Characterization of Complexes Synthesized Using Schiff Base Ligands and Their Screening for Toxicity Two Fungal and One Bacterial Species on Rice Pathogens

Table 7

Characteristic IR data for the L1-BHFH (tridentate –O, –O, and –N) and its participation in complex formation with metal ions.

S. number	Complex	IR cm^−1 (s = sharp; b = broad; d = doublet; w = weak; vw = very weak)
		Coord water^e	vO–H and vN–H^e	vC=O^e	vC=N^e	vC=O phenolic^e	M–O, M–N, or M–Cl^e
1	BHFH-L1^c,d,e	—	3260^a	1640 (s)	1610 (s)	1220 (s)^b	—
2	[Cu(BHFH)]2	—	Absent	Absent	1590 (d)	1250 (s)	490, 475, 430
3	[Cu(BHFH)H2O]	3420–3220 (b)	Absent	Absent	1590 (s)	1190	830 (s), 485, 430, 410
4	[Ni(BHFH)H2O]	3500–3400 (b)	Absent	Absent	1620 (s), 1590 (s)	1255 (s)	830 (s), 580, 560
5	[Ni(BHFH)2]	—	3210 (s)	Absent	1610 (d)	1250 (s)	450, 370
6	[Co(BHFH)(H2O)Cl]2	3500–3400 (b)	3210 (s)	Absent	1615 (s) 1580 (s)	1255 (s)	870 (s), 550, 440, 360
7	[Fe(BHFH)Cl2]2	—	3220 (s)	Absent	1615 (s), 1585 (s)	1250 (s)	550, 440, 360
8	[Mn(BHFH)(H2O)Cl]2	3500–3400 (b)	3220 (s)	Absent	1610 (s), 1575 (s)	1245 (s)	845–835 (d), 440, 390, 350
9	[VO(BHFH)Cl]2	—	3175 (s)	Absent	1610 (s), 1585 (s)	1250 (s)	970 (V=O)^f, 550, 420, 370

Overlap of hydrogen bonded O–H and N–H; ^bStretching frequency; ^cNo change in vN=N at 1075 cm⁻¹, Shyamal and Kale [88]; ^dNo change in symmetric and asymmetric frequencies of furfural ring vC–O–C at 1020 (s); 895 (s) cm⁻¹ indicates noninvolvement of O of furfural ring in complexation; ^eThe enolization of the hydrazide residue and the subsequent deprotonation of both the hydroxyl groups or cleavage of hydrogen bond forming M–O bonds confirmed by vC–O phenolic shift, doublet for two vC=N groups (one azomethine participating in complex formation and one formed due to enolization of ligand), absence of vC=O, and new bands for vN–H, vC=N, M–O, and M–N vibrations; Nakamoto [91], Ueno and Martell [92, 93]; ^fSelbin [94].