Synthesis, and characterization of ruthenium(II) polypyridyl complexes containing α-amino acids and its DNA binding behavior

Article abstract of DOI:10.1016/j.jorganchem.2009.07.014

Reactivity of the ruthenium complexes [Ru(κ³-tptz)(PPh₃)Cl₂] (1) and [Ru(κ³-tpy)(PPh₃)Cl₂] (2) [tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine; tpy = 2,2′:6′,2″-terpyridine] with several α-ami

Full text of DOI:10.1016/j.jorganchem.2009.07.014

Journal of Organometallic Chemistry 694 (2009) 3570–3579
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis, and characterization of ruthenium(II) polypyridyl complexes
containing a-amino acids and its DNA binding behavior
Prashant Kumar a, Ashish Kumar Singh a, Jitendra Kumar Saxena b, Daya Shankar Pandey a,
*
a Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221 005, UP, India
b Division of Biochemistry, Central Drug Research Institute, Chattar Manzil, P.O. Box 173, Lucknow 226 001, UP, India
a r t i c l e i n f o
a b s t r a c t
3-tptz)(PPh3)Cl2] (1) and [Ru(
j
3-tpy)(PPh3)Cl2] (2)
-amino acids [gly-
cine (gly); leucine (leu); isoleucine (isoleu); valine (val); tyrosine (tyr); proline (pro) and phenylalanine
Article history:
Received 6 June 2009
Received in revised form 1 July 2009
Accepted 6 July 2009
Available online 3 August 2009
Reactivity of the ruthenium complexes [Ru(
j
[tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine; tpy = 2,20:60,200-terpyridine] with several
a
(phe)] have been investigated. Cationic complexes with the general formulations [Ru(j
3-L)(j2-L00)(PPh3)]+
(L = tptz or tpy; L00 = gly, leu, isoleu, val, tyr, pro, and phe] have been isolated as tetrafluoroborate salts.
The resulting complexes have been thoroughly characterized by analytical, spectral and electrochemical
Keywords:
Ruthenium complexes
Polypyridyl
Topoisomerase
Heme polymerase
studies. Molecular structures of the representative complexes [Ru(
tpy)(leu)(PPh3)]BF4 (10) and [Ru(
3-tpy)(tyr)(PPh3)]BF4 (13) have been determined crystallographically.
The complexes [Ru(
BF4 (10) [Ru(
j -
3-tptz)(val)(PPh3)]BF4 (6), [Ru(j3
j
j
3-tptz)(leu)(PPh3)]BF4 (4), [Ru( 3-tptz)(val)(PPh3)]BF4 (6), [Ru( 3-tpy)(leu)(PPh3)]-
j j
j
3-tpy)(tyr)(PPh3)] BF4ꢀ3H2O (13) exhibited DNA binding behavior and acted as mild Topo
II inhibitors (10–40%). The complexes also inhibited heme polymerase activity of the malarial parasite
Plasmodium yoelii lysate.
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
containing
a-amino acids has been of significant interest [19,20].
The synthesis of complexes containing
a-amino acids has become
Ruthenium(II) polypyridyl complexes have drawn immense re-
search interest over past couple of decades due to their interesting
photophysical and photochemical properties that makes them
potentially useful in diverse areas [1–5]. Owing to intense MLCT
luminescence, excited state redox properties and ability to bind
DNA, Ru(II) polypyridyl complexes serve as promising DNA probes
[6,7]. Ligands present in the complexes play an important role in
determining and improving light emitting and electron-transfer
performances [8–10]. Ru(II) complexes may bind DNA through
non-covalent interactions such as electrostatic binding, groove
binding and intercalation [11,12]. Many of the complexes bind
DNA through a combination of binding modes that is dependent
on the structural characteristics of compounds. An understanding
of how the metal complexes bind DNA will not only pave the
way to understand fundamentals of these interactions but also,
about the variety of potential applications [13–16].
increasingly important due to their significant role in biological
fields [19,20]. The amino acids are known to bind metal ions as a
bi-dentate N,O-donor ligand forming five membered chelate rings
after dissociation of the acidic proton [17,18]. It is noteworthy that
while the chemistry of many transition metal complexes contain-
ing amino acids has been studied in detail, the chemistry of ruthe-
nium complexes has received only little attention [21,22].
Furthermore, DNA topoisomerases which are intricately involved
in maintaining the topographic structure of DNA transcription
and mitosis, have been identified as an important biochemical
target in cancer chemotherapy, microbial infections and in the
development of anti-filarial compounds [23–25]. Recently, ruthe-
nium(II) complexes based on polypyridyl and pyridyl-azine ligands
as inhibitors of Topo II activity were reported [23–26]. It has been
shown that the inhibition percentage largely depends on nature of
the complexes, ligands involved and the presence of uncoordinated
sites on polypyridyl ligands.
It has been observed that the complexes [Ru(j
3-L)(EPh3)Cl2]
(E = P, As; L = tpy and tptz) containing both the EPh3 and polypyr-
idyl ligands behave as good precursors and act as metallo-ligands
in the syntheses of homo-/hetero-bimetallic complexes [17,18].
Also, these behave as inhibitors of Topo II and heme polymerase
activity. Further, the chemistry of transition metal complexes
In addition, the complexes containing polypyridyl ligands like
tptz or tpy and
a-amino acids along with EPh3 are yet to be
explored. It was felt that incorporation of bio-relevant ligands like
amino acids in the complexes may lead to significant changes
in their properties. With this aim we have synthesized new
cationic complexes [Ru(
and L0 =
-amino acids [glycine (gly); leucine (leu); isoleucine (iso-
leu); valine (val); tyrosine (tyr); proline (pro) and phenylalanine
j
3-L)(j2-O,N-L0)(PPh3)]+ [(L = tptz or tpy
a
* Corresponding author. Tel.: +91 542 2307321 105.
E-mail address: dspbhu@bhu.ac.in (D.S. Pandey).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.07.014

P. Kumar et al. / Journal of Organometallic Chemistry 694 (2009) 3570–3579
3571
(phe)] containing amino acids. In this paper we report reproducible
synthesis of the mixed-ligand polypyridyl ruthenium complexes
imparting 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), 2,20:60,200-ter-
Infrared spectra of [3] BF4–[8]BF4 exhibited sharp and strong
bands at ꢁ1630 and ꢁ1390 cmꢂ1, while those of [9] BF4–[15]BF4
showed bands at ꢁ1610 and ꢁ1380 cmꢂ1, respectively. These
pyridine (tpy) and
a-amino acids. We also describe herein inhibi-
bands has been assigned to mas(CO) and ms(CO) stretching vibra-
tory activity of the complexes on DNA–Topoisomerase II of the
filarial parasite S. cervi and b-hematin/hemozoin formation in the
presence of Plasmodium yoelii lysate.
tions of the coordinated carboxylate group [27]. The bands
at ꢁ3300 cmꢂ1 has been assigned to N–H stretching vibrations
m
(N–H). The vibrations due to counter ion BF4ꢂ and PF6ꢂ appeared
at ꢁ1055 and 840 cmꢂ1 in the IR spectra of respective complexes
[28,29].
