Synthesis, characterisation and antimicrobial activity of new palladium and nickel complexes containing Schiff bases

Article abstract of DOI:10.1016/j.ica.2015.11.017

New Schiff base ligands were synthesized by condensation of 2-(3,4-dimethoxyphenyl)ethanamine with 2-hydroxy benzaldehyde (L¹H) and 2′-hydroxy acetophenone (L²H) respectively. Reaction of L¹H or L²H with Na

Full text of DOI:10.1016/j.ica.2015.11.017

Accepted Manuscript
Synthesis, characterization and antimicrobial activity of new paladium and
nickel complexes containing Schiff bases
C.E. Satheesh, P. Raghavendra Kumar, P. Sharma, K. Lingaraju, B.S.
Palakshamurthy, H. Rajanaika
PII:
S0020-1693(15)00571-X
http://dx.doi.org/10.1016/j.ica.2015.11.017
ICA 16775
DOI:
Reference:
Inorganica Chimica Acta
To appear in:
Received Date:
Revised Date:
Accepted Date:
22 August 2015
11 November 2015
12 November 2015
Please cite this article as: C.E. Satheesh, P. Raghavendra Kumar, P. Sharma, K. Lingaraju, B.S. Palakshamurthy,
H. Rajanaika, Synthesis, characterization and antimicrobial activity of new paladium and nickel complexes
containing Schiff bases, Inorganica Chimica Acta (2015), doi: http://dx.doi.org/10.1016/j.ica.2015.11.017
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Synthesis, characterization and antimicrobial activity of new paladium and
nickel complexes containing Schiff bases
Satheesh C.E.1, Raghavendra Kumar P. 1*, Sharma P.2, Lingaraju K.4, Palakshamurthy B.S.3, Rajanaika
H.4
1Department of Chemistry, University College of Science, Tumkur University, Tumkur 572 103
2Instituto de Quimica, UNAM, Circuito Exterior, Coyoacan, D. F. 04510, Mexico
3Department of Physics, University College of Science, Tumkur University, Tumkur 572 103
4Department of Studies and Research in Environmental Science, Tumkur University, Tumkur 572 103
*Corresponding author: raghukp1@gmail.com, Ph. No. +91-9901511112
Keywords: Schiff’s base, 2-(3,4-Dimethoxyphenyl) ethanamine, Palladium, Nickel, Complex,
Antimicrobial activity
Abstract:
New Schiff base ligands were synthesized by condensation of 2-(3,4-dimethoxyphenyl)
ethanamine with 2-hydroxy benzaldehyde (L1H) and 2’-hydroxy acetophenone (L2H)
respectively. Reaction of L1H or L2H with Na2PdCl4 or NiCl2.6H2O in 2:1 ratio obtained four
new coordination complexes [M(L1-2)2] (where M = Pd(II); 1 and 2 and M = Ni(II); 3 and 4).
Both the ligands and four complexes were characterized by elemental analysis, FT-IR and UV-
1
Vis., spectroscopy. L1H, L2H, 1 and 2 were also characterized by H and 13C{1H} NMR
spectroscopy. The molecular structures of 1 and 3 were determined by single crystal X-ray
diffraction. The spectroscopic and crystal structure data showed that the ligands coordinated to
M(II) ion in a bidentate monoanionic (O-, N) fashion. The Pd-O and Pd-N bond lengths in 1 are
1.984(11) and 2.020(12) Å in 3 the Ni-O and Ni-N bond lengths are 1.8222(13) and 1.9262(15)
Å respectively. The C=N bond length in 3 found 1.290(2) Å which was shorter than 1.310(19)
Å in 1. The bond angles provided square planar geometry around Pd(II) and Ni(II) in both 1
and 3. There exists C-H…O type (2.50 – 2.52 Å) intermolecular hydrogen bonding in both 1 and
3 resulting in supramolecular structures. The antimicrobial activity of new Schiff base ligands
and their Pd(II) and Ni(II) complexes against pathogenic microbial strains by agar well
diffusion method was conducted. All the ligands and complexes showed significant antibacterial
and antifungal activities. The bacterial and fungi growth inhibition activity of ligands has been
1

increased on complexation as well as among complexes palladium complexes were found better
antibacterial and antifungal agents than the nickel complexes of corresponding ligands. Ligand
L1H and the complex 2 showed highest antibacterial activity against P. desmolyticum and
highest antifungal activity against C. Albicans.
Graphical Abstract:
O
CH
CH
3
3
N
O
O
CH
3
Pd
CH
O
O
3
N
H C
CH
3
3
O
[Pd(L2)2] (2)
Antibacterial activity of [Pd(L2)2] (2) by agar well diffusion method
Highlights:
•
Pd(II) and Ni(II)) complexes, [M(L)2] of Schiff base ligands were synthesised from 2-(3,4-
dimethoxyphenyl) ethanamine, a dimethyl derivative of dopamine, a starting material for
many nuerotransmitting agents.
1
13
•
•
FT-IR, H, C{1H} NMR and UV-Vis., spectroscopy, elemental analysis and single crystal
X-ray diffraction have been used as characterization techniques.
The spectroscopic data and single crystal X-ray diffraction studies on complexes revealed
that the ligands coordinated to M(II) ions in bidentate monoanionic (O-, N) mode. In the
crystals of complexes [Pd/Ni(L1)2] (1 and 3) contain C-H…O intermolecular secondary
interactions.
•
New ligands and the complexes were screened for their antibacterial and antifungal
activities by agar well diffusion method. The antimicrobial activity of complexes was higher
than the free ligands and in particular the Pd complexes are better inhibitors than Ni.
The L1H and 2 are among the ligands and complexes showing highest antifungal and
antibacterial activity especially against P. desmolyticum and highest antifungal activity
against C. Albicans.
•
2

1. Introduction
Transition metal complexes of Schiff base ligands have been extensively studied due to
their ease of preparation, availability of low cost raw materials, and formation of stable and
chelated coordination complexes with most of the transition metals [1]. Applications of Schiff
bases and their transition metal complexes have been largely investigated in the fields of
biochemistry [2], catalysis [3] and medicine [4].
Schiff base ligands synthesized generally by condensation of aldehydes or ketones with
aliphatic or aromatic amines. Their transition metal complexes have been evaluated for their
variety of biological properties [5] such as antibacterial [6], antioxidant [8], antifungal and anti-
HIV [7], anticancer [9], antiamoebic [10a], herbicidal [11] activities. Investigation of biological
activities Schiff bases derived from compounds (amines, aldehydes or ketones) of biologically
important, for example isatin [7], 2-azetidinone [12a], cephalothin [12b] and their metal
complexes have been the current interest. In this regard metal complexes of Schiff bases never
been prepared from 2-(3,4-dimethoxyphenyl) ethanamine, a dimethyl derivative of dopamine,
which is a starting material for many nuerotransmitting agents [13] and other biologically
important compounds [14] and investigated their biological activities.
Transition metal complexes are potential to show biological activity and are the current
area of research [8c]. Schiff base ligands derived are very effective metal chelators on
coordination, chelated complexes enhance the biological activity under the identical
experimental conditions [15].
Azomethine (>C=N-) group of Schiff bases play an important role in the antimicrobial
activities. The actual mechanism of increased activity of complexes is expected due to other
than structural factors like solubility, dipole moment and cell permeability [16] and also their
enzymatic action. A possible mode of increased toxicity may be considered in the light of
Tweedy’s chelation theory [17].
Therefore we have reported herein the synthesis, characterization and evolution of
antimicrobial activities such as antibacterial and antifungal activities of Schiff base ligands L1H
and L2H derived from 2-(3,4-dimethoxyphenyl) ethanamine, 2-hydroxy benzaldehyde and 2-
hydroxy acetophenone and their Pd(II) and Ni(II) complexes [M(L1-2)2] (1-4).
2. Experimental
2.1. Materials
3

