Synthesis, characterization, and biological activity of complexes derived from E-N′-(3,4,5-trimethoxybenzylidene)benzofuran-2-carbohydrazide and ortho-phenylenediamine/2,6-diaminopyridine

Article abstract of DOI:10.1080/00958972.2011.553222

Mixed ligand complexes of the type MLL′Cl₂ (where M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II), L = ligand derived from the reaction between benzofuran-2-carbohydrazide and 3,4,5-trimethoxybenzaldehyde (TMeOBFC), and L′ = ortho-phenylenediamine (opd)/2,6-diaminopyridine (2,6-dap)) have been synthesized. The complexes have been characterized by analytical data, IR, UV-Vis, ¹H NMR, DART-MS and ESR spectral data, and magnetic studies. Molar conductance values indicate that the complexes are non-electrolytic in DMF. Antibacterial and antifungal activities of the ligands and complexes have been screened against bacteria Escherichia coli and Staphylococcus aureus and against fungi Aspergillus niger and Aspergillus flavus.

Full text of DOI:10.1080/00958972.2011.553222

Journal of Coordination Chemistry
Vol. 64, No. 4, 20 February 2011, 651–662
Synthesis, characterization, and biological activity of complexes
derived from E-N9-(3,4,5-trimethoxybenzylidene)benzofuran-2-
carbohydrazide and ortho-phenylenediamine/
2,6-diaminopyridine
M.B. HALLI*, VIJAYALAXMI B. PATIL, MALLIKARJUN KINNI
and R.B. SUMATHI
Department of Chemistry, Gulbarga University, Gulbarga – 585106, Karnataka, India
(Received 7 September 2010; in final form 22 November 2010)
Mixed ligand complexes of the type MLL0Cl2 (where M ¼ Co(II), Ni(II), Cu(II), Zn(II), Cd(II),
and Hg(II), L ¼ ligand derived from the reaction between benzofuran-2-carbohydrazide and
3,4,5-trimethoxybenzaldehyde (TMeOBFC), and L0 ¼ ortho-phenylenediamine (opd)/2,6-dia-
minopyridine (2,6-dap)) have been synthesized. The complexes have been characterized by
analytical data, IR, UV-Vis, 1H NMR, DART-MS and ESR spectral data, and magnetic
studies. Molar conductance values indicate that the complexes are non-electrolytic in DMF.
Antibacterial and antifungal activities of the ligands and complexes have been screened against
bacteria Escherichia coli and Staphylococcus aureus and against fungi Aspergillus niger and
Aspergillus flavus.
Keywords: Benzofuran Schiff bases; Mixed ligand complexes; Spectral studies; Biological
activity
1. Introduction
Schiff bases have many applications in food industry, dye industry, analytical
chemistry, catalysis, fungicidal, agrochemical, and biological activities. Schiff bases
exhibit a broad spectrum of pharmacological and biological properties, such as
analgesics, anticancer agents, anti-inflammatory, etc., which may be due to the
azomethine linkage [1]. Schiff-base complexes containing nitrogen and oxygen donors
play an important role in biological systems and represent models for metalloproteins
and metalloenzymes that catalyze the reduction of nitrogen and oxygen [2]. Schiff bases
show the ability to complex with many metal ions [3] and such complexes play an
important role in coordination chemistry, enzyme reactions, and molecular architec-
tures [4, 5]. Metal complexes play an essential role in agriculture, pharmaceutical, and
industrial chemistry [6]. Many drugs possess modified toxicological and pharmacolog-
ical properties when administered as metal complexes [7, 8]. Metal complexes with
*Corresponding author. Email: mbhalli@rediffmail.com
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2011 Taylor & Francis
DOI: 10.1080/00958972.2011.553222

