Spectral and in vitro antimicrobial properties of 2-oxo-4-phenyl-6-styryl- 1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid transition metal complexes

Article abstract of DOI:10.1016/j.saa.2012.02.096

2-oxo-4-phenyl-6-styryl-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid (ADP) was complexed with acetates of Mn(II), Ni(II), Cu(II) and Zn(II). The structures of the ligand and its metal complexes were characterized by microanalysis, IR, NMR, UV-vis spectroscopy, magnetic susceptibility and TGA-DTA analyses. Octahedral and square planar geometries were suggested for the complexes in which the central metal ion coordinated with-O donors of ligand and acetate ions. Each ligand binds the metal using carboxylate oxygens. The ligand and complexes were evaluated for their antimicrobial activities against different species of pathogenic bacteria and fungi. The present novel pyrimidine containing complexes could constitute a new group of antibacterial and antifungal agents.

Full text of DOI:10.1016/j.saa.2012.02.096

Spectrochimica Acta Part A 93 (2012) 348–353
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Spectral and in vitro antimicrobial properties of
2-oxo-4-phenyl-6-styryl-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid
transition metal complexes
Raksha P. Dhankara, Anjali M. Rahatgaonkarb,∗, Mukund S. Chorghadec, Ashutosh Tiwarid,∗
a Department of Chemistry, Sardar Patel Mahavidyalaya, Ganjward, Chandrapur 442402, Maharashtra, India
b Chemistry Department, Institute of Science, Civil Lines, Nagpur 440001, Maharashtra, India
c Chorghade Enterprises, 14 Carlson Circle, Natick, MA, USA
d Biosensors and Bioelectronics Centre, Institute of Physics, Chemistry and Biology, Linköping University, S-58183 Linköping, Sweden
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 August 2011
Received in revised form 21 February 2012
Accepted 23 February 2012
2-oxo-4-phenyl-6-styryl-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid (ADP) was complexed with
acetates of Mn(II), Ni(II), Cu(II) and Zn(II). The structures of the ligand and its metal complexes were
characterized by microanalysis, IR, NMR, UV–vis spectroscopy, magnetic susceptibility and TGA–DTA
analyses. Octahedral and square planar geometries were suggested for the complexes in which the cen-
tral metal ion coordinated with O donors of ligand and acetate ions. Each ligand binds the metal using
carboxylate oxygens. The ligand and complexes were evaluated for their antimicrobial activities against
different species of pathogenic bacteria and fungi. The present novel pyrimidine containing complexes
could constitute a new group of antibacterial and antifungal agents.
Keywords:
Pyrimidine transition metal complexes
Spectral
Octahedral
Square planar geometry
Anti-microbial activity
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
active metal ion or one of its bio-transformation products, (v) the
enhancer metal after radiation, (vi) the radioactive metal, and (vii)
The design of ligands is an important part of the synthetic reper-
toire of chemists. It gets via subtle control coordination of ligands
on a metal centre [1–3]. Ligands contain significantly different
chemical functionalities, such as hard and soft donors, often called
hybrid ligands that find utility in molecular chemistry [4–6]. The
incorporation of pyrimidine moieties in multifunctional ligands
of increasing complexity makes for excellent complexation; have
rarely been documented in pyrimidine chemistry [7]. The coordi-
nation chemistry of pyrimidine derived ligands is of relevance due
to their biological implications.
In general, the three dimensional coordination of metal with
ligands allows molecule to identify and interact with definite
site of the target bio-molecules. Also, deviation in the oxidation
state of transition metal is important feature for the bio-redox
chemistry. The exchange processes of metal complexes permit the
bio-molecule to interact and coordinate with metals centre [8]. The
systematic study of metal based bio-active complex are summa-
rized with (i) the active entire inert complex, (ii) the active entire
reactive complex, (iii) a active fragment of the complex, (iv) the
responsible for the bio-activity via one or more of the ligands [9].
In recent years, a number of studies have reported on synthesis
and structural analysis of metal complexes of pyrimidine con-
taining bi- and tri-dentate ligands (ONO donors) having microbial
activity, i.e., from donor ligands and complexes [10,11]. Pyrimidines
are endowed with a wide range of biological activities [12–15].
