DNA binding, BSA interaction and in-vitro antimicrobial studies of Cu(II), Co(III), Ni(II) and VO(IV) complexes with a new Schiff base

Figures & data

Figure 1. Schematic representation of synthesis of Schiff base ligand

Figure 2. MS spectrum of L

Figure 3. ¹H-NMR spectrum of L

Figure 4. ¹³C-NMR spectrum of L

Figure 5. FT IR spectrum of L

Table 1. FTIR spectral data of the Schiff base ligand [L] and its metal complexes

Compound	ν(C = N)	ν(Ph-O)	ν(V = O)	ν(M-O)	ν(M-N)
L	1609	1267	__	__	__
C1	1564	1259	__	477	517
C2	1571	1251	__	462	525
C3	1579	1237	__	459	533
C4	1585	1260	__	474	537
C5	1577	1240	__	468	540
C6	1581	1257	__	484	545
C7	1598	1249	985	493	529
C8	1593	1244	963	470	523

Figure 6. IR spectra of L and its metal complexes

Figure 7. The electronic spectra of ligand L and its metal complexes in DMSO

Figure 8. Thermograms of Cu(II), Co(III), Ni(II) and VO(IV) complexes

Table 2. EPR spectral parameters for copper and oxidovanadium complexes in DMSO at 77 K

Complex	A║	A┴	gavg	g║	g┴	α^2
C1	163	47	3.59	2.154	2.017	0.73
C2	157	53	3.45	2.137	2.056	0.71
C7	187	76	1.971	1.95	1.97	0.70
C8	185	79	1.985	1.93	2.02	0.75

Figure 9. ESR spectrum of C1, C2, C7 and C8

Figure 10. Proposed structures of the prepared metal complexes

Table 3. Antimicrobial results of the Schiff base ligand and its metal complexes

	Zone of inhibition (in mm)
	Antibacterial
	Gram-positive bacteria		Gram-negative bacteria		Antifungal
Compound	B. subtilis	S. aureus	S. typhi	E. coli	A. niger	A. flavus	C. albicans	A. solani
L	12	13	11	10	9	10	7	8
C1	25	17	16	20	15	19	11	14
C2	29	25	19	21	18	20	15	19
C3	30	24	20	28	20	21	19	20
C4	33	29	22	30	22	22	20	23
C5	27	20	18	23	23	18	13	17
C6	34	27	23	32	21	20	22	21
C7	28	23	20	25	19	17	15	18
C8	32	28	21	31	22	21	24	22
Gentamicin	38	33	26	35	^__	^__	^__	^__
Fluconazole	^__	^__	^__	^__	27	24	29	26

Table 4. MIC [μg/ml] values for antimicrobial activity of Schiff base ligand and its corresponding metal complexes

	Bacteria
	Gram-positive bacteria		Gram-negative bacteria		Fungi
Compound	B. subtilis	S. aureus	S. typhi	E. coli	A. niger	A. flavus	C. albicans	A. solani
L	>100	>100	>100	>100	>100	>100	>100	>100
C1	76	70	71	75	68	71	73	60
C2	79	72	73	70	63	69	71	66
C3	64	66	70	68	71	67	63	69
C4	55	51	57	60	52	59	61	58
C5	74	72	77	79	80	77	72	76
C6	61	62	58	65	63	57	52	55
C7	72	76	75	71	78	74	72	77
C8	56	63	67	59	62	58	66	60
Gentamicin	37	37	37	37	^__	^__	^__	^__
Fluconazole	^__	^__	^__	^__	37	37	37	37

Figure 11. Electronic absorption spectra of complexes C3 and C8 (50 μM) in Tris/NaCl buffer (pH = 7.2) upon addition of CT-DNA (0–25 μM). Arrow shows the absorbance changing upon increase of DNA concentration. Inset: linear fit of [DNA]/(ɛa-ɛf) v/s [DNA] for the titration of the C3 and C8 complexes with CT-DNA

Figure 12. Emission spectra of EB bound to DNA in the presence of the complexes C3 and C8; λ_ex = 450 nm, at the concentration 0–30 μM in Tris–HCl/NaCl buffer (pH 7.2). [EB] = 10 µM, [CT-DNA] = 100 µM. The arrow shows the intensity changes upon increasing concentrations of the complex. Inset: linear fit I_O/I v/s [complex], Stern-Volmer quenching curves for the fluorescence titration of complexes C3 and C8 to DNA-EB bound system

Figure 13. Effect of increasing the concentration of the complexes on the relative viscosities of CT‐DNA at 27.0 ± 0.1°C in 5 mM tris‐HCl buffer (pH = 7.2)

Figure 14. Emission spectra of BSA (λ_ex = 280 nm; λ_em = 341 nm for C3, 342 nm for C8) as a function of concentration of the complexes. Arrow indicates the effect of metal complexes C3 and C8 on the fluorescence emission of BSA. Insert: shows the Stern-Volmer plot

Figure 15. Absorption spectrum of BSA in the presence of complexes C3 and C8 having concentration range (0–35 µM) at room temperature. An arrow shows the absorbance changes upon increasing BSA concentration