2-(3,4-dimethoxyphenyl) ethylamine (97%) and Na2PdCl4 (98%) were obtained from
Sigma Aldrich, India. 2-Hydroxy benzaldehyde (99.5%) and 2’-Hydroxy acetophenone (99%)
were purchased from Merck Specialities Pvt. Ind. Ltd. NiCl2.6H2O was obtained from S.D.
Fine-Chem Ltd., India. All solvents (EtOH, MeOH, Pet-ether, Hexane, CHCl3 and MDC) were
of reagent grade and used without further purification. The microorganisms used in this study
are Klebsiella aerogenes (K. aerogenes) [NCIM-2098], Escherichia coli (E. coli) [NCIM-5051],
Pseudomonas desmolyticum (P. desmolyticum) [NCIM-2028] and Staphylococcus aureus (S.
aureus) [NCIM-5022] as pathogenic bacterial strains and Aspergillus flavus (A. flavus) [NCIM-
544] and Candida albicans (C. albicans) [NCIM-3100] as pathogenic fungal strains. These
microorganisms were purchased from National Chemical Laboratory (NCL), Pune, India. These
strains were maintained on nutrient agar slant at 4 °C. Standard antibiotics Ciprofloxacin and
Fluconazole were purchased from Hi Media, Mumbai, India.
2.2 Analytical methods
Elemental analysis (C, H and N) was performed on a LECO–CHSNO – 9320 type
1
elemental analyser. H and 13C{1H} NMR spectra of ligands and Pd(II) complexes were
recorded in CDCl3 or DMSO-d6 solutions on a Bruker WM-400 spectrometer (400 MHz) using
TMS as an internal standard. The FT-IR spectra of all the compounds were recorded by scan
method in the range of 4000–500 cm-1 with an Agilent FT-IR spectrometer. UV–Vis., spectra
were recorded on UNI-CAM-UV 2-100 spectrophotometer. Melting points of ligands and
complexes were determined with a Gallenkamp melting point apparatus in an open capillary
and are reported uncorrected. Single crystal X-Ray diffraction data of 1 and 3 were collected on
a Bruker SMART APEX CCD-based X-ray diffractometer with Mo Kα-radiation (λ, 0.71073 Å,
at T 193 K). The molecular structures of 1 and 3 were solved by direct methods and refinement
was carried out with SHELXL-97 [18] package and empirical absorption correction has been
applied (SADABS). All refinements were made by full-matrix least-squares on F2 with
anisotropic displacement parameters for all non-hydrogen atoms. Hydrogen atoms were
included in the refinement in calculated positions.
2.3 Synthesis of ligands L1H and L2H
2-(3,4-dimethoxyphenyl) ethanamine (200 mg, 1.1 mmol) was dissolved in 20 ml of dry
ethanol and this solution was stirred for 0.5 h at room temperature. 2-hydroxy benzaldehyde
4

(0.115 ml, 1.1 mmol) or 2’-hydroxy acetophenone (0.133 ml, 1.1 mmol) dissolved in 20 ml of
dry ethanol was added to the above solution drop wise with stirring. The mixture was stirred
further for 1.5–2.0 h at room temperature during which the solution changes to yellow colour.
The progress of the reaction was monitored on TLC using pet-ether and ethyl acetate (70:30 %)
as mobile phase. After completion, the reaction solution was concentrated by rotary evaporator
which resulted yellow precipitate. The yellow precipitate was washed with hexane or petroleum
ether (10 ml X 2) and then dried under vacuum. The dry solid was recrystallized from a mixture
(1:1) of chloroform and hexane gave yellow single crystals of L1H or L2H.
L1H: Yellow Crystalline solid; Yield: 290 mg (93%); M.P.: 122-123 °C; Element. Anal.
Calcd. (Found) for C17H19NO3: C, 71.56(71.16); H, 6.71(6.63); N, 4.91(4.96); FT-IR (ν, cm-1):
3418, 2992, 2957, 2835, 1634, 1588, 1515, 1333, 1261, 1138, 1025, 851, 761, 655, 554; UV-
Vis., λmax in nm: 261, 279, 315, 408; 1H NMR (CDCl3, δ ppm): 13.44 (s, 1H, OH), 8.18 (s, 1H,
CH=N), 7.270-7.313 (t, 1H, H4), 7.160-7.184 (d, 1H, H6), 6.864-6.962 (d, 1H, H3), 6.707-
6.848 (m, 4H, H5, H11, H14, H15), 3.849 (s, 3H, -OCH3), 3.807 (s, 3H, -OCH3), 3.817-3.837
(q, 2H, =NCH2), 2.934-2.968 (t, 2H, -CH2Ar ); 13C{1H} NMR (CDCl3, δ, ppm): 36.241 (C9),
55.222 (OCH3), 55.412 (OCH3), 59.909 (C8), 111.748 (C5), 112.725 (C11), 116.458 (C14),
118.372 (C15), 118.557 (C10), 120.587 (C4), 131.528 (C3), 131.765 (C1), 132.192 (C6),
147.176 (C13), 148.492 (C12), 160.772 (C2), 165.849 (C7).
L2H: Yellow Crystalline solid; Yield: 310 mg (94 %); M.P.: 125-126 °C. Element. Anal.
Calcd. (Found) for C18H21NO3: C, 72.22(72.32); H, 7.07(7.08); N, 4.68(4.75); FT-IR (ν, cm-1):
3392, 2934, 2912, 2836, 1607, 1516, 1454, 1230, 1137, 1024, 857, 816, 763, 653, 566, 527;
UV-Vis.: λmax in nm: 257.6, 277, 319, 392; 1H NMR (CDCl3, δ ppm): 16.55 (s, 1H, OH), 7.443-
7473 (d, 1H, H6), 7. 249-7.292 (t, 1H, H4), 6.907-6.937 (d, 1H, H3), 6.723-6.825 (m, 4H, H5,
H11, H14, H15), 3.853 (s, 3H, OCH3), 3.815 (s, 3H, OCH3), 3.785-3.802 (t, 2H, =NCH2),
2.993-3.027 (t, 2H, ArCH2), 2.180 (s, 3H, CH3); 13C{1H} NMR (CDCl3, δ ppm): 14.211 (CH3),
35.605 (C9), 50.222 (C8), 55.257 (OCH3), 55.454 (OCH3), 111.848 (C5), 112.819 (C11),
116.429 (C14), 118.093 (C15), 118.703 (C10), 120.582 (C4), 128.608 (C3), 131.924 (C1),
132.252 (C6), 147.230 (C13), 148.537 (C12), 163.883 (C2), 172.402 (C7).
2.4 Synthesis of palladium complexes, [Pd(L1-2)2] (1-2)
5

