Synthesis, characterization, thermal decomposition and antifungal studies of Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) complexes of n,n′-bis[1,3-benzodioxol-5ylmethylene]ethane-1, 2-diamine

Article abstract of DOI:10.1080/15533170903433295

A bidentate/tetradentate Schiff base namely, N,N′-bis[1,3benzodioxol- 5-ylmethylene] ethane-1,2-diamine was synthesized by condensing piperonaldehyde (3,4-dioxymethylenebenzaldehyde) with ethylenediamine. Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II

Full text of DOI:10.1080/15533170903433295

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Synthesis and Reactivity in Inorganic, Metal-Organic,
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Synthesis, Characterization, Thermal Decomposition
and Antifungal Studies of Cr(III), Mn(II), Fe(III),
Co(II), Ni(II) and Cu(II) Complexes of N,N′-bis[1,3-
benzodioxol-5ylmethylene]ethane-1, 2-diamine
a
b
Prasad M. Alex & K. K. Aravindakshan
a
Department of Chemistry, Marthoma College, Chungathara, Nilambur , University of
Calicut , Kerala, India
b
Department of Chemistry , University of Calicut , Kerala, India
Published online: 14 Dec 2009.
To cite this article: Prasad M. Alex & K. K. Aravindakshan (2009) Synthesis, Characterization, Thermal
Decomposition and Antifungal Studies of Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) Complexes of N,N′-bis[1,3-
benzodioxol-5ylmethylene]ethane-1, 2-diamine, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal
Chemistry, 39:10, 718-733
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 39:718–733, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533170903433295
Synthesis, Characterization, Thermal Decomposition and
Antifungal Studies of Cr(III), Mn(II), Fe(III), Co(II), Ni(II)
ꢀ
and Cu(II) Complexes of N,N -bis[1,3-benzodioxol-5-
ylmethylene]ethane-1, 2-diamine
1
2
Prasad M. Alex and K. K. Aravindakshan
1
Department of Chemistry, Marthoma College, Chungathara, Nilambur. Affiliated to the University
of Calicut, Kerala, India
Department of Chemistry, University of Calicut, Kerala, India
2
being devoted to the synthesis of new Schiff base complexes of
A bidentate/tetradentate Schiff base namely, N,N -bis[1,3- transition metal ions. The chelating Schiff base ligands derived
ꢀ
benzodioxol-5-ylmethylene] ethane-1,2-diamine was synthesized from diamines and various carbonyl compounds, encompass
by condensing piperonaldehyde (3,4-dioxymethylenebenzalde-
a highly remarkable class of compounds having a wide range
hyde) with ethylenediamine. Cr(III), Mn(II), Fe(III), Co(II), Ni(II)
and Cu(II) complexes of this chelating/bridging ligand were synthe-
sized using acetates, chlorides, bromides, nitrates and perchlorates
[13−15]
[16]
[17]
of applications in analytical,
industrial, clinical and
[18,19]
biochemical
areas, and they possess considerable physio-
of these metals. The ligand and the complexes were characterized logical activities.[
20,21]
Piperonaldehyde and a few Schiff bases
1
by elemental analysis, H NMR, UV-vis and IR spectra, conduc- derived fromit arealso having noteworthy biological andantimi-
tance and magnetic susceptibility measurements and thermogravi-
metric analysis. The ligand showed bridging nature in some of its
complexes, as evidenced by magnetic- and microanalytical data.
The thermograms of three complexes were analyzed and the ki-
[22−24]
crobial activities.
A search through literature revealed that
no work had been done on Schiff bases derived from diamines
and piperonaldehyde. Therefore, a new Schiff base ligand de-
netic parameters for the different stages of decompositions were rived from piperonal and ethylenediamine and its transition
determined. The antifungal activities of the ligand and some of its metal complexes were synthesized and characterized. The lig-
complexes against Phytophthora capsici were tested in carrot agar
ꢀ
and named as N,N -bis[1,3-benzodioxol-5-ylmethylene]ethane-
,2-diamine (L), (Figure 1) has 4 potential donor sites, two
medium.
1
nitrogen atoms as azomethine groups and two oxygen atoms
as two dioxymethylene groups. Complexes of Cr(III), Mn(II),
Fe(III), Co(II), Ni(II) and Cu(II) were synthesized using ac-
etates, chlorides, bromides, nitrates and perchlorates of these
metals. Investigations on thermal decomposition behaviur and
antifungal activities of some of these complexes were also
done.
Keywords antifungal activity, diamine, piperonal, Schiff base,
thermal decomposition, transition metal complexes
INTRODUCTION
Schiff base derivatives and their transition metal complexes,
known from the 19th century, have made considerable contri-
[
1,2]
butions to the advances in coordination chemistry
and have
found a broad-spectrum of applications in very diverse fields
[
3]
[4]
[5]
[6]
such as biochemical, analytical, catalytic, therapeutic
EXPERIMENTAL
[7]
and biomimetic activities. These applications include their
[8]
[9]
Materials and Measurements
All chemicals used in the present work viz, piperonaldehyde,
ethylenediamine, metal salts, solvents etc., were of A R grade
uses as MRI contrast agents, biological markers, antitumor
agents,[10] etc. In addition, the capacity of Schiff bases to form
stable complexes with transition metal ions[2,11,12] has inspired
(E.Merck or B D H).
attention to such compounds so that extensive research effort is
Carbon, hydrogen and nitrogen analyses were carried out
by using Hitachi CHN-O rapid analyzer at CDRI, Lucknow.
The anions present in complexes were estimated by stan-
Received 29 August 2009; accepted 2 October 2009.
dard methods.[
25] 1
H-NMR spectra of the ligand was recorded
on a Varien-300 nuclear magnetic resonance instrument us-
ing DMSO-d6 as solvent. Infrared spectra were measured
Address correspondence to Prasad M. Alex, Dept. of Chemistry,
Marthoma College, Chungathara, Nilambur, Affiliated to the University
of Calicut, Kerala, India. E-mail: prasdmalex@gmail.com
718

