Antimicrobial, spectral, magnetic and thermal studies of Cu(II), Ni(II), Co(II), UO₂(VI) and Fe(III) complexes of the Schiff base derived from oxalylhydrazide

Figures & data

Figure 1 Proposed structure of Zn(II) complex, from Ref. [16].

Table I.  Characteristic of H₂L and its corresponding mono- and binuclear metal complexes.

			Elemental analysis, Calc. (Found) %
Compound (F.W)^c	Colour	Yield%	C	H	N	Cl	M
H2L C16H14N4O4 (326.0)	Light yellow	70	58.90 (59.10)	4.29 (4.50)	17.18 (17.40)	–	–
(1) [Cu(L)].EtOH C18H18N4O5Cu (434.5)	Light green	25	49.71 (50.14)	4.14 (4.63)	12.89 (13.30)	–	14.84 (14.95)
(2) [Ni(L)(OH2)2].2EtOH C20H28N4O8Ni (510.7)	Pale green	30	46.99 (47.22)	5.48 (5.81)	10.97 (11.30)	–	11.49 (12.10)
(3) [Co(L)(OH2)2]. 2EtOH C20H28N4O8Co (511)	Brown	33	46.97 (47.40)	5.48 (4.82)	10.96 (11.54)	–	11.55 (12.47)
(4) [Fe(L)Cl(OH2)].EtOH C18H20N4O6ClFe (479.5)	Reddish brown	45	45.05 (45.53)	4.17 (4.56)	11.68 (11.80)	7.40 (7.60)	11.68 (12.02)
(5) [UO2(L)(EtOH)].EtOH C20H24N4O6U (686)	Light red	65	34.99 (35.32)	3.50 (3.75)	8.16 (8.48)	–	34.69 (35.33)
(6) [(Cu)2(L)(Cl)2].EtOH C18H18N4O5Cl2Cu2 (570)	Green	35	37.89 (38.13)	3.16 (3.42)	9.82 (10.20)	12.46 (12.25)	22.63 (22.73)
(7) [(Ni)2(L)(Cl)2(OH2)4].2EtOH C20H32N4O10Cl2Ni2 (676.4)	Yellowish green	40	35.48 (35.71)	4.73 (4.27)	8.28 (8.45)	10.50 (11.08)	17.37 (17.52)
(8) [(Co)2(L)(Cl)2(OH2)4].2EtOH C20H32N4O10Cl2Co2 (677)	Brown	38	35.45 (35.81)	4.73 (5.12)	8.27 (8.55)	10.49 (10.70)	17.43 (17.84)
(9) [(Fe)2(L)(Cl)4(OH2)2].EtOH C18H22N4O7Cl4Fe2 (660)	Deep violet	55	32.73 (32.82)	3.33 (3.73)	8.48 (8.91)	21.52 (21.93)	16.97 (17.30)
(10) [(UO2)2(L)(OEt)2]. EtOH C22H28N4O11U2 (1000)	Red	60	26.40 (26.52)	2.80 (3.21)	5.60 (6.04)	–	47.60 (47.82)

EtOH = C₂H₅OH

Figure 2 Keto, enol forms and H-bonding occurring in the Schiff base ligand.

Table II.  ¹H NMR data for the ligand HL in DMSO-d₆.

oxalic bis[(2-hydroxybenzylidene)hydrazide], H2L
Chemical shift, δTMS (ppm)	Assignment^a
7.9	[s, 2H] (1)
16.1	[s, 2H] (2)
11.1	[s, 2H] (3)
7.2	[m, 2H] (4)
7,1	[m, 2H] (5)
7.3	[m, 2H] (6)
6.8	[m, 2H] (7)

^as = singlet, d = multiplet.

Table III.  Infrared frequencies of the ligand and its metal complexes.