2. Results and discussion
The 1H and 31P NMR spectra of complexes were recorded in
CDCl3 and spectral data are summarized in the experimental sec-
tion. Shift in the position of signals associated with protons of tptz
and tpy, suggested coordination of amino acids to the metal centre
ruthenium in bi-dentate fashion [26]. The position and integrated
intensity of various signals corresponding to tptz corroborated to
The reactions of [Ru(
with -amino acids (glycine, leucine, isoleucine, valine, tyrosine,
j
3-L)(EPh3)Cl2] (E = P, As; L = tpy or tptz)
a
proline and phenylalanine) in methanol in presence of a base
(KOH) under refluxing conditions afforded cationic complexes
[Ru(
[Ru(
[Ru(
[Ru(
j
j
j
j
3-tptz)(gly)(PPh3)]BF4 (3), [Ru( 3-tptz)(leu)(PPh3)]BF4 (4),
j
a system involving coordination of tptz with ruthenium in j
3-man-
3-tptz)(isoleu)(PPh3)]BF4 (5), [Ru(
3-tptz)(tyr)(PPh3)]BF4 (7), [Ru(
3-tpy)(gly)(PPh3)]BF4 (9), [Ru(
j
3-tptz)(val)(PPh3)]BF4 (6),
3-tptz)(pro)(PPh3)]BF4 (8),
ner with two magnetically equivalent coordinated pyridyl and one
uncoordinated pyridyl rings [30]. Well resolved signals associated
with coordinated amino acids appeared in 1H NMR spectra of the
respective complexes. The aromatic protons (12) corresponding
to pyridyl rings of tptz in [3] BF4–[8] BF4, resonated in the range
d 7.48–8.95 ppm. Further, this region displayed overlapping signals
arising from protons of the uncoordinated pyridyl ring. The aro-
matic protons of triphenylphosphine in the complexes [3–15] BF4
resonated at ꢁd 7.02–7.32 ppm as a broad multiplet.
j
j
j
3-tpy)(leu)(PPh3)]BF4 (10),
[Ruj
3-tpy)(isoleu)PPh3)]BF4 (11), [Ru(
3-tpy)(val)(PPh3)]BF4 (12),
3-tpy)(pro)(PPh3)]BF4 (14)
[Ru(j
3-tpy)(tyr)(PPh3)]BF4 (13), [Ru(
j
and [Ru(
j
3-tpy)(phe)(PPh3)]BF4 (15) in excellent yields. The
complexes have been isolated as tetrafluoroborate salt. A sim-
ple scheme showing syntheses of the complexes is depicted in
Scheme 1.
The complexes have been characterized by satisfactory elemen-
tal analyses, spectral and electrochemical studies. Analytical data
of the complexes under study conformed well to their respective
formulations. Information about composition of the complexes
has also been obtained by FAB-MS spectral studies. FAB-MS spectra
of representative complexes 7 and 13 are shown in Fig. 1, and
resulting data with their assignments are recorded in the Section 3.
In the 1H NMR spectrum of complex 15 signals corresponding to
phenyl ring protons (two) of phenylalanine merged with broad
multiplet associated with aromatic protons of PPh3. Similar obser-
vation has been made in the case of [7] BF4 and [13] BF4, where
phenyl ring protons of the tyrosine resonated as doublet at d
6.88 and 6.57 and d 6.85 and 6.54 ppm, respectively. Main feature
N
N
N
N
N
N
Am
ino
=
aci
ds
N
O
N
Me
OH
,
N
Cl
O
Ru
N
N
N
Ru
N
Ph3P
Cl
Ph3P
N
(1)
(3-8)
[ L-glycine (3),Leucine(4),Isoleucine(5),
Valine(6),Tyrocine(7), Proline(8)]
=
N
O
N
A
min
o a
cid
=
s
N
N
O
O
Cl
N
Ru
N
N
N
Ru
Me
OH
,
Ph3P
Ph3P
N
Cl
(9-15)
(2)
[ L-Glycine(9), Leucine (10),Isoleucine(11), Valine(12),
Tyrocine(13), Proline(14), Phenylalanine(15)]
=
N
O
Scheme 1.

3572
P. Kumar et al. / Journal of Organometallic Chemistry 694 (2009) 3570–3579
Fig. 1. FAB-MS spectra with peak assignment for 7 (a) and 13 (b).
of the 1H NMR spectra of all the complexes containing amino acids
is the presence of multiplets and doublets in low-frequency side
for methyl, methylene, methene and coordinated NH2 protons of
the amino acids. In 31P{1H} NMR spectra of the complexes [3]
BF4–[8] BF4, the 31P nuclei of coordinated PPh3 resonated as a sharp
singlet in the range d 40.77–39.01 ppm while, it resonated at ꢁd
45.38–43.30 ppm and for [9] BF4 to [15] BF4, as sharp singlet in
the high-frequency side in comparison to that in the tptz contain-
ing complexes.
The complexes under study displayed absorptions in the visible
and ultraviolet region. UV–Visible spectral data of the complexes
3–15 are recorded in experimental section and representative
spectra for [3] BF4–[8] BF4 and [9] BF4–[15] BF4 is depicted in
Fig. 2a and b. Electronic spectra of these complexes exhibited in-
tense absorptions in the UV region due to
p–p* intra-ligand
charge-transfer (ILCT) transitions, together with broad dRu(II) to
pꢃðLÞ pyridyl MLCT bands in the visible region. On the basis of its po-
sition and intensity the lowest energy absorption bands at
ꢁ490 nm in the spectra of the complexes [3]BF4–[8]BF4 containing
amino acids have been assigned to dp(Ru)
?
pꢃðtptzÞ MLCT transi-
tions, while the one in high energy side at ꢁ350, 276–297 and
*
ꢁ240 nm to the intra-ligand
p
?
p
/n ?
p*
transitions. Red
shifting in the position of MLCT bands in the complexes containing
amino acids may be attributed to greater back bonding.
p
Further, the complexes containing tpy displayed a red shift in
the position of lowest energy absorption bands at ꢁ500 nm for
[9] BF4–[15] BF4 in comparison to the tptz complexes. It may be
*
attributed to the greater stabilization of
p
orbitals on tpy ligand
relative to tptz. The main feature of the UV spectra of the com-
plexes containing amino acids is a decrease in the absorbance with
a decrease in molecular weight of the amino acids. The intense
absorption bands in the ultraviolet region has been assigned to in-
tra-ligand transitions The absorptions in the visible region are
rather weak and are probably due to ligand-field transitions
[31,32].
Electrochemical properties of the complexes 3, 5, and 13 were
followed by cyclic voltammetry in acetonitrile solution (0.1 M
TBAP) at room temperature (scan rate 100 mV/s). Resulting data
is summarized in Table 1 and selected voltammograms are shown
Fig. 2. UV–Vis spectra molecular complexes 3–8 (a) and 9–15 (b) in dichloro-
methane.

P. Kumar et al. / Journal of Organometallic Chemistry 694 (2009) 3570–3579
3573
Table 1
Cyclic voltammetric data for mononuclear ruthenium(II) complexes.
