Synthesis, characterization, redox property and biological activity of Ru(II) carbonyl complexes containing O,N-donor ligands and heterocyclic bases

Article abstract of DOI:10.1016/j.saa.2004.02.011

Stable ruthenium(II) carbonyl complexes having the general composition [RuCl(CO)(PPh₃)(B)(L)] (where B=PPh₃, pyridine, piperidine or morpholine; L = anion of bidentate Schiff bases (Vanmet, Vanampy, Vanchx)) were synthesized from the reaction of [RuHCl(CO)(PPh₃) ₂(B)] with bidentate Schiff base ligands derived from condensation of o-vanillin with primary amines such as methylamine, 2-aminopyridine and cyclohexylamine. The new complexes were characterized by elemental analysis, IR, UV-Vis and ¹H NMR spectral data. The redox property of the complexes were studied by cyclic voltammetric technique and the stability of the complexes towards oxidation were related to the electron releasing or electron withdrawing ability of the substituent in the phenyl ring of o-vanillin. An octahedral geometry has been assigned for all the complexes. In all the above reactions, the Schiff bases replace one molecule of PPh₃ and hydride ion from the starting complexes, which indicate that the Ru-N bonds present in the complexes containing heterocyclic nitrogen bases are stronger than the Ru-P. The Schiff bases and their ruthenium(II) complexes have been tested in vitro to evaluate their activity against bacteria, viz., Staphylococus aureus (209p) and E. coli (ESS 2231).

Full text of DOI:10.1016/j.saa.2004.02.011

Spectrochimica Acta Part A 60 (2004) 2913–2918
Synthesis, characterization, redox property and biological
activity of Ru(II) carbonyl complexes containing
O,N-donor ligands and heterocyclic bases
K. Naresh Kumar, R. Ramesh∗
Department of Chemistry, Bharathidasan University, Tiruchirappalli 620024, India
Received 15 December 2003; accepted 3 February 2004
Abstract
Stableruthenium(II)carbonylcomplexeshavingthegeneralcomposition[RuCl(CO)(PPh3)(B)(L)](whereB = PPh3, pyridine, piperidineor
morpholine; L = anion of bidentate Schiff bases (Vanmet, Vanampy, Vanchx)) were synthesized from the reaction of [RuHCl(CO)(PPh3)2(B)]
with bidentate Schiff base ligands derived from condensation of o-vanillin with primary amines such as methylamine, 2-aminopyridine and
cyclohexylamine. The new complexes were characterized by elemental analysis, IR, UV-Vis and 1H NMR spectral data. The redox property
of the complexes were studied by cyclic voltammetric technique and the stability of the complexes towards oxidation were related to the
electron releasing or electron withdrawing ability of the substituent in the phenyl ring of o-vanillin. An octahedral geometry has been assigned
for all the complexes. In all the above reactions, the Schiff bases replace one molecule of PPh3 and hydride ion from the starting complexes,
which indicate that the Ru–N bonds present in the complexes containing heterocyclic nitrogen bases are stronger than the Ru–P. The Schiff
bases and their ruthenium(II) complexes have been tested in vitro to evaluate their activity against bacteria, viz., Staphylococus aureus (209p)
and E. coli (ESS 2231).
© 2004 Elsevier B.V. All rights reserved.
Keywords: Ruthenium(II) carbonyl Schiff bases complexes; Redox properties; Bioactivity
1. Introduction
Schiff bases offer opportunities for inducing substrate chi-
rality, tuning metal centered electronic factor, enhancing
solubility and stability of either homogeneous or heteroge-
neous catalyst [6–8]. In the use of transition metal carbonyls
as reactive species in homogeneous catalytic reactions such
as hydrogenation, hydroformylation and carbonylation,
carbon monoxide serves simply as ligand providing the
complex with the necessary reactivity and stability to allow
reaction [9]. In contrast to the considerable growth of lit-
erature on the chemistry of Schiff base complexes of first
row transition metal, the chemistry of ruthenium complexes
is less well developed [10–13].
As a part of our continuous work reported on syntheses
and characterization of several ruthenium(II) and ruthe-
nium(III) complexes containing tertiaryphosphine/arsine
[14–17], we report here the synthesis, spectral characteri-
zation and antibacterial activity of a series of ruthenium(II)
bindentate Schiff base complexes with triphenylphosphine
and nitrogen heterocycles. The Schiff base ligands used in
this study are shown in (Fig. 1).
