Studies on complexes of Co(II), Ni(II), Cu(II), and Cd(II) with acetophenone and 4-hydroxyacetophenone benzoylhydrazones

Article abstract of DOI:10.1081/SIM-100107204

Metal(II) complexes of the types [M(L)₂Cl₂] · H₂O and [Cu(4-HOABH)SO₄(H₂O)₂] [M = Co(II), Ni(II), Cu(II) and Cd(II), L = acetophenone benzoylhydrazone (ABH), C₆H₅CONH-

Full text of DOI:10.1081/SIM-100107204

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STUDIES ON COMPLEXES OF Co(II), Ni(II),
Cu(Il), AND Cd(II) WITH ACETOPHENONE AND 4-
HYDROXYACETOPHENONE BENZOYLHYDRAZONES
B. Singh a , K. K. Narang b & Rachana Srivastava a
a Department of Chemistry , Banaras Hindu University , Varanasi, 221 005, India
b Department of Applied Chemistry , Institute of Technology, Banaras Hindu University ,
Varanasi, 221 005, India
Published online: 09 Dec 2011.
To cite this article: B. Singh , K. K. Narang & Rachana Srivastava (2001) STUDIES ON COMPLEXES OF Co(II), Ni(II), Cu(Il), AND
Cd(II) WITH ACETOPHENONE AND 4-HYDROXYACETOPHENONE BENZOYLHYDRAZONES, Synthesis and Reactivity in Inorganic and
Metal-Organic Chemistry, 31:8, 1375-1386, DOI: 10.1081/SIM-100107204
To link to this article: http://dx.doi.org/10.1081/SIM-100107204
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SYNTH. REACT. INORG. MET.-ORG. CHEM., 31(8), 1375±1386 (2001)
STUDIES ON COMPLEXES OF Co(II),
Ni(II), Cu(Il), AND Cd(II) WITH
ACETOPHENONE AND
4-HYDROXYACETOPHENONE
BENZOYLHYDRAZONES
2
B.Singh, *,1 K.K.Narang, and Rachana Srivastava1
1Department of Chemistry, Banaras Hindu University,
Varanasi-221 005, India
2Department of Applied Chemistry, Institute of
Technology, Banaras Hindu University,
Varanasi-221 005, India
ABSTRACT
Metal(II) complexes of the types [M(L)2Cl2] Á H2O and [Cu(4-
HOABH)SO4(H2O)2] [M ˆ Co(II), Ni(II), Cu(II) and Cd(II),
L ˆ acetophenone benzoylhydrazone (ABH), C6H5CONH-
NˆC(CH3)C6H5 and 4-hydroxyacetophenone benzoylhydra-
zone (4-HOABH), C6H5CONHNˆC(CH3)C6H4OH], were
prepared and characterized by elemental and thermal ana-
lyses, molar conductance, infrared, ESR and electronic spec-
tralstudies. Some of the compelxes were screened against
E. coli and Aspergillus niger for biological activity.
*Corresponding author. E-mail: bsingh@banaras.ernet.in
1375
Copyright # 2001 by MarcelDekker, Inc.
www.dekker.com

1376
SINGH, NARANG, AND SRIVASTAVA
INTRODUCTION
The copper(II) complexes of 2-pyridinecarboxaldehyde 2-pyridylhy-
drazone1 and salcylaldehyde benzoylhydrazone2 show antitumor activity.
The transition metal complexes of isonicotinoylhydrazine have been found
to be usefulin poyl mer coating inks and pigments 3. Monoacylhydrazones
and acyldihydrazones have been found to be ¯exidentate ilgands and form
complexes of structural and biochemical interest4.
Acetophenone benzoylhydrazone (ABH) and 4-hydroxyacetophenone
benzoylhydrazone (4-HOABH) (Fig. 1) have a number of potential bonding
sites such as the carbonyloxygen, phenolic oxygen, the azomethine and imine
nitrogens. Further, ABH di€ers from 4-HOABH in having a C6H5 moiety in
place of C6H4OH. We have, therefore, synthesized Co(II), Ni(II), Cu(II) and
Cd(II) complexes of ABH and 4-HOABH to study the e€ect of this moiety
on the composition, generalproperties, bonding and stereochemistry of the
complexes. The structures of the complexes have been investigated by using
infrared, electronic, magnetic susceptibility and ESR spectral studies. Anti-
fungal and antibacterial activities of some of the complexes have also been
studied. The results are described in the present paper.
EXPERIMENTAL
Materials and Methods
The chemicals used in the present investigations were of analytical
reagent grade. Acetophenone, 4-hydroxyacetophenone (CentralDrug
House, New Delhi) and metal salts (British Drug House, Bombay) were
used as obtained.
Figure 1. Structures of the ligands.

