Synthesis of NNNN tetradentate macrocyclic ligand and its Pd(II), Pt(II), Ru(III), and Ir(III) complexes: Spectroscopic, Thermal, and antimicrobial studies

Article abstract of DOI:10.1080/15533174.2010.522663

Pd(II), Pt(II), Ru(III), and Ir(III) complexes of general stoichiometry [PdL]Cl₂, [PtL]Cl₂, [Ru(L)Cl₂]Cl, and [Ir(L)Cl₂]Cl, with tetradentate macrocyclic ligand, derived from 2,6-diaminopyridine with 3-methyl 2,4-pentanedione has been synthesized. The ligand was characterized on the basis of elemental analyses, IR, mass, and ¹H NMR and ¹³C NMR spectral studies. All the complexes were characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, mass, electronic spectral techniques, and thermal studies. The value of magnetic moments indicates that all the complexes are diamagnetic except Ru(III) complex, which shows magnetic moments corresponding its one unpaired electron. The macrocyclic ligand and all its metal complexes were tested in vitro against some plant pathogenic fungi and bacteria to assess their biocidal properties. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2010.522663

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:940–946, 2010
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2010.522663
Synthesis of NNNN Tetradentate Macrocyclic Ligand and its
Pd(II), Pt(II), Ru(III), and Ir(III) Complexes: Spectroscopic,
Thermal, and Antimicrobial Studies
Soni Rani,1 Sumit Kumar,2 and Sulekh Chandra1
1Department of Chemistry, Zakir Husain College, University of Delhi, New Delhi, India
2Department of Biotechnology, Japuria Institute, Vasundhara, Ghaziabad, India
compounds[7] due to its resemblance with natural proteins like
Pd(II), Pt(II), Ru(III), and Ir(III) complexes of general sto-
ichiometry [PdL]Cl2, [PtL]Cl2, [Ru(L)Cl2]Cl, and [Ir(L)Cl2]Cl,
with tetradentate macrocyclic ligand, derived from 2,6-
diaminopyridine with 3-methyl 2,4-pentanedione has been synthe-
sized. The ligand was characterized on the basis of elemental anal-
yses, IR, mass, and 1H NMR and 13C NMR spectral studies. All the
complexes were characterized by elemental analyses, molar con-
ductance measurements, magnetic susceptibility measurements,
IR, mass, electronic spectral techniques, and thermal studies. The
value of magnetic moments indicates that all the complexes are dia-
magnetic except Ru(III) complex, which shows magnetic moments
corresponding its one unpaired electron. The macrocyclic ligand
and all its metal complexes were tested in vitro against some plant
pathogenic fungi and bacteria to assess their biocidal properties.
hemerythrin and enzymes. These complexes are very useful in
industrial and synthetic process such as catalysis, photochem-
istry and biological systems.[8] Metal complexation can change
biological activity of the macromolecules and new properties
can be utilized in many cases in pharmaceutical practice.[8] It is
generally known that the complexes of the transition elements,
including several examples of Ni, Pd and Pt-derivatives, play an
important role in biochemistry.[9] Palladium(II) complexes have
been found to cleave proteins selectively in high yield.[10] Pal-
ladium amine complexes have also been investigated for their
potential use as anticancer agents[11] and some Palladium(II)
complexes of Schiff base ligands have been found to exhibit
marked cytotoxicity against leukemia.[12] For a number of years,
Platinum-based chemotherapeutic regimens have been the main-
stay for the management of epithelial ovarian cancer,[13] testic-
ular cancer, head and neck tumors, and a number of other solid
tumor types.[14] The platinum analogue oxaliplatin has been de-
veloped and is now licensed for use in matastatic colon cancer
in the U.S.[15] The accessibility of ruthenium in higher oxidation
states[16,17] converts the transition metal complexes into excel-
lent species that act as catalyst for redox reactions. Complexes
of ruthenium have demonstrated to be more used in laboratory
and industry as homogenous catalysts.[18,19(a)] Pd(II) complexes
of various donor atom ligands possess anti-tumor and anti-viral,
-malarial, -fungal, and -microbial activities. This review focuses
on such properties of Pd(II) complexes and makes comparisons
with similar properties of other metals.[19(b)]
Keywords iridium(III), metal complexes, palladium(II), plat-
inum(II), ruthenium(III), tetradentate macrocyclic
INTRODUCTION
The multifarious role of transition metal complexes of macro-
cyclic ligands in biological systems suggest that considerable
potential exists for the development of new chemistries with
these metals in ligand systems.[1−4] The complexes of transition
metal ions with synthetic macrocyclic ligands are significant
because of their resemblance with many natural systems such
as porphyrins and cobalamines[5] and have received much at-
tention as a active part of metalloenzymes[6] as biomimic model
In continuation of our interest in the synthesis, char-
acterization, and biological activity of transition metal
complexes, in this paper we report the complexes of
Pd, Pt, Ru and Ir of the ligand (L) 3,4,5,13,14,15-hexamethyl-
2,6,12,16,21,22-hexaazatricyclo[15.3.I1−17I7−11]dicosa-1(21),
2,5,7,9,11(22),12,15,17,19-decaene. These complexes were
characterized on the basis of IR, NMR, mass and UV spectral
techniques, and all the compounds were tested in vitro against
some plant pathogenic fungi and bacteria.