The interest in the synthesis and characterization of
transition metal complexes containing a Schiff base lies
in their biological and catalytic activity in many reactions
[1,2]. Schiff bases derived from the condensation of alde-
hyde with primary amines represent an important class of
chelating ligands, the metal complexes of which have been
studied widely [3]. The transition metal complexes having
oxygen and nitrogen donor Schiff bases possess unusual
configuration, structural lability and are sensitive to molec-
ular environment. The environment around the metal center
‘as co-ordination geometry, number of coordinated ligands
and their donor group’ is the key factor for metalloprotein
to carry out specific physiological function [4,5]. Further,
∗
Corresponding author. Tel.: +91-431-2407053;
fax: +91-431-2407045/431-2407020.
E-mail address: ramesh bdu@rediffmail.com (R. Ramesh).
1386-1425/$ – see front matter © 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2004.02.011

2914
K.N. Kumar, R. Ramesh / Spectrochimica Acta Part A 60 (2004) 2913–2918
resulting solution was concentrated to ca. 3 cm3 and cooled.
OCH3
Light petroleum ether (60–80 ◦C) (5 cm3) was then added
where upon the complex was separated. The solid was
filtered off, washed and recrystallised from CH2Cl2/light
petroleum ether mixture and dried in vacuo. The purity of
the compounds were checked by TLC (yield: 62–73%).
OH
C
H
N
R
Fig. 1. Structure of the Schiff bases. R = –CH3, –C5H4N, –C6H12
.
2.4. Antibacterial study
2. Experimental
The in vitro antimicrobial activity of the investigated com-
plexes were tested against the bacteria such as Staphylo-
cocus aureus (209P) and E. coli (2231) by well diffusion
method using agar nutrient as the medium. The bacterial
cultures were incubated at 37 ◦C for 18 h. The ligands and
the complexes were stored dry at room temperature and dis-
solved in 10% DMSO in methanol. In a typical procedure
[21], a well was made on the agar medium inoculated with
micro-organisms. The well was filled with test solution us-
ing a micropipette and the plate was incubated at 35 ◦C for
24 h for bacteria. During this period, the test solution was
diffused and the growth of the inoculated microorganisms
was affected. The inhibition zone developed on the plate was
measured.
2.1. Material and physical measurements
All the reagents used were chemically pure or ana-
lytical reagent grade. Solvents were purified and dried
according to standard procedures. RuCl3·3H2O was pur-
chased from Loba chemie Pvt. Ltd., Bombay, India and
was used without further purification. [RuHCl(CO)(PPh3)3]
[18], [RuHCl(CO)(PPh3)2(B)] [19] (where B = py, pip
or morp) and the ligands [20] were prepared by reported
literature methods. The analysis of carbon, hydrogen and
nitrogen were performed on Carlo Erba 1160 and model
240 Perkin-Elmer CHN analyzer at the Central Drug Re-
search Institute, Lucknow, India. IR spectra were recorded
in KBR pellets in the 4000–200 cm−1 region in Jasco 400
plus spectrophotometer. Electronic spectra were recorded
in CH2Cl2 solution with a Cary 300 Bio UV-Vis Varian
3. Results and discussion
1
spectrophotometer in the range of 800–200 nm. H NMR
Diamagnetic low spin ruthenium(II) complexes of gen-
eral formula [RuCl(CO)(PPh3)(B)(L)] (where B = PPh3,
py, pip or morp; L = bidentate Schiff bases) were prepared
by reacting [RuHCl(CO)(PPh3)2(B)] with Schiff bases in a
1:1 molar ratio in benzene as shown in (Fig. 2). All of the
new Schiff base ruthenium(II) complexes are highly colored,
stable to air and light and soluble in chloroform, methylene
chloride, benzene, DMF and DMSO. The analytical data
(Table 1) are in good agreement with the general molecular
formula proposed for all the complexes.
spectra were recorded on a Bruker 400 MHz instrument
using TMS as an internal reference. Cyclic voltammetric
measurements were carried out on a Bio Analytical Sys-
tem (BAS) model CV-50W electrochemical analyzer using
acteonitrile as solvent. Antibacterial activity studies were
carried out at the Nicholas Piramal India Ltd., Quest Insti-
tute of Life Science, Mumbai. Melting points were recorded
with a Boetius micro-heating table and are uncorrected.