		IR frequencies^a,b (cm^− 1)
Compound (F.W)	ν(OH phenolic, H2O or alcohol)	ν(C = N)	ν(C = O)	ν(NH)	ν(M–O)	ν(M–N)
H2L C16H14N4O4 (326.0)	3530 m, br (νOH-phenolic)	1541 s	1677 vs	3176 s	–	–
(1) [Cu(L)].EtOH C18H18N4O5Cu (434.5)	3426 m, br (νOH-alcohol)	1508 s	1671 vs	3178 m	540 m	420 w
(2) [Ni(L)(OH2)2].2EtOH C20H28N4O8Ni (510.7)	3440 m, br (νOH-coordinated water). Overlapped with (νOH-alcohol)	1512 m	1679 vs	3177 m	520 m	425 w
(3) [Co(L)(OH2)2]. 2EtOH C20H28N4O8Co (511)	3440 m, br (νOH-coordinated water). Overlapped with (νOH-alcohol)	1509 s	1678 vs	3179 m	515 m	410 w
(4) [Fe(L)Cl(OH2)].EtOH C18H20N4O6ClFe (479.5)	3440 m, br (νOH-coordinated water). Overlapped with (νOH-alcohol)	1501 sh	1677 vs	3177 m	520 w	445 w
(5) [UO2(L)(EtOH)].EtOH C20H24N4O6U (686)	3440 m, br (νOH alcohol)	1507 s	1675 vs	3177 m	520 m	465 w
(6) [(Cu)2(L)(Cl)2].EtOH C18H18N4O5Cl2Cu2 (570)	3426 m, br (νOH-alcohol)	1512 s	1651 vs	3178 m	540 m	420 w
(7) [(Ni)2(L)(Cl)2(OH2)4].2EtOH C20H32N4O10Cl2Ni2 (676.4)	3440 m, br (νOH-coordinated water). Overlapped with (νOH-alcohol)	1502 m	1650 vs	3177 m	520 m	425 w
(8) [(Co)2(L)(Cl)2(OH2)4].2EtOH C20H32N4O10Cl2Co2 (677)	3440 m, br (νOH-coordinated water). Overlapped with (νOH-alcohol)	1519 s	1655 vs	3179 m	515 m	410 w
(9) [(Fe)2(L)(Cl)4(OH2)2].EtOH C18H22N4O7Cl4Fe2 (660)	3400 m, br (νOH-coordinated water). Overlapped with (νOH-alcohol)	1515 m	1649 vs	3177 m	520 w	445 w
(10) [(UO2)2(L)(OEt)2]. EtOH C22H28N4O11U2 (1002)	3440 m, br (νOH alcohol)	1517 s	1654 vs	3180 sh	520 m	465 w

^aOther bands: H₂L 1558 ν(s C = C), 1140 ν(s N–N), 1336nν(s C-N), 3107 ν(s OH enolic), 1228 (δ phenolic OH); (1) 1559 ν(s C = C), 1136 ν(s N–N), 1337 ν(s C–N), 357 m ν(s Cu–Cl); (2) 1557 ν(s C = C), 1140 ν(s N–N), 1332ν(s C–N); (3) 1554 ν(s C = C), 1125 ν(w N–N), 1321ν(s C–N); (4) 1565 ν(s C = C), 1130 ν(m N–N), 1325 ν(s C–N); (5) 1554 ν(s C = C), 1125 ν(w N–N), 1320ν(s C–N), 901 ν₃(s O = U = O)., (6) 1557 ν(s C = C), 1140 ν(s N–N), 1337 ν(s C–N), 1357 m; (7 and 8) 1557 ν(s C = C), 1139 ν(s N–N), 1335 ν(s C–N), 357 ν(m Ni–Cl), 355 ν(m Co–Cl); (9) 1558 ν(s C = C), 1132 ν(w N–N), 1321ν(s C–N), 350 ν(m Fe–Cl); (10) (5) 1554 ν(s C = C), 1130 ν(w N–N), 1325ν(s C–N), 901 ν₃(s O = U = O)

^b v = very, s = strong, m = medium, w = weak, br = broad, ^bsh = shoulder.

Table IV.  Magnetic moment, electronic and conductance measurements spectral data (nm) for H₂L and its metal complexes.