1378
SINGH, NARANG, AND SRIVASTAVA
Figure 2. Representative structures of the complexes.

COMPLEXES OF Co(II), Ni(II), Cu(II), AND Cd(II)
1379
Benzoylhydrazine was prepared by re¯uxing methyl benzoate
(10 mmol, 13.6 mL) with hydrazine hydrate (10 mmol, 5.0 mL) in ethanol
(30 mL) for ꢀ 7 h. A white compound separated on standing over night.
This was ®ltered and washed with distilled water. The pure hydrazide was
obtained by recrystallization from hot benzene.
Acetophenone benzoylhydrazone and 4-hydroxyacetophenone ben-
zoylhydrazone were prepared by re¯uxing the benzoylhydrazine (10 mmol,
1.36 g) with acetophenone (10 mmol, 1.20 mL) or 4-hydroxyacetophenone
(10 mmol, 1.36 g) in ethanol (50 mL) for ꢀ 8 h. The hydrazones precipitated
during the reaction and were ®ltered and recrystallized from hot ethanol.
The hydrazones were characterized by elemental analyses, hydrazine
determination and infrared spectra.
Synthesis of Complexes
The ABH complexes were synthesized by adding an aqueous ethanol
(50:50, v=v) solution (25 mL) of the metal chloride or sulfate (5 mmol) to a
hot ethanolsoultion (50 mL) of ABH (10 mmo,l 4.76 g). The reaction so-
lutions were heated on a water bath for ꢀ 1 h. The compounds which pre-
cipitated during the reaction were ®ltered and washed with distilled water
and ethanol to remove unreacted metal salts and ligand, if any. They were
®nally washed with diethyl ether and dried over anhydrous calcium chloride
in a desiccator under reduced pressure.
The complexes of 4-HOABH were prepared by heating a suspension
of the ®nely powdered ligand (5 mmol, 2.54 g) in an aqueous ethanol (50:50,
v=v) solution (50 mL) of the metal chloride=sulfate (10 mmol). During the
reaction of the ligand dissolved and the colour of the solution changed in-
dicating reaction between the metal salt and the hydrazone. The solution
was poured in a beaker and the complexes precipitated during evaporation
of the solvent. The compounds were ®ltered and washed several times with
hot distilled water to remove unreacted metal salts followed by ethanol and
®nally with diethyl ether. They were dried in a desiccator at room tem-
perature under reduced pressure.
Analyses and Instrumentation
The complexes were analysed for their metal content using literature
procedures5 after decomposition with aqua regia followed by sulfuric acid,
sulfate and chloride were determined gravimetrically as BaSO4 and AgCl,
respectively. Hydrazine was determined volumetrically by titrating with

1380
SINGH, NARANG, AND SRIVASTAVA
6
KBrO3 after hydrolysing the complexes in 6N HCl for ꢀ 4 h. Carbon,
hydrogen and nitrogen were determined microanalytically on a Perkin
Elmer 240 DC elemental analyser.
Molar conductances in DMSO solution (10À3 M) were measured at
room temperature on a Systronics conductivity meter. Room temperature
magnetic susceptibilities were determined on a Cahn Faraday balance using
[CoHg(SCN)4] as standard and were corrected for diamagnetism7. The
electronic spectra of the ligands and complexes were recorded on a Cary
2390 spectrophotometer in Nujol. IR spectra were recorded in Nujol mulls
on a JASCO FT-IR 5300 spectrophotometer.
RESULTS AND DISCUSSION
Reaction of ABH and 4-HOABH with metal(II) salts yielded com-
plexes having 1:1 and 1:2 metal-ligand stoichiometries. Formation of the
complexes may be shown below.
H2O-EtOH
!
MCl2 Á nH2O ‡ 2L
‰MꢁL†2Cl2Š Á H2O ‡ ꢁn À 1†H2O
heat
H2O-EtOH
!
CuSO4 Á 5H2O ‡ 4-HOABH
‰Cuꢁ4-HOABH†SO4ꢁH2O† Š
‡ 3H2O
2
heat
‰MꢁII† ˆ Co; Ni; Cu and Cd; L ˆ ABH or 4-HOABHŠ
The complexes are insoluble in water and common organic solvents such as
ethanol, methanol, benzene, chloroform but are slightly soluble in DMF and
DMSO. They melt with decomposition in the 1807250 ꢂC temperature range.
The [M(4-HOABH)2Cl2]ÁH2O complexes decompose in the 1807237 ꢂC
temperature range. The hydrated complexes lose water molecules at
1107180 ꢂC. The low molar conductances (16.6727.5 O ÀM1 cm2 molÀ1) of the
complexes suggest that they are non-electrolytes8 in solution.
Magnetic Measurements
The magnetic moment of the cobalt(II) and nickel(II) complexes lie
in the range reported for octahedralgeometry 9. The me€ values of the