652
M.B. Halli et al.
mixed ligands provide new materials with useful properties such as magnetic exchange
[9], electrical conductivity [10], non-linear optical activity [11], and many other activities
[12]. Mixed ligand complexes are involved in the exchange and transport mechanism of
trace metal ions in the human body [13].
Benzofuran compounds are abundant in nature, particularly among plants. Natural
products possessing benzofuran have useful pharmacological properties [14]. Baker’s
yeast contains a benzofuran derivative which acts as an antioxidant preventing
hemorrhaging liver necrosis in rats and hemolysis of red cells during vitamin-E
deficiency [15]. Some benzofuran derivatives such as 2-acetylbenzofuran and
2-nitrobenzofuran are well-known biodynamic agents possessing various pharmaco-
logical properties [16–18]. Amiodarone hydrochloride, used as an antiarrhythmic drug
[19], contains a 2,3-disubstituted benzofuran.
This work deals with the synthesis and characterization of Co(II), Ni(II), Cu(II),
Zn(II), Cd(II), and Hg(II) complexes with primary ligand derived from benzofuran-2-
carbohydrazide and 3,4,5-trimethoxybenzaldehyde (TMeOBFC) and ortho-phenylene-
diamine (opd) or 2,6-diaminopyridine (2,6-dap). The Schiff base and metal complexes
are screened for antibacterial and antifungal activities.
2. Experimental
Chemicals used in this work were of analytical reagent (AR) grade and of highest
purity available. Benzofuran-2-carbohydrazide was synthesized according to the
literature procedure [20]. Metal and chloride contents were determined as per Vogel’s
procedure [21].
2.1. Synthesis of (E)-N0-(3,4,5-trimethoxybenzylidene)benzofuran-2-carbohydrazide
[TMeOBFC]
A solution of benzofuran-2-carbohydrazide (1.76 g, 0.01 mol) in ethanol (25 mL) was
added to 3,4,5-trimethoxybenzaldehyde (1.96 g, 0.01 mol) in ethanol (20 mL) and
refluxed on a water bath for 4–5 h. On the partial removal of solvent and cooling to
room temperature, the Schiff base was separated as yellowish crystalline solid, which
was then filtered, washed with ethanol, and recrystallized from ethanol. The synthesis of
the Schiff base is shown in scheme 1.
2.2. Synthesis of metal(II) mixed ligand complexes
An ethanolic solution (20 mL) of 0.01 mol of the appropriate metal chloride, MCl2
(M ¼ Co, 2.378 g; M ¼ Ni, 2.377 g; M ¼ Cu, 1.705 g; M ¼ Zn, 1.363 g; M ¼ Cd, 2.013 g;
M ¼ Hg, 2.715 g), was added to an ethanolic solution (30 mL) of the Schiff base,
TMeOBFC (3.54 g, 0.01 mol). An ethanolic solution (20 mL) of 0.01 mol of ortho-
phenylenediamine (1.08 g) or 2,6-diaminopyridine (1.09 g) was added to the previous
solution and the reaction mixture was refluxed for 3 h on a water bath, and then
aqueous alcoholic solution of sodium acetate was added to adjust the pH to 6–7 and
further refluxed for an hour. The precipitated complexes were filtered and washed with