Received 25 May 2010; accepted 4 August 2010.
The authors thank to the principal, Zakir Husain College Delhi,
University of Delhi, for providing the laboratory facilities. The authors
are also thankful to the DRDO, Delhi, for financial assistance.
Address correspondence to Sulekh Chandra, Department of
Chemistry, Zakir Husain College, University of Delhi, J.L. Nehru
Marg, New Delhi-110002, India. E-mail: schandra 00@yahoo.com;
sumitsoni.biochem@gmail.com
940

TETRADENTATE MACROCYCLIC METAL COMPLEXES
941
EXPERIMENTAL
Physical Methods
CH3
C
H
2
H C
CH3
2
3
+
Elemental analyses of C, H, and N were performed on a
Carlo-Erba EA 1106 analyzer; the nitrogen contents of the com-
plexes were determined using Kjeldahl’s method. Metal con-
tents were estimated on an AA-640-13 Shimadzu flame atomic
absorption spectrophotometer in solution prepared by decom-
position of the complex in hot concentrated HNO3. IR spectra
were recorded as KBr pellets in the region 4000–200 cm−1 on a
FT-IR spectrum BX-II spectrophotometer. The 1H NMR spectra
at 300 MHz were recorded on a Bruker Advance DPX-300 spec-
trometer using CDCl3 as solvent. Chemical shifts are given in
ppm relative to tetramethylsilane. Electron impact mass spectra
were recorded on JEOL, JMS, DX-303 mass spectrometer. The
electronic spectra were recorded in DMF on Shimazdu UV mini-
1240 spectrophotometer. Molar conductance was measured on
an ELICO (CM 82T) conductivity bridge. Magnetic suscepti-
bility was measured at room temperature on a Gouy balance
using CuSO4.5H2O as a callibrant. The complexes were stud-
ied by thermogravimetry (TG) in a static nitrogen atmosphere
with a sample heating rate 5◦C/min., using Rigaku model 8150
thermoanalyzer.
C
O
C
O
N
H2N
NH2
few drops of
conc. HCl
Reflux for 11 h
at 70oC
d
e
e
a
CH3
a
H3C
N
C
C
N
N
N
N
C
c
C
H
b
b
c
H3C
HC CH3
C
N
a
CH3
a
H3C
e
e
d
FIG. 1. Synthesis of ligand (L).
(C2H5OC2H5). This was filtered, washed with cold methanol,
and dried under vacuum over silica gel (yield 60–67%).
Materials
All the chemicals used were of AnalaR grade and procured
from Sigma Aldrich and Fluka. Solvents were dried and dis-
tilled before use according to standard procedure. Metal salts
(E. Merck) were commercially available pure samples.
RESULTS AND DISCUSSION
Ligand
The newly synthesized ligand is very stable at room tempera-
ture in the solid state and is soluble in common organic solvents.
The spectrum shows a strong band at 1640 cm−1 which may
be assigned to the ν(C=N) stretching vibration (azomethine
Synthesis of Ligand (L)
The ligand was synthesized by refluxing a hot ethanolic solu-
tion (20 mL) of 2,6-diaminopyridine (2.1826 g, 0.02 mol) with
a hot ethanolic solution (20 mL) of 3-methyl 2,4-pentanedione
(2.2830 g, 0.02 mol) in a 2:2 molar ratio. This reaction mixture
was refluxed for 11h at 70◦C in the presence of conc. HCl. On
cooling, the contents overnight at 0◦C a light brown crystalline
compound was separated out. It was filtered, washed several
times with cold ethanol, and dried under vacuum over P4O10
(Figure 1). The yield was 61%; m.p. 210◦C.