The chelation of metal ions with pyrimidine ring enhances their
activities due to easy availability of potential sites for binding. The
complexed metal ions give information on their coordination prop-
erties and insights towards understanding the role of metal ions
in the biological systems [17]. Herein, we expand on the scope of
pyrimidine ligands, emphasize hybrid ligands, and explain the syn-
ergies obtained by combining these two facets of ligand design. The
synthesis and physical properties of new Ni(II), Cu(II) and Zn(II)
pyrimidine complexes were determined and the ligands investi-
gated for potential microbial activities.
2. Experimental
2.1. Materials
∗
Corresponding authors.
E-mail addresses: anjali rahatgaonkar@yahoo.com (A.M. Rahatgaonkar),
Benzaldehyde (Qualigen Fine Chemicals, 99.9%), ethylace-
toacetate (Qualigen Fine Chemicals, 99%), urea (Qualigen Fine
ashutosh.tiwari@liu.se, ashtiwa@gmail.com (A. Tiwari).
1386-1425/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2012.02.096

R.P. Dhankar et al. / Spectrochimica Acta Part A 93 (2012) 348–353
349
metal salts in 2:1 molar ratio in ethanol. The complexes obtained
were soluble in acetic acid, DMSO, DMF and sparingly soluble in
other common solvents. The physical data of the ligand and com-
plexes are presented in Table 1.
O
2.4. Characterizations
HO
NH
Microanalysis of pyrimidine based ligand and its metal com-
plexes were performed on a Perkin Elmer Model 240C elemental
analyser. IR spectra were obtained on a Perkin Elmer 1800 spec-
trophotometer using KBr discs. 1H NMR spectra were recorded from
CDCl3/DMSO-d6 solution on a Brucker Avance II 400 (400 MHz)
NMR Spectrometer. Chemical shifts are reported as in ı values
(ppm) downfield relative to TMS (0.00 ppm) as an internal stan-
dard. Magnetic susceptibilities of complexes were measured were
by the Gouy’s method using Hg[Co(SCN)4] as calibrant at room tem-
perature. The effective magnetic moments were calculated using
the relation:
N
H
O
Fig. 1. Chemical structure of 2-oxo-4-phenyl-6-styryl-1,2,3,4-tetrahydro-
pyrimidine-5-carboxylic acid (ADP).
Chemicals, 99.8%), sodium hydroxide (Qualigen Fine Chemicals,
99%) and metal acetates (Qualigen Fine Chemicals, 99.9%) were
used without further purification. All supplementary chemicals
were of analytical grade and aqueous solutions were prepared with
sterilized Milli-Q water (18.2 ꢀ/cm2).
ꢂeff = 2.828(ꢃmT)1/2 BM
where ꢃm is the molar susceptibility corrected using Pascal’s con-
stants for diamagnetism of all atoms in the compounds.
2.2. Synthesis of ligand (E)-2-oxo-4-phenyl-6-styryl-1,2,3,4-
tetrahydro-pyrimidine-5-caboxylic acid
(ADP)
The TG-DTA measurements were carried out on a Perkin Elmer
Thermogravimetric analyser in dry nitrogen atmosphere and at
heating rate of 10 ◦C/min using Pyris program. Mass spectra were
measured with a GC–MS (70 eV). The X-ray diffraction patterns
have been recorded in 2ꢄ range from 13 to 60◦ on Philips (Holland)
automated X-ray powder diffractometer. The operating target volt-
age was 35 kV and tube current was 20 mA. The scanning speed was
A
mixture of 6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydro-
pyrimidine-5-carboxylic ethyl ester (1.9 mM, 500 mg), and 25 mL
of 10% NaOH was refluxed for 4 h [18]. It was cooled and poured
into 20% HCl solution, filtered and washed with water. The solid
obtained was recrystallized from ethanol. Yield, 70%; m.p. 220 ◦C
[19,20]. Anal. Calcd for C19H16N2O3: C, 71.23; H, 5.0; N, 8.74. Found
(%): C, 71.56; H; 5.10, N, 8.76. IR data: (KBr, ꢁmax/cm−1) 3410 (N H),
˚
0.5 2ꢄ/min. Radiation used was Cu-K of wavelength 1.54056 A pro-
vided with a monochromator for filtering ˇ radiations to reduce
noise due to white radiations and to increase the resolution. The
values of interplaner spacing (d) corresponding to Bragg reflections
(2ꢄ) were obtained. Indexing and calculations of unit cell parame-
ters were performed with the help of Powder-X-Software [16,17].