E0ox, V (
DE, mV)
Complexes
E0ox, V (
D
E, mV)
3
5
13
0.37(76)
0.525(49)
0.530(58)
ꢂ1.07, ꢂ1.86
ꢂ1.09, ꢂ1.79
ꢂ1.06, ꢂ1.61
in Fig. S4. The complexes 3, 5, and 13 exhibited an oxidative poten-
tial in the range 0.30–0.55 V vs. glassy carbon electrode, which is
assigned to Ru(II)/Ru(III) oxidation. The peak-to-peak separation
(D
Ep) of ꢁ100 mV and the fact that anodic peak current (ipa) is al-
most equal to the cathodic peak current (ipc), suggested for a
reversible electron-transfer process. One-electron nature of the
oxidation was established by comparing its current height with
that of standard ferrocene/ferrocenium couple under identical
experimental conditions. The magnitudes of the oxidation poten-
tial indicate that the bivalent state of ruthenium is comfortable
in this N, O and P coordination sphere. Further, Ru(II)/Ru(III) oxida-
tion potential in the complexes [Ru(
(L = tptz, tpy; L00 = -amino acids) is lower than that in [Ru(j3
L)(PPh3)Cl2] (0.70 V). It suggested that the anions resulting from
-amino acids are better stabilizers of the trivalent state of ruthe-
j
3-L)(j2-L00)(PPh3)]BF4,
a
-
a
nium compared to tptz/tpy, An interesting feature of the cyclic vol-
tammetry of complexes 3, 5, and 13 is an increase in the positive
potential as the molecular weight of amino acid increases. Succes-
sive two-electron reductions were displayed by all the complexes,
at ꢁ1.07–1.09 and 1.69–1.86 V in case of the tptz and 0.56–0.77
and 1.11–1.69 V in case of tpy complexes. For both the tptz Ru2+
and tpy Ru2+ series, coordinated ligands with a higher number of
the nitrogen atoms result in more anodic oxidation potentials (Ta-
ble 1). It is consistent with the earlier studies showing that as li-
gand becomes more electron deficient there is concomitant
Fig. 3. Molecular structure of 6.
lowering of the ligand LUMO resulting in an enhanced
p acceptor
properties and more anodic RuIII/II oxidation couples [32]. The first
ligand-based reduction also reflects the relative electron deficiency
within in a series with couples becoming more facile as number of
the nitrogen atom increases in the ligand.
Molecular structures of the complexes 6, 10 and 13 have been
determined crystallographically (Figs. 3–5). Details about data col-
lection, solution and refinement are recorded in Table 2 and impor-
tant geometrical parameters are summarized in Table 3.
A
common structural feature of the complexes 6, 10, and 13 is the
arrangement of various ligands about the metal centre. In these
complexes two of the coordination sites about the metal centre
are occupied by N7–O1, N4–O1, N2–O1 from the amino acids,
one position by P1 of the coordinated PPh3 and along with tptz/
tpy coordinated in
j
3-manner. The angles N1–Ru–N2 and N2–
Ru–N3 6 and 13 are essentially equal and are 79.07(19) (6),
78.70(18) (6), 79.9(3) (13) and 79.4(2)° (13), whereas in 10 these
are 79.3(3) and 79.4(3)°, respectively. It suggested an inward bend-
ing of the coordinated pyridyl group and it may be the reason for
observed octahedral distortion [24]. Further, the distortion from
regular octahedral geometry is supported by intra-ligand trans an-
gles N1–Ru–N3 in 6, 13, and 10 (Table 3). The Ru1 to central tri-
azine nitrogen bond length Ru1–N2 in 6 is 1.936(4) Å, which is
shorter than Ru1 to coordinated pyridyl nitrogen bond lengths
Ru1–N1 [2.101(5) Å] and Ru1–N3 [2.090(5) Å]. The Ru–N bond
lengths Ru1–N2, Ru1–N1 and Ru1–N3 are 2.12(2), 2.167(19), and
1.94(2) Å in 10, while these are 1.951(5), 2.075(6) and 2.072(6) Å,
Fig. 4. Molecular structure of 10.
C–Hꢀꢀꢀ
p interactions. These types of interactions play significant
role in building huge supramolecular moieties [34–36]. The matri-
ces for various weak interactions are recorded in Table S1 and the
motifs resulting thereof are depicted in Figs. S5–S7. Weak interac-
tion studies in 6 displayed face to face C–Hꢀꢀꢀ
p interactions leading
to formation of straight chains, which are interlinked to another
chain through C–HꢀꢀꢀN interactions. Interestingly, in 13 parallelo-
gram-shaped water hexamers aggregated into tape like infinite
water chain (Fig. 6). On one side of the water chain water molecules
(O1w, O2w, O3w) are connected into infinite one dimensional
water chain in ABC fashion through strong hydrogen-bonding
interactions. The OꢀꢀꢀO distances are in the range of 2.792–2.892 Å
[O1wꢀꢀꢀO2w(2.823); O2wꢀꢀꢀO3w(2.892); O3wꢀꢀꢀO1w(2.792)], and
in 13. The Ru–N bond distances are consistent with
j
3-coordina-
tion of the tptz/tpy and comparable to those in other RuII tptz/
tpy complexes [24,25,33]. The uncoordinated pyridyl ring in 6 is
inclined at 18.6° from the central triazine ring plane.
Crystal structures of 6, 13, and 10 revealed the presence of
extensive intra- and intermolecular C–HꢀꢀꢀX (X = N, Cl, and F) and

3574
P. Kumar et al. / Journal of Organometallic Chemistry 694 (2009) 3570–3579
processes are significantly controlled by Topo II [42]. Anti-Topo II
agents control Topo II activity either by trapping Topo II-DNA com-
plex or acting as Topo II inhibitors [43]. DNA–metal interactions
provided important informations about inhibitory effect of the me-
tal complexes on Topo II activity of the filarial parasite. Gel electro-
phoresis shows that the ruthenium–tptz/tpy complexes imparting
various a-amino acids (Figs. 7–9) display different modes of inter-
action with Topo II of S. cervi. Gel mobility assays of ruthenium(II)
complexes (4, 6, 10 and 13) were examined at different concentra-
tion levels. Observed complex formation with the ruthenium–tptz/
tpy complexes containing various
a-amino acid series of com-
plexes indicated that the complexes bind to Topo II-DNA complex,
or DNA, or the enzyme. However, closely related complexes
[Ru(j j
3-tptz)Cl2(PPh3)], and Ru( 3-tpy)(PPh3)Cl2], where both the
labile chloro groups are replaced by amino acids, leads to relaxa-
tion of supercoiled DNA, with an inhibition percentage of
10–40%, where bulky PPh3 and amino acid group destabilizes
interaction with DNA strand. These results are consistent with
other reports [44–47].
Fig. 5. Molecular structure of 13.
The complexes 4, 6, 10 and 13 exhibited strong complex forma-
tion at concentrations of 40 and 20
DNA topoisomerase of the filarial parasite (Fig. 7). The effect of
these complexes at 10, 5 and 0.2 g was also measured (Figs. 8
lg per reaction mixture with
Table 2
Crystal data for complexes 6, 10 and 13.
l
Complexes
6
10
13
and 9). It was found that at these concentrations also, it showed
complex formation as indicated by presence of DNA in the well.
Chemical
formula
Formula weight
Color, habit
Crystal size
(mm)
Space group
Cryst system
a (Å)
C41H35O2F4N7PBF4Ru C42H47BF4N4O3PRu C39H38ClN4O2PRu
Further, reduction of the concentration to 0.2
in the complex intensity.
lg led to a decrease
876.61
874.69
833.13
Dark red, block
0.33 ꢄ 0.27 ꢄ 0.21
Dark brown, block Dark red, block
Extensive scientific attention has been paid towards anomalous
morphology of Z-DNA and its involvement in gene expression and
recombination [48,49]. Transition of the B–Z DNA in presence of
complexes under study was followed spectrophotometrically.
Complexes4, 6, 10 and 13 were effective in causing conformational
changes in DNA structure from B–Z transition. All other complexes
also proved to have strong effect on DNA conversion (B–Z transi-
tion). The conformational changes in the structure of DNA from
0.38 ꢄ 0.34 ꢄ 0.31
0.36 ꢄ 0.34 ꢄ 0.31
ꢀ
P212121
Orthorhombic
12.5482(3)
14.3005(3)
21.5070(7)
90
P21
P212121
Orthorhombic
10.8288(9)
12.6184(10)
31.197(2)
90.00
Monoclinic
12.1446(16)
9.7376(12)
16.401(2)
90.00
b (Å)
c (Å)
a
(°)
b (°)
90
90
90
90
101.857(2)
90.00
c
(°)
B–Z form is evidenced by observed change in the ratio A295/A260
.