linkage).[20] In addition, the bands at 1403 cm−1, 666 cm−1
,
and 430 cm−1 appeared in the spectrum, which are due to the
pyridine-ring-stretching, in-plane-ring-deformation, and out-
of-plane-ring deformation,[21] respectively. On coordination
with metal ions the position of IR bands due to azomethine
group are shifted to the lower wave number, which indicates
that coordination takes place through the nitrogen of the
(C N) group, and the ligand acts as a tetradentate. The ESI
mass spectrum[22] of the ligand displays the mol+ecular ion peak
(M+) at m/z = 374 which is due to (C22H26N6 ) parental ion
with 80% intensity. The other fra+gments appeared in the spec-
For C22H26N6, calcd. %: C, 70.58; H, 6.95; N, 22.45. Found,
%: C, 70.49; H, 6.91; N, 22.61.
trum are as m/z = 375 (C22H26N6 + C or 15N) isotopic peak,
13
Synthesis of Metal Complexes
Complexes of macrocyclic ligand (L) were prepared by the 284 (C16H8N+6 , 70%) macrocyclic moiety, 79 (C5H5N+, 100%)
dropwise mixing of a hot ethanolic solution (20 mL) of the base peak.1H NMR spectrum[23] of ligand (L) in (DMSO-d6)
ligand (0.001 mole) to a hot ethanolic solution (20 mL) of cor- displays a singlet at ca. δ 1.25 ppm (s.,12H, 4N=C CHa3) due
responding metal salt (0.001 mol) with constant stirring. This to the protons of four methyl groups, another signal as a doublet
reaction mixture was refluxed at 70–75◦C for 9–15 h. On cool- at ca. δ 2.59 ppm (d., 6H, 2C CHb3) due to the six protons of
ing, a colored complex was separated out, which was filtered, methyl groups, a quartet signal at ca. δ 3.29 ppm (q., 2HcC)
washed with cold ethanol, and dried under vacuum over P4O10 due to two protons of CH groups. Two signals as a doublet
(yield 60–64%) for Pd and Pt complexes, but the complexes and a triplet at ca. δ 7.06 ppm (d., 2Hd) and at ca. δ 7.36 ppm
of Ru and IR were separated out with the help of diethyl ether (t., 4He), respectively, are obtained due to the two types of non

942
S. RANI ET AL.
TABLE 1
Physical properties and elemental analysis data of the ligand and its complexes
Melting
point,
Molar
Elemental analysis found/calculated,%
Yield,
%
conductance,
ꢀ
Complexes
Color
◦C
−1cm2mol−1
M
C
H
N
C22H26N6(L)
[Pd(L)]Cl2
[Pt(L)]Cl2
[Ru(L)Cl2]Cl Dark green
[Ir(L)Cl2]Cl Black
Light brown
Brown
Brown
210
289
>300
280
61
60
58
65
60
—
196
230
99
—
70.49/70.58 6.91/6.95 22.61/22.45
19.21/19.23 48.06/47.91 4.59/4.71 15.21/15.24
29.86/30.46 40.99/41.25 4.19/4.06 13.24/13.12
17.38/17.31 45.43/45.37 4.47/4.41 14.45/14.49
28.57/28.60 39.28/39.23 3.86/3.89 12.50/12.54
>300
104
equivalent pyridine ring protons. 13C NMR spectrum of lig- 374 (PdC16H18N+4 + 2H), 414 (PdC18H20N+5 + 2H), 442
and (L) in (DMSO-d6) shows the signals at ca. δ 10.24 ppm (PdC20H24N+5 + 2H), and 482 (PdC22H26N6+ + 2H). The elec-
(CH3 CH) due to methyl carbon atom, at ca. δ 18.26 ppm tronic spectrum of the palladium(II) complex displays the ab-
(CH3 CN) due to carbon atom of methyl group, at ca. δ 57.67 sorption (Table 2) at 18348 cm−1, 31347 cm−1 and 42016 cm−1
1
1
1
ppm (>CH Me) due to carbon atom of CH, at ca. δ 152.09, corresponding to 1A1g → A2g(dxy → dx −y )ν1, A1g → Eg
2
2
[26]
155.67 and158.41 ppm due to pyridine ring carbon atoms and at
2
2
(dxz, dyz → dx −y )ν3 due to spin allowed d−d transitions
and high intensity charge transfer absorption band, respectively.