STUDIES OF CR(III), MN(II), FE(III), CO(II), NI(II), AND CU(II)
719
the reaction mixtures were concentrated and the pasty mass
obtained in each case was repeatedly washed with diethylether
and/or petroleum ether and/or acetone to get the solid complexes
separated. The complexes were filtered, washed with suitable
solvents and then dried over anhydrous CaCl2.
Biological Assay
The antifungal activities of the ligand, its Mn(II), Co(II),
Ni(II) and Cu(II) complexes were tested on the four stages of the
growth of Phytophthora capscici, the pathogen that causes foot-
rot or quick-wilt disease in black pepper, viz, mycelial growth,
sporangial production, zoospore release and zoospore germi-
nation were investigated by incorporating the test solutions in
DMSO-water (1:40) mixtures to carrot-agar media. DMSO of
corresponding concentration was used as control.
ꢀ
FIG. 1. N,N -bis[1,3-benzodioxol-5-ylmethylene] ethane-1,2-diamine.
−1
in the range 4000–400 cm
on a Schimadzu FTIR-8101
spectrophotometer with KBr pellets. The solid-state electronic
spectra of complexes were recorded using a Schimadzu UV-
RESULTS AND DISCUSSION
1
601 spectrophotometer. The magnetic measurements were
Characterization of Ligand
In this paper we designed and synthesized a biden-
tate/tetradentate Schiff base ligand N,N -bis[1,3-benzodioxol-
made at room temperature by the Gouy method using
Hg[Co(NCS)4] as calibrant. The thermal decomposition behav-
iors of complexes were monitored using a Perkin Elmer TGA-7
Analyzer.
ꢀ
5-ylmethylene]ethane-1,2-diamine (L) as shown in the scheme
(
Figure 2).
1
The H NMR spectrum of the ligand has been recorded in
Synthesis of the Ligand and Complexes
6
DMSO-d at room temperature. The spectrum of the ligand
Ethylenediamine (20mmol, 120 mg) solution in ethanol showed strong signal at 8.21 ppm, due to the azomethine pro-
50 mL) was mixed with a solution of piperonaldehyde tons. The spectrum also showed several signals in the range
40 mmol, 604 mg) in ethanol (50 mL) in 1:2 molar ratio and 7.50 to 6.84 ppm, assigned to the different types of aromatic
(
(
was refluxed for about 1h and then cooled. The white precipi- protons on the piperonal moieties in the molecule. The sig-
tate formed was filtered off, washed with water and a few ml of nals at 5.96 ppm and in the range 3.86–3.84 ppm were as-
alcohol and then purified by recrystallyzing from ethanol (yield signed to the methylenic protons of the dioxymethyene groups
=
635 mg, 88%).
on the piperonal moieties and of the ethylenediamine group in
Complexes of Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and the molecule. The IR spectrum of the ligand showed bands at
−1
Cu(II) with this ligand were synthesized using acetate, chloride, 3050 and 2905 cm assigned to the C H stretching of aro-
bromide, nitrate and perchlorate salts of these metals. Solutions matic and methylene groups, respectively. The bands present
−1
of the ligand and metal salts in methanol (10 mmol in 50 ml) (1:1 at 1639 and 1255 cm were assigned to the C N and C N
molar ratio) were refluxed for 2 to 3 h. In the case of Co(II), solu- stretchings, respectively.[ Bands at 1191 and 1099 cm were
26]
−1
tions of the salts and ligand in acetone were used. Metal acetates assigned to the in plane bending of the aromatic C H and those
−1
were dissolved in methanol-water or acetone-water mixture and at 873 and 817 cm to the out of plane bending vibration of
added to refluxing solutions of the ligand in methanol or acetone. the aromatic C H. The characteristic absorption frequency of
[27]
Several complexes, especially those with metal chlorides, pre- the dioxymethylene group of piperonal moiety was present at
−1
cipitated during refluxing and were filtered off. In other cases, 926 cm . The absence of the characteristic stretching frequency
FIG. 2. Scheme for reaction between ethane-1,2-diamine and piperonaldehyde.