V (Å3)
3859.34(18)
4
4262.8(6)
4
1898.2(4)3
3
An increase in the ratio of A295/A260 from 0.18 (for free DNA) to
0.77(3), 0.66(6), 0.78(7) and 0.56(13) suggested destabilization of
the DNA helix. Further, condensation of calf thymus CT DNA in-
duced by the complexes was monitored spectrophotometrically
by UV-absorption ratio of A320/A260. Above mentioned Ru(II) com-
plexes showed enhancement in the absorption ratio at 320 nm
[50,51]. All the complexes were found to cause condensation of
Z
Dcalc (g cmꢂ3
)
1.509
1.363
2.218
l
(mmꢂ1
)
0.514
0.465
1.061
T (K)
Number of
reflections
Number of
parameters
R factor all
150(2)
6280
293(2)
10 528
293(2)
6877
517
519
464
DNA at 20 lg concentration. The condensation of DNA was moni-
0.0581
0.0441
0.0899
0.0727
0.0834
0.0674
R factor
[I > 2
tored by measuring increase in the value of absorption at 320 nm
[0.075 for free DNA to 0.38(4), 0.28(6), 0.45(10), and 0.53(13)].
The mononuclear ruthenium(II) polypyridyl complexes, 4, 6, 10,
and 13 also exhibited significant inhibitory effect on heme poly-
merase activity of P. yoelii lysate, which was studied by b-hematin
r(I)]
WR2
0.1261
0.1118
1.037
0.2585
0.2151
1.052
0.2109
0.1722
1.431
WR2 [I > 2
r
(I)]
Goodness-of-fit
(GOF)
formation [52]. The parent complex [Ru(j
3-tptz)Cl2(PPh3)] showed
94% inhibition of heme polymerase activity while the complexes 4,
6, 10, and 13 exhibited 50%, 50%, 54%, and 62% inhibition. The
anomalous behavior of above result could be attributed to an
increase in the steric hindrance by replacement of the chloro group
in [Ru(
metal centre. All the complexes formed complex with DNA or
hydrogen-bonded OꢀꢀꢀOꢀꢀꢀO angles ranges from
87.86°
(O2wꢀꢀꢀO3wꢀꢀꢀO1w) to 124.01° (O1wꢀꢀꢀO3wꢀꢀꢀO1w). Both the dis-
tances and angles are in the range reported in ice and water clusters
[37–39].
j
3-tptz)Cl2(PPh3)] and coordination of the amino acids to
Change in the electrophoretic mobility of plasmid DNA on aga-
rose gel is commonly taken as evidence for direct DNA–metal
interactions. Alteration of the DNA structure causes retardation
in the migration of supercoiled DNA and a slight increase in the
mobility of open circular DNA to a point where both forms comi-
grate. Interaction of the ruthenium(II) polypyridyl complexes con-
caused condensation of DNA at concentration 20
reaction mixture.
lg or above per
3. Experimental
taining
a-amino acids on Topo II activity of the filarial parasite S.
3.1. Materials and physical measurements
cervi was determined by enzyme-mediated supercoiled pBR322
relaxation assay [40,41]. Non-covalent interaction of protein with
DNA is the key step in topoisomerase II catalytic cycle. Under
physiological conditions, DNA replication repair, and transcription
Analytical grade chemicals were used through out. Solvents
were dried and distilled before use following the standard

P. Kumar et al. / Journal of Organometallic Chemistry 694 (2009) 3570–3579
3575
Table 3
Selected bond lengths and angles for complexes 6, 10 and 13.
Complex 6
Complex 10
Complex 13
Ru(1)–N(2)
Ru(1)–N(3)
Ru(1)–N(1)
Ru(1)–O(1)
Ru(1)–N(7)
Ru(1)–P(1)
1.936(4)
2.090(5)
2.101(5)
2.109(4)
Ru(1)–(2)
Ru(1)–N(3)
Ru(1)–N(1)
Ru(1)–O(1)
Ru(1)–N(4)
Ru(1)–P(1)
1.951(5)
2.072(6)
2.075(6)
2.108(5)
2.139(5)
2.3108(16)
79.9(3)
Ru(1)–N(2)
Ru(1)–N(3)
Ru(1)–N(1)
Ru(1)–O(1)
Ru(1)–N(4)
Ru(1)–P(1)
2.12(2)
1.94(2)
2.167(19)
2.116(17)
2.14(2)
2.317(5)
171.0(7)
79.4(3)
103.7(7)
81.1(8)
95.7(7)
160.1(8)
158.6(3)
78.1(6)
90.8(8)
88.6(7)
87.7(6)
92.7(6)
173.5(6)
96.0(4)
94.9(5)
2.151(5)
2.3204(16)
79.07(19)
78.70(18)
156.99(17)
172.16(17)
100.77(17)
100.44(16)
93.39(18)
87.9(2)
N(2)–Ru(1)–N(3)
N(1)–Ru(1)–N(2)
N(3)–Ru(1)–N(1)
N(2)–Ru(1)–O(1)
N(3)–Ru(1)–O(1)
N(1)–Ru(1)–O(1)
N(2)–Ru(1)–N(7)
N(3)–Ru(1)–N(7)
N(1)–Ru(1)–N(7)
O(1)–Ru(1)–N(7)
N(2)–Ru(1)–P(1)
N(3)–Ru(1)–P(1)
N(1)–Ru(1)–P(1)
O(1)–Ru(1)–P(1)
N(7)–Ru(1)–P(1)
N(2)–Ru(1)–N(3)
N(2)–Ru(1)–N(1)
N(3)–Ru(1)–N(1)
N(2)–Ru(1)–O(1)
N(3)–Ru(1)–O(1)
N(1)–Ru(1)–O(1)
N(2)–Ru(1)–N(4)
N(3)–Ru(1)–N(4)
N(1)–Ru(1)–N(4)
O(1)–Ru(1)–N(4)
N(2)–Ru(1)–P(1)
N(3)–Ru(1)–P(1)
N(1)–Ru(1)–P(1)
O(1)–Ru(1)–P(1)
N(4)–Ru(1)–P(1)
N(3)–Ru(1)–O(1)
N(3)–Ru(1)–N(2)
O(1)–Ru(1)–N(2)
N(3)–Ru(1)–N(4)
O(1)–Ru(1)–N(4)
N(2)–Ru(1)–N(4)
N(3)–Ru(1)–N(1)
O(1)–Ru(1)–N(1)
N(2)–Ru(1)–N(1)
N(4)–Ru(1)–N(1)
N(2)–Ru(1)–P(1)
N(3)–Ru(1)–P(1)
N(1}–Ru(1)–P(1)
O(1)–Ru(1)–P(1)
N(4)–Ru(1)–P(1)
79.4(2)
158.5(2)
170.81(18)
101.7(2)
97.84(19)
93.0(2)
85.4(2)
89.9(2)
78.1(2)
94.66(15)
94.12(16)
93.35(15)
94.25(12)
172.08(17)
87.5(2)
78.78(16)
93.34(13)
91.15(14)
95.98(14)
94.49(12)
172.90(13)
Fig. 6. (a) The two-dimensional sheet in complex 13 made up of one dimensional water chain. (b) Hydrogen-bonding motif of the self-assembled infinite water chain.
phenylalanine) were obtained from Aldrich Chemical Company,
Inc., USA and were used without further purifications. The precur-
sor complexes [Ru(
j j
3-tptz)Cl2(PPh3)], [Ru( 3-tpy)Cl2(PPh3)] and
[Ru(j
3-tpy)Cl3] were prepared and purified following the literature
procedures [26,54]. Various buffers were prepared in triply dis-
tilled de-ionized water. Calf thymus (CT) DNA and supercoiled
pBR322 DNA was procured from Sigma Chemical Co., St. Louis,
MO. Topoisomerase II (Topo II) isolated from the filarial parasite
S. cervi was partially purified following the literature procedures
[55,56].