These bands suggest that the complex possess D4h symmetry
and square planar geometry.[27]
ca. δ 162.39 ppm (>C=N) due to azomethine carbon atom.[24]
Complexes
Schiff base complexes are very stable at room temperature in
the solid state and are soluble in nitrobenzene and coordinating
solvents like DMF and DMSO. The analytical data are in good
agreement with the proposed stoichiometry of the complexes
(Table 1).
Pt(II) Complex
The molar conductance of the Pt(II) complex is 230
ohm−1 cm2 mol−1 (in DMF solution), which indicates that
complex is 1:2 electrolyte in nature,[28] so the complex may
be formulated as [PtL]Cl2. The magnetic moment indicates
that the complex is diamagnetic in nature. On complexation,
Pd(II) Complex
The molar conductance of the complex (196 ohm−1cm2 there is no change in the position of IR bands due to pyridine
mol−1) was measured in DMF solution, which indicates that ring, which suggests that pyridine nitrogens do not take part
the complex is 1:2 electrolyte[25] in nature. Thus the complex in coordination with metal ions. However, the position of band
may be formulated as [PdL]Cl2. The value of magnetic moment corresponding to ν(C=N) is shifted towards lower side. This
indicates that the complex is diamagnetic (as expected) with indicates that the coordination takes place via the nitrogen of
spin-paired d8 system. In the IR spectrum of ligand, the bands ν (C=N) groups. In the ESI mass spectrum of the complex
corresponding to the pyridine ring are not affected on complexa- the parental ion peak is present at m/z = 643 corresponding
tion, which indicates the non-involvement of pyridine nitrogens to (PtC22H26N6 Cl+2 + 3H). The different fragments of the
in coordination with metal. The ESI mass spectrum of the Pd(II) complex with different m/z values are present at 79 (C5H5N+),
complex [Pd(C22H26N6)Cl2] shows the parental ion peak at 187 (C11H13N+3 ), 266 (C16H18N4+), 464 (PtC16H18N4+ + 3H),
m/z = 553 corresponding to (PdC22H26N6 Cl+2 + 2H). The other 544 (PtC20H22N6+ + 3H) and 572(PtC22H26N++3H). The
fragments of the complex give the peak with various intensit+ies platinum(II) complex is diamagnetic with low-spin d8 system
at different m/z values like at 79 (C5H5N+), 119 (C7H7N2 ), having square planar geometry. The spin allowed d-d tran-
147 (C9H11N+2 ), 187 (C11H13N+3 ), 295 (PdC11H13N+3 + 2H), sitions are observed in electronic spectra at 21413 cm−1
,
TABLE 2
Electronic spectrals (cm−1) and magnetic moment (B.M.) data of Pd(II) and Pt(II) complexes
Spectral bands in (cm−1
)
1
1
1
Complexes
ν1(1A1g → A2g)
ν2(1A1g → B1g)
ν3(1A1g → Eg)
C.T.
µeff (B.M.)
ꢁ1
DqE
[Pd(L)]Cl2
[Pt(L)]Cl2
18348
21413
—
—
31347
29761
42016
−
Diamagnetic
Diamagnetic
20148
23513
1834.8
2141.3

TETRADENTATE MACROCYCLIC METAL COMPLEXES
1
943
29761 cm−1 corresponding to 1A1g
→ A2g, and
TABLE 3
1A1g → Eg,[29] respectively. The electronic spectrum of
1
Ligand field parameters of Ru(III) and Ir(III) complexes
complex (Table 2) also shows the high energy absorption band
Complexes
ν2/ν1
ꢁ(cm−1
)
B(cm−1
)
β
1
1
at 35971 cm−1. It may be due to charge transfer A1g → A2u
transition. The position of electronic spectral bands indicate
that the complex possess square planar geometry.[30]
[Ru(L)Cl2]Cl
[Ir(L)Cl2]Cl
1.20
—
25491
21174
497
325
0.78
0.49
Ru(III) Complex
Ligand Field Parameters
The molar conductivity measurement (99 ohm−1cm2
mol−1) in nitrobenzene solution indicates that the complex
is 1:1 electrolyte[31] in nature. Thus, the complex may be
formulated as [Ru(L)Cl2]Cl. The magnetic moment of Ru(III)
complex at room temperature is 1.87 B.M., which is lower than
the predicted value of 2.10 B.M. the lowering in µeff values may
be due to lower symmetry, metal-metal interaction, or extensive
electron delocalization. In the IR spectrum of ligand, the bands
corresponding to the pyridine ring are not affected on complex-