720
P. M. ALEX AND K. K. ARAVINDAKSHAN
of C O of the aromatic aldehyde group,[26] indicated that the most of the complexes behaved as nonelectrolytes[28], indicating
condensation was complete. The elemental analysis and spectral the coordinated nature of the anions. The data also indicated that
data for L are consistent with the formula C18H16O4N2and the the nitrato complexes of Mn(II) and Ni(II) and the nitrato and
perchlorato complexes of Cu(II) behaved as 1:2 electrolytes.[
28]
structure given in Figure 1.
Formulae and General Properties of Complexes
IR Spectra of Complexes
The reaction of the ligand (L) with different salts of Cr(III),
Tables 4, 5 and 6 lists the most important IR spectral bands
Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) ions in appropriate of the metal complexes. In the spectra of all the complexes the
molar ratios gave different types of metal complexes of the given ν(C N) was shifted to lower frequency, due to its involvement
−1
formulae, as evidenced by the micro-analytical and spectral data. in coordination. Instead of the band at 1639 cm present in the
The reaction of acetates, chlorides and bromides of Cr(III) and spectrum of the free ligand, new bands appeared in the ranges
Fe(III) and acetates and chlorides of Mn(II), Co(II) , Ni(II) and of 1600–1583, 1619–1595, 1600–1595, 1626–1595, 1633–1624
−1
Cu(II) with the ligand in 2:1 molar ratios produced bimetallic and 1624–1564 cm in the Cr(III), Mn(II), Fe(III), Co(II),
complexes as evidenced by micro analytical data and effective Ni(II), Cu(II) complexes, respectively, and were assigned to the
magnetic moment per metal atom. The acetates of all the metal coordinated azomethine groups.[
29,30,31]
ions used here, yielded hydroxo complexes. The reactions are
represented by the following schemes.
The characteristic absorption frequency of the dioxymethy-
lyne group was found to be present in the spectra of majority
of the complexes at the same frequency as it was observed
in the ligand spectrum. This indicated the non-involvement of
dioxymethylene groups in coordination in these complexes. But
in a few cases, either this band was absent or significantly shifted
to lower frequency region. The hydroxo and chloro complexes
of Mn(II), the chloro complexes of Ni(II) and Cu(II) (No.7, 8,
23 and 28) showed significant shift or absence of this band.
Hence, it could be reasonably assumed that one of the oxygen
atoms of the dioxymethylene groups had been coordinated in
them.[
2
MA3 + L + 2H2O → [M2LA6(H2O)2],
−
−
−
−
where M = Cr(III) or Fe(III) and A = OH , Cl or Br
M(AcO)3 + L + 8H2O → [M2L(OH)6(H2O)2] + 6AcOH
2
−
−
where M = Cr(III) or Fe(III) and AcO = CH3COO
MA3 + L + H2O → MLA3(H2O)],
−
−
−
where M = Cr(III) or Fe(III) and A = NO or ClO4
3
2MCl2 + L + 2H2O → [M2LCl4(H2O)2],
27]
−
−
where M = Mn(II), Ni(II) or Cu(II) and A = Cl
The IR spectra of all the complexes revealed new bands at
−
1
2
Mn(AcO)2 + L + 6H2O → [Mn2L(OH)4(H2O)2] + 4AcOH 678–440 and 525–412 cm , assigned to ν(M–N) and ν(M–
O), respectively.[
29,32,33]
The M-O band may be either due to
−
−
where AcO = CH3COO
coordinated nitrate-, perchlorate- or hydroxyl anion or water
molecule, or due to the coordination of the oxygen atoms of the
dioxymethylene groups. In the chloro complex of Co(II) (No.
18), ν (M–O) band could not be identified, indicating the ab-
sence of Co-O bond. The inclusion of water molecules in the
coordination sphere of the metal complexes, except for hydroxo
and chloro complexes of Co(II) and hydroxo complexes of Ni(II)
and Cu(II) (Nos. 17, 18, 22 and 23) was supported by the ap-
pearance of broad bands in the range 3440–3286 and medium
MA2 + L + 2 H2O → [MLA2(H2O)2],
−
−
−
where M = Mn(II) and A = Br or ClO
4
−
−
−
−
or M = Co(II) and A = Br , NO or ClO4
3
−
−
−
or M = Ni(II) and A = Br or ClO
4
−
−
or M = Cu(II) and A = Br
M(NO3)2 + L + 4 H2O → [ML(H2O)4](NO3)2,
where M = Mn(II) or Cu(II)
−1
or weak bands at 962–956 and 631–638 cm , owing to ν(OH),
ρKrock(H2O) and ρwagg(H2O), respectively of coordinated water
molecules.[
2
CoCl2 + L → [Co2LCl4],
2
M(AcO)2 + L + 4 H2O → [M2L(OH)4] + 4AcOH
31,32]
−
−
where M = Co(II), Ni(II) or Cu(II) and AcO = CH3COO
MA2 + L + 2 H2O → [ML(H2O)2] A2,
Coordination of Anions
−
−
where M = Ni(II) and A = NO
3
The acetato ligand may coordinate to a metal center in ei-
ther a monodentate, bidentate or bridging manner. The ν (CO )
−
−
or M = Cu(II) and A = ClO
4
a
2
and νs(CO2) bands of the free acetate ions are around 1560 and
−1
The colors, magnetic susceptibilities and molar conductivi- 1416 cm , respectively. In monodentate coordination νa(CO2)
−1
ties and melting points of the complexes are listed in Table 1 is found at higher energy than 1560 cm and νs(CO2) is lower
and the micro-analytical data in Tables 2 and 3. These air sta- than 1416 cm−1. As a result, the separation between the ν(CO2)
ble metal complexes were non-hygroscopic, partially soluble in bands is much larger in monodentate complexes than the free
most organic solvents, but freely soluble in DMF and DMSO. ion. The opposite trend is observed in bidentate acetato coor-
−3
The molar conductivities in DMF (10 M) solution showed that dination; the separation between ν(CO2) bands is smaller than

STUDIES OF CR(III), MN(II), FE(III), CO(II), NI(II), AND CU(II)
721
TABLE 1
Formulae and general properties of ligand and complexes
◦
−1
2
−1
No.
Compound
Color
Colorless
Brown
Green
Greenish yellow
Green
Green
Yellowish brown
Yellowish brown
Yellowish brown
Yellowish brown
Yellowish brown
Orange
Orange
Orange
Orange
Orange
Greenish blue
Bright green
Orange
Orange brown
Orange
Grey
Greenish yellow
Green
Yield %
M.P C
µeff B.M.
ꢀm ohm cm mol
1
2
3
4
5
6
7
8
9
C18H16O4N2 (L)
[Cr2L(OH)6(H2O)2]
[Cr2LCl6(H2O)2]
[Cr2LBr6(H2O)2]
[CrL(NO3)3((H2O)]
[CrL(ClO4)3(H2O)]
[Mn2L(OH)4(H2O)2]
[Mn2LCl4(H2O)2]
[MnLBr2(H2O)2]
[MnL(H2O)4](NO3)2
[MnL(ClO4)2(H2O)2]
[Fe2L(OH)6(H2O)2]
[Fe2LCl6(H2O)2]
[Fe2LBr6(H2O)2]
[FeL(NO3)3((H2O)]
[FeL(ClO4)3(H2O)]
[Co2L(OH)4]
88
65
67
62
88
87
71
68
82
79
76
67
63
64
82
79
61
64
67
82
79
59
63
73
75
72
63
61
58
69
71
166
254
243
222
304
326
238
247
280
>300
>300
264
248
290
260
256
275
283
3.49
3.24
3.52
3.82
3.91
4.92
4.72
5.91
6.10
6.20
4.56
5.02
4.92
6.12
5.94
3.31
3.42
4.84
5.02
5.19
D
2.45
3.35
D
3.42
1.37
1.45
2.10
1.98
1.90
28.46
—
28.43
56.25
14.82
21.4
12.24
42.8
148.42
41.6
23.92
16.32
24.63
49.45
51.82
—
11.51
42.47
31.83
36.59
28.21
14.69
31.21
137.44
26.68
—
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
[Co2LCl4]
[CoLBr2(H2O)2]
[CoL(NO3)2(H2O)2]
[CoL(ClO4)2(H2O)2]
[Ni2L(OH)4]
[Ni2LCl4(H2O)2]
[NiLBr2(H2O)2]
[NiL(H2O)2] (NO3)2
[NiL(ClO4)2(H2O)2]
[Cu2L(OH)4]
[Cu2LCl4(H2O)2]
[CuLBr2(H2O)2]
[CuL(H2O)4](NO3)2
[CuL(H2O)2](ClO4)2
235
>300
>300
285
292
285
>300
>300
>300
>300
284
Brown
Green
Brown
Blue
Green
Bluish green
Brown
13.1
38.06
162.23
138.45
>300
>300
for the free ion. For bridging acetate, however, the two ν(CO2) spectra of nitrato complexes of Cr(III), Fe(III) and Co(II) such
[
34,36,37]
bands are close to the free ion.
But in the spectra of bands were absent and new bands appeared in the ranges 1449–
−1
−
complexes synthesised using metal acetates, the characteristic 1445, 1361–1326 and 1041–1036 cm , assigned to νNO of
3
frequencies of either free or coordinated acetate ions could not unidentate nitrate ions.[
31,39]
The non-conducting nature of these
be identified.[
33,37]
The strong absorption bands present at 3420, complexes confirmed the presence of coordinated nitrate ions in
381, 3430, 3257, 3417 and 3390 cm in the spectra of the them.
−
1
3
hydroxo complexes of Cr(III), Mn(II), Fe(III), Ni(II),Co(II) and
The IR spectra of perchlorato complexes of Cr(III), Mn(II),
Cu(II), respectively, were assigned to the ν(O H) of the hy- Fe(III), Co(II) and Ni(II) (No. 6,11,16,21 and 26) showed bands
droxo groups,[
33,38]
which were coordinated to the metal ions. in the ranges 1117–1120, 1038–1043 and 934–938 cm in-
−1
Elemental analyses data and conductance values of these com- dicating the presence of monodentatively coordinated perchlo-
rate ion of C3v symmetry.[
31,40]
The spectrum of Cu(II) per-
plexes also supported the assumption.
The IR spectra of nitrato complexes of Mn(II), Ni(II) and chlorato complex (No.31) showed a strong band at 1112 and
−
1
Cu(II) (No. 10, 25 and 30) showed sharp bands at 1384, 1385 and a week band at 981 cm assigned to the triply degenerate
−1
1
384 cm , respectively, which corresponded to the νNO(asy) of ν(ClO)(asy) and to the symmetry forbidden ν(ClO)(sy) of the
[31,38,39]
free nitrate ion.
The conductance values of these com- free perchlorate ion, which further confirmed its conductance
plexes confirmed the presence free nitrate ions. But in the IR value.[
35,41]