3231 (N H), 3115 (O H), 1685 (C O), 970 (CH CH) cm−1 1H NMR
.
(400 MHz, CDCl3) ı = 11.5 (s, 1H, OH), 8.5 (s, 1H, N1H), 7.9 (s, 1H,
N3H), 7.4–7.1 (m, 10H, aromatic), 6.9 (d, 1H, J = 16.4, CH CH), 6.4
(d, 1H, J = 16.5, CH CH), 5.4 (s, 1H, methine). 13C NMR (200 MHz
CDCl3) 50.03, 106.4, 126.1, 126.4, 126.9, 127.1, 127.3, 127.4, 127.6,
127.7, 128.0. LC–MS, m/z 320 M+ (Fig. 1).
2.5. Screening of antibacterial and antifungal activities
2.3. Synthesis of metal complexes
The in vitro evaluation of antimicrobial activity was per-
formed according to the diffusion technique [21]. The bacteria
including Staphylococcus aureus and Escherichia coli were grown
in nutrient broth at 37 ◦C for 24 h. Candidaalbicans and Fusar-
ium solani were grown in malt broth at 28 ◦C for 48 h. The
ligand and its complexes were tested using the diffusion tech-
nique on solid media. Sterile (5 mm) diameter sensitivity discs
were impregnated with different concentrations of the com-
pounds in DMF (50 ␮g or 100 ␮g mL−1). Discs of each tested
compound were laid onto nutrient agar for bacteria or potato
dextrose agar for fungi. Plates were surface spread with 0.2 mL
of logarithmic phase bacteria or fungi cultures. A 0.5 mL spore
The ligand ADP (2 mM, 320 mg) was dissolved in ethanol (20 mL)
and to this metal acetates (1 mM) Mn2+, Cu2+, Ni2+, Zn2+ dissolved in
ethanol were added slowly, with constant stirring, over a period of
10 min. The reaction mixture was refluxed for 4–8 h. The solid com-
plex obtained was collected on a fine frit filter and dried over fused
calcium chloride in a vacuum desiccator. The complexes obtained
were MPMC, CPMC, NPMC and ZPMC respectively Mn2+, Cu2+
Ni2+, Zn2+ respectively. All complexes with [Mn(ADP)2(OAC)2]2−
,
,
[Cu(ADP)2(OAc)2]2−, [Ni(ADP)2(OAc)2]2− and [Zn(ADP)2(OAc)2]2−
were obtained by refluxing a mixture of ligand and appropriate
Table 1
Physical and analytical data of ligand and metal complexes.
Compound
Molecular
Colour
m.p.
Yield (%)
Found (calculated) %
composition
C
H
N
Ligand
MPMC
CPMC
NPMC
ZPMC
C19H16N2O3
MW = 320
Light yellow
Brown
220
268
287
265
291
70
89
86
84
72
71.22 (71.24)
5.05 (5.03)
8.72 (8.74)
C43H38MnN4O10
MW = 825.72
C42H36CuN4O10
MW = 819.32
C42H36NiN4O10
MW = 815.45
C42H36ZnN4O10
MW = 820.17
62.56 (62.55)
61.49 (61.50)
71.25 (71.24)
61.35 (61.36)
4.67 (4.64)
4.45 (4.42)
4.41 (4.45)
4.43 (4.41)
6.77 (6.79)
6.82 (6.83)
6.86 (6.87)
6.80 (6.81)
Dark brown
Bluish yellow
Yellow

350
R.P. Dhankar et al. / Spectrochimica Acta Part A 93 (2012) 348–353
Table 2
shifts in NH stretching frequencies indicating that NH groups do
not participate in coordination with metal ions. The characteristic
bands at 1535 and 1385 cm−1 belong to asymmetric (ꢅasym(COO ))
and symmetric (ꢅsym(COO )) vibrations of the acetate groups [22].