The Na2[PdCl4] (100 mg, 0.3 mmol) was dissolved in 10 ml of water and the solution
was stirred for 5 min. A solution of ligand L1H (194 mg, 0.68 mmol) or L2H (203 mg, 0.68
mmol) made in 20 ml of acetone was added to the above solution with vigorous stirring and the
stirring was continued further for 1.5–2.0 h. The progress of the reaction was monitored by TLC
using pet-ether and ethyl acetate (50:50) as mobile phase. The resulting orange solution was
extracted into 100 ml of chloroform. The chloroform layer was washed with water (25 ml x 3)
and treated with anhydrous sodium sulfate crystals. The solvent was evaporated to dryness on
rotary evaporator to obtain an orange-red powder. The orange-red powder subjected to
recrystallization in a 1:1 mixture of chloroform and hexane gave yellowish-orange coloured
crystals of 1 or 2 after 24 h.
1: Yellow-Orange crystalline solid; Yield: 390 mg (85 %); M.P.: 190-192 °C; Element. Anal.
Calcd.(Found) for C34H36N2PdO6: C, 60.49(60.30); H, 5.38(5.27); N, 4.15(4.18); FT-IR: (ν,
cm-1): 3444, 2921, 1618, 1599, 1514, 1447, 1321, 1231, 1143, 1023, 912, 760, 583, 438; UV-
1
Vis., λmax in nm: 257.8, 280.7, 392; H NMR (CDCl3, δ ppm): 7.383 (s, 1H, CH=N), 7.219-
7.544 (t, 1H, H4), 7.059-7.083 (d, 1H, H3), 6.905-6.926 (d, 1H, H6), 6.782-6.832 (m, 3H, H11,
H14, H15), 6.537-6.576 (t, 1H, H5) 3.951-3.987 (t, 2H, NCH2) 3.853 (s, 3H, OCH3), 3.777 (s,
3H, OCH3), 3.067-3.103 (t, 2H, CH2Ar ).
2: Yellow-orange crystalline solid; Yield: 400 mg (84 %); M.P.: 191-192 °C; Element. Anal.
Calcd.(Found) for C36H40N2PdO6: C, 61.49(61.42); H, 5.73(5.65); N, 3.98(3.98); FT-IR: (ν,
1
cm-1): 3444, 2951, 2833, 1595, 1515, 1436, 1317, 1235, 1143, 1023, 859, 816, 761, 590; H
NMR (CDCl3, δ ppm): 7.409-7.429 (d, 1H, H6), 7.082-7.112 (t, 1H, H4), 7.002 (s, 1H, H11),
6.800-6.895 (m, 2H, H5, H15), 6.708-6.769 (d, 1H, H14), 6.528-6.565 (d, 1H, H3), 4.001-
4.112 (t, 2H, =NCH2), 3.675 (s, 3H, -OCH3), 3.617 (s, 3H, -OCH3), 3.227-3.333 (t, 2H,
ArCH2), 2.201 (s, 3H, CH3); 13C{1H} NMR (CDCl3, δ ppm): 13C{1H} NMR (CDCl3, δ ppm):
14.094 (CH3), 38.224 (C9), 55.644 (OCH3), 55.825 (OCH3), 59.851 (C8), 111.157 (C5),
112.557 (C11), 115.002 (C14), 120.164 (C4, C10), 121.061 (C15), 131.476 (C1), 134.127 (C6),
134.497 (C3), 147.447 (C13), 148.649 (C12), 162.077 (C2), 164.456 (C7).
2.5 Synthesis of nickel complexes, [Ni(L1-2)2] (3-4)
To a solution of NiCl2.6H2O (100 mg; 0.42 mmol) and triethylamine (0.117 ml; 0.84
mmol) made in 20 ml of methanol, added slowly a methanolic solution (50 mL) of L1H (240
6

mg, 0.84 mmol) or L2H (252 mg, 0.84mmol). The reaction mixture was stirred at room
temperature for 6-7 h. The progress of the reaction was monitored by TLC using pet ether and
ethyl acetate (50:50) as mobile phase. The resulting green solution was evaporated to dryness
using rotary evaporator gave a green powder. This powder was dissolved in chloroform,
filtered, washed with small volume of ether and then dried under vacuum resulted a green solid.
This solid was recrystallized from a mixture of chloroform and hexane (1:1) and obtained
crystals of 3 or 4.
o
3: Green crystalline solid. Yield: 424 mg (80 %); M.P.: 189-191 C; Element. Anal. Calcd.
(Found) for C34H36N2NiO6: C, 65.09(65.24); H, 5.78(5.82); N, 4.47(4.61); FT-IR (ν, cm-1):
3444, 2922, 1614, 1541, 1514, 1470, 1417, 1330, 1278, 1232, 1143, 1025, 915, 845, 807, 761,
602, 441; UV-Vis.: λmax in nm: 259, 372.
o
4: Pale brown crystalline solid; Yield: 468 mg (85 %); M.P.: 196-197 C; Element. Anal.
Calcd. (Found) for C36H40N2NiO6: C, 65.97(65.83); H, 6.15(6.11); N, 4.27(4.26); FT-IR (ν,
cm-1): 3418, 2950, 2832, 1597, 1539, 1514, 1442, 1363, 1335, 1284, 1224, 1142, 1023, 929,
863, 817, 761, 592, 526; UV-Vis.: λmax in nm: 260, 274, 319 and 390.
2.6 Evaluation of antimicrobial activity
The antimicrobial activity of new Schiff base ligands and their Pd(II) and Ni(II)
complexes were screened by agar well diffusion method [24-27] against four bacterium namely
Gram -ve bacteria K. aerogenes, E. coli, P. desmolyticum, Gram +ve bacteria S. aureus and two
fungi such as A. flavus and C. albicans.
Nutrient and potato dextrose broth was used to culture the bacteria and fungi
respectively. Nutrient agar plates were prepared and swabbed using sterile L-shaped glass rod
with 100 µl of 24 h mature broth culture of individual bacterial strains. The wells of 6 mm
were created into the each petri plate using sterile cork borer. Two test solutions of each L1H,
L2H, 1, 2, 3 and 4 were prepared by dissolving 500 and 1000 µg in 50 and 100 µl of sterile
water respectively to get 10 µg / µl concentration of each compound and assessed their
antibacterial activity. Similarly a standard antibiotic solution was prepared by dissolving 5 µg
Ciprofloxacin (as positive control) in 50 µl of sterile water to get 0.1 µg / µl concentration.
These solutions were added into the wells by sterile micropipettes. The plates were incubated at
37 °C for 36 h. After the incubation period, the zone of inhibition of each well was measured
7