2.2. Preparation of Schiff base ligands
OCH3
HO
The monobasic bidentate Schiff base ligands were
prepared by the condensation of o-vanillin (0.38 g;
0.0025 mmol) with primary amine such as methylamine,
2-aminopyridine and cyclohexylamine (0.23 g; 0.0025 mmol)
in 1:1 molar ratio in EtOH (25 cm3). The solution was
heated under reflux for 2 h and then concentrated to 5 cm3.
On cooling the product was separated out. The crude prod-
ucts were purified by column chromatography on silica gel
using petroleum ether/EtOAc (95/5%) as eluent.
[RuHCl(CO)(PPh3)2(B)]
+
N
C
H
R
1
:
1
Benzene
6h
PPh3
OCH3
2.3. Synthesis of Ru(II) carbonyl Schiff base complexes
OC
Ru
O
All the new complexes were prepared by the following
general procedure. To a solution of [RuHCl(CO)(PPh3)2(B)]
(where B = PPh3, py, pip or morp) (100 mg; 0.10–0.13 mmol)
in benzene the appropriate Schiff base (15–23 mg;
0.10–0.13 mmol) was added and under reflux for 6 h. The
Cl
N
C
H
B
R
Fig. 2. Formation of new ruthenium(II) carbonyl complexes. (Where
B = PPh3 or py or pip or morp; R = –CH3, –C5H4N, –C6H12).

K.N. Kumar, R. Ramesh / Spectrochimica Acta Part A 60 (2004) 2913–2918
2915
Table 1
Analytical data of Ru(II) carbonyl Schiff base complexes
Complex
Empirical formula
Colour
Melting point (◦C)
Found (calculated) (%)
C
H
N
[RuCl(CO)(PPh3)2(Vanmet)]
[RuCl(CO)(PPh3)2(Vanampy)]
[RuCl(CO)(PPh3)2(Vanchx)]
C46H40NO3ClP2Ru
C40H42N2O3ClP2Ru
C40H42NO3ClP2Ru
Green
Brown
Green
Green
Brown
Green
Green
Brown
Green
Green
Brown
Green
124
120
129
126
132
105
125
130
112
131
129
110
59.9 (60.4)
55.6 (55.9)
57.5 (57.1)
56.1 (56.5)
57.9 (58.2)
59.4 (59.3)
55.9 (56.1)
57.6 (57.8)
59.7 (59.6)
56.5 (56.8)
58.5 (58.4)
59.2 (59.6)
4.2 (4.4)
4.7 (4.9)
5.5 (5.6)
4.6 (4.3)
4.0 (4.2)
4.8 (4.9)
5.1 (4.9)
4.9 (4.7)
5.4 (5.5)
4.8 (4.9)
4.7 (4.6)
5.7 (5.5)
1.4 (1.5)
2.9 (3.3)
1.5 (1.6)
2.2 (2.0)
5.3 (5.5)
3.8 (3.6)
3.5 (3.9)
5.1 (5.5)
3.8 (3.6)
4.3 (4.1)
5.5 (5.7)
3.6 (3.8)
[RuCl(CO)(PPh3)(py)(Vanmet)]
[RuCl(CO)(PPh3)(py)(Vanampy)]
[RuCl(CO)(PPh3)(py)(Vanchx)]
[RuCl(CO)(PPh3)(pip)(Vanmet)]
[RuCl(CO)(PPh3)(pip)(Vanampy)]
[RuCl(CO)(PPh3)(pip)(Vanchx)]
[RuCl(CO)(PPh3)(morp)(Vanmet)
[RuCl(CO)(PPh3)(morp)(Vanampy)]
[RuCl(CO)(PPh3)(morp)(Vanchx)]
C
C
41H48N2O3ClP2Ru
31H37N3O3ClPRu
C38H38N3O3ClPRu
C33H36N2O3ClPRu
C37H37N3O3ClPRu
C39H44N2O3ClPRu
C32H34N2O3ClPRu
C
C
36H35N3O4ClPRu
37H42N2O4ClPRu
3.1. FT-IR spectra
bands due to triphenylphosphine are also present around
1435 cm−1 in the spectra of all the Schiff base complexes. A
medium intensity band is observed in the 1020 cm−1 region
characteristic of the coordinated pyridine or piperidine [25].
The co-ordination of the azomethine nitrogen and pheno-
lic oxygen are further supported by the appearance of two
bands at 510–540 and 400–460 cm−1 due to νM–O [24] and
νM–N [25], respectively. For all the complexes, the νRu–Cl
absorption has been observed around 320 cm−1 region [26].
The infrared spectra of the free Schiff base ligands
showed a strong band in the region 1610–1617 cm−1 which
is characteristic of the azomethine ( C N) group [22].