The energy separation between (ꢅasym(COO )) and (ꢅsym(COO ))
is found to be >144 cm−1 (150–185 cm−1), and this indicates the
monodentate nature of the acetate ion [23], since in the event
of bidentate coordination, the energy separation is reported to
be <144 cm−1. Further, the IR spectra of the complexes exhibit a
new band in the far-IR region at 550–560 cm−1. This absorption is
assigned to ꢅ(M O) [24]. The other significant vibrations of Zn(II)
and Ni(II) complexes are depicted in Table 2. [Mn(ADP)2(OAc)2]2−
exhibited an octahedral geometry. The octahedral coordination of
manganese ions was confirmed through the evidences provided by
IR frequencies of acetate ions. The energy separation of the asym-
metric (ꢅasym(COO )) and symmetric vibrations (ꢅsym(COO )) is
Characteristics IR bands (cm−1) for ligand and complexes.
Compound
ꢅ( OH)
ꢅ(C O)
ꢅ(N H)
ꢅ(CH3COO)
ꢅ(M O)
Ligand
CPMC
NPMC
ZPMC
MPMC
3115
1686
1676
1686
1686
1688
3410, 3231
3410,3249
3410,3229
3405,3228
3402,3232
–
–
559
503
498
403
–
–
–
–
1535,1385
1560,1344
1568,1344
1508,1390
suspension (108 spores mL−1
) for bacteria or for filamentous
fungi was also spread onto potato dextrose agar plates. The plates
were then incubated for 24 h at 37 ◦C for bacteria and 28 ◦C for 48 h
for fungi. Additionally antibiotic discs for Cephalosporin and/or
Streptomycin were tested as positive control. The results were
repeated two times and recorded by measuring the zones of growth
inhibition surrounding the discs. The mean values of the results are
presented in the Table 5.
found as <144 (1508–1390) cm−1 thus indicating that both the
O
atoms of acetate ions are involved in coordination as bidentate
ligands (Scheme 1) [25].
3. Result and discussion
3.2. NMR spectra
3.1. IR spectra
In the 1H NMR of ADP a singlet at ı 11.5 confirmed the pres-
ence of COOH moiety. N1 and N3 protons appeared at ı 8.5 and
ı 7.6 as singlets. The multiplets at ı 7.4 to ı 7.1 for 10 aromatic
protons indicate the presence of two phenyl rings. Two doublets
at ı 6.9 (J = 16.4) and at ı 6.4 (J = 16.5) respectively account for a
styryl group. Considering the model of Zn(II) complex, the disap-
pearance of O H peak at ı 11.5 signifies oxygen–metal bonding.
N1 and N3 protons appeared at ı 8.5 and ı 7.6 as singlets. Other
peaks appear at ı 3.2(s, 6H, acetate H) indicating two acetate ions
to be attached to the metal ions. The ligand coordination to metal
via oxygen atom is evidently strong because of easy deprotonation
of the COOH group. Two singlets at ı 5.1 and ı 4.9 are due to Si
and Re configurations of pyrimidine nuclei.
The derivatives of carboxylic acids are characterized by sev-
eral intense absorptions in infrared Spectrum. The most prominent
ones are in carbonyl stretching region (1700–1725 cm−1). Their
exact position depends on the type of acid derivative. In addition
to carbonyl stretching absorption, the acids themselves exhibit a
strong, broad OH stretching at a range from 3500 to 2500 cm−1
Bands at 3231 and 1686 cm−1 are characteristic of OH and C
.
O
group at free ligand. The disappearance of 1686 cm−1 band of Cu(II)
complex suggests coordination of carboxylic oxygen after deproto-
nation [20]. The spectrum of free ligand (ADP) attributed to NH
stretching at 3410 and 3115 cm−1. A comparison of IR spectra of
complexes with those of free ligands do not display any appreciable
Scheme 1. Synthesis of metal complexes and their suggested structures.

R.P. Dhankar et al. / Spectrochimica Acta Part A 93 (2012) 348–353
351
of one unpaired electron per Cu(II) ion and suggesting that the
square-planar geometry [26].
2-
O
Ph
H
O
C O
C CH3
O
Electronic absorption spectra of Ni(II) are characterized by a
broad band in the range of 270–300 nm. This behaviour can be
HN
1
1
1
1
assigned to A1g → B1g and A1g → E1g transitions confirmed
square planar geometry of these complexes. The magnetic moment
for Ni(II) in complex is zero which is in good agreement with elec-
tronic data.
N
H
Ph
O
Cu
Ph H
NH
O
O C
O
3.4. Molar conductance
H3C C
O
N
H
O
The complexes were dissolved in DMF and the molar con-
ductivities of 10−3 M of their solutions at room temperature
were measured. Table 3 shows the molar conductance values of
the complexes. It is concluded from the results that complexes
are found to have molar conductance values in the range of
2–14 ohm−1 mol−1 cm2 indicating the non-electrolytic nature of
these complexes [27].