and the values were noted. The measurements were made in triplicate for each compound and
their average values are reported.
Antifungal activity of the culture strains of fungi performed on potato dextrose agar
(PDA) slant at 27 0.2 °C for 48 - 96 h, till sporulation. Spore of strains were transferred into 5
mL of sterile, 1% saline solution. 100 µL of each fungal spore suspension was spread on each
sterile PDA plate. Using the sterile cork borer, wells of 6 mm were made into the each petri
plate. The solutions of compounds L1H, L2H, 1, 2, 3 and 4 were made by dissolving 250, 500
and 750 µg of in 25, 50, 75 µL in sterile water to get 10 µg / µl concentration and these
solutions were used to assess the dose dependent activity of each compound. Similarly a
solution of standard antifungal drug solution was made by dissolving 200µg of Fluconazole (as
positive control) in 50 µL in sterile water to get 10 µg / µl concentration. The plates were
incubated for 72ꢀh at 27 °C. After the incubation period, the zone of inhibition of each well was
measured and the values were noted. Triplicates were maintained for each compound and the
average values are reported.
3. Results and discussion
3.1 Synthesis of ligands and complexes
Schiff base ligands L1H and L2H were obtained in high yields (90-95 %) by
condensation reaction of 2-(3,4-dimethoxyphenyl) ethanamine with 2-hydroxy benzaldehyde
and 2’-hydroxy acetophenone respectively in equi-molar ratio in dry ethanol as a solvent.
14
R
13
OMe
15
R
H N
2
OMe
8
6
12
OMe
O
+
1
5
7
N
10
9
11
OMe
OH
2
4
OH
2-hydroxybenzaldehyde (R = H)
2-hydroxyacetophenone (R = Me)
2-(3,4-dimethoxyphenyl)ethanamine
R = H; L1H
R = CH3; L2H
3
R
N
OMe
1. Na2PdCl4/water/acetone
MeO
O
M
O
2. Chloroform:Hexane
OMe
N
R
1. NiCl2. 6 H2O/methanol
2. Chloroform:Hexane
MeO
R = CH3; M = Pd; 2
R = CH3; M = Ni; 4
R = H; M = Pd; 1
R = H; M = Ni; 3
Scheme 1: Synthesis of Schiff base ligands L1H and L2H and complexes [M(L1-2)2] (1-4)
8

The mononuclear Pd(II) (1 and 2) and Ni(II) (3 and 4) complexes were obtained by
direct reaction of ligands (L1H and L2H) with metal ion precursors (Na2PdCl4 and NiCl2.6H2O)
in 1:2 molar ratio. The equations for the reactions of the synthesis of ligands and complexes are
given in the Scheme 1.
The ligands are yellow crystalline solids and are freely soluble in some of the common
polar organic solvents such as CHCl3, CH2Cl2, CH3OH, DMSO and DMF whereas partially
soluble in diethyl ether, while they are insoluble in non-polar solvents like hexane, heptane,
benzene and toluene at room temperature. The yields of the complexes (85-90 %) are also as
high as that of ligands. The ligands and complexes were recrystallized in mixture solvents.
Single crystals of complexes 1 and 3 suitable for the X-Ray diffraction studies were grown and
their molecular structures were determined.
3.2 FT-IR Spectra
Bands in the region of 3418 and 3392 cm-1 are due to ν(O-H) stretching vibration for
L1H and L2H. The strong bands at 1634 and 1607 cm-1 were assigned to ν(C=N) stretching
mode of the imine group for ligands. These bands showed a red shift of about 15-20 cm-1 in all
the complexes, thus indicating there is a strong coordination of imine nitrogen to the metal ions
[19]. Ligands also display bands at 1261 and 1230 cm-1 which were assigned to ν(C–O)
stretching vibration. These bands were strongly affected due to the chelation ligands through the
phenoxide (O-) group and the bands shifted to higher wave numbers and hence indicated the
coordination of phenoxide [20]. The strong absorption bands between 1550 and 1500 cm−1 in all
ligands and complexes could be reasonably attributed to the presence of the ν(C=C) stretching
vibration of the aromatic ring backbone.
3.3 UV-Vis. Spectra
In the UV-Vis., spectra of ligands, in DMSO, there were intense absorption bands at λ,
261, 279, 315 and 408 nm in L1H and at 258, 277, 319 and 392 nm in L2H. In both the ligands
the first two absorptions observed at 261, 279 nm and 257, 277 nm in L1H and L2H respectively
can be assigned to the π– π* transitions of the aromatic rings. The latter absorption bands at
315, 319 and 392, 408 nm in L1H and L2H respectively can be attributed to the charge transfer
transitions within the delocalized π system [10b]. In the electronic spectra of complexes 1, 3 and
4 the intense higher-energy bands observed at around 260 nm were attributed to an intra-ligand
9

charge transfer (π→π*). The shoulder at λ, 392 nm in 1 was blue-shifted relative to its free
ligand L1H which expected due to charge transfer from the phenolate to metal ion. Similar
spectra were observed for Ni(II) complexes 3 and 4 [10b] . The combined UV-Vis. spectra of
ligands and complexes are shown in Fig. 1.
3.4 NMR Spectroscopy
The proton NMR spectra of ligands are characteristic. In the proton NMR spectra of
L1H and L2H the ArCH2 and CH2N protons were appeared as triplets at δ, 2.93-3.02 and 3.78-
3.83 ppm respectively and they were matches with the reported values of 2.87 and 3.82 ppm for
the similar Schiff bases of 2-hydroxy arylaldehydes and 4-hydroxy phenylethylamine [21a]. The
methoxy protons gave two singlets at δ, 3.849 and 3.807 in L1H whereas in L2H these protons
are slightly deshielded and obtained at 3.853 and 3.815 ppm [21b]. The OH signal in L1H and
L2H was observed at 13.44 and 16.50 ppm respectively as these protons are highly deshielded
due to intramolecular O-H…N hydrogen bonding [21c]. A singlet for CH=N proton in L1H was
obtained at 8.18 ppm. In the proton spectra of Pd(II) complexes (1 and 2) the signals due to OH
protons were absent that indicated the coordination ligands to the metal in the deprotonated
phenoxide ion (O-) fashion. The ArCH2 and CH2N protons were slightly deshielded (0.1 ppm)
whereas these protons in 2 showed higher deshielding effect (0.2 ppm). The CH=N proton in 1
was shielded by 0.8 ppm and this indicated strong coordination of L1H to Pd(II).
In the 13-C NMR spectrum of L1H and L2H, the ArCH2 carbon signals were appeared
at δ, 36.24 and 38.22 ppm respectively whereas the NCH2 signals were highly deshielded and
observed at δ, ~59.9 ppm [21a-b]. In 2, the ArCH2 carbon was shielded by about 3 ppm and the
NCH2 carbon was by 9.8 ppm. The CH=N carbon was appeared at 165.85 ppm in 2.
3.5 Single crystal X-ray diffraction
The molecular structures of 1 and 3 were confirmed by single crystal X-ray diffraction.
Crystal data and structure refinement parameters of [Pd(L1)2] (1) and [Ni(L1)2] (3) are given in
Table 1. The selected bond lengths and bond angles of 1 and 3 are given in Table 2. Both the
compounds 1 and 3 were crystallized in monoclinic crystal system. The Pd-O and Pd-N bond
lengths in 1 are 1.984 (11) and 2.020(12) Å. These bond lengths are comparable with the values,
1.983(3) and 2.020(4) Å, reported for the similar complex [22]. The C=N bond length in 1 was
found 1.310(19) Å. The O1—Pd1—O1(i) and N1—Pd1—N1(i) angles are 180.0°. Therefore
10