Co-ordination of the Schiff bases to the metal through ni-
trogen atom is expected to reduce the electron density in
the azomethine link and lower the νC
=
absorption fre-
=
N
quency. The band due to νC
showed a negative shift
=
N
and appeared at 1588–1608 cm−1 indicating co-ordination
of azomethine nitrogen [23] to ruthenium metal (Table 2).
A strong band observed at 1265–1276 cm−1 in free Schiff
bases has been assigned to phenolic C–O stretching. On
complexation, this band is shifted to higher frequency range
1270–1286 cm−1 indicating co-ordination through the phe-
nolic oxygen [23,24]. This has been further supported by
the disappearance of the broad νOH band around 3410 cm−1
in the complexes indicating deprotonation of the phenolic
proton prior to co-ordination [22]. A sharp band appeared
3.2. Electronic absorption spectra
The electronic spectra of all the complexes in dichloro-
methane showed two to three bands in the region
709–290 nm. All the Schiff base ruthenium complexes are
diamagnetic, indicating the presence of ruthenium in the +2
oxidation state. The ground state of ruthenium(II) in octahe-
6
1
dral environment is A1g arising from the t2g configuration
and the excited states corresponding to the t52geg1 configura-
3
2
1
1
around 1935–1952 cm−1 due to νC
of the carbonyl
tion are T1g, T2g, T1g and T2g. Hence, four bands cor-
≡
O
1
3
1
3
responding to the transition A1g → T1g, A1g → T2g,
group in all the complexes. In addition other characteristic
Table 2
Important IR (cm−1) and Electronic spectral data (nm) of the Ru(II) carbonyl Schiff base complexes
Complexes
νC
(cm−1
)
νC–O (cm−1
)
νC
(cm−1
)
λmax (ε)a (dm3 mol−1 cm−1
)
=
≡
N
O
1
2
3
4
5
6
7
8
9
1609
1604
1605
1606
1605
1610
1588
1604
1606
1588
1588
1606
1282
1270
1274
1282
1270
1280
1286
1270
1270
1283
1283
1273
1952
1949
1942
1941
1945
1937
1943
1943
1935
1940
1940
1935
391b (6690), 294c (34200)
469b (2769), 290c (31849)
709a (980), 399b (5871), 295c (35770)
657a (1780), 390b (5460), 293c (25510)
446b (664), 294b (7678)
656a (2480), 393b (14530), 294c (29920)
401b (3228), 298c (24932)
453b (6196), 359 (9267), 298c (38569)
675a (1230), 473b (2970), 290c (8721)
385b (2310), 293c (21770)
10
11
12
457b (13400), 298c (41090)
395b (3420), 329c (6450)
a
1A1g
→
1T1g
Charge transfer.
Ligand-centered transitions.
.
b
c

2916
K.N. Kumar, R. Ramesh / Spectrochimica Acta Part A 60 (2004) 2913–2918
Table 3
1H NMR data for Ru(II) carbonyl Schiff base complexes
Complexes
1H NMR data (ppm)
1
2
6.8–7.8 (Ar. m), 8.72 (CH, s), 3.9 (OCH3,s), 2.5 (CH3,s)
6.8–8.1 (Ar. m), 8.72 (CH, s), 3.9 (OCH3,s)
3
6.8–8.2 (Ar. m), 8.9 (CH3, s), 3.9 (OCH3, s), 1.4 (CH2, s)
4
6.9–7.8 (Ar. m), 8.72 (CH, s), 3.9 (OCH3, s), 2.4 (CH3, s)
5
6.7–8.0 (Ar. m), 8.9 (CH, s), 3.9 (OCH3, s)
6
6.8–8.1 (Ar. m), 8.8 (CH, s), 4.1 (OCH3, s), 1.45 (CH2, s)
7
8
9
10
11
12
6.7–8.0 (Ar. m), 8.7 (CH, s), 4.0 (OCH3, s), 2.5 (CH3, s), 1.5 (CH2, s), 9.8 (NH, s)
6.8–7.9 (Ar. m), 8.7 (CH, s), 3.9 (OCH3, s), 1.63 (CH2, s), 9.6 (NH, s)
6.8–7.9 (Ar. m), 8.9 (CH, s), 3.8 (OCH3, s), 1.35 (CH2, s), 10.1 (NH, s)
6.8–8.1 (Ar. m), 8.72 (CH, s), 3.9 (OCH3, s), 2.5 (CH3, s), 3.8 (CH2, s), 2.8 (CH2, s), 9.9 (NH, s)
6.9–8.0 (Ar. m), 8.7 (CH, s), 4.0 (OCH3, s), 3.6 (CH2, s), 2.9 (CH2, s), 9.8 (NH, s)
6.9–8.1 (Ar. m), 8.9 (CH, s), 4.2 (OCH3, s), 3.7 (CH2, s), 2.73 (CH2, s), 1.35 (CH2, s), 10.1 (NH, s)
1
1
1
1A1g → T1g and A1g → T2g are possible in order of
=