Benzofuran Schiff bases
653
CHO
H
N
OCH
3
C
O
NH
O
H CO
2
3
OCH
3
Reflux for 4–5h
Ethanol
H
H
N
C
O
O
N
C
OCH
OCH
3
3
OCH
3
Scheme 1. Synthesis of TMeOBFC (C19H18O5N2 [TMeOBFC]: mol. wt ¼ 354, m.p. ¼ 233ꢁC, yield ¼ 72%).
distilled water, then with alcohol, and finally dried in vacuum over fused calcium
chloride (yield ¼ 55–60%).
2.3. Physical measurements
Carbon, hydrogen, and nitrogen analyses were carried out microanalytically on a
Perkin-Elmer 240C model at the Central Drug Research Institute (CDRI), Lucknow.
IR spectra of the Schiff base and complexes were recorded in KBr pellets from 4000 to
350 cmꢀ1 on a Perkin-Elmer 783 FT-IR spectrophotometer. Electronic spectra of the
Co(II), Ni(II), and Cu(II) complexes were recorded on an Elico-SL-164 double beam
1
UV-Vis spectrophotometer from 200 to 1100 nm in DMF (10ꢀ3 mol Lꢀ1). H NMR
spectra were recorded in DMSO-d6 on a Bruker 300 MHz spectrophotometer using
TMS as an internal standard. The ESR spectrum of the Cu(II) complex in
polycrystalline state was recorded on a Varian-E-4X band EPR spectrophotometer
using TCNE as ‘‘g’’ marker (g ¼ 2.00277) at room temperature. Direct analysis in real
time-mass spectra (DART-MS) were recorded on a JEOL-AccuTOF JMS-T100LC
mass spectrometer having a DART source. Dry helium was used with 4 L minꢀ1 flow
rate for ionization at 350ꢁC, the orifice 1 set at 28 V. Molar conductivity measurements

654
M.B. Halli et al.
were recorded on an Elico CM-180 conductivity bridge in DMF (10ꢀ3 mol Lꢀ1) using a
dip-type conductivity cell fitted with a platinum electrode and magnetic susceptibility
measurements were made at room temperature on a Gouy balance using Hg[Co(NCS)4]
as the calibrant.
2.4. Biological activities
The Schiff base and complexes have been studied for antibacterial and antifungal
activities by agar diffusion in DMF against Escherichia coli and Staphylococcus aureus
bacterial and Aspergillus niger and Aspergillus flavus fungi species [22, 23].
2.5. Antibacterial screening
Media used: peptone 10 g, NaCl 10 g, yeast extract 5 g, and agar 20 g in 1000 mL of
distilled water.
Initially, stock cultures of E. coli and S. aureus were revived by inoculating in broth
media and grown at 37ꢁC for 18 h. The agar plates of the above media were prepared
and wells were made in the plate. Each plate was inoculated with 18-h-old cultures and
spread evenly on the plate. After 20 min, the wells were filled with test solutions.
Gentamycin was used as the standard antibacterial drug. All the plates were incubated
at 37ꢁC for 24 h and the diameters of inhibition zones were noted.
2.6. Antifungal screening
Media used: potato dextrose agar (PDA). 250 g of peeled potatoes were boiled for
20 min and squeezed and filtered. 20 g of dextrose was added to this filtrate and the
volume was made up to 1000 mL by distilled water.
Initially, stock cultures of A. flavus and A. niger were revived by inoculating in broth
media and grown at 37ꢁC for 48 h. The agar plates of the above media were prepared
and wells were made in the plate. Each plate was inoculated with 18-h-old cultures and
spread evenly on the plate. After 20 min, the wells were filled with test solutions.
Fluconazole was used as the standard antifungal drug. All the plates were incubated at
37ꢁC for 48 h and the diameters of inhibition zones were noted.
3. Results and discussion
Analytical data show that all the complexes have 1 : 1 : 1 (metal : primary ligand : sec-
ondary ligand) stoichiometry (table 1). The molar conductance values (11.74–
20.23 Ohmꢀ1 cm2 molꢀ1) are too low to account for the dissociation of the complexes
in DMF, indicating the presence of non-electrolytes [24]. All the complexes are light in
color, stable, non-hygroscopic, and possess high melting points. The complexes are
insoluble in common organic solvents but soluble in DMF and DMSO.

