Antibacterial and antifungal studies of macrocyclic complexes of trivalent transition metal ions with their spectroscopic approach

Figures & data

Scheme 1.  Template condensation of 1,8-diaminonaphthalene and glyoxal in the presence of trivalent metal salts. M = Cr(III), Mn(III), Fe(III), X = Cl⁻, NO₃⁻, CH₃COO⁻.

Table 1.  Analytical data for trivalent chromium, manganese, and iron complexes derived from 1,8-diaminonaphthalene and glyoxal.

	Complex	Found (calcd.) (%)				Color	Mol. wt.
		M	C	H	N
(1)	[Cr(C24H16N4)Cl]Cl2	9.89 (10.03)	54.58 (54.59)	3.06 (3.08)	10.75 (10.81)	Green	518
(2)	[Cr(C24H16N4) (NO3)](NO3)2	8.61 (8.69)	48.05 (48.16)	2.62 (2.67)	16.35 (16.38)	Light green	598
(3)	[Cr(C24H16N4) (OAc)](OAc)2	8.73 (8.82)	55.98 (56.02)	4.20 (4.24)	9.43 (9.50)	Gray	589
(4)	[Mn(C24H16N4) (OAc)](OAc)2	9.19 (9.27)	60.80 (60.81)	4.19 (4.22)	9.44 (9.45)	Black	592
(5)	[Fe(C24H16N4)Cl]Cl2	10.67 (10.69)	55.10 (55.17)	2.98 (3.06)	10.70 (10.72)	Black	522
(6)	[Fe(C24H16N4) (NO3)](NO3)2	9.25 (9.27)	47.81 (47.84)	2.55 (2.65)	16.08 (16.28)	Dark gray	602
(7)	[Fe(C24H16N4) (OAc)](OAc)2	9.40 (9.41)	60.69 (60.71)	4.11 (4.21)	9.37 (9.44)	Brown	593

Figure 1.  Thermogravimetric analysis curves. (a) TGA/DTG curve for [Cr(C₂₄H₁₆N₄)Cl]Cl₂ complex. (b) TGA/DTG curve for [Fe(C₂₄H₁₆N₄)Cl]Cl₂ complex.

Figure 2.  Proposed structure of the complexes. M = Cr(III), Mn(III), Fe(III), X = Cl⁻, NO₃⁻, CH₃COO⁻.

Figure 3.  Comparison of MIC of compounds with standard antibiotics up to the concentration 32 μg/mL. a, Bacillus subtilis (MTCC 8509); b, Bacillus stearothermophilus (MTCC 8508); c, Pseudomonas putida (MTCC 121); d, Escherichia coli (MTCC 51). Chloramphenicol, streptomycin: standard antibiotics.

Table 2.  Minimum inhibitory concentration (MIC) of complexes against test bacteria using agar dilution assay.

	Compound	MIC (μg/mL)^a
		a	b	c	d
(1)	[Cr(C24H16N4)Cl]Cl2	>64	32	16	16
(2)	[Cr(C24H16N4)(NO3)](NO3)2	4	8	16	8
(3)	[Cr(C24H16N4)(OAc)](OAc)2	>64	>64	32	>64
(4)	[Mn(C24H16N4)(OAc)](OAc)2	2	4	2	2
(5)	[Fe(C24H16N4)Cl]Cl2	>64	>64	32	>64
(6)	[Fe(C24H16N4) (NO3)](NO3)2	4	8	16	8
(7)	[Fe(C24H16N4) (OAc)](OAc)2	>64	>64	64	32
	Chloramphenicol	2	2	4	2
	Streptomycin	2	2	4	4

Note. a, Bacillus subtilis (MTCC 8509); b, Bacillus stearothermophilus (MTCC 8508); c, Pseudomonas putida (MTCC 121); d, Escherichia coli (MTCC 51). Chloramphenicol, streptomycin: standard antibiotics.

^aMean of three replicates.

Figure 4.  Comparison of percentage inhibition of compounds against fungal strains with standard drug cyclohexamide. f, Aspergillus flavus; g, Aspergillus niger. Cyclohexamide: standard drug.

Table 3.  Antifungal (percentage inhibition) activities of complexes against fungal strains (for concentration 100 μg/mL).

	Compound	Percentage inhibition
		f	g
(1)	[Cr(C24H16N4)Cl]Cl2	25.77	24.66
(2)	[Cr(C24H16N4) (NO3)](NO3)2	39.19	41.33
(3)	[Cr(C24H16N4) (OAc)](OAc)2	16.44	19.91
(4)	[Mn(C24H16N4) (OAc)](OAc)2	39.19	40.28
(5)	[Fe(C24H16N4)Cl]Cl2	31.72	20.33
(6)	[Fe(C24H16N4) (NO3)](NO3)2	34.60	34.29
(7)	[Fe(C24H16N4) (OAc)](OAc)2	21.66	20.44
	Cyclohexamide	87.34	89.91

Note. f, Aspergillus flavus; g, Aspergillus niger. Cyclohexamide: standard drug.