Ph
Fig. 2. Suggested geometry of [Cu(ADP)2(OAc)2]2−
.
The 1H NMR spectral data of ligand was supplemented by 13C
NMR spectral data. The chemical shifts for carbon of aromatic rings
were recorded between ı 126 and ı 128;the signal for carbon of
COOH group was observed at ı 171.23. Other signals at ı 124
and ı 131 were attributed to styryl carbon atoms. The 13C NMR
of all the complexes displayed characteristic signals ranging from
ı 22.7–23.1 and ı 176.41–177.28 and thus providing additional
evidence for the proposed coordination with O of acetate ions
(Fig. 2).
3.5. Mass spectra
The mass spectra of ligand and the complexes showed peaks
attributed to the molecular ions m/z at 320 [L]+, 825 M+, 815 M+,
819 M+ and 820 M+ for ligand, manganese, copper, nickel and zinc
complexes, respectively.
3.6. X-ray powder diffraction analysis
3.3. Electronic spectra
All complexes were found to be crystalline and their X-ray
powder diffractograms were collected. The lattice parameters and
Miller indices were computed. The indexing and calculation of unit
cell parameters are performed with the help of Powder-X Software.
The calculated and observed 2ꢄ value, the relative intensity, inter-
planar distance along with Miller’s indices for corresponding angles
are tabulated for the complexes. On the basis of X-ray powder pat-
terns and unit cell refinements, it is found that all the complexes
adopt triclinic crystal system with p-type of lattice space group.
The lattice constants calculated, complex (MPMC) and (CPMC) are
depicted in Table 4.
The electronic spectra of ligand and complexes were recorded in
DMF at room temperature. The diamagnetic Zn(II) and Ni(II) com-
plexes had bands in 280–250 nm range due to n → ␲* and ␲ → ␲*
transitions of benzene, pyrimidine and carbonyl group respec-
tively. In the spectra of complexes, less intense and broad bands
in the 445–250 nm range result from overlap of low energy ␲ → ␲*
transitions and LMCT (ligand to metal charge transfer bands from
electronic lone pairs of carboxylate oxygen to the M2+ ions.)
The electronic spectra of the Cu(II) complexes (Table 3) are com-
pared with those of the ligands. Two bands appeared at 356 cm−1
and 270 cm−1, which can be assigned to ␲ → ␲* and n → ␲ transi-
*
tions, respectively, in the complex. Apart from this a broad band
3.7. Themogravimetric analysis
centred at 560 cm−1 can be assigned to d → d transitions of the
2
metal ions (2B1g → A1g
;
2B2g) and which strongly favour square-
Thermal behavioural analysis of complexes CPMC, NPMC, ZPMC
and MPMC were conducted in the temperature range of 23–800 ◦C
with the heating rate of 10 ◦C/min. The calculated decomposition
planar geometry around the central metal ion [21]. In addition,
the ꢂeff values for this compound calculated as 1.85 BM, indicative
Table 3
Electronic spectral data, magnetic moment and geometry for ligand and metal complexes.
Compound
Absorption (nm)
Band assignments
Transitions
Magnetic moment
Geometry
Molar Conductance
(ohm−1 mol−1 cm2)
(ꢂeff
)
279
256
n → ␲*
␲ → ␲*
Ligand
CPMC
2B1g–6A1g
560
356
270
d → d
Intraligand
Intraligand
Square planar
1.85
2
257
243
Intraligand
Intraligand
Diamagnetic
Diamagnetic
Square planar
Square planar
NPMC
ZPMC
7.5
283
247
Intraligand
Intraligand
12.3
550
401
379
d→d
Intraligand
Intraligand
MPMC
5.83
Octahedral
14

352
R.P. Dhankar et al. / Spectrochimica Acta Part A 93 (2012) 348–353
Table 4
role in various metabolic pathways of these microorganisms. Other
Powder XRD data of metal complexes.
factors such as solubility, conductivity and dipole moment which
affected by the presence of metal ions, may also be possible rea-
sons for increasing the biological activity of the metal complexes
as compared to the corresponding ligand.