722
P. M. ALEX AND K. K. ARAVINDAKSHAN
TABLE 2
Micro-analytical data of ligand, Cr(III), Mn(II) and Fe(III) complexes
Found (calculated) %
Compound
Metal
C
H
N
Anion
C18H16O4N2 (L)
66.74 (66.67)
37.64 (38.16)
30.85 (31.91)
21.84 (22.88)
36.34 (37.24)
30.5 (31.19)
39.43 (40.15)
34.93 (35.29)
38.13 (37.57)
38.2 (37.57)
36.11 (35.18)
36.81 (37.63)
30.86 (31.53)
21.9 (22.69)
36.1 (36.99)
30.1 (31.01)
4.94 (4.93)
4.67 (4.59)
2.74 (2.95)
2.04 (2.12)
2.98 (3.10)
2.46 (2.60)
4.32 (4.46)
3.14 (3.27)
3.52 (3.48)
4.42 (4.17)
3.31 (3.26)
4.38 (4.53)
2.81 (2.92)
2.0 (2.10)
8.61 (8.64)
4.72 (4.95)
4.01 (4.14)
2.84 (2.97)
11.7 (12.07)
3.96 (4.04)
5.1 (5.20)
4.35 (4.58)
4.93 (4.87)
9.54 (9.74)
4.72 (4.56)
4.59 (4.88)
3.92 (4.10)
2.81 (2.94)
11.2 (11.99)
3.87 (4.02)
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
Cr2L(OH)6(H2O)2]
Cr2LCl6(H2O)2]
Cr2LBr6(H2O)2]
19.23 (18.37)
16.12 (15.36)
11.83 (11.02)
9.12 (8.97)
32.6 (31.46)
52.14 (50.85)
CrL(NO3)3((H2O)]
CrL(ClO4)3(H2O)]
Mn2L(OH)4(H2O)2]
Mn2LCl4(H2O)2]
MnLBr2(H2O)2]
MnL(H2O)4](NO3)2
MnL(ClO4)2(H2O)2]
Fe2L(OH)6(H2O)2]
Fe2LCl6(H2O)2]
7.86 (7.51)
43.91 (43.11)
21.12 (20.45)
18.21 (17.97)
9.12 (9.57)
9.08 (9.57)
8.74 (8.96)
20.34 (19.51)
17.12 (16.35)
12.2 (11.76)
10.1 (9.59)
23.62 (23.20)
27.15 (27.83)
31.93 (32.41)
43.67 (42.86)
51.9 (50.42)
Fe2LBr6(H2O)2]
FeL(NO3)3((H2O)]
FeL(ClO4)3(H2O)]
2.96 (3.08)
2.43 (2.58)
8.46 (8.04)
43.6 (42.86)
Magnetic- and Electronic Spectral Studies
The solid-state electronic spectra of the complexes were
Cr(III) Complexes
In the spectra of all the Cr(III) complexes, two peaks were
recorded by the procedure recommended by Venenzi.[ Tables identified in the ranges 582–542 and 442–384 nm and were
42]
4
4
4
4
7
and 8 list important electronic spectral bands of the complexes assigned to the A2g → T1g(P) and the A2g → T2g transi-
tions in an octahedral geometry.[
43,44]
The Cr(III) complexes,
and their assignments.
TABLE 3
Micro-analytical data of ligand, Co(II), Ni(II) and Cu(II) complexes
Found (calculated) %
Compound
Metal
C
H
N
Anion
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
Co2L(OH)4]
Co2LCl4]
23.83 (23.14)
21.82 (20.20)
11.01 (10.19)
11.64 (10.87)
8.93 (9.55)
23.75 (23.05)
19.32 ( 18.95)
10.91 (10.14)
11.72 (10.82)
9.92 (9.50)
25.19 (24.47)
21.13 (20.19)
11.21 (10.88)
11.32 (10.88)
10.80 (10.20)
41.77 (42.35)
35.48 (36.97)
36.67 (37.31)
38.39 (39.78)
35.22 (34.95)
41.87 (42.40)
33.96 (34.87)
38.42 (37.33)
38.66 (39.81)
33.89 (34.97)
40.89 (41.62)
33.53 (34.34)
35.99 (37.02)
36.2 (37.01)
33.84 (34.70)
3.78 (3.92)
2.61 (2.74)
3.32 (3.45)
3.43 (3.68)
3.36 (3.24)
3.73 (3.93)
3.13 (3.23)
3.24 (3.46)
3.53 (3.69)
3.13 (3.24)
3.71 (3.85)
2.95 (3.18)
3.24 (3.43)
3.92 (4.11)
3.11 (3.21)
5.22 (5.49)
4.63 (4.80)
4.72 (4.84)
9.97 (10.31)
4.62 (4.53)
5.13 (5.50)
4.43 (4.52)
4.71 (4.84)
11.1 (10.32)
4.36 (4.53)
5.17 (5.40)
4.38 (4.45)
4.69 (4.80)
9.12 (9.60)
4.28 (4.50)
25.1 (24.32)
28.3 (27.63)
CoLBr2(H2O)2]
CoL(NO3)2(H2O)2]
CoL(ClO4)2(H2O)2]
Ni2L(OH)4]
Ni2LCl4(H2O)2]
NiLBr2(H2O)2]
NiL(H2O)2] (NO3)2
NiL(ClO4)2(H2O)2]
Cu2L(OH)4]
Cu2LCl4(H2O)2]
CuLBr2(H2O)2]
CuL(H2O)4](NO3)2
CuL(H2O)2](ClO4)2
31.48 (32.20)
23.71 (22.93)
29.01 (27.65)
33.43 (32.22)
23.37 (22.58)
29.1 (27.42)
32.61 (31.97)