Microanalytical data on the complexes were provided by the
microanalytical laboratory of the Sophisticated Analytical Instru-
ment Facility, Central Drug Research Institute, Lucknow. Infrared
spectra in nujol mull in the region 4000–400 cmꢂ1 and electronic
spectra were recorded on Shimadzu-8201 PC and Shimadzu UV-
1601 spectrophotometers, respectively. 1H and 31P{1H} NMR spec-
tra at room temperature were obtained on a Bruker DRX-300 NMR
machine. Electrochemical experiments were carried out in an
airtight single compartment cell using platinum as the counter
electrode, glassy carbon as the working electrode and Ag/Ag+
reference electrode on a CHI 620c electrochemical analyzer. Fast
Fig. 7. Gel mobility shift assay of S. cervi topoisomerase II by complexes 4, 6, 10 and
13 (20 g). Lane 1: pBR322 (0.25 g) alone; lane 2: pBR322 + S. cervi Topo II; lane 3:
4; lane 4: 6; lane 5: 10; lane 6: 13.
l
l
literature procedures [53]. Hydrated ruthenium (III) chloride,
2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), 2,20:60,200-terpyridine
(tpy), triphenylphosphine, ammonium tetrafluoroborate and ami-
no acids (glycine, leucine, isoleucine, valine, tyrosine, proline and

3576
P. Kumar et al. / Journal of Organometallic Chemistry 694 (2009) 3570–3579
Fig. 8. Gel mobility shift assay of S. cervi topoisomerase II by complexes 4, 6, 10 and 13 (20
lg, lane 3, 6, 9, and 12; 10 lg, lane 4, 7, 10, and 13; 5 lg, lane 5, 8, 11, 14). Lane 1:
pBR322 (0.25 g) alone; lane 2: pBR322 + S. cervi Topo II; lanes 3–5: 4; lanes 6–8: 6; lanes 9–11: 10, and lanes 12–14: 13.
l
(83%). Anal. Calc. for BC42F4H39N7O2PRu: C, 56.50; H, 4.37; N,
10.98. Found: C, 56.54; H, 4.40; N, 10.96%. 1H NMR (CDCl3, d,
ppm): 8.94 (d, 1H, J = 4.2 Hz), 8.72 (m, 5H), 7.96 (m, 3H), 7.55 (m,
3H), 7.32–7.13 (br. m, 15H, aromatic proton of PPh3), 3.22 (d, 1H,
J = 6.9 Hz), 2.0 (m, 1H), 1.39 (t, 2H, J = 10.2 Hz), 0.73 (dd, 6H,
J = 6.6 Hz), 2.98 (s, 2H of –NH2), 31P{1H} NMR (CDCl3, H3PO4, d,
ppm): 40.08 (s). IR (cmꢂ1, nujol):
1382 cmꢂ1 (COas) 1634 cmꢂ1. UV–Visible, kmax, nm (
(38 690), 281 (37 610), 350 (24 240), 487 (12 180).
m
(BF4ꢂ) 1060 cmꢂ1
,
m
(COs)
,
m
e): 240
3.2.3. Preparation of [Ru(
j
3-tptz)(isoleu)(PPh3)]BF4
The complex 5 was prepared from the reaction of [Ru(j3
tptz)Cl2(PPh3)] (0.746 g, 1.0 mmol) or [Ru(
3-tptz)(PPh3)2Cl]BF4,
5
-
j
with isoleucine(0.131 g, 1.0 mmol) in methanol following the pro-
cedure for complex 3. Yield: 0.605 g (81%). Anal. Calc. for
BC42F4H39N7O2PRu: C, 56.50; H, 4.37; N, 10.98. Found: C, 56.34;
H, 4.38; N, 10.94%. FAB-MS (obsd(calcd). rel intens, assignment):
Fig. 9. Gel mobility shift assay of S. cervi topoisomerase II by complexes 4, 6, 10 and
13 (0.2 g). Lane 1: pBR322 (0.25 g) alone; lane 2: pBR322 + S. cervi Topo II; lane 3:
4; lane 4: 6; lane 5: 10, and lane 6: 13.
l
l
m/z 806 (806), 60, [Ru(
j
3-tptz)(isoleucine)(PPh3)]+; 675 (675), 50
3-tptz)]2+ 1H NMR
[Ru( 414 (414), 80 [Ru(
j
3-tptz)(PPh3)]2+
;
j
.
atom bombardment (FAB) mass spectra were recorded on a JOEL
SX 102/ DA-6000 Mass spectrometer system using Xenon as the
FAB gas (6 kV, 10 mA). The accelerating voltage was 10 kV and
spectra were recorded at room temperature using m-nitrobenzyl
alcohol as the matrix.
(CDCl3, d, ppm): 8.95 (d, 1H, J = 5.4 Hz), 8.71 (m, 5H), 7.94 (m,
3H), 7.57 (m, 3H), 7.26–7.16 (br. m, 15H, PPh3), 3.50 (d, 1H,
J = 10.5 Hz), 3.17 (m, 1H), 2.26 (m, 2H), 0.87 (m, 6H), 31P{1H}
ꢂ
NMR (CDCl3, H3PO4, d, ppm): 39.88 (s). IR (cmꢂ1, nujol):
m
(BF4
)
,
1055 cmꢂ1
,
m
(COs) 1394 cmꢂ1
,
m
(COas) 1625 cmꢂ1. UV–Visible, kmax
nm ( ): 237 (36 400), 276 (27 170), 356 (9420), 491 (9940).
e
3.2. Syntheses
3.2.4. Preparation of [Ru(
j
3-tptz)(val)(PPh3)]BF4
The complex 6 was prepared from the reaction of [Ru(j3
tptz)Cl2(PPh3)] (0.746 g, 1.0 mmol) or [Ru(
6
3.2.1. Preparation of [Ru(
j
j
3-tptz)(gly)(PPh3)]BF4
3-tptz)Cl2(PPh3)] (0.746 g, 1.0 mmol) in
3
-
A suspension of [Ru(
j
3-tptz)(PPh3)2Cl]BF4,
methanol (25 ml) was treated with deprotonated solution of gly-
cine (0.075 g, 1.0 mmol) and heated under reflux for four hours.