ation, which indicates the non-involvement of pyridine nitrogen
in coordination with the metal ion. The ESI mass spectrum of
the Ru(III) complex shows the molecular ion peak at m/z = 585
corresponding to (RuC22H26N6Cl+3 + 3H). The other fragments
of the complex show the peaks at different m/z values like+at
51(C3HN+), 79 (C5H5N+), 119 (C7H7N2+), 147 (C9H11N2 ),
The value of ꢁ1 can be calculated for palladium(II) and plat-
inum(II) (Table 2) from the first spin-allowed d-d transition by
assuming a value of F2 = 10F4 = 600 for the slater-condon
interelectronic repulsion parameter. The splitting parameter in-
creases in the expected order, Pt > Pd. The ligand field parame-
ters (for Ru and Ir) ꢁ, B and β in (Table 3) have been calculated
by using the following equations.[35]
ν1 = ꢁ − 4B + 86(B)2/ꢁ
ν2 = ꢁ + 12B + 2(B)2/ꢁ
The values of β have been calculated by using the formula
β = B(complex)/B(free ion)
187 (C11H13N+3 ), 266 (C16H18N4+), 370 (RuC16H18N+
+
3H), 450 (RuC20H22N+ + 3H), 478 (RuC22H26N+ + 43H),
The value of B for free ion Ru(III) and Ir(III) is 630 and
660 cm−1, respectively. The value of β lies in the range of
0.49–0.78, which indicates that there is considerable orbital
overlap with strong covalency in the metal ligand σ-bond.
6
6
549 (RuC22H26N6Cl+2 + 3H), and 585 (RuC22H26N6Cl+3 + 3H).
The electronic spectrum of the complex shows the absorption
at 18621 cm−1 and 22371 cm−1 corresponding to 2T2g → T1g
4
2
4
and T2g → T2g transitions, respectively. The bands observed
in the region at 27322 cm−1 and 38610 cm−1 are corresponding
to π − π* and n–π* transitions. These positions of bands are
in tune with the prediction for octahedral complex.[32]
Thermal Studies
The thermal decomposition studies of the complexes were
carried out in the temperature range 30–600◦C. There is no
weight loss in the range 100–220◦C, which indicates the ab-
sence of coordinated or uncoordinated water molecule. All the
complexes undergo first step decomposition with weight loss ex-
perimentally 11.09–18.20% (ca.11.04–18.25%) at 240–260◦C
due to the removal of chloride anions. The complexes show
the second step decomposition experimentally 55.43–63.97%
(ca.55.48–63.93%) in the temperature range 350–540◦C due
IR(III) Complex
The molar conductivity measurement (104 ohm−1 cm2
mol−1) in nitrobenzene solution indicates that the complex
is 1:1 electrolyte[33] in nature and may be formulated as
[Ir(L)Cl2]Cl. The magnetic moment indicates that the complex
is diamagnetic in nature. The IR spectrum of complex doesn’t
show any change in the position of IR bands corresponding
to pyridine ring, which confirms that pyridine nitrogen of the
ligand does not take part in the coordination with metal ion.
The ESI mass spectrum of the complex shows the molecular
ion peak at m/z = 674 corresponding to (IrC22H26N6Cl+3 + H).
The other fragments of the complex are present as at different
m/z values like at 79, 119, 147,187, 380, 459, 499, 527, 567,
and 638. The electronic spectrum of the complex shows the
+2
H3C
CH3
N
C
C
N
N
N
N
C
C
H C C
H
HC CH3
CH3
M
N
3
[34]
band at 26385 cm−1 corresponding to 1A1g → T1g transition.
1
The complex also shows a band at 18621 cm−1 attributed to
H3C
1
3
the spin-forbidden transition A1g → T2g. The band at 35971
cm−1 is also observed in the spectrum corresponding to the
ππ* transition. All these transitions confirm that this com-
plex has (Oh) symmetry.
FIG. 2. Structure of complex, where M = Pd(II) or Pt(II)

944
S. RANI ET AL.
Cl
N
+
H3C
CH3
C
C
N
N
N
N
C
C
H C C
H
HC CH3
CH3
M
N
3
H3C
Cl
FIG. 3. Structure of complex, where M = Ru(III) or Ir(III).
to the loss of the total ligand. The final residue was analyzed
by IR spectra and identified as metal oxide corresponds to the
calculated value.
Structure of the Complexes
On the basis of the above spectral studies, the following
structures (Figures 2 and 3) can be suggested for the complexes.