the structure of the complex 1 was square planar as expected. The molecular structure of
compound 1 is shown in Fig. 2.
The molecular structure of 3 is given in Fig. 3. In 3 the Ni-O and Ni-N bond lengths are
1.8222(13) and 1.9262(15) Å respectively. The bond lengths and bond angles matches with
those reported for the complex [Ni(L)2].2DMF, where L is a Schiff base of 4-hydroxy
phenylethylamine and 2-hydroxy naphthaldehyde [21a]. The C=N bond length in 3 was found
1.290(2) Å which was slightly shorter than that found in 1 (1.310(19) Å) [21d]. This suggested
that the ligand L1H is coordinated to Pd(II) ion strongly in 1 than to Ni(II) in 3. The O1(i)—
Ni1—O1 and N1—Ni1—N1(i) bond angles are 180.0° each which also suggested square planar
geometry around Ni in 3.
The crystals of both 1 and 3 contain C—H···O (2.50(0) and 2.52(0) Å, respectively as
given in Table 3) intermolecular hydrogen bonding [23a] which is shorter than their sum of the
vander Waal’s radii (2.60 Å) [23b]. These secondary interactions resulted supramolecular
structure in 1 and 3 as depicted in Fig. 4 and Fig. 5 respectively. The spectral data of 1 – 4 and
single crystal data of 1 and 3 complexes revealed that the ligands coordinated to M(II) ion
through (N, O-) donor set forming two coplanar six-membered chelated rings so that the overall
molecular structure of 1 to 4 is square planar. The attempts made to grow single crystals of 2
and 4 in various solvents like chloroform, dichloromethane does not gave the crystals suitable
for X-ray diffraction.
3.6 Antibacterial activity and Antifungal activity
The antimicrobial properties of new Schiff base ligands, L1H and L2H and their
complexes, 1, 2, 3 and 4 were evaluated by Agar well diffusion method. To assess the biological
potential of synthesised compounds, the antibacterial activity against four bacteria strains such
as K. aerogenes, E. coli, P. desmolyticum, S. aureus and antifungal activity against two fungi
strains A. flavus and C. albicans were performed. Nutrient agar and potato dextrose agars were
used to culture the bacteria and fungi respectively.
The experimental details and zone of inhibition in respect of both antibacterial and
antifungal activity of compounds L1H, L2H, 1-4 against the pathogenic microbial strains with
different concentration are given in Table 4 and Table 5 and their graphical representations are
shown in Fig. 6 and Fig. 7 respectively. These experimental observations indicated that the new
ligands and complexes have been shown significant antibacterial activity in P. desmolyticum
and S. aureus and whereas they showed moderate activity in K. aerogenes and E. coli.
11

Antifungal activities of above compounds were also found significant effect in A. flavus and but
moderate activity in C. albicans. The synthesized complexes were found to be more toxic
compared with their parent free ligands against the same micro-organism and under the identical
experimental conditions. The enhanced biological activity of the chelated metal complexes may
be due to the effect of the metal ion on the normal cell process.
The bacterial and fungi inhibition was also found to be metal dependent. The palladium
complexes have shown better inhibition than the nickel complexes. Among these new
compounds screened the ligand L1H and the complex 2 showed highest antibacterial and
antifungal activity. Schiff bases which contain azomethine (>C=N-) group played an important
role in these antimicrobial activities such as antibacterial and antifungal and as chelation
increases, the bacterial and fungal growth inhibition also increases. Previously reported [28-29]
that, compounds containing heterocyclic ring damaged the cell wall but which was not observed
with the present compounds.
Chelation considerably reduces the polarity of the metal ion because of partial sharing of
its positive charge with the donor group and possible π-electron delocalization within the whole
chelate ring system that is formed during coordination. Such chelation could enhance the
lipophilic character of the central metal atom and hence increase the hydrophobic character and
liposolubility of the complex favouring its permeation through the lipid layers of the cell
membrane. The enhanced biological activity of the chelated metal complexes may be due to the
effect of the metal ion on the normal cell process.
Conclusions
New Schiff’s base ligands have been synthesized via condensation of 2-(3,4-
dimethoxyphenyl) ethanamine with 2-hydroxy benzaldehyde (L1H) and 2-hydroxy
acetophenone (L2H) respectively. Pd(II) and Ni(II) complexes [M(L1-2)2] (1 to 4) have been
synthesized. The ligands and complexes were characterized by elemental analysis, FT-IR, UV-
1
Vis., H and 13C{1H} NMR spectroscopy. The molecular structures of Pd(II) and Ni(II)
complexes of L1H were determined by single crystal X-ray diffraction. The crystal and
spectroscopic data revealed that the ligands bind Ni(II) and Pd(II) ions in 1-4 in bidentate
monoanionic (O-, N) mode. The bond lengths Pd-O [1.984(11) Å] and Pd-N [2.020(12) Å] in 1
and Ni-O [1.8222(13) Å] and Ni-N [1.9262(15) Å] in 3 are comparable with the reported
values. The >C=N bond length in 3 found 1.290(2) Å which was shorter than that in 1,
1.310(22) Å indicating strong coordination of ligand to Pd(II) than to Ni(II). The complexes
12

have square planar geometry around Pd and Ni in 1 - 4. The crystals of 1 and 3 contain C—
H···O (2.50(0) and 2.52(0) Å respectively) intermolecular hydrogen bonds which results in
supramolecular structure.
The antimicrobial activity of new Schiff base ligands L1H and L2H and their complexes,
1 to 4 was evaluated by agar well diffusion method against pathogenic bacterial and fungal
strains. Nutrient and potato dextrose agars were used to culture the bacteria and fungi
respectively. The antibacterial activity against K. aerogenes, E. coli, P. desmolyticum, S. aureus
strains and antifungal activity against A. flavus and C. albicans strains was investigated. The
new ligands and complexes have shown higher antibacterial activity against P. desmolyticum,
and S. aureus and moderate activity in K. aerogenes and E. coli bacteria. Furthermore, Schiff
bases and their derived complexes also showed higher antifungal activity against A. flavus than
C. albicans. The inhibition of growth of bacteria and fungi has been enhanced on Complexation
of ligands. The palladium complexes have shown better inhibition than the nickel complexes.
Among these new compounds screened the ligand L1H and the complex 2 showed highest
antibacterial and antifungal activity.
Acknowledgements
Raghavendra Kumar P., thank CSIR, New Delhi, India for funding the project No.
01(2701)/12/EMR-II.
Supplementary data:
More details on the structural determinations have been deposited with the Cambridge
Crystallographic Data Centre under the deposition number CCDC 1417813 and 1417818.
13