Resulting purple solution was cooled to room temperature and
filtered to remove any solid residue. The filtrate was concentrated
under reduced pressure and a saturated solution of ammonium tet-
rafluoroborate dissolved in methanol was added to it and left for
slow crystallization in refrigerator. Slowly, a microcrystalline prod-
uct separated which was filtered, washed with diethyl ether and
dried in vacuo. Yield: 0.463 g (62%). Anal. Calc. for BC38F4H31N7O2-
PRu: C, 54.48; H, 3.70; N, 11.70. Found: C, 54.44; H, 3.72; N,
11.68%. 1H NMR (CDCl3, TMS, d, ppm): 8.58 (d, 2H, J = 5.1 Hz),
8.38 (d, 2H, J = 7.8 Hz), 8.25 (d, 2H, J = 8.1 Hz), 7.98 (t, 2H,
J = 7.8 Hz), 7.76 (t, 1H, J = 8.1 Hz), 7.54 (t, 2H, J = 6.3 Hz), 7.28–
with valine (0. 117 g, 1.0 mmol) in methanol under refluxing con-
ditions, following the procedure for complex 3. Yield: 0.559 g
(74%). Anal. Calc. for BC41F4H37N7O2PRu: C, 56.04; H, 4.21; N,
11.16. Found: C, 56.06; H, 4.26; N, 11.10%. 1H NMR (CDCl3, d,
ppm): 8.90 (d, 1H, J = 7.2 Hz), 8.70 (m, 5H), 7.95 (m, 3H), 7.54 (m,
3H), 7.26–7.16 (br. m, 15H, PPh3), 3.44 (d, 1H, J = 10.2 Hz), 3.13
(m, 1H), 0.86–0.76 (dd, 6H, J = 6.6 Hz), 31P{1H} NMR (CDCl3,
H3PO4, d, ppm): 40.21 (s). IR (cmꢂ1, nujol):
1395, (COas) 1633. UV–Visible, kmax, nm (
(34 780), 354 (10 770), 491 (12 080).
m m(COs)
(BF4ꢂ) 1053,
m
e): 240 (35 440), 279
3.2.5. Preparation of [Ru(
j
3-tptz)(tyr)(PPh3)]BF4
7
The complex 7 was prepared from the reaction of [Ru(j3
-
7.01 (br. m, 15H, PPh3), 3.96 (s, 2H), 2.92 (s, 2H of –NH2), 31P{1H}
tptz)Cl2(PPh3)] (0.746 g, 1.0 mmol) or [Ru(j
3-tptz)(PPh3)2Cl]BF4,
ꢂ
NMR (CDCl3, H3PO4, d, ppm): 39.18 (s). IR (cmꢂ1, nujol):
m
(BF4
)
,
1052 cmꢂ1
,
m
(COs) 1398 cmꢂ1
,
m
(COas) 1625 cmꢂ1. UV–Visible, kmax
with tyrosine (0.181 g, 1.0 mmol) in methanol under refluxing con-
ditions, following the procedure for complex 3. Yield: 0.586 g
(78%). Anal. Calc. for BC45F4H37N7O3PRu: C, 57.32; H, 3.92; N,
10.40. Found: C, 57.29; H, 3.95; N, 10.38%. FAB-MS (obsd(calcd).
nm ( ): 238 (29 030), 282 (24 980), 354 (8330), 491 (7990)
e
3.2.2. Preparation of [Ru(
j
3-tptz)(leu)(PPh3)]BF4
The complex 4 was prepared from the reaction of [Ru(j3
tptz)Cl2(PPh3)] (0.746 g, 1.0 mmol) or [Ru(
4
rel intens, assignment): m/z 856(856),70, [Ru(
sine)(PPh3)]+; 675 (675), 85 [Ru( 3-tptz)(PPh3)]2+; 414 (414),80
[Ru(
3-tptz)]2+ 1H NMR (CDCl3, d, ppm): 8.88 (d, 1H, J = 7.8 Hz),
8.70 (d, 1H, J = 7.8 Hz), 8.63 (d, 1H, J = 5.1 Hz), 8.55 (d, 1H,
j
3-tptz)(tyro-
-
3-tptz)(PPh3)2Cl]BF4,
j
j
j
.
with leucine (0.131 g, 1.0 mmol) in methanol under refluxing
conditions, following the procedure for complex 3. Yield: 0.624 g

P. Kumar et al. / Journal of Organometallic Chemistry 694 (2009) 3570–3579
3577
J = 7.8 Hz), 8.35 (d, 1H, J = 7.5 Hz), 7.92 (m, 4H), 7.65 (d, 1H,
ppm): 44.22 (s). IR (cmꢂ1, nujol):
1382 cmꢂ1 (COas) 1610 cmꢂ1. UV–Visible, kmax, nm (
(25 330), 275 (12 790), 312 (18 170), 449 (2630), 496 (3390).
m
(BF4ꢂ) 1060 cmꢂ1
,
m
(COs)
J = 5.1 Hz), 7.48 (m, 2H), 7.12–7.02 (br. m, 15H, PPh3), 6.88 (d,
2H, J = 7.8 Hz), 6.57 (d, 2H, J = 7.2 Hz), 3.56 (m, 1H, J = 7.8 Hz),
2.47 (m, 2H, J = 7.8 Hz), 31P{1H} NMR (CDCl3, H3PO4, d, ppm):
,
m
e): 235
39.01 (s). IR (cmꢂ1, nujol):
1621. UV–Visible, kmax, nm (
(16 000), 488 (17 500).
m
(BF4ꢂ) 1056,
m
(COs) 1396,
m
(COas)
3.2.10. Preparation of [Ru(
j
3-tpy)(val)(PPh3)]BF4 12
The complex 12 was prepared from the reaction of [Ru(j3
e
): 244 (39 060), 284 (39 170), 351
-
tpy)Cl2(PPh3)] (669 mg, 1.0 mmol) with valine (117 mg, 1 mmol)
in methanol under refluxing condition, following the procedure
for complex 3. Yield: 0.537 g (80%). Anal. Calc. for BC38F4H36N4O2-
PRu: C, 57.07; H, 4.50; N, 7.00. Found: C, 57.04; H, 4.54; N, 6.98%.
1H NMR (CDCl3, d, ppm): 8.62 (d, 1H, J = 5.1 Hz), 8.55 (d, 1H,
J = 4.8 Hz), 7.80 (m, 7H), 7.57 (t, 2H, J = 8.1 Hz), 7.29–7.09 (br. m,
15H, PPh3), 3.10 (d, 1H, J = 6.7 Hz), 2.17 (m, 1H), 0.87 (d, 3H of
3.2.6. Preparation of [Ru(
The complex 2f was prepared from the reaction of [Ru(j3
tptz)Cl2(PPh3)] (0.746 g, 1.0 mmol) or [Ru(
3-tptz)(PPh3)2Cl]BF4,
j 8
3-tptz)(pro)(PPh3)]BF4
-
j
with proline (0.115 g, 1.0 mmol) in methanol under refluxing con-
ditions following the procedure for complex 3. Yield: 0.613 g (82%).
Anal. Calc. for BC41F4H36N7O2PRu: C, 56.16; H, 4.11; N, 11.19.