Compound	μeff.^a B.M.	μcompl^b found (expected)^c B.M.			EC^d
H2L C16H14N4O4 (326.0)	–	–	244, 360, 395 (sh)^e	–	–
(1) [Cu(L)].EtOH C18H18N4O5Cu (434.5)	1.76	–	240,311, 325, 348	665	11.4
(2) [Ni(L)(OH2)2].2EtOH C20H28N4O8Ni (510.7)	3.19	–	240,311, 325, 355	670 (sh), 768	11.0
(3) [Co(L)(OH2)2]. 2EtOH C20H28N4O8Co (511)	5.20	–	249, 311, 359, 395	656, 477, 414	12.6
(4) [Fe(L)Cl(OH2)].EtOH C18H20N4O6ClFe (479.5)	4.20	–	247, 315, 350, 395	552, 392	38.4
(5) [UO2(L)(EtOH)].EtOH C20H24N4O6U (686)	–	–	247, 317, 350, 395	552, 392	13.6
(6) [(Cu)2(L)(Cl)2].EtOH C18H18N4O5Cl2Cu2 (570)	–	2.82 (3.56)	240, 320, 359, 395	245,315, 330, 350, 670	11.5
(7) [(Ni)2(L)(Cl)2(OH2)4].2EtOH C20H32N4O10Cl2Ni2 (676.4)	–	4.44 (6.40)	250, 322, 350, 369	659, 837	11.5
(8) [(Co)2(L)(Cl)2(OH2)4].2EtOH C20H32N4O10Cl2Co2 (677)	–	7.52 (10.40)	249, 312, 359, 390	675, 477, 414	12
(9) [(Fe)2(L)(Cl)4(OH2)2].EtOH C18H22N4O7Cl4Fe2 (660)	–	5.94 (8.42)	247, 314, 350, 395	552, 392	48.5
(10) [(UO2)2(L)(OEt)2]. EtOH C22H28N4O11U2 (1002)	–	–	247, 315, 350, 395	580, 567,523, 530	11

^aμ_eff. is the magnetic moment of only one cationic species in the complex

^bμ_compl. is the magnetic moment of all cations in the complex

^cThe expected values were calculated by adding known susceptibilities of the metal cations present in the complex in the suggested structures

^dEC = Electrical Conductance, 10^{− 3} M solution in DMF, Ohm^{− 1} cm²mol^{− 1}

^esh = shoulder.

Figure 3 Suggested structures for mono- and binuclear nuclear complexes.

Table V.  Thermal analyses data for some metal complexes of H₂L.