Table 1 Crystal data and structure refinement parameters of [Pd(L1)2] (1) and [Ni(L1)2] (3)
Complex
[Pd(L1)2] (1)
C34H36N2PdO6
675.05
[Ni(L1)2] (3)
C34H36N2NiO6
627.36
Formula
Molecular weight
Temperature (K)
Wavelength (Mo Kα radiation)
Crystal system
Space group
Unit cell dimensions
a (Å)
293
296
0.71073 Å
Monoclinic
P21/c
0.71073 Å
Monoclinic
P21/c
10.7959 (5)
5.8833 (3)
23.3478 (11)
90.00
10.8616 (7)
5.8893 (4)
23.1314 (17)
90.00
b (Å)
c (Å)
α and γ (°)
β (°)
Volume (Å3)
93.106 (4)
1480.77 (12)
2
93.419 (6)
1477.02 (18)
2
Z
Calculated density (mg/m3)
µ (mm-1)
1.514
1.411
0.68
0.71
F(000)
696
660
Crystal size (mm)
θmin - θmax range (°)
Index ranges
0.30 × 0.26 × 0.24
3.2 to 25.0
-12 ≤ h ≥ 12,
-6 ≤ k ≥ 6,
-27 ≤ l ≥ 27
30650
0.38 × 0.34 × 0.26
3.5 to 25.0
-12 ≤ h ≥ 12,
-6 ≤ k ≥ 7,
-27 ≤ l ≥ 27
23474
Reflections collected
Independent reflections [Rint]
Reflections observed [I > 2σ(I)]
Absorption correction Integration
Max. and min. transmissions
Reflections/Parameters/Restraints
Goodness-of-fit (S) on F2
Final R indices [F2>2σ(F2)]
Largest diff. peak and hole
∆ρ (min and max) (e Å3)
(∆/σ)max
2634 [0.074]
2378
2581 [0.039]
2180
0.9158 and 0.7757
2634/200/0
0.9158 and 0.7757
2581/198/0
1.15
1.04
R1 = 0.136; wR2 = 0.392
4.84 and -1.25
R1 = 0.028; wR2 = 0.071
0.19 and -0.21
< 0.001
0.007(3)
912128
< 0.001
--
Extinction coefficient*
CCDC No
912128
*Extinction correction: SHELXL2014/7 (Sheldrick-2014, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
14

Table 2 Bond lengths (Å) and bond angles (°) of [Pd(L1)2] (1) and [Ni(L1)2] (3)
[Pd(L1)2] (1)
[Ni(L1)2] (3)
Bond lengths (Å)
Ni1—O1(i)
Pd1—O1
Pd1—O1i
Pd1—N1
Pd1—N1i
N1—C8
1.984 (11)
1.984 (11)
2.020 (12)
2.020 (12)
1.481 (17)
1.310 (19)
1.40 (2)
1.8222 (13)
1.8222 (13)
1.9262 (15)
1.9262 (15)
1.290 (2)
1.489 (2)
1.369 (2)
1.426 (2)
1.313 (2)
1.371 (2)
1.421 (2)
Ni1—O1
Ni1—N1
Ni1—N1(i)
N1—C7
C7—N1
N1—C8
O2—C16
O3—C17
O1—C2
O3—C13
O3—C17
O1—C2
1.43 (2)
1.30 (2)
O2—C12
O3—C13
1.381 (18)
1.381 (17)
O2—C12
O2—C16
Bond angles (°)
O1—Pd1—O1i
O1—Pd1—N1
O1i—Pd1—N1
O1—Pd1—N1i
O1i—Pd1—N1i
N1—Pd1—N1i
C7—N1—Pd1
C8—N1—Pd1
C2—O1—Pd1
N1—C7—C1
N1—C8—C9
O2—C12—C13
C14—C13—O3
O3—C13—C12
C7—N1—C8
C12—O2—C16
C13—O3—C17
O1—C2—C1
O1—C2—C3
C11—C12—O2
180.0 (11)
92.9 (5)
O1(i) —Ni1—O1
O1—Ni1—N1
O1(i) —Ni1—N1
O1—Ni1—N1(i)
O1(i) —Ni1—N1(i)
N1—Ni1—N1(i)
C2—O1—Ni1
C7—N1—Ni1
C8—N1—Ni1
C7—N1—C8
180.00 (10)
93.31 (6)
87.1 (5)
86.69 (6)
87.1 (5)
86.70 (6)
92.9 (5)
93.30 (6)
180.0 (5)
121.8 (9)
121.6 (9)
125.8 (11)
129.7 (14)
112.4 (12)
115.1 (13)
127.0 (15)
115.0 (13)
116.4 (12)
117.2 (13)
116.0 (13)
126.7 (13)
116.3 (16)
124.7 (14)
180.0(0)
130.32 (12)
124.05 (12)
121.64 (11)
114.25 (15)
112.55 (15)
127.30 (17)
122.77 (16)
118.84 (18)
125.07 (16)
114.99 (15)
125.37 (17)
115.75 (15)
117.55 (14)
117.43 (15)
N1—C8—C9
N1—C7—C1
O1—C2—C1
O1—C2—C3
O2—C12—C11
O2—C12—C13
O3—C13—C14
O3—C13—C12
C12—O2—C16
C13—O3—C17
Symmetry code: (i) −x, −y+1, −z.
Symmetry code: (i) -x+1, -y+1, -z+2..
15

Table 3 Secondary interactions in [Pd(L1)2] (1) and [Ni(L1)2] (3)
Complex
[Pd(L1)2] (1)*
[Ni(L1)2] (3)**
D—H···A
C4—H4···O3(ii) 0.95
C4—H4···O3(ii)
0.93
D—H
H···A
2.50
D ···A
D—H···A
155
3.39 (2)
3.405 (2)
2.52
158(0)
*Symmetry code: (ii) x-1, -y+3/2, z-1/2; **Symmetry codes: (ii) x+1, −y+1/2, z+1/2.
Fig. 1 UV-Vis. Spectra of L1H, L2H, 1, 3 and 4
Fig. 2 ORTEP of [Pd(L1)2] (1)
16

Fig. 3 ORTEP of [Ni(L1)2] (3)
Fig. 4 C-H…O Intermolecular secondary interactions in [Pd(L1)2] (1)
Fig. 5 C-H…O Intermolecular secondary interactions in [Ni(L1)2] (3)
17