723

724

725

726
P. M. ALEX AND K. K. ARAVINDAKSHAN
TABLE 7
Electronic spectral bands of Cr(III), Mn(II) and Fe(III) complexes and their assignments
Bands
No.
2
Compound
(nm)
Assignment
Geometry
Octahedral
4
4
4
4
4
4
4
4
[Cr2L(OH)6(H2O)2]
542
A2g → T2g A2g → T1g(F)
4
42
582
84
552
01
563
12
558
18
4
4
4
3
4
5
6
[Cr2LCl6(H2O)2]
[Cr2LBr6(H2O)2]
[CrL(NO3)3((H2O)]
[CrL(ClO4)3(H2O)]
A2g → T2g A2g → T1g(F)
Octahedral
Octahedral
Octahedral
Octahedral
3
4
4
4
A2g → T2g A2g → T1g(F)
4
4
4
4
A2g → T2g A2g → T1g(F)
4
4
4
4
A2g → T2g A2g → T1g(F)
4
6
6
6
6
6
6
4
7
8
9
[Mn2L(OH)4(H2O)2]
[Mn2LCl4(H2O)2]
[MnLBr2(H2O)2]
[MnL(H2O)4](NO3)2
[MnL(ClO4)2(H2O)2]
[Fe2L(OH)6(H2O)2]
393 w
398 w
402 w
369 w
384 w
492
A1g(F) → T2g(G)
Octahedral
Octahedral
Octahedral
Octahedral
Octahedral
Octahedral
4
A1g(F) → T2g(G)
4
A1g(F) → T2g(G)
4
10
11
12
A1g(F) → T2g(G)
4
A1g(F) → T2g(G)
4
A1g → T2g CT
3
98
512
02
502
99
488
01
505
99
6
6
6
6
4
13
14
15
16
[Fe2LCl6(H2O)2]
[Fe2LBr6(H2O)2]
[FeL(NO3)3((H2O)]
[FeL(ClO4)3(H2O)]
A1g → T2g CT
Octahedral
Octahedral
Octahedral
Octahedral
4
4
A1g → T2g CT
3
4
A1g → T2g CT
4
4
A1g → T2g CT
3
3
3
respectively, indicating probable bimetallic nature and the con-
sequent antiferromagnetic coupling[
having d configuration, with a ground term A2g are expected
to show magnetic moments very close to the spin-only value.[
In the present investigation the hydroxo, chloro and bromo com-
plexes of Cr(III) showed slightly lower values of magnetic mo-
ments viz. 3.24, 3.49 and 3.52 B.M., respectively, indicating
some sort of molecular association that could lead to magnetic
49,52]
45]
Fe(III) Complexes
The complexes of Fe(III) were orange in color and gave
weak bands in the range 400–500 nm, assigned to the spin- and
[46,47]
exchange interaction through a bridging ligand.
trato and perchlorato complexes showed magnetic moments of
The ni-
6
4
parity forbidden A1g → T2g transitions of Fe(III) ion in an oc-
tahedral field.[
53,54]
In the present investigation, the nitrato and
3
.82 and 3.91 B.M., respectively, indicating sufficient magnetic
perchlorato complexes of Fe(III) showed magnetic moments of
[45,48]
dilution.
6
.12 and 5.94 B.M., respectively, indicating high-spin octahe-
[45,55]
dral symmetry.
The hydroxo, chloro and bromo complexes
showed lower values of magnetic moments of 5.02, 4.56 and
Mn(II) Complexes
The electronic spectra of the Mn(II) complexes showed a
number of weak bands around 400 nm which were assigned to
4
.92 B.M., respectively, indicating probable bimetallic nature
[45,56]
with bridging ligands.
6
4
the spin- and parity forbidden A1g(F) → T2g(G) transitions
[49,50]
in an octahedral field.
The bromo, nitrato and perchlorato Co(II) Complexes
complexes of Mn(II) showed magnetic moments in the range
The hydroxo and chloro complexes of Co(II) were having
bright greenish-blue color and their spectra showed bands at
5.91 to 6.20 B.M. which was consistent with the spin-only value
[49,51]
for high-spin octahedral geometry.
complexes showed magnetic moments of 4.72 and 4.92 B.M.,
The hydroxo and chloro
1
641–1627, 652–673 and 514–501 nm assigned, respectively,
4
4
4
4
4
to the A2(F) → T2(F), A2(F) → T1(F) and A2(F) →

