Table 2.

FTIR data.

Compound	Observed frequencies (cm−1)
	BEF ligand	BEF–Cu	BEF–Ni	BEF–Zn
ν NH (asym. and sym.)	3455−3297	3408–3296	3348–3295	3345–3280
ν NH (bending)	1532	1527	1526	1521
CH (stretching)	2731	2697	2712	2725
ν CH2 (asym. and sym.)	3078–2936	3093–2912	3098–2932	3087–2945
ν CH2 (bending in N–CH2–CH2–N)	1450	1448	1449	1446
2,6,8-tri substitution (benzothiazole)	1296−825	1298–825	1293–827	1292–825
ν N→M	—	432	433	433
ν C–NO2	1505–1518	1503–1576	1524–1575	1513–1583
ν C=N	1540	1590	1586	1580
ν C–S–C	740	753	763	748