Compound M.F. (M.W.)	dissociation Stages	Temp range in TG ^oC	Weight loss Found (Calcd.) %	Decomposition assignment
(1) [Cu(L)].EtOH C18H18N4O5Cu (434.5)	Stage I	61–110	10.40 (10.61)	1 mol outer sphere EtOH
	Stage II	224–235	25.86 (26.30)	2 CO, N2H2 and N2
	Stage III	385–450	39.64 (39.20)	C2H2 and (C6H4)2O
(2) [Ni(L)(OH2)2].2EtOH C20H28N4O8Ni (510.7)	Stage I	61–110	26.00 (25.10)	2 mol outer sphere EtOH
	Stage II	130–210	7.57 (7.10)	2 mol coordinated water
	Stage III	228–240	21.94 (22.32)	2 CO, N2H2 and N2
	Stage IV	385–450	37.73 (38.00)	C2H2 and (C6H4)2O
(3) [Co(L)(OH2)2]. 2EtOH C20H28N4O8Co (511)	Stage I	61–110	26.00 (25.12)	2 mol outer sphere EtOH
	Stage II	130–210	7.57 (7.11)	2 mol coordinated water
	Stage III	228–240	21.94 (22.33)	2 CO, N2H2 and N2
	Stage IV	385–450	37.73 (38.03)	C2H2 and (C6H4)2O
(4) [Fe(L)Cl(OH2)].EtOH C18H20N4O6ClFe (479.5)	Stage I	65–110	9.74 (9.59)	outer sphere EtOH
	Stage II	130–220	7.77 (7.50)	2 mol coordinated water
	Stage III	240–260	38.80 (38.50)	2 CO, N2H2 and N2 and Cl
	Stage IV	285–465	37.23 (38.80)	C2H2 and (C6H4)2
(5) [UO2(L)(EtOH)].EtOH C20H24N4O6U (686)	Stage I	61–110	6.30 (6.71)	outer sphere EtOH
	Stage II	130–212	6.35 (6.71)	coordinated ethanol
	Stage III	228–246	17.10 (16.62)	2 CO, N2H2 and N2
	Stage IV	385–450	28.70 (28.30)	C2H2 and (C6H4)2O
(6) [(Cu)2(L)(Cl)2].EtOH C18H18N4O5Cl2Cu2 (570)	Stage I	61–110	8.50 (8.10)	1 mol outer sphere EtOH
	Stage II	238–260	13.20 (12.81)	2 mol HCl
	Stage III	330–370	25.70 (25.30)	2 CO, and 2N2
	Stage IV	385–455	37.67 (37.12)	2 C7H6O
(7) [(Ni)2(L)(Cl)2(OH2)4].2EtOH C20H32N4O10Cl2Ni2 (676.4)	Stage I	61–120	13.20 (13.60)	2 mol outer sphere EtOH
	Stage II	125–220	11.20 (10.64)	4 mol coordinated water
	Stage III	238–260	10.73 (10.80)	2 mol HCl
	Stage IV	335–375	22.30 (21.80)	2 CO, and 2N2
	Stage V	385–455	31.50 (31.33)	2 C7H6O
(8) [(Co)2(L)(Cl)2(OH2)4].2EtOH C20H32N4O10Cl2Co2 (677)	Stage I	61–120	13.27 (13.58)	2 mol outer sphere EtOH
	Stage II	125–220	10.17 (10.63)	4 mol coordinated water
	Stage III	238–260	10.73 (10.80)	2 mol HCl
	Stage IV	335–375	21.18 (21.30)	2 CO, and 2N2
	Stage V	385–455	31.50 (31.31)	2 C7H6O
(9) [(Fe)2(L)(Cl)4(OH2)2].EtOH C18H22N4O7Cl4Fe2 (660)	Stage I	61–120	6.74 (7.00)	mol outer sphere EtOH
	Stage II	125–220	5.80 (5.5.0)	2 mol coordinated water
	Stage III	238–260	23.21 (21.82)	2 mol HCl, Cl2
	Stage IV	335–375	16.86 (17.00)	2 CO, and 2N2
	Stage V	385–455	32.50 (32.12)	2 C7H6O
(10) [(UO2)2(L)(OEt)2]. EtOH C22H28N4O11U2 (1000)	Stage I	61–120	4.50 (4.60)	mol outer sphere EtOH
	Stage II	112–130	9.50 (9.00)	mol coordinated EtO-OEt
	Stage III	335–375	14.80 (14.40)	2 CO, and 2N2
	Stage IV	385–465	21.56 (21.20)	2 C7H6O

Table VI.  Anti-microbial activity of the tested complexes.

	MIC**
Compound	Staphylococcus aureus ATCC* 6538	Escherichia.coli ATCC 8739	Candida albicans ATCC 10231
H2LC16H14N4O4 (326)	50%	25%	–
(1) [Cu(L)].EtOH C18H18N4O5Cu (433.5)	25%	25%	25%
(2) [Ni(L)(OH2)2].2EtOH^c C20H28N4O8Ni (510.7)	25%	25%	25%
(3) [Co(L)(OH2)2].2EtOH^c C20H28N4O8Co (511)	50%	25%	–
(4) [Fe(L)Cl(OH2)2].EtOH^c C18H22N4O7ClFe (497.5)	1%	25%	1%
(5) [UO2(L)(EtOH)].EtOH^c C20H24N4O6U (686)	25%	50%	25%
(6) [(Cu)2(L)(Cl)2].EtOH C18H18N4O5Cl2Cu2 (568)	50%	25%	–
(7) [(Ni)2(L)(Cl)2(OH2)4]. 2EtOH C20H28N4O8Cl2Ni2 (640)	50%	25%	–
(8) [(Co)2(L)(Cl)2(OH2)4]. 2EtOH C20H28N4O8Cl2Co2 (641)	25%	50%	25%
(9) [(Fe)2(L)(Cl)2(OH2)2].EtOH C18H22N4O7Cl4Fe2 (660)	1%	50%	1%
(10) [(UO2)2(L)(OEt)2]. EtOH C22H28N4O11U2 (1000)	25%	50%	25%

*number of strain in the American collection

**MIC is the lowest concentration of the compound solution to inhibit the growth of the microorganism.