Table 4: Antibacterial activity of L1H, L2H, 1, 2, 3 and 4
K. aerogenes
(Mean SE)
12.33 0.03
1.60 0.06
E. coli
S. aureus
P. desmolyticum
(Mean SE)
15.60 0.03
1.60 0.06
3.67 0.17
2.00 0.00
3.23 0.07
1.00 0.00
3.67 0.17
4.67 0.17
6.67 0.17
1.00 0.00
2.53 0.03
2.00 0.00
4.00 0.00
Sample
Treatment
(Mean SE) (Mean SE)
13.67 0.03 14.00 0.00
Ciprofloxacin 5 µg/50 µL
500 µg/50 µL
1.33 0.12
1.67 0.17
0.50 0.00
1.67 0.17
1.00 0.00
2.60 0.06
1.00 0.00
1.67 0.17
1.10 0.06
2.00 0.00
1.30 0.06
2.53 0.03
1.00 0.00
1.67 0.17
1.00 0.00
2.67 0.17
1.00 0.00
3.00 0.00
1.00 0.00
2.50 0.07
2.07 0.07
3.23 0.07
1.10 0.06
3.43 0.12
L1H
1000 µg/100 µL 2.53 0.03
500 µg/50 µL 1.00 0.00
1000 µg/100 µL 2.00 0.00
500 µg/50 µL 1.00 0.00
1000 µg/100 µL 2.37 0.09
500 µg/50 µL 2.00 0.00
1000 µg/100 µL 3.43 0.23
500 µg/50 µL 1.00 0.00
1000 µg/100 µL 2.50 0.07
500 µg/50 µL 0.50 0.00
1000 µg/100 µL 1.17 0.17
L2H
1
2
3
4
Values are the mean SE of inhibition zone in mm.
Fig. 6 Antibacterial activity of compounds L1H, L2H, 1, 2, 3 and 4
18

Table 5: Antifungal activity of L1H, L2H, 1, 2, 3 and 4
A. flavus
C. albicans
Sample
Treatment
(Mean SE)
10.27 0.03
1.33 0.03
3.57 0.03
5.23 0.03
1.50 0.06
2.33 0.03
4.57 0.03
1.60 0.03
2.33 0.03
5.00 0.00
1.57 0.03
3.67 0.03
6.33 0.03
1.50 0.06
2.00 0.00
3.67 0.03
1.00 0.00
1.67 0.03
2.37 0.09
(Mean SE)
11.50 0.06
0.55 0.00
2.27 0.03
3.20 0.06
1.00 0.00
2.50 0.06
4.27 0.03
1.37 0.03
2.17 0.03
3.50 0.06
0.00 0.00
1.00 0.00
1.67 0.03
1.00 0.00
2.33 0.33
3.00 0.00
1.33 0.03
2.67 0.03
3.17 0.09
Fluconazole
(200 µg/50 µL)
(250 µg/25 µL)
(500 µg/50 µL)
(750 µg/75 µL)
(250 µg/25 µL)
(500 µg/50 µL)
(750 µg/75 µL)
(250 µg/25 µL)
(500 µg/50 µL)
(750 µg/75 µL)
(250 µg/25 µL)
(500 µg/50 µL)
(750 µg/75 µL)
(250 µg/25 µL)
(500 µg/50 µL)
(750 µg/75 µL)
(250 µg/25 µL)
(500 µg/50 µL)
(750 µg/75 µL)
L1H
L2H
1
2
3
4
Values are the mean SE of zone of inhibition in mm.
19

Fig. 7 Antifungal activity of compounds L1H, L2H, 1, 2, 3 and 4
20

References:
1. K.C. Gupta, A.K. Sutar, Coord. Chem. Rev. 252 (2008) 1420–1450.
2. A. Garoufis, S.K. Hadjikakou, N. Hadjiliadis, Coord. Chem. Rev. 253 (2009) 1384–1397.
3. (a) S.A. Sadeek, M.S. Refat, S.M. Teleb, Bull. Chem. Soc. Ethiopia, 18 (2004) 149-156; (b)
A. Garoufis, S.K. Hadjikakou, N. Hadjiliadis, in: M. Gielen, E.R.T. Tiekink (Eds.), Metals
in Medicine, Palladium (Pd), in Metallotherapeutic Drugs and Metal-based Diagnostic
Agents: The Use of Metals in Medicine, John Wiley & Sons, Ltd., 2005, p. 399 (Ch. 21).
4. (a) M. Sarv, O. Atakol, N. Yilmaz, D. Ulku, Anal. Sci. 15 (1999) 401-402; (b) M.
Bagherzadeh, M. Amini, A. Ellern, L. K. Woob, Inorg. Chim. Acta 383 (2012) 46–51.
5. (a) D. Sinha, A.K. Tiwari, S. Singh, G. Shukla, P. Mishra, H. Chandra, A.K. Mishra, Eur. J.
Med. Chem. 43 (2008) 160–165; (b) B. Witkop, L.K. Ramachandran, Metabolism 13 (1964)
1016–1025; (c) K. Singh, M.S. Barwa, P. Tyagi, Eur. J. Med. Chem. 41 (2006) 147–153; (d)
D. Sinha, A.K. Tiwari, S. Singh, G. Shukla, P. Mishra, H. Chandra, A.K. Mishra, Eur. J.
Med. Chem. 43 (2008) 160–165; (e) A.M. Asiri, S.A. Khan, Molecules 15 (2010) 6850–
6858.
6. (a) C. Gerdemann, C. Eicken, B. Krebs, Chem. Res. 35 (2002) 183–191; (b) M. Tumer, N.
Deligonul, A. Golcu, E. Akgun, M. Dolaz, H. Demirelli, M. Dıgrak, Transit. Met. Chem. 31
(2006) 1–12; (c) A.M. Asiri, S.A. Khan, Molecules 15 (2010) 4784–4791.
7. S.N. Pandeya, D. Sriram, G. Nath, E. De-Clercq, Arzneimittelforschung 50 (2000) 55–59;
8. (a) L.X. Cheng, J.J. Tang, H. Luo, X.L. Jin, F. Dai, J. Yang, Y.P. Qian, X.Z. Li, B. Zhou,
Bioorg. Med. Chem. Lett. 15 (2010) 2417–2420; (b) M.S. Alam, J.H. Choi, D.U. Lee,
Bioorg. Med. Chem. 20 (2012) 4103–4108; (c) S. Medici, M. Peanaa, V.M. Nurchi, J.I.
Lachowicz, G. Crisponi, M.A. Zoroddua, Coord. Chem. Rev. 284 (2015) 329–350; (d) M.N.
Patel, C.R. Patel, H.N. Joshi, Inorg. Chem. Commun. 27 (2013) 51–55; (e) R.R. Coombs,
M.K. Ringer, J.M. Blacquiere, J.C. Smith, J.S. Neilsen, Y.-S. Uh, J.B. Gilbert, L.J. Leger,
H. Zhang, A.M. Irving, S.L. Wheaton, C.M. Vogels, S.A.Westcott, A. Decken, F.J.
Baerlocher, Transition Met. Chem. 30 (2005) 411-418; (f) H. Zhang, D.W. Norman, T.M.
Wentzell, A.M. Irving, J.P. Edwards, S.L. Wheaton, C.M. Vogels, S.A. Westcott, F.J.
Baerlocher, A. Decken, Transition Met. Chem. 30 (2005) 63-68; (g) X. Dong, Y. Li, Z. Li,
Y. Cui, H Zhu, J. Inorg. Biochem. 108 (2012) 22–29.
9. (a) E.I. Solomon, M.D. Lowery, Science 259 (1993) 1575-1581; (b) M. Tumer, E. Akgun, S.
Toroglu, A. Kayraldız, L. Donbak, J. Coord. Chem. 61 (2008) 2935-2949; (c) A. Golcu, M.
Tumer, H. Demirelli, R.A. Wheatley, Inorg. Chim. Acta, 358 (2005) 1785–1797.
21