Benzofuran Schiff bases
655

656
M.B. Halli et al.
3.1. Magnetic properties
Magnetic susceptibility measurements at room temperature exhibit paramagnetism for
Co(II), Ni(II), and Cu(II) complexes; ꢀeff values are listed in table 1. The Co(II)
complexes exhibit magnetic moments of 4.81 and 4.92 BM, suggesting an octahedral
geometry [25, 26]. The Ni(II) complexes show magnetic moment values of 2.98 and
3.11 BM, slightly higher than the spin only value (2.83 BM), indicating an octahedral
environment around Ni(II) [27, 28]. The observed magnetic moments for the Cu(II)
complexes are 1.78 and 2.01 BM, suggesting a distorted octahedral geometry for Cu(II)
complexes [29]. The primary and secondary ligands are bidentate in all complexes.
3.2. Electronic spectral studies
Electronic spectra of the Co(II), Ni(II), and Cu(II) complexes were recorded for freshly
prepared solution in DMF (10ꢀ3 mol Lꢀ1) at room temperature (table 2). Spectra of
Co(II) complexes show two bands at 15,314, 19,763 cmꢀ1 and at 16,155, 20,450 cmꢀ1
,
4
4
4
4
assignable to T1g (F ) ! A2g (F ) (ꢁ2) and T1g (F ) ! T2g (P) (ꢁ3) transitions in an
octahedral environment [30]. The ꢁ1 band could not be observed; however, ꢁ1 was
calculated using an equation suggested by Underhill and Billing [31].
Ni(II) complexes exhibit two bands at 15,983, 26,523 cmꢀ1 and at 15,423,
3
3
3
3
26,423 cmꢀ1 assignable to A2g (F ) ! T1g (F ) (ꢁ2) and A2g (F ) ! T1g (P) (ꢁ3)
transitions, respectively, in an octahedral environment. The ꢁ1 could not be observed
due to limited range of the instrument used. However, it is calculated by using band-
fitting procedure [31].
The Cu(II) complexes exhibit a single broad asymmetric band at 13,141–17,560 cmꢀ1
.
The broadness of the band indicates that the three expected transitions 2B1g ! A1g (ꢁ1),
2
2B1g ! B2g (ꢁ2), and B1g ! Eg (ꢁ3) are similar in energy and give rise to only one
broad band. The broadness of the band may be due to dynamic Jahn–Teller distortion.
All these data suggest a distorted octahedral geometry around Cu(II).
2
2
2
The octahedral geometry [32] is further supported by the values of ligand field
parameters such as Racah inter-electronic repulsion parameter (B0), ligand-field
splitting energy (10 Dq), covalency factor (ꢂ), and ligand-field stabilization energy
(LFSE) [33]. The B0 values for the complexes were lower than the free ion values,
Table 2. Electronic spectral bands and ligand field parameters of the Co(II), Ni(II), and Cu(II) complexes
in DMF (10ꢀ3 mol Lꢀ1).
Transitions in cmꢀ1
Dq
B0
LFSE
(kcal)
a
b
b
Complexes
ꢁ1
ꢁ2(")
ꢁ3(")
(cmꢀ1
)
(cmꢀ1
)
ꢂ
ꢂ%
ꢁ2/ꢁ1
[CoL(opd)Cl2]
[NiL(opd)Cl2]
[CuL(opd)Cl2]
[CoL(2,6-dap)Cl2] 7515 16155 (360) 20450 (480)
[NiL(2,6-dap)Cl2] 9390 15423 (270) 26423 (560)
7114 15314 (260) 19763 (440)
9860 15983 (250) 26523 (580)
13223–16821 (310)
820
986
1502
864
939
1535
915
860
–
938
911
–
0.942 5.767 2.152 15.685
0.827 17.308 1.621 33.806
–
0.966
–
–
25.749
3.399 2.150 14.811
0.876 12.404 1.642 32.194
26.314
[CuL(2,6-dap)Cl2]
13141–17560 (340)
–
–
–
aCalculated values.
bMolar extinction coefficient values are given in parenthesis in units of L molꢀ1 cmꢀ1
.