thine proton ( CH N). The position of azomethine signal in
the complexes are downfield in comparison with that of the
free ligands, suggesting deshielding of the azomethine pro-
ton due to its co-ordination to ruthenium through the azome-
thine nitrogen. Multiplet are observed around δ 6.8–8.1 ppm
in all the complexes have been assigned to aromatic pro-
tons of triphenylphosphine, pyridine and Schiff base lig-
ands [30,31]. One sharp singlet appeared at δ 3.8–4.2 ppm
indicates the presence of methoxy proton in all the com-
plexes [32]. Methyl protons appear as singlet in the region δ
2.4–2.5 ppm in 1, 4, 7 and 10 and a representative spectra of
1 is shown in Fig. 3. The signal for methylene protons appear
as a broad singlet in the region δ 1.35–1.63 ppm in 3, 7–9
and 12. The spectra of 11, 11 and 12 showed two signals for
methylene protons which are nearer to oxygen and nitrogen.
The signal in the region δ 3.6–3.7 ppm is due to methylene
protons nearer to oxygen and the region δ 2.7–2.9 ppm is
due to methylene protons nearer to the nitrogen. The spec-
tra of 7–11 and 12 showed a singlet in the δ 9.6–10.1 ppm
which have been assigned to NH proton of piperidine and
morpholine. This signal was not found in 1–6 which con-
increasing energy. The bands around 709–656 nm are as-
1
signed to A1g
→
1T1g. The bands around 476–359 nm
have been assigned to charge transfer transitions arising
from the excitation of electron from the metal t2g level to
the empty molecular orbitals derived from ␲ level of the
∗
ligands [15,27–29]. The other high intensity bands in the
329–290 nm region were characterized by ligand-centered
(LC) bands and has been designated as ␲–␲∗ and n–␲∗ tran-
sitions for the electrons localized on the azomethine group
of the Schiff base. The pattern of the electronic spectra of
all the complexes indicated the presence of an octahedral
environment around ruthenium(II) ion, similar to that of
other ruthenium(II) octahedral complexes [15,27,28].
3.3. 1H NMR spectra
The 1H NMR spectra of all the complexes were recorded
to confirm the binding of Schiff bases to the ruthenium ion
(Table 3). Spectra of all the complexes showed a singlet in
the region δ 8.6–8.9 ppm, which has been assigned to azome-
Fig. 3. 1H NMR spectrum of [RuCl(CO)(PPh3)2(Vanmet)].

K.N. Kumar, R. Ramesh / Spectrochimica Acta Part A 60 (2004) 2913–2918
2917
Table 4
Cyclic voltammetric data of Ru(II) carbonyl Schiff base complexes
Complexes
Metal based oxidation
Ru(III)/Ru(II)
Metal based reduction
Ru(II)/Ru(I)
Ligand based reduction
Epa (V)
Epc (V)
E1/2 (V)
ꢀEp (mV)
Epc (V)
Epc (V)
Epa (V)
E1/2 (V)
ꢀEp (mV)
1
2
3
4
5
6
7
8
9
0.93
0.94
0.80
0.96
0.98
0.93
0.80
0.91
0.80
0.82
0.92
0.93
0.86
0.87
0.86
0.90
0.91
0.86
0.87
0.83
0.87
0.89
0.86
0.86
0.80
0.91
0.83
0.93
0.95
0.90
0.84
0.87
0.84
0.86
0.89
0.90
70
70
60
70
70
70
70
80
70
70
60
70
−0.80
−0.79
−0.76
−0.69
−0.73
−0.73
−0.77
−0.76
−0.78
−0.75
−0.78
−0.76
−1.07
−0.96
−1.07
−1.07
−1.02
−1.05
−1.09
−1.08
−1.08
−1.05
−1.05
−1.07
−0.76
−0.76
−0.75
−0.72
−0.69
−0.73
−0.73
−0.74
−0.75
−0.75
−0.72
−0.74
−0.92
−0.86
−0.91
−0.90
−0.86
−0.89
−0.91
−0.91
−0.92
−0.90
−0.89
−0.91
−310
−200
−320
−350
−330
−320
−360
−340
−330
−300
−330
−330
10
11
12
Note: Supporting electrolyte, [NBu4]ClO4 (0.05 mol); all potentials are referenced to Ag/AgCl; Ef = 0.5(Epa + Epc), where Epa and Epc are anodic and
cathodic peak potentials, respectively; scan rate, 100 mV s−1
.