Data
CPMC
MPMC
Chemical formula
Molecular weight (g/mol)
Crystal system
C42H36CuN4O10
819.32
Triclinic
P−1
C43H38MnN4O10
825.72
Triclinic
P−1
Space group
4. Conclusion
Unit cell dimensions
a
b
c
˛
ˇ
ꢆ
4.9168
4.9865
5.4089
78
90
104
4.9160
4.9153
5.4084
82
85
115
MPMC, CPMC, NPMC and ZPMC complexes were synthesized
and characterized. Analytical data, electronic spectra, magnetic
susceptibility, IR and 1H NMR have been revealed octahedral geom-
etry of MPMC and square planar geometry of CPMC, NPMC and
ZPMC, respectively. The low conductance values showed non-
electrolytic behaviour of the complexes. Single crystals of the
compounds could not be isolated; however, powder XRD data,
spectroscopic and magnetic data enabled us to elucidate possible
structures. The complexes were evaluated in vitro for the antibacte-
rial and the antifungal activities. All metal complexes had effective
and selective antibacterial activity against bacterial strains. The
results speculate regions for higher activity of complexes: (1)
the metal complexes could be inactivated to several structural
enzymes, catalysing biosynthetic reactions inessential metabolic
pathways of the microorganisms; and (2) they act as a whole, are
able to cross the cell membranes and interfere with the vital cell
mechanisms including DNA replication, transcription, and protein
synthesis.
Volume
132.61
6.1
299 K
130.68
6.3
299 K
(Calc.) density (g/cm−3
Temperature
)
patterns of the complexes are in agreement with the theoretical
data. All complexes decompose in three major phases.
The first phase corresponds to the loss of 2 moles of acetate
ions between 100 and 300 ◦C with mass losses of (obs. = 14.26%,
calc. = 14.31%). The second phase is from 305 to 410 ◦C and is
attributed to the loss of the organic moiety of styryl and phenyl
ring with mass losses of C8H7 (obs. = 24.91%, calc. = 25.1%). The final
phase shows the loss of the organic moiety of pyrimidine and
phenyl ring of 408 at 450–800 ◦C with mass losses of (obs. = 49.53%,
calc. = 49.33%) leaving metal oxides as residues.
Acknowledgements
RPD gratefully acknowledges UGC, New Delhi for financial assis-
tance under faculty improvement program of XI plan. The authors
wish to express their gratitude to the Department of Pharmacy,
Nagpur for IR spectroscopic analysis; the Sophisticated Analytical
Instrumentation Facility (SAIF), Chandigarh for 1H NMR spectro-
scopic analysis and mass analysis; and the University of Pune, Pune
for 13C NMR spectroscopic data. We also wish to acknowledge
Metallurgical and Materials Engg. Department, VNIT, Nagpur for
TGA–DTA analysis and Powder XRD; and Department of Chemistry,
R.T.M. University, Nagpur for magnetic moment. We do acknowl-
edge Department of Physics, Institute of Science, Nagpur for UV
spectral data.
3.8. In vitro biological evaluation
The ligand and its metal complexes were evaluated for antimi-
crobial activity against one strain Gram positive bacteria (S. aureus)
(a), Gram negative bacteria(E. coli) (b), fungus (Candida albicans) (c)
and fungus F. solani (d) and the results are summarized in Table 5.
The ligand was found to be biologically active and their metal com-
plexes enhanced antimicrobial activity against one or more strain.
Remarkably, the complexes showed appreciable inhibition against
S. aureus (a), C. albicans (c) and F. solani (d) ranging from 43 to
86%. It is known that chelation tends to make the ligand a more
powerful and potent bactericidal agent. A possible explanation for
the observed increased activity upon chelation is that the positive
charge of the metal in chelated complex is partially shared with
the ligand’s donor atoms so that there is an electron delocalization
over the whole chelate ring. This, in turn, will increase the lipophilic
character of the metal chelate and favours its permeation through
the lipoid layers of the bacterial membranes. Typically, chelated
complexes deactivate various cellular enzymes, which play a vital
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Ligand (ADP)
NPMC
CPMC
+++
++
+++
++
+++
++++
++++
++
+++
+
++
++
++
++
++
+
++
+
+++
+++
+++
+++
+++
+++
ZPMC
MPMC
Cephalosporina
Streptomycinb
+++
+++
++++
++
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