Benzofuran Schiff bases
657
indicating orbital overlap and delocalization of d-orbitals. The ꢂ values obtained are
less than unity, suggesting considerable covalent character for the metal–ligand bonds.
The ꢂ value for Ni(II) complexes are less than the Co(II) complexes, indicating more
covalency of M–L bonds [34].
3.3. IR spectral studies
IR spectra of the ligand and complexes are presented in table 3. The spectra are
complex and it is not possible to assign all the bands.
TMeOBFC shows medium broad bands at 3448 and 3216 cmꢀ1 due to ꢁ(NH) of
hydrazine. These bands are assigned to ꢁasym and ꢁsym stretching vibrations of
secondary amide and shift to a higher wavenumber by 5–15 cmꢀ1 in the complexes,
showing non-involvement of ‘‘N’’ of NH in bonding with metal ions [35]. The strong
intensity bands at 1695 and 1626 cmꢀ1 are assigned to ꢁ(C¼O) and ꢁ(C¼N),
respectively, in free ligand. These bands shift to a lower wavenumber by about 20–
45 cmꢀ1 in the complexes, indicating coordination to metal through the oxygen of C¼O
and nitrogen of –N¼CH– [36, 37]. The band at 1031 cmꢀ1 is assigned to ꢁ(N–N) of
hydrazine, which shifts to a higher wavenumber by 10–15 cmꢀ1 in metal complexes,
confirming bonding through one nitrogen of hydrazine [38].
ortho-Phenylenediamine shows broad bands at 3365 and 3360 cmꢀ1 due to ꢁ(NH) of
primary amine [39]. In all metal complexes the band shifts to a lower wavenumber,
3335–3295 cmꢀ1, indicating the involvement of nitrogen of amine in bonding with
metal ion.
The 2,6-diaminopyridine shows broad bands at 3392 and 3386 cmꢀ1 due to ꢁ(NH) of
primary amine. In metal complexes the band shifts to a lower wavenumber, 3362–
3331 cmꢀ1, indicating the involvement of amino nitrogen in bonding with metal. An
absorption at 1578 cmꢀ1 can be assigned to ꢁ(C¼N) of pyridine in 2,6-diaminopyridine.
There is not much change in the position of this band in the metal complexes, indicating
non-involvement of pyridine nitrogen in bonding with metal [40].
Metal–ligand vibrations are difficult to assign on an empirical basis since they are
sensitive to both ligand and metal. However, non-ligand new bands at 530–515 and
408–460 cmꢀ1 are assigned to ꢁ(M–O) and ꢁ(M–N) [41, 42]. The weak intensity bands
at 340–305 cmꢀ1 are assigned to ꢁ(M–Cl) vibrations.
Table 3. IR frequencies (in cmꢀ1) of TMeOBFC and metal complexes.
Schiff base/complexes
ꢁ(C¼O)
ꢁ(C¼N)
ꢁ(N–N)
ꢁ(M–O)
ꢁ(M–N)
ꢁ(M–Cl)
TMeOBFC (L)
[CoL(opd)Cl2]
[NiL(opd)Cl2]
[CuL(opd)Cl2]
[ZnL(opd)Cl2]
1695
1672
1675
1666
1658
1667
1656
1670
1659
1662
1650
1671
1674
1626
1598
1589
1606
1601
1592
1594
1590
1581
1604
1596
1587
1592
1031
1042
1046
1041
1043
1045
1044
1043
1042
1046
1041
1044
1045
–
–
–
526
519
530
523
516
528
524
518
515
527
520
517
432
416
408
445
450
428
456
441
460
423
438
421
320
326
318
340
332
315
336
323
305
328
316
321
[CdL(opd)Cl2]
[HgL(opd)Cl2]
[CoL(2,6-dap)Cl2]
[NiL(2,6-dap)Cl2]
[CuL(2,6-dap)Cl2]
[ZnL(2,6-dap)Cl2]
[CdL(2,6-dap)Cl2]
[HgL(2,6-dap)Cl2]