COMPLEXES OF Co(II), Ni(II), Cu(II), AND Cd(II)
1381
copper(II) complexes indicate the presence of one unpaired electron and give
no de®nite information about the geometry.
Electronic Spectra
In the spectrum of ABH absorption bands are observed at 35,714,
43,859 and 47,619 cmÀ1 while in that of 4-HOABH they were observed at
35,971, 45,454 and 48,544 cmÀ1 which are assigned to n?p* and p?p*
transitions of > CˆO and > CˆN groups, respectively. The corresponding
bands of the metal complexes are observed at lower energies at
32,258735,714, 40,985745,045 and 45,454747,719 cmÀ1, respectively, in-
dicating bonding of > CˆO and > CˆN groups to the metalions.
The spectrum of [Co(ABH)2Cl2] Á H2O shows two absorption bands at
15,060 (n2) and 19,607 (n3) cmÀ1 while that of [Co(4-HOABH)2Cl2] Á H2O
exhibits two bands at 14,471 (n2) and 18,050 (n3) cmÀ1. They are assigned to
4
4
4
the T1gꢁF† ! A2gꢁF† (n2) and T1gꢁP† (n3) transitions, respectively. These
features are characteristic of octahedralgeometry of the compelxes as in-
dicated by the magnetic susceptibility measurement.
The absorption bands at 12,820 (n2) and 22,935 (n3) cmÀ1 in the
spectrum of [Ni(ABH)Cl2] Á H2O and at 14,637 (n2) and 24,154 (n3) cmÀ1 in
10
3
3
that of [Ni(4-HOABH)2Cl2] Á H2O are attributed to the A2gꢁF† ! T1gꢁF†
3
(n2) and T1gꢁP† (n3) transitions , respectively, and show an octahedral
geometry for the complexes11.
The ligand ®eld parameters, such as crystal ®eld splitting energy
(10 Dq), interelectronic repulsion parameter (B0), nephalauxetic ratio (b),
percentage covalency (b0) and ligand ®eld stabilization energy (LFSE) have
been evaluated for cobalt(II) and nickel(II) complexes12. The values of these
parameters in Table II are indicative of considerable metal-ligand orbital
overlap.
The copper(II) complexes of ABH and 4-HOABH shows only one
absorption band at 12,670 and 14,865 cmÀ1, respectively, which is assigned
2
to the 2Eg ! T2gꢁD† transition on the basis of a distorted octahedral
geometry13.
ESR Spectra
The ESR spectrum of [Cu(4-HOABH)SO4(H2O)2] shows a broad
signal yielding a g-value of 2.005. This may be due to dipolar exchange and
unresolved hyper®ne interactions14. The spectrum also supports the octa-
hedralstructure of the copper(II) compelx.