firms the absence of nitrogen bases in these complexes. A
sharp singlet observed for OH protons for all the ligands in
the region 13.0 ppm was disappeared in all the complexes.
reversible or approaches reversibility and the mass transfer
is limited. The electron donating group (OCH3) ability of
the substituent in the phenyl ring of the Schiff bases favored
oxidation of Ru2+ to Ru3+ [31]:
3.4. Electrochemical study
[RuIICl(CO)(PPh3)(B)(L)]
ꢀ [RuIIICl(CO)(PPh3)(B)(L)]+ + e−
(1)
The electrochemical properties of all the complexes were
studied in acetonitrile solution by cyclic voltammetry and
voltammetric data are presented in (Table 4). Cyclic voltam-
mogram of all the complexes (1 × 10−3 M) exhibit a re-
versible oxidation and an irreversible reduction peaks at the
scan rate of 100 mV s−1. Representative cyclic voltammo-
gram of 5 is shown in Fig. 4. All the complexes showed
well defined waves in the range 0.80–0.95 V (RuIII/RuII) and
−0.69 to–0.80 V (RuII/RuI) versus Ag/AgCl. The oxidation
processes are reversible with peak-to-peak separation (ꢀEp)
values ranging from 60 to 80 mV, close to that anticipated
for a Nernstian One-electron process [33,34]. For scan rate
(SR) 100 mV s−1, the ratio ip/SR (ip = peak current) was
approximately one, the peak separation being independent
of the scan rate. This indicates that the electron transfer is
The reason for irreversibility observed for reduction of all
the complexes may be due to short lived reduced state of the
metal ion [35] or due to oxidative degradation [36] of the
ligands. Further, a quasi-reversible ligand based reduction
peak is observed in the range −0.86 to −0.92 V in all the
complexes, which corresponds to reduction of azomethine
=
(C N) moiety of the Schiff base ligands and the reductions
occurred at more negative values:
[RuIICl(CO)(PPh3)(B)(L)] + e−
ꢀ [RuIICl(CO)(PPh3)(B)(L)]−
(2)
It has also been observed from the electrochemical data
that there is little variation in the redox potentials due to re-
placement of triphenylphosphine by pyridine or piperidine or
morpholine [14]. Hence, it is inferred from the electrochem-
ical data that the present ligand system is ideally suitable
for stabilizing the higher oxidation state of ruthenium ion.
3.5. Antibacterial activity
The in vitro antibacterial screening of the ligands Vanmet,
Vanampy and Vanchx and their ruthenium(II) complexes has
been carried out against gram-positive bacteria, viz., S. au-
reus (209p) and gram-negative E. coli (ESS 2231) using agar
medium and the test solutions were prepared in DMSO. It
has been observed from the antibacterial screening studies
that the ruthenium chelates have higher activity than the cor-
responding free ligands against the same microorganisms
Fig. 4. Cyclic voltammogram of [RuCl(CO)(PPh3)(py)(Vanampy)].

2918
K.N. Kumar, R. Ramesh / Spectrochimica Acta Part A 60 (2004) 2913–2918
Table 5
[2] P.K. Battacharya, Proc. Ind. Acad. Sci. (Chem. Sci.) 102 (1990)
247.
Antibacterial activities of Ru(II) carbonyl Schiff base complexes
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Complexes
Diameter of inhibition zone (mm)
S. aureus (209p)
E. coli (ESS 2231)
Vanmet
Vanampy
Vanchx
1
2
3
4
5
6
7
8
9
10
11
12
–
–
–
–
–
–
10
12
11
10
11
10
10
9
11
11
10
10
9
9
10
9
9
10
9
10
10
10
11
12
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Symbol “–” denotes no activity.
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Acknowledgements
We express sincere thanks to Prof. P.R. Athappan, School
of Chemistry, Madurai Kamaraj University, for providing
cyclic voltammetric facility. The authors also thank Nicholas
Piramal India Ltd., Mumbai, for the evaluation of biological
studies.
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