STUDIES OF CR(III), MN(II), FE(III), CO(II), NI(II), AND CU(II)
727
TABLE 8
Electronic spectral bands of Co(II), NI(II) and Cu(II) complexes and their assignments
Bands
No.
Complex
(nm)
Assignment
Geometry
Tetrahedral
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
1
1
3
3
3
3
3
3
1
1
3
3
3
2
4
17
18
19
20
21
[Co2L(OH)4]
1641
A2(F) → T2(F)
4
6
5
52
14
A2(F) → T1(F)
4
A2(F) → T1(P)
4
[Co2LCl4]
1627
A2(F) → T2(F)
Tetrahedral
Octahedral
Octahedral
Octahedral
4
6
5
73
01
A2(F) → T1(F)
4
A2(F) → T1(P)
4
[CoLBr2(H2O)2]
[CoL(NO3)2(H2O)2]
[CoL(ClO4)2(H2O)2]
1015
T1g(F) → T2g(F)
4
6
4
22
78
T1g(F) → A2g(F)
4
T1g(F) → T1g(P)
4
1115
T1g(F) → T2g(F)
4
6
4
78
09
T1g(F) → A2g(F)
4
T1g(F) → T1g(P)
4
1098
T1g(F) → T2g(F)
4
5
4
89
23
T1g(F) → A2g(F)
4
T1g(F) → T1g(P)
1
2
2
3
[Ni2L(OH4]
610
A1g → B1g
Square-planar
Octahedral
1
413
A1g → Eg
3
2
[Ni2LCl4(H2O)2]
1140
A2g(F) → T2g(F)
3
7
4
00
10
A2g(F) → T1g(F)
3
A2g(F) → T1g(P)
3
24
[NiLBr2(H2O)2]
1148
A2g(F) → T2g(F)
Octahedral
3
7
3
10
89
A2g(F) → T1g(F)
3
A2g(F) → T1g(P)
1
2
5
6
[NiL(H2O)2] (NO3)2
[NiL(ClO4)2(H2O)2]
548
A1g → B1g
Square-planar
Octahedral
1
394
A1g → Eg
3
2
1152
A2g(F) → T2g(F)
3
7
3
26
98
A2g(F) → T1g(F)
3
A2g(F) → T1g(P)
2
27
[Cu2L(OH)4]
790
B1g → A1g
Square-planar
468
CT
2
2
28
29
30
31
[Cu2LCl4(H2O)2]
[CuLBr2(H2O)2]
[CuL(H2O)4](NO3)2
[CuL(H2O)2](ClO4)2
694 b
730 b
655 b
810
Eg → T2g
Distorted octahedral
Distorted octahedral
Distorted octahedral
Square-planar
2
2
2
2
Eg → T2g
2
Eg → T2g
2
B1g → A1g
442
CT
4T1(P) transitions in a tetrahedral geometry.[57,58] The spectra
of the bromo, nitrato and perchlorato complexes showed bands
in the ranges 1115–1018, 678–589 and 478–404 nm assigned,
corresponded to those of high-spin octahedral geometry with
sufficient magnetic diluion.[
53,55]
4
4
4
4
respectively, to the T1g(F) → T2g(F), T1g(F) → A2g(F) and Ni(II) Complexes
4
4
[53,55]
T1g(F) → T1g(P) transitions.
The hydroxo and chloro
The electronic spectra of chloro, bromo and perchlorato
complexes of Co(II) showed magnetic moments of 3.31, 3.42 complexes of Ni(II) showed bands in the ranges 1152–1140,
B.M., respectively, indicating tetrahedral geometries without 726–700 and 410–394 nm and were assigned, respectively, to
[59,60]
3
3
3
3
3
any orbital contribution.
The slightly lower values indi- the A g(F) → T (F), A g(F) → T (F) and A g(F) →
2
2g
2
1g
2
3
[53,62]
cated bimetallic nature and the resulting anti-ferromagnetic cou-
T (P) transitions in octahedral geometry.
Moreover, the
1
g
pling in them.[
57,61]
The bromo, nitro and perchlorato complexes ratios of wave numbers of the transitions assigned as A (F)
3
2g
3
3
3
showed magnetic moments in the range 4.84–5.19 B.M., which → T (F) and A (F) → T (F) were found to be in the
2g
2g
1g

728
P. M. ALEX AND K. K. ARAVINDAKSHAN
FIG. 3. TG-DTG traces of [Co2LCl4].
FIG. 5. TG-DTG traces of [Cu2LCl4(H2O)2].
range 1.6 to 1.8, a distinctive feature of octahedral geometries.
The spectra of the hydroxo and nitrato complexes of Ni(II)
1
1
showed bands at 610 and 548 nm assigned to A1g → B1g
transitions and at 413 and 394 nm assigned to A1g → Eg tran-
1
1
[32,63]
sitions in square planar geometry.
These Ni(II) complexes
were found to be diamagnetic, supporting their square-planar
geometries.[
32,63]
The chloro complex showed a low magnetic
moment of 2.45 B.M., which could be due to its bimetallic na-
ture and the subsequent antiferromagnetic coupling.[
45,64]
But
the greenish-yellow color of the complex and its electronic spec-
trum indicated an octahedral geometry. The bromo and the per-
chlorato complexes showed the magnetic moments of 3.35 and
FIG. 6. Structure suggested for [Cr2L(OH)6(H2O)2], [Cr2LCl6(H2O)2],
[Cr2LBr6(H2O)2],
Fe2LBr6(H2O)2].
[Fe2L(OH)6(H2O)2],
[Fe2LCl6(H2O)2]
and
[
3
.28 B.M., respectively, indicating octahedral geometry without
[53,65]
any orbital contribution
Cu(II) Complexes
The chloro, bromo and nitrato complexes of Cu(II), presently
investigated, were greenish-blue in color and their electronic
spectra showed bands at 694, 730 and 655 nm, respectively,
2
2
assigned to the E → T2 transitions in a distorted octahedral
geometry.[
62,66]
The spectra of hydroxo and perchlorato com-
2 4 2 4
FIG. 7. Structure suggested for [Ni L(OH) ] and [Cu L(OH) ].
plexes of Cu(II), showed bands at 790 and 810 nm, respectively,
2
2
which were assigned to the B1g → A1g transitions in square-
planar geometry.[
32,53,63]
The hydroxo and chloro complexes
of Cu(II) showed magnetic moments of 1.37 and 1.45 B.M.,
FIG. 8. Structure suggested for [MnL(Br)2(H2O)2], [MnL(ClO4)2(H2O)2],
CoL(Br)2(H2O)2], [CoL(ClO4)2(H2O)2], [CoL(NO3)2(H2O)2], [NiL(ClO4)2
(H O) ] [NiL(Br) (H O) ] and [CuL(Br) (H O) ].
[
FIG. 4. TG-DTG traces of [Ni2LCl4(H2O)2].
2
2
2
2
2
2
2
2