10. (a) N. Bharti, M.R. Maurya, F. Naqvi, A. Azam, Bioorg. Med. Chem. 10 (2010) 2243–2245;
(b) Z. Chu, W. Huang, J. Mol. Str. 837 (2007) 15–22.
11. M. Tumer, H. Koksal, S. Serin, M. Dıgrak, Transit. Met. Chem. 24 (1999) 13–17.
12. (a) B.K. Ishwar, S.K. Mishra, P.J. Jainey, C.S. Shastry, J. Chem. Pharm. Res. 3 (2011)
114–118; (b) J.R. Anacona, N. Noriega, J. Camus, Spectrochim. Acta Part A: Mol. Biomol.
Spectroscopy 137 (2015) 16-22.
13. (a) M.R. Gluck, G.D. Zeevalk, J. Neurochem. 91 (2004) 788–795; (b) M.-J. Oliva-Madrid,
J.-A. Garcıa-Lopez, I. Saura-Llamas, D. Bautista, J. Vicente, Organometallics 31 (2012)
3647−3660; (c) K.N. Kumar, R. Ramesh, Spectrochim. Acta Part A, 60 (2004) 2913-2918;
(d) G. Venkatachalam, R. Ramesh, Spectrochim. Acta Part A, , 61 (2005) 2081-2087; (e)
V.P. Daniel, B. Murukan, B.S. Kumari, K. Mohanan, Spectrochim. Acta Part A, 70 (2008)
403-410; (f) M.M. Abd-Elzaher, Appl. Organomet. Chem. 18 (2004) 149-155; (g) B.K.
Singh, U.K. Jetley, R.K. Sharma, B.S. Garg, Spectrochim. Acta Part A, 68 (2007) 63-73.
14. (a) K. Neuvonen, F. Fulop, H. Neuvonen, A. Koch, E. Kleinpeter, K Pihlaja, J. Org. Chem.
70 (2005) 10670-10678; (b) E.J. Cony, J.O. Link, J. Org. Chem. 56 (1991) 442-444; (c) J.-
X. Gu, Z.-Y. Li, G.-Q. Lin, Chin. J. Chem. 13 (1995) 475-480. d) M.D. Rozwadowskar, A.
Sulima, Tetrahedron 57 (2001) 3499-3506. (e) R. Quevedo, E. Baquero, M. Rodriguez,
Tetrahedron Lett. 51 (2010) 1774–1778.
15. (a) K.R. Grunwald, G. Saischek, M. Volpe, F. Belaj, N.C. Mosch-Zanetti, Eur. J. Inorg.
Chem. 15 (2010) 2297–2305; (b) M. Shebl, S.M.E. Khalil, S.A. Ahmed, H.A.A. Medien, J.
Mol. Struct. 980 (2010) 39–50; (c) A. Bodakoti, M. Abid, A. Azam, Eur. J. Med. Chem. 41
(2006) 63–70.
16. G. Shen, J. Li, J. Appl. Polym. Sci. 78 (2000) 676-684.
17. B.G. Tweedy, Phytopathology, 55, (1964) 910-917.
18. G.M. Sheldrick, SHELXL 97, Program for Crystal Structure Refinement, University of Go ¨
ttingen, Germany, 1997.
19. (a) U. Ozdemir, P. Guvenç, E. Sahin, F. Hamurcu, Inorg. Chim. Acta 362 (2009) 2613-
2618; (b) U. Ozdemir, F. Arslan, F. Hamurcu, Spectrochim. Acta, Part A 75 (2010) 121-
126; (c) U.O. Ozdemir, G. Olgun, Spectrochim. Acta, Part A 70 (2008) 641-645.
20. (a) E. Keskiog˘lu, A.B. Gündüzalp, S. Çete, F. Hamurcu, B. Erk, Spectrochim. Acta, Part A
70 (2008) 634-640; (b) Z. Chu, W. Huang, J. Mol. Str. 837 (2007) 15–22.
21. (a) X. Dong, Y. Li, Z. Li, Y. Cui, H. Zhu, J. Inorg. Biochem. 108 (2012) 22–29; (b) A.A.
Vitale, A.E. Stahl, P.C.S. Claro, M.A.F. Addato, R.P. Diez, A.H. Jubert, J. Mol. Str. 881
22

(2008) 167–174; (c) P.R. Kumar, A.K. Singh, R.J. Butcher, P. Sharma, R.A. Toscano, Eur.
J. Inorg. Chem. (2004) 1107-1114.
22. M. Bagherzadeh, M. Amini, A. Ellern, L.K. Woob, Inorg. Chim. Acta 383 (2012) 46–51.
23. (a) P.R. Kumar, B.S. Palakshamurthy, U. Shailesh, Heteroatom Chem. 00 (2015) 000-000
(Published online) (b) S.S. Batsanov, Inorg. Mat. 37 (2001) 871–885.
24. C. Perez, M. Paul, P. Bazerque, Actabiologiaeet Med. Experimentalis, 15 (1990) 113-115.
25. Raja Naika, K. Lingaraju, K. Manjunath, D. Kumar, G. Nagaraju, H. Nagabhushana, D.
Suresh, J. Taibah Uni. Sci. 9 (2015) 7–12.
26. J. Meletiadis, J.W. Mouton, J. Meis, B.A. Bouman, P.E. Verweij, N. Eurofung., J. Clinic.
Microbio. 40 (2002) 2876-2885.
27. S. Sahoo, P.K. Panda, S. Tripathy, S.K. Nayak, S.K. Dash., Ind. Drugs 44 (2007) 352-356.
28. R. Dabur, A.K. Chhillar, V. Yadav, K. Kamal, P. Gupta, G.L. Sharma., J. Med. Micro. 54
(2005) 549-552.
29. N. Kawabata, Prog. Polym. Sci. 17 (1992) 1-34.
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Fig. 6
24