1382
SINGH, NARANG, AND SRIVASTAVA

COMPLEXES OF Co(II), Ni(II), Cu(II), AND Cd(II)
Infrared Spectra
1383
The spectrum of ABH exhibits bands at 3270, 1640, 1624 and
996 cmÀ1 while that of 4-HOABH at 3265, 1660, 1625 and 998 cmÀ1 which
are attributed to n(NH), n(CˆO), n(CˆN) and n(NÀN), respectively. A
band at 3320 cmÀ1 is assigned to n(OH) in the spectrum of 4-HOABH.
In the metalcompelxes,
n(CˆO) shifted to lower frequency by
15
5715 cmÀ1 and suggests bonding through the carbonyloxygen
.
The n(CˆN) band is observed in the 160571620 cmÀ1 region in the
spectra of ABH and 4-HOABH complexes indicating that the azomethine
nitrogen is involved in bonding16. The n(NÀN) band shifted from
9967998 cmÀ1 in the ligand to higher frequency (100071010 cmÀ1) in the
complexes which further supports bonding through the azomethine nitro-
gen17. The band due to n(OH) remains unaltered compared to the ligand
indicating non-involvement of the phenolic oxygen in bonding. Thus, both
hydrazones behave as bidentate ligands bonding through the carbonyl
oxygen and azomethine nitrogen. All complexes show a broad band in the
340073600 cmÀ1 region indicating the presence of water molecules. [Cu(4-
HOABH)SO4(H2O)2] shows bands in the 9507900, 7607750 and
6607650 cmÀ1 region due to wagging, twisting and rocking modes char-
acteristic of coordinated water. In [Cu(4-HOABH)SO4(H2O)2] three new
bands appeared at 950, 1050 and 1220 cmÀ1 which suggest the presence of
the chelating sulfate group18.
Table III. Important IR SpectralBands (cm À1) and Their Assignments
Amide I
n(CˆO)
Complexes
n(OH)=NH
3280 b
n(CˆN)
n(NÀN)
ABH
1640 s
1635 s
1630 s
1635 s
1635 s
1660 s
1640 s
1645 m
1635 m
1650 m
1614 s
998 w
[Co(ABH)2Cl2]ÁH2O
[Ni(ABH)2Cl2]ÁH2O
[Cu(ABH)2Cl2]ÁH2O
[Cd(ABH)2Cl2]ÁH2O
4-HOABH
[Co(4-HOABH)2Cl2]ÁH2O
[Ni(4-HOABH)2Cl2]ÁH2O
[Cu(4-HOABH)2Cl2]ÁH2O
[Cu(4-HOABH)
3415 b=3270 m
3410 b=3258 m
3410 b=3260 m
3415 b=3270 w
3320 b=3255 m
3311 b=3260 m
3315 m=3265 m
3320 w=3260 m
3320 w=3260 m
1610 m
1610 m
1610 m
1610 m
1625 m
1608 m
1620 m
1620 m
1610 m
1010 w
1005 w
1010 w
995 w
1005 w
1005 w
1010 w
1005 w
1010 w
SO4](H2O)2]
[Cd(4-HOABH)2Cl2]ÁH2O
3320 m=3265 w
1650 w
1605 m
1010 w

1384
SINGH, NARANG, AND SRIVASTAVA
Table IV. AntibacterialActivity
Zone of Inhibition (cm)
Compounds
500 mg=mL
1000 mg=mL
1500 mg=mL
ABH
0.022
0.866
0.431
0.040
1.201
0.781
0.024
0.886
0.441
0.048
1.360
0.881
0.028
0.896
0.466
0.499
1.440
0.888
[Cu(ABH)2Cl2]ÁH2O
[Zn(ABH)2Cl2]ÁH2O
4-HOABH
[Cu(4-HOABH)2Cl2]ÁH2O
[Zn(4-HOABH)2Cl2]ÁH2O
Biological Activity
Acetophenone and 4-hydroxyacetophenone benzoylhydrazones and
their Cu(II) and Zn(II) complexes have been screened against E. coli (a gram
‡ve bacteria) and Aspergllus niger at three di€erent concentrations, 500,
1000 and 1500 mg=mL. The results are shown in Tables IV and V.
The experimentaldata show that 4-HOABH has a greater inhibitory
e€ect than ABH which may be due to the presence of the phenolic group in
4-HOABH which is more e€ective than other groups19.
The complexes have a greater inhibitory e€ect than their parent li-
gands20. The region behind the good activity may be the combined e€ect of
metal toxicity and availability of uncoordinated binding sites of ligands
which interact with metaltrace metasl of bacteria and fungi. In the
a
Table V. AntifungalActivity
Percentage of Inhibition
Compounds
500 mg=mL
1000 mg=mL
1500 mg=mL
ABH
‡‡‡‡
‡‡‡‡
‡‡‡
‡‡‡
‡‡‡
‡‡
‡‡‡
‡‡‡
‡‡
‡‡
‡
‡‡‡‡
‡‡‡
‡
[Cu(ABH)2Cl2]ÁH2O
[Zn(ABH)2Cl2]ÁH2O
4-HOABH
‡‡‡
‡‡
[Cu(4-HOABH)2Cl2]ÁH2O
[Zn(4-HOABH)2Cl2]ÁH2O
‡‡
‡‡
a
‡‡‡‡ ˆ 100% germination, ‡‡‡ ˆ 75% germination, ‡‡ ˆ 50% germination,
‡ ˆ 25% germination.

COMPLEXES OF Co(II), Ni(II), Cu(II), AND Cd(II)
1385
4-HOABH metal complexes the phenolic group is uncoordinated so these
complexes have greater inhibitory e€ect that the ABH complexes.
ACKNOWLEDGMENT
The authors thank the Head, Department of Chemistry, Banaras
Hindu University, for providing laboratory facilities.
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Received February 17, 2000
Accepted June 23, 2001
Referee I: M. T. Caudle
Referee II: I. F. Cheng