Found: C, 56.14; H 4.15,; N, 11.22%. 1H NMR (CDCl3, d, ppm):
8.94 (d, 1H, J = 4.2 Hz), 8.72 (m, 5H), 7.98 (m, 3H), 7.54 (m, 3H),
7.26–7.12 (br. m, 15H, PPh3), 3.76 (t, 1H, J = 8.4 Hz), 2.19 (t, 2H,
J = 7.2 Hz), 1.45 (m, 4H), 31P{1H} NMR (CDCl3, H3PO4,d): 39.32 (s)
i
iPr, J = 7.2 Hz), 0.72 (d, 3H of Pr, J = 6.9 Hz), 31P{1H} NMR (CDCl3,
H3PO4, d, ppm): 43.67 (s). IR (cmꢂ1, nujol):
m
m ,
(BF4ꢂ) 1062 cmꢂ1
(COs) 1379 cmꢂ1
, m . UV–Visible, kmax, nm
(COas) 1610 cmꢂ1
(e):240 (37 500), 276 (23 050), 314 (31 200), 454 (426).
ppm. IR (cmꢂ1, nujol):
(COas) 1639 cmꢂ1. UV–Visible, kmax, nm (
(35 160), 358 (12 910), 495 (14 860).
m
(BF4ꢂ) 1048 cmꢂ1
,
m
(COs) 1399 cmꢂ1
,
3.2.11. Preparation of [Ru(
j
3-tpy)(tyr)(PPh3)]BF4.3H2O 13
The complex 13 was prepared from the reaction of [Ru(j3
-
m
e): 240 (37 680), 279
tpy)Cl2(PPh3)] (0.669 g, 1.0 mmol) with tyrosine (0.181 g,
1.0 mmol) in methanol under refluxing conditions following the
procedure for complex 3. Yield: 0.447 g (67%). Anal. Calc. for
BC48F4H36N4O4PRu: C, 60.58; H, 3.81; N, 5.89. Found: C, 60.54; H,
3.84; N, 5.84%. FAB-MS(obsd(calcd). rel intens, assignment): m/z
3.2.7. Preparation of [Ru(
j
3-tpy)(gly)(PPh3)]BF4
9
The complex 9 was prepared from the reaction of [Ru(j3
-
tpy)Cl2(PPh3)] (0.669 g, 1.0 mmol) with glycine (0.075 g, 1.0 mmol)
in methanol under refluxing conditions, following the procedure
for complex 3. Yield: 0.423 g (63%). Anal. Calc. for BC35F4H30N4O2-
PRu: C, 55.40; H, 3.96; N, 7.39. Found: C, 55.37; H, 3.98; N, 7.34%.
1H NMR (DMSO, d, ppm): 8.54 (d, 2H, J = 5.1 Hz), 8.30 (d, 2H,
J = 7.8 Hz), 8.15 (d, 2H, J = 8.1 Hz), 7.95 (t, 2H, J = 7.8 Hz), 7.72 (t,
1H, J = 8.1 Hz), 7.54 (t, 2H, J = 6.3 Hz), 7.28–7.01(br. m, 15H,
PPh3), 3.96 (s, 2H), 2.93 (s, 2H of ꢂNH2), 31P{1H} NMR (DMSO,
777 (777), 70 [Ru(
j
3-tpy)(tyrosine)(PPh3)]+; 596 (596), 85
2+
[Ru(j
3-tpy)(tyrosine)(PPh3)];]2+; 334 (334), 80 [Ru(
j
3-tpy)]
.
1H
NMR (Acetone, d, ppm): 8.75 (d, 1H, J = 5.4 Hz), 8.30 (d, 1H,
J = 5.4 Hz), 8.21 (t, 2H, J = 7.8 Hz), 8.06 (t, 2H, J = 5.4 Hz), 7.94 (m,
2H), 7.72 (t, 1H, J = 8.1 Hz), 7.55 (t, 1H, J = 6.6 Hz), 7.42 (t, 1H,
J = 5.7 Hz), 7.31–7.15 (br. m, 15H, PPh3), 6.85 (d, 2H, J = 8.4 Hz),
6.54 (d, 2H, J = 8.4 Hz), 4.12 (s, 2H, J = 6.3 Hz), 3.38 (d, 2H,
H3PO4, d, ppm): 45.16 (s). IR (cmꢂ1, nujol):
m
(BF4ꢂ) 1059 cmꢂ1
,
J = 6.6 Hz), 31P{1H} NMR (Acetone, H3PO4, d, ppm): 45.38 (s). IR
ꢂ
m
(COs) 1404 cmꢂ1
,
m
(COas) 1612 cmꢂ1. UV–Visible, kmax, nm (
e
):
(cmꢂ1
,
nujol):
m
(BF4
)
1060 cmꢂ1
,
m
(COs) 1389 cmꢂ1
,
m
(COas)
): 241 (38 600), 276 (32 940),
312 (37 820), 453 (6760), 500 (9500).
236 (27 720), 275 (14 040), 312 (20 990), 450 (2850), 500 (3940).
1602 cmꢂ1. UV–Visible, kmax, nm (
e
3.2.8. Preparation of [Ru(
j
3-tpy)(leu)(PPh3)]BF4 10
The complex 10 was prepared from the reaction of [Ru(j3
-
3.2.12. Preparation of [Ru(
j
3-tpy)(pro)(PPh3)]BF4 14
The complex 14 was prepared from the reaction of [Ru(j3
tpy)Cl2(PPh3)] (0.669 g, 1.0 mmol) with leucine (0.131 g, 1.0 mmol)
in methanol under refluxing condition, following the procedure for
complex 3. Yield: 0.494 g (73%). Anal. Calc. for BC39F4H38N4O2PRu:
C, 57.56; H, 4.67; N, 6.89. Found: C, 57.51; H, 4.63; N, 6.88%. FAB-
-
tpy)Cl2(PPh3)] (0.669 g, 1.0 mmol) with proline (0.115 g, 1.0 mmol)
in methanol under refluxing conditions following the procedure for
complex 3. Yield: 0.518 g (77%). Anal. Calc. for BC38F4H35N4O2PRu:
C, 57.21; H, 4.39; N, 7.03. Found: C, 57.19; H, 4.36; N, 6.98%. 1H
NMR (CDCl3, d, ppm): 8.65 (d, 1H, J = 5.4 Hz), 8.50 (d, 1H,
J = 5.4 Hz), 8.01 (d, 1H, J = 8.1 Hz), 7.72 (m, 7H), 7.63 (t, 1H,
J = 8.1 Hz), 7.32–7.09 (br. m, 15H, PPh3), 3.90 (t, 1H, J = 6.6 Hz),
MS(obsd (calcd). rel intens, assignment): m/z 727 (727), 75, [Ru(j3
-
tpy)(leucine)(PPh3)] +; 596 (596), 80, [Ru(
j
3-tpy)(PPh3)]2+; 335
(335), 70, [Ru(
j
3-tpy)]2+ 1H NMR (Acetone, d, ppm): 8.78 (m,
.
2H), 8.27 (t, 2H, J = 5.4 Hz), 8.13 (d, 2H, J = 6.3 Hz), 8.00 (m,
2H),7.77 (t, 1H, J = 7.8 Hz), 7.60 (t, 2H, J = 6.3 Hz), 7.30–7.18 (br.
3.63 (t, 2H, J = 8.7 Hz), 2.07 (m, 2H), 1.42 (m, 2H), 31P{1H} NMR
i
ꢂ
m, 15H, PPh3), 3.37 (t, 1H, J = 6.6 Hz), 2.05 (m, 1H of Pr), 1.36 (m,
(CDCl3, H3PO4, d, ppm): 43.30 (s). IR (cmꢂ1, nujol):
m(BF4
)
2H), 0.66 (dd, 6H, J = 6.3 Hz), 31P{1H} NMR (Acetone, H3PO4, d,
1063 cmꢂ1
, m , m ,
s(CO) 1379 cmꢂ1 as(CO) 1611 cmꢂ1. UV–Visible, kmax
ppm): 45.14 (s). IR (cmꢂ1, nujol):
m
(BF4ꢂ) 1057 cmꢂ1
,
e
m
(COs)
): 240
(36 960), 276 (27 070), 312 (35 760), 448 (5340), 497 (7630).
nm ( ): 235 (25 550), 275 (12 620), 312 (18 120), 447 (2630), 499
e
1380 cmꢂ1
,
m
(COas) 1625 cmꢂ1. UV–Visible, kmax, nm (
(3390).