658
M.B. Halli et al.
Table 4. 1H NMR spectral data of TMeOBFC and Zn(II) and Cd(II) complexes [chemical shifts in
ꢃ (ppm)].
Ligands/complexes
–CONH–
–N¼CH–
Aromatic protons
Methoxy protons
[TMeOBFC]
12.13 (s, 1H)
12.60 (s, 1H)
12.51 (s, 1H)
12.47 (s, 1H)
12.38 (s, 1H)
8.44 (s, 1H)
8.74 (s, 1H)
8.71 (s, 1H)
8.64 (s, 1H)
8.68 (s, 1H)
6.94–7.83 (m, 7H)
6.33–7.93 (m, 15H)
6.35–7.89 (m, 15H)
7.01–7.88 (m, 14H)
7.03–7.86 (m, 14H)
3.29, 3.67, 3.91 (s, 9H)
3.32, 3.70, 3.90 (s, 9H)
3.31, 3.68, 3.89 (s, 9H)
3.31, 3.72, 3.89 (s, 9H)
3.29, 3.69, 3.90 (s, 9H)
[ZnL(opd)Cl2]
[CdL(opd)Cl2]
[ZnL(2,6-dap)Cl2]
[CdL(2,6-dap)Cl2]
3.4. 1H NMR spectral studies
1H NMR spectra of [TMeOBFC] and the Zn(II) and Cd(II) complexes were recorded in
DMSO-d6 (table 4).
The signal at ꢃ (12.13) (s, 1H) is assigned to amide proton (–CONH–) and the signal
at ꢃ (8.44) (s, 1H) is assigned to azomethine proton (–N¼CH–) in [TMeOBFC]. Signals
due to (ꢀCONH–) are shifted downfield in the spectra of Zn(II) ꢃ (12.60, 12.47) (s, 1H)
and Cd(II) ꢃ (12.51, 12.38) (s, 1H) complexes, indicating the coordination of the oxygen
of –CONH– with metal. The azomethine protons shift downfield ꢃ (8.64–8.74) (s, 1H),
supporting the coordination of nitrogen of –N¼CH– with metal. The aromatic protons
at 6.94–7.83 shift downfield in the complexes. Signals at ꢃ 3.29 (s, 3H, –OCH3), ꢃ 3.67
(s, 3H, –OCH3), and ꢃ 3.91 (s, 3H, –OCH3) are due to the protons of three –OCH3
1
groups present on the phenyl ring. Thus, H NMR spectra supplement the assigned
geometry.
3.5. Mass spectral studies
The DART-MS of TMeOBFC shows a molecular ion peak at m/z 355, one mass unit
more than the molecular weight of the Schiff base. The DART-MS of
[Co(TMeOBFC)(opd)Cl2] shows a molecular ion peak at m/z 592, which is same as
that of the molecular weight of the complex. The DART-MS of [Ni(TMeOBFC)(2,6-
dap)Cl2] shows a molecular ion peak at m/z 593, the same as the molecular weight of the
complex. Mass spectral studies support the proposed composition.
3.6. ESR spectra of Cu(II) complexes
The ESR spectra of copper complexes in a polycrystalline state have been recorded at
room temperature. The g|| and g values are 2.358, 2.339 and 2.089, 2.074, respectively.
?
The gav was calculated to be 2.182 and 2.166. The spectra have asymmetric bands with
g|| 4 g 4 2.00277 (TCNE) observed, indicating that the unpaired electron lies
?
predominantly in the dx2ꢀy2 orbital with possible mixing of dz2 because of low symmetry
[43]. The axial symmetry parameter ‘‘G’’ is determined as G ¼ (g|| ꢀ 2.00277)/
(g ꢀ 2.00277) ¼ 4.123, 4.709, respectively, more than 4 [44].
?