STUDIES OF CR(III), MN(II), FE(III), CO(II), NI(II), AND CU(II)
729
TABLE 9
Thermal decomposition data of Co(II), Ni(II) and Cu(II) complexes
Loss of mass
Temp range Peak
From
Complex
Stage
in TG
temp From TG Theoretical Pyrolysis
Assignments
[
Co2LCl4]
I
II
220–380
380–580
290
490
21.3
51.4
20.7
51.8
Loss of 1 piperonal moiety
−
Loss of rest of the ligand, 4 Cl ions
subsequent formation of metal
&
oxide
Total
I
II
72.7
6
19.8
72.5
5.8
19.5
71.9
75.5
74.7
Co2LCl4 → 2/3Co3O4
[
Ni2LCl4(H2O)2]
110–180
180–400
135
310
Loss of 2H2O
Loss of 1 piperonal moiety
(220–400)*
−
III
400–600
500
48.8
50.6
Loss of remaining ligand , 4Cl ions
formation of metal oxide
&
Total
I
II
75.6
5.9
38.1
74.9
5.7
38.4
Ni2LCl42H2O → 2 NiO
[
Cu2LCl4(H2O)2]
110–200
200–460
160
350
Loss of 2H2O
Loss of 2piperonal moieties
(240–460)*
−
III
460–620
560
31.2
75.2
32.2
76.3
Loss of remaining ligand, 4Cl ions
formation of metal oxide
Cu2LCl42H2O → 2 CuO
&
Total
∗
Temperature range of significant mass-loss in the stage
respectively. The lower values indicated some sort of molec- gave NiO and CuO, respectively, as the end products at tempera-
◦
ular association that could be achieved through either a direct tures around 600 C and the decomposition patterns were in good
copper–copper interaction and/or magnetic exchange interac- agreement with the suggested formulae. The Ni(II) and Cu(II)
[45,53]
◦
tion through a bridging ligand.
The bromo, nitrato and complexes underwent dehydration reactions around 150 C, los-
perchlorato complexes were found to have magnetic moments ing two molecules of water, thus confirming the presence of
in the range 1.90 to 2.10 B.M., indicating sufficient magnetic coordinated water molecules in them. However, the Co(II) com-
dilution.[
45,53]
plex did not show any mass-loss in this range and were stable
◦
up to ∼220 C, thus indicating the absence of water molecules
in them. By the analysis of the non-isothermal TG, using the
integral method of Coats-Redfern, kinetic parameters, viz, or-
Thermogravimetric Analysis
Thermograms of three complexes, viz, [Co2LCl4], der of reaction(n), activation energy(E ), frequency factor(A)
a
∗
[
Ni2LCl4(H2O)2] and [Cu2LCl4(H2O)2], were analyzed. The and entropy of activation(ꢁS ) were calculated. The enthalpies
Co(II) complex gave Co3O4 and the Ni(II) and Cu(II) complexes and free energies of activation for various decomposition stages
TABLE 10
Kinetic parameters for the decomposition of Co(II), Ni(II) and Cu(II) complexes
−1
Complex
Stage Ea kJ/mol
A s
ꢁS* J/K/mol ꢁH* kJ/mol ꢁG* kJ/mol
γ
n
2
5
6
2
5
5
2
6
[
Co2LCl4]
I
II
I
II
III
I
57.50
114.59
68.98
59.82
116.13
67.51
5.13 × 10
1.60 × 10
3.01 × 10
4.50 × 10
1.50 × 10
8.83 × 10
2.58 × 10
9.26 × 10
−198.31
−153.09
−123.51
−199.68
−153.76
−131.99
−204.86
−120.07
52.81
108.25
65.59
54.98
109.70
64.74
164.47
225.06
115.98
171.38
228.56
108.69
182.62
243.04
−0.9926566
−0.9941095
−0.9997576
−0.9997821
−0.9948807
−0.9951084
−0.9972724
−0.9986331
1
1
1
1
1
1
1
1
[
Ni2LCl4(H2O)2]
[
Cu2LCl4(H2O)2]
II
III
60.17
149.94
54.99
143.01