FIG. 4. Graphical representation of antifungal activities of ligand (L) and its
complexes.
Antimicrobial Screening
placed on the medium. The petriplate were sealed by para film
and then placed in incubator at 26 1◦C for 7 days. The in-
hibition of fungal growth expressed in percentage terms was
determined from the growth in the test plates compared to the
respective control plates as given below
The antifungal and antibacterial screening of palladium(II),
platinum(II), ruthenium(III), and iridium(III) complexes of lig-
and (L) (Tables 4 and 5) were carried out using food poison
and disc diffusion method against plant pathogenic fungi and
bacteria Alternaria porri, Fusarium oxysporum, Xanthomonas
compestris and Pseudomonas aeruginosa, respectively.
The fungicidal activity of the ligand and complexes was
determined in vitro by food poison technique.[36,38] The com-
pounds were dissolved in DMSO to get the required concen-
tration of test solutions (Figure 4). The required quantity of
this solution was added to PDA medium and poured into the
petriplate. After that, the 5 mm mycelial disc of fungus was
Inhibition % = (C − T)/C × 100
where C = Diameter of fungal growth in the control plate, and
T = Diameter of fungal growth in the test plate.
TABLE 5
Antibacterial activities of ligand (L) and its complexes
TABLE 4
Bacterial inhibition zone,
Antifungal activities of ligand (L) and its complexes
mm (conc. in µgml−1
)
Fungal inhibition, % (conc. in µgml−1
)
Xanthomonas
compestris
Pseudomonas
aeruginosa
Alternaria porri Fusarium oxysporum
Compounds
50
100
150
50
100
150
Compounds
100 250 500 100 250 500
Ligand (L)
[Pd(L)]Cl2
[Pt(L)]Cl2
[Ru(L)Cl2]Cl
[Ir(L)Cl2]Cl
Standard
32
58
54
59
53
45
66
64
70
61
52
71
69
79
63
30
40
39
41
32
49
54
52
58
50
52
66
61
69
59
Ligand (L)
[Pd(L)]Cl2
[Pt(L)]Cl2
[Ru(L)Cl2]Cl
[Ir(L)Cl2]Cl
Standard
07
12
11
14
10
11
15
14
17
12
15
18
19
23
17
08
15
17
19
12
13
18
21
24
16
17
21
23
26
18
(Captan)
70
82
90
50
64
78
(Streptomycin)
30
30
30
35
35
35

TETRADENTATE MACROCYCLIC METAL COMPLEXES
945
planar geometry while the ruthenium(III) and iridium (III) com-
plexes were found with octahedral geometry. The mass spectra
support the proposed structure of complexes by elemental anal-
yses. Different parameters, i.e., ꢁ, B and β were calculated
on the basis of absorption spectra, and the values suggest the
metal-ligand covalent bonding. The antifungal and antibacterial
screening of the compounds indicates that the Ru(III) complex
is highly active while the other metal complexes show moderate
activity in comparison of the free ligand
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FIG. 5. Graphical representation of antibacterial activities of ligand (L) and
its complexes.
The activities were compared with the activity of the standard
fungicide Captan.
The antibacterial activity of the ligand and its complexes were
determined by disc diffusion method.[37,38] The compounds
were dissolved in DMSO to get the test solutions. 20 mL of
the nutrient agar medium was poured on each petriplate, and af-
ter it 0.5 mL of test bacterial broth was spread over the medium.
25 µL of test solution was applied on the 10 mm diameter sterile
disc. After evaporating the solvent, the discs were placed at the
center of inoculated petriplates and sealed by para film. After
keeping the petriplates at 2◦C for 2 h, they were incubated at
26 1◦C for 24 h. The diameters of the inhibition zones were
measured in millimeters (Figure 5).
It has been found that the activity of the ligand was al-
ways less pronounced than those of its complexes, demonstrat-
ing that complexation with metals enhance the anti-pathogenic
activity of the ligand. The antifungal and the antibacterial
screening data of the free ligand and its metal indicate that all
the complexes are more active as compared to the free ligand.
The ligand and its complexes show fungal and bacterial growth
inhibition in the following order.
Ru(III) > Pd(II) > Pt(II) > Ir(III) > ligand(L)
Ru(III) > Pt(II) > Pd(II) > Ir(III) > ligand(L)
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CONCLUSION
On the basis of IR, mass and UV spectral studies the pal-
ladium(II) and platinum(II) complexes were found with square

946
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