Benzofuran Schiff bases
659
Table 5. Antimicrobial activity of the ligands and complexes.
Zone of inhibition (mm)
Bacteria
S. aureus
Fungi
Schiff base/complexes
E. coli
A. niger
A. flavus
TMeOBFC (L)
opd
11
14
16
15
17
18
19
17
13
14
14
16
19
17
18
20
–
12
13
15
14
16
20
17
19
15
16
17
16
21
18
20
22
–
14
17
18
18
19
21
18
19
14
17
16
18
20
18
19
–
16
15
18
17
19
20
19
18
13
18
19
17
21
19
20
–
[CuL(opd)Cl2]
[NiL(opd)Cl2]
[CoL(opd)Cl2]
[ZnL(opd)Cl2]
[CdL(opd)Cl2]
[HgL(opd)Cl2]
2,6-dap
[CuL(2,6-dap)Cl2]
[NiL(2,6-dap)Cl2]
[CoL(2,6-dap)Cl2]
[ZnL(2,6-dap)Cl2]
[CdL(2,6-dap)Cl2]
[HgL(2,6-dap)Cl2]
Gentamycine
Fluconazole
22
23
E. coli
S. aureus
20
15
10
5
0
L
opd Cu Ni Co Zn Cd Hg dap Cu Ni Co Zn Cd Hg Std
Compounds/antibiotic
Figure 1. Antibacterial results of TMeOBFC, ortho-phenylenediamine (opd), 2,6-diaminopyridine (dap),
.
metal(II) complexes, and Gentamycin (Std) at 1 mg mLꢀ1
3.7. Antibacterial and antifungal activities
The Antibacterial and antifungal activities of the ligands and complexes have been
tested by agar diffusion method for their activity against two bacteria E. coli and
S. aureus and two fungi A. niger and A. flavus.

660
M.B. Halli et al.
A. niger
A. flavus
20
15
10
5
0
L
opd Cu Ni Co Zn Cd Hg dap Cu Ni Co Zn Cd Hg Std
Compounds/antibiotic
Figure 2. Antifungal results of TMeOBFC, opd, 2,6-dap, metal(II) complexes, and Fluconazole (Std) at
1 mg mLꢀ1
.
H
N
OCH
OCH
3
N
O
O
3
Cl
Cl
M
OCH
3
NH
2
NH
2
Figure 3. Suggested structures of Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) complexes, TMeOBFC,
and opd (M ¼ Co(II), Ni(II), Cu(II), Zn(II), Cd(II), or Hg(II)).
The activities of TMeOBFC, opd, and 2,6-dap are shown in table 5 along
with standards. From table 5 it is clear that Zn(II), Cd(II), and Hg(II) complexes
show good activity against both bacteria and fungi, having higher activity than
ligands against the same microorganisms under the same experimental conditions
[45, 46] (figures 1 and 2).

Benzofuran Schiff bases
661
H
N
N
OCH
OCH
3
O
O
3
Cl
Cl
M
N
OCH
3
H N
NH
2
2
Figure 4. Suggested structures of metal complexes of TMeOBFC and 2,6-dap (M ¼ Co(II), Ni(II), Cu(II),
Zn(II), Cd(II), or Hg(II)).
4. Conclusion
We report new complexes of the type MLL0Cl2, where M ¼ Co(II), Ni(II), Cu(II),
Zn(II), Cd(II), and Hg(II), L ¼ TMeOBFC and L0 ¼ opd or 2,6-dap. TMeOBFC is
neutral bidentate, coordinating through the azomethine nitrogen and oxygen of –
CONH–, whereas opd or 2,6-dap coordinate through amino groups. Based on
analytical data and spectral studies, we propose octahedral structures to all the
complexes (figures 3 and 4). Biological activity results show that metal complexes are
more active compared to the parent ligands.
Acknowledgments
Authors are thankful to Chairman, Department of Chemistry, Gulbarga University,
Gulbarga, for encouragement and facilities. V.B. Patil is thankful to UGC New Delhi
for UGC Research Fellowship for meritorious students under RFSMS Scheme.
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