M–O)
9	16.2	4.38	8680, 17 523, 29 831	3368 (OH), 1611 (HC = N), 1377 (C–O), 540 (M–N), 449 (M–-O)
10	15.2	3.48	8786, 17 777, 25 719, 29 781	3367 (OH), 1610 (HC = N), 1376 (C–O), 524 (M–N), 453 (M–O)
11	16.0	1.74	8727, 17 765, 29 788	3370 (OH), 1612 (HC = N), 1375 (C–O), 536 (M–N), 448 (M–O)
12	15.0	Dia	28 841	3377 (OH), 1608 (HC = N), 1377 (C–O), 528 (M–N), 451 (M–O)
13	14.6	4.45	8790, 17 800, 29 805	3470 (H2O), 1620 (HC = N), 540 (M–N), 455 (M–O)
14	16.5	3.51	8696, 17 871, 25 719, 29 778	3471 (H2O), 1622 (HC = N), 544 (M–N), 459 (M–O)
15	15.4	1.70	8866, 17 857, 29 858	3470 (H2O), 1623 (HC = N), 541 (M–N), 460 (M–O)
16	15.1	Dia	28 932	3473 (H2O), 1619 (HC = N), 543 (M–N), 463 (M–O)

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

Table 3. Antibacterial bioassay of ligands (L¹)–(L⁴) and metal(II) complexes (1)–(16).

[Zone of inhibition (mm)]
	Gram-negative				Gram-positive
Compounds	(a)	(b)	(c)	(d)	(e)	(f)	(SA)	Average
L^1	08	13	11	10	13	07	2.50	10.33
L^2	13	11	12	08	09	11	1.86	10.67
L^3	16	12	11	17	16	12	2.61	14.00
L^4	16	17	15	17	16	15	0.89	16.00
1	14	19	17	15	19	14	2.59	16.50
2	17	18	12	17	18	14	2.45	16.00
3	16	17	18	13	16	12	2.34	15.33
4	13	16	19	16	20	15	2.59	16.50
5	18	17	19	14	12	18	2.73	16.33
6	16	18	16	13	14	16	1.76	15.50
7	17	19	15	16	16	16	1.38	16.50
8	20	17	19	15	16	17	2.50	17.67
9	20	21	17	22	22	18	2.10	20.00
10	22	16	19	19	23	21	2.53	20.00
11	20	17	16	21	19	20	1.94	18.83
12	18	24	19	23	20	21	2.32	20.83
13	21	23	16	20	19	18	2.58	19.67
14	20	17	21	22	24	22	2.37	21.00
15	19	22	17	19	25	20	2.80	20.33
16	22	21	22	24	21	21	1.17	21.83
SD	25	26	25	27	27	28	1.17	25.83

Average activity of ligand (L¹)–(L⁴) = 12.75 mm; Average activity of complexes (1)–(16) = 18.74 mm; (a) E. coli (b) S. flexneri (c) P. aeruginosa (d) S. typhi (e) S. aureus (f) B. subtilis; SD: standard drug (Imipenum); weaker = 0–08 mm, moderate = 09–14 mm, above 14 mm = significant, SA: statistical analysis.

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

Table 4. Antifungal bioassay of ligands (L¹)–(L⁴) and metal(II) complexes (1)–(16).

[% Inhibition (mm)]
Compounds	(a)	(b)	(c)	(d)	(e)	(f)	(SA)	Average
L^1	45	17	55	37	00	40	20.18	32.33
L^2	38	56	49	00	43	30	19.77	36.00
L^3	56	60	61	56	63	59	2.79	59.17
L^4	62	58	59	63	61	55	2.94	59.67
1	62	37	63	49	16	61	18.63	48.00
2	55	25	75	77	26	58	22.81	52.67
3	59	42	62	55	23	69	16.66	51.67
4	65	36	64	56	37	57	12.91	52.50
5	57	68	66	17	75	66	20.97	58.17
6	61	69	72	28	69	71	16.94	61.67
7	55	73	67	30	66	75	16.72	61.00
8	56	64	68	25	68	69	17.03	58.33
9	71	75	70	67	72	74	2.88	71.50
10	75	69	57	73	70	67	6.32	68.50
11	69	74	70	65	69	65	3.39	68.67
12	70	78	68	74	73	60	6.19	70.50
13	72	75	70	61	72	64	5.37	69.00
14	78	65	57	73	70	67	7.20	68.33
15	69	58	70	65	72	65	5.01	66.50
16	75	68	72	77	79	68	4.62	73.17
SD	A	B	C	D	E	F	–	–

Average activity of ligands (L¹)–(L⁴) = 46.79%; Average activity of complexes (1)–(16) = 62.51%; (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 × 10⁻⁷ 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); weaker = 0–33%, moderate = 34–54%, 55–100% = significant; SA = statistical analysis.

Table 5. MIC (μg/mL) of the selected compounds (9), (10) and (12)–(16) against selected bacteria.

Compounds	E. coli	S. flexneri	P. aeruginosa	S. typhi	S. aureus
9	–	46.21	–	37.16	25.17
10	30.16	–	–	–	39.24
12	–	36.35	–	43.22	–
13	23.71	28.67	–	–	–
14	–	–	32.11	46.62	16.11
15	–	25.00	–	–	26.35
16	39.10	18.17	42.65	25.31	–

Table 6. Cytotoxicity (in vitro) of ligands (L¹)–(L⁴) and their metal(II) complexes (1)–(16).

Compounds	LD50 (M/mL)	Compounds	LD50 (M/mL)	Compounds	LD50 (M/mL)
L^1	>2.19 × 10^−3	4	>1.64 × 10^−3	11	>4.71 × 10^−3
L^2	>1.81 × 10^−3	5	>3.19 × 10^−3	12	>2.68 × 10^−3
L^3	>3.11 × 10^−3	6	>4.04 × 10^−3	13	>2.51 × 10^−3
L^4	>2.19 × 10^−3	7	>4.59 × 10^−4	14	>2.11 × 10^−3
1	>3.81 × 10^−3	8	>2.81 × 10^−3	15	>4.19 × 10^−4
2	>2.11 × 10^−3	9	>3.15 × 10^−3	16	>3.81 × 10^−3
3	>4.10 × 10^−3	10	>1.98 × 10^−3