730
P. M. ALEX AND K. K. ARAVINDAKSHAN
TABLE 11
The inhibitory effects of the ligand and its metal complexes on the mycelial growth of Phytophthora capsici
Sample
Complex
Conc. of
sample
Ligand
Mn(II)
Co(II)
Ni(II)
Cu(II)
Control
34
2
5 ppm
0 ppm
5 ppm
00 ppm
Diameter mm
of inhibition
Diameter mm
of inhibition
Diameter mm
of inhibition
Diameter mm
of inhibition
31.2
8.24
29
14.7
23.2
31.8
14.2
58.2
32.6
4.12
30.4
10.6
26.9
20.9
23.2
31.8
31.6
7.06
29.2
14.1
20.3
40.3
10.3
69.7
28.3
16.8
22.6
33.5
17.2
49.4
9.2
22.8
32.9
12.9
62.1
7.5
%
5
7
1
34
34
34
%
%
77.9
5.8
%
72.9
82.9
∗
have also been calculated using the relations, ꢁH - Ea – RTs pepper. Among them, foot-rot caused by Phytophthora capsici,
∗
∗
∗
and ꢁG − ꢁH – TsꢁS where Ts is the peak temperature of is highly prevalent in almost all the pepper growing areas and is
[67]
the decomposition stage investigated. Figures 3, 4 and 5 give reported to inflict considerable damage to the plants. Crop loss
the TG-DTG traces of the complexes. Table 9 gives the different due to foot-rot in Kerala is estimated to be about 10% of the total
stages of decomposition and Table 10 gives the kinetic parame- production and in India it ranges from 20 to 30 percent.[
68−70]
ters. Based on inception temperature and activation energy, for The ligand and the Mn(II) Co(II), Ni(II) and Cu(II) hydroxo
the first stage of decomposition excluding the dehydration stage, complexes were screened for antifungal activities against Phy-
stabilities of the complexes were found to be in the order, Cu > tophthora capsici and were found to be active on different stages
Ni > Co.
of growth of the microorganism. In all the four stages, the metal
The structures suggested for different complexes are given complexes were generally found to show more antifungal ac-
in Figures 6, 7 and 8.
tivity than the free ligand. The complex of Cu(II) was found to
be the more effective in inhibiting the growth of Phytophthora
capsici, compared to those of the other metal ions. The Ni(II)
and Co(II) complexes followed it. The data of inhibitory effects
Anti Fungal Studies
Black pepper or Piper nigram L, a perennial climber, be- of the ligand and the complexes on various stages of the growth
longing to the family, Piperacia is one of the main exports of Phytophthora capsici are given in Tables 11–14. Figure 9
earning spice crops of Kerala state in India. Several diseases gives graphical comparison of inhibitory effects of ligand and
caused by fungi, bacteria, virus and mycoplasma, affect black complexes on mycelial growth. Mn(II) complex was found to be
TABLE 12
The inhibitory effects of the ligand and its metal complexes on the sporangial production of Phytophthora capsici
Sample
Complex
Conc. of
Ligand
Co(II)
Ni(II)
Cu(II)
Control
64
25 ppm
50 ppm
75 ppm
100 ppm
no of sporangia per field
of inhibition
no of sporangia per field
of inhibition
no of sporangia per field
of inhibition
no of sporangia per field
of inhibition
52
49
46.6
27.2
38.8
39.4
26.2
59.1
18
43.2
32.5
33.8
47.2
15.6
75.6
11
%
18.8
48.4
24.4
41
35.9
31.4
50.9
23.4
44.8
30
32.4
49.4
17.4
72.8
64
64
64
%
%
%
71.9
82.8

STUDIES OF CR(III), MN(II), FE(III), CO(II), NI(II), AND CU(II)
731
TABLE 13
The inhibitory effect of the ligand and its metal complexes on the sporangial release of Phytophthora capsici
Sample
Complex
Conc. of
Ligand
Co(II)
Ni(II)
Cu(II)
Control
51.4
25 ppm
50 ppm
75 ppm
100 ppm
% of zoospore release
of inhibition
% of zoospore release
of inhibition
% of zoospore release
of inhibition
% of zoospore release
of inhibition
36.4
29.2
23.2
54.9
17.4
66.1
9.8
28
45.5
19
23
55.3
14
72.8
5.8
88.7
0
19
63.0
11
78.6
0
100
0
100
%
51.4
51.4
51.4
%
63
8.6
83.3
1.8
96.5
%
%
80.9
100
TABLE 14
The inhibitory effect of ligand and its metal complexes on the zoospore germination of Phytophthora capsici
Sample
Complex
Conc. of
Ligand
41.8
Co(II)
Ni(II)
Cu(II)
Control
68.6
2
5 ppm
0 ppm
5 ppm
00 ppm
% of zoospore germination
of inhibition
% of zoospore germination
of inhibition
% of zoospore germination
of inhibition
% of zoospore germination
of inhibition
46.3
32.5
40.2
41.4
26.2
61.8
7.8
30.2
56
26.8
60.9
13.2
80.8
5.8
91.5
1.8
97.4
%
39.1
36
47.5
28
59.2
18.6
72.9
5
7
1
23.4
65.9
14.2
79.3
6.8
68.6
68.6
68.6
%
%
%
88.6
90.2
less effective than the ligand in inhibiting the mycelial growth
and therefore, was not screened for the other stages of growth.
From the data it was clear that most of these complexes and
the ligand were inhibitory to all the four stages in the growth of
Phytophthora capsici. But the metal complexes were generally
found to show more antifungal activity than the parent ligand in
all four stages of investigation. The acetates of Cu(II), Co(II),
Ni(II) and Mn(II) were also reported to be antifungal in nature,
capable of inhibiting the mycelial growth of Phytophthora cap-
sici, but the activities were generally far lower than those of the
complexes.[ Among the four stages, the inhibition was more
pronounced in zoosporangial production and zoospore release.
The complex of Cu(II) was found to be more effective than
the complexes of other metal ions in retarding the growth of
Phytophthora capsici at various stages. The Ni(II) and Co(II)
complexes followed it.
71]
Series 1 – ligand, series 2, 3, 4 & 5 – Mn(II), Co(II), Ni(II) and Cu(II) complex.
The higher activities of the metal complexes in comparison
to the free metal ions may be due to the increased lipophilicity
FIG. 9. Gaphical representation of inhibitory effects of the ligand and com-
plexes on the mycelial growth of Phytophthora capsici.

732
P. M. ALEX AND K. K. ARAVINDAKSHAN
that enhances the penetration of the complexes into lipid mem- 15. Fakhar, A.R., Khorrami, A.R., and Naeimi, H. Synthesis and analytical
application of a novel tetradentate N2O2 Schiff base as a chromogenic
branes and blocks the metal binding sites in the enzymes of the
organisms.[
72]
reagent for determination of nickel in some natural food samples. Talanta,
005, 66(4), 813–817.
These complexes may also disturb the respira-
2
tion process of the cell and thus block the synthesis of proteins,
1
6. Shearer, J.M., and Rokita, S.E. Diamine preparation for synthesis of a water
soluble Ni(II) salen complex. Bioorg. Med. Chem. Lett., 1999, 9, 501–504.
[32]
which restricts further growth of the organism. Furthermore,
the mode of action of the compounds may involve the forma- 17. Kovelskaya, T., Ganusevich, I., Osinsky, S.P., Levitin, I., Bubnovskaya,
L., Sigan, A., Michailenko, V. Inorganic cobalt(III) complexes with Schiff
bases as a new anticancer agents with radio/thermosensitizing activities.
Poster #33, 6th Internet World Congress for Biomedical Sciences (online).
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[73]
with normal cell division process.
The observation that not
1
only the Cu(II) complex of the Schiff bases, but the Co(II) and
Ni(II) complexes, also showed sufficient antifungal activity may
open up new avenues in the quest for tackling the problem of
foot-rot disease in black pepper.
1
6
(7), 762–769.
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