3.2.13. Preparation of [Ru(j
3-tpy)(phe)(PPh3)]BF4 15
3.2.9. Preparation of [Ru
j
3-tpy)(isoleu)PPh3)]BF4 11
The complex 11 was prepared from the reaction of [Ru(j3
The complex 15 was prepared from the reaction of [Ru(j3
-
-
tpy)Cl2(PPh3)] (669 mg, 1.0 mmol) with phenylalanine (165 mg,
1 mmol) in methanol under refluxing conditions following the pro-
cedure for complex 3. Yield: 0.565 g (84%). Anal. Calc. for
BC42F4H36N4O2PRu: C, 59.43; H, 4.24; N, 6.60. Found: C, 59.42; H,
4.26; N, 6.58%. 1H NMR (CDCl3, d, ppm): 8.55 (d, 1H, J = 5.1 Hz),
7.91 (d, 1H, J = 7.8 Hz), 7.74 (m, 7H), 7.61 (t, 1H, J = 7.8 Hz), 7.51
(t, 1H, J = 8.1 Hz), 7.26–7.04 (br. m, 15H, PPh3, and 4H of Ph ring
of phenylalanine), 6.87 (t, 1H, J = 6.3 Hz), 3.88 (t, 1H, J = 10.2 Hz),
3.64 (d, 2H, J = 13.2 Hz), 2.11 (s, 2H of H2N–) 31P{1H} NMR (CDCl3,
tpy)Cl2(PPh3)] (0.669 g, 1.0 mmol) with isoleucine (0.131 g,
1.0 mmol) in methanol under refluxing conditions following the
procedure for complex 3. Yield: 0.513 g (76%). Anal. Calc. for
BC39F4H38N4O2PRu: C, 57.56; H, 4.67; N, 6.89. Found: C, 57.58; H,
4.69; N, 6.81%. FAB-MS(obsd (calcd). rel intens, assignment): m/z
727(727), 60, [Ru(
j
3-tpy)(isoleucine)(PPh3)]+; 596 (596), 50,
3-tpy)]2+ 1H NMR (CDCl3,
[Ru(j
3-tpy)(PPh3)]2+; 334(334), 80 [Ru(
j
.
d): 8.59 (d, 1H, J = 5.4 Hz), 8.51 (d, 2H, J = 5.9 Hz), 7.92 (t, 3H,
J = 8.4 Hz), 7.78 (t, 4H, J = 7.8 Hz), 7.56 (t, 1H, J = 7.8 Hz),
7.33–7.09 (br. m, 15H, PPh3), 3.23 (d, 1H, J = 10.5 Hz), 2.24 (m,
1H), 1.36 (m, 2H), 0.83 (m, 6H), 31P{1H} NMR (CDCl3, H3PO4, d,
H3PO4, d, ppm): 44.02 (s). IR (cmꢂ1, nujol):
m
(BF4ꢂ) 1056 cmꢂ1
,
m
(COs) 1380 cmꢂ1 (COas) 1627 cmꢂ1. UV–Visible, kmax, nm (
,
m
e):
241 (38 800), 276 (35 540), 312 (38 900), 452 (7530), 497 (10 120).

3578
P. Kumar et al. / Journal of Organometallic Chemistry 694 (2009) 3570–3579
3.3. X-ray crystallography
4. Conclusions
Suitable crystals for X-ray diffraction analyses for complexes 6,
10 and 13, were obtained from slow diffusion of CH2Cl2/petroleum
ether (40–60 °C) at room temperature. Preliminary data on the
space group and unit cell dimensions as well as intensity data were
collected on an OXFORD DIFFRACTION XCAUBER-S’ and Bruker
Smart Apex diffractometer using graphite-monochromatized Mo
Through this study we have shown that the syntheses of com-
plexes containing both a polypyridyl ligand tptz/tpy or bio-rele-
vant ligands,
a
-amino acids can be achieved by reactions of
Ru(j
3-tptz)Cl2(PPh3), and Ru(
j
3-tpy)Cl3 with
a-amino acids.
Resulting complexes moderately interact with DNA causing con-
densation and exhibit inhibitory activity against DNA Topo II of
the filarial parasite S. cervi at higher concentrations by complex
formation with DNA. These also exhibit heme polymerase activity
against malarial parasite P. yoelii.
Ka radiation .The structures were solved by direct methods and re-
fined by using SHELX-97 [57]. The non-hydrogen atoms were refined
with anisotropic thermal parameters. All the hydrogen atoms are
geometrically fixed and allowed to refine using a riding model.
The computer program PLATON was used for analyzing the interac-
tion and stacking distances [58].
Acknowledgements
We gratefully acknowledge the support of the Department of
Science and Technology, Ministry of Science and Technology,
New Delhi, India (grant SR/SI/IC-15/2007) for providing financial
assistance and Prof. P. Mathur, In-charge, National Single Crystal
X-ray Diffraction Facility, Indian Institute of Technology, Bombay,
Mumbai, for providing single X-ray data. We also thank Miss Rima
Ray Sarkar, Central Drug Research Institute, India for technical sup-
port regarding Topo II activity.
3.4. Gel mobility shift assay
Interaction of the complexes with DNA Topo II was governed by
enzymatic-mediated super coiled pBR322 relaxation [35]. For the
relaxation of super coiled pBR322 DNA a reaction mixture (20
containing 50 mM Tris–HCl, pH 7.5, 50 mM KCl, 1 mM MgCl2
1 mM ATP, 0.1 mM EDTA, 0.5 mM DTT, 30 g/ml BSA and enzyme
protein was employed. Super coiled pBR322 DNA (0.25 g) was
ll)
l
l
Appendix A. Supplementary material
used as the substrate for above reaction mixture. The reaction mix-
ture was incubated for 30 min at 37 °C and stopped by addition of
5 ll of the loading buffer containing 0.25% bromophenol blue, 1 M
sucrose, 1 mM EDTA, and 0.5% SDS. Samples were applied on hor-
izontal 1% agarose gel in 40 mM tris acetate buffer, pH 8.3, and
1 mm EDTA and run for 10 h at room temperature at 20 V. The
CCDC 710601, 710602 and 710603 contain the supplementary
crystallographic data for 6, 10 and 13. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2009.07.014.
gel was stained with ethidium bromide (0.10 lg/ml) and photo-
graphed in a GDS 7500 UVP (Ultra Violet Product, Cambridge,
UK) trans-illuminator. One unit of topoisomerase activity is de-
fined as the amount of enzyme required to relax 50% of the super
coiled DNA under the standard assay conditions.
The conformational transitions of B to Z in CT DNA in the
presence of mononuclear ruthenium complexes were determined
References
[1] V. Balzani, A. Juris, M. Venturi, S. Campagna, F. Puntariero, S. Serroni, Coord.
Chem. Rev. 96 (1996) 759.
[2] K. Chichak, U. Jacquemard, N.R. Branda, J. Eur. Inorg. Chem. (2002) 357.
[3] Xue W. Liu, Jun Li, Hong Deng, Kang C. Zheng, Zong W. Mao, Liang N. Ji, Inorg.
Chim. Acta 358 (2005) 3311.
[4] A. Cindy Puckett, K. Jacqueline Barton, J. Am. Chem. Soc. 129 (2007) 46.
[5] N. Maribel, B. Adelmo, H. Clara, M. Edgar, J. Braz. Chem. Soc. (2008) 1355.
[6] C.J. Elsevier, J. Reedijk, P.H. Walton, M.D. Ward, Dalton Trans. (2003) 1869.
[7] K.D. Demadis, C.M. Hartshorn, T.J. Meyer, Chem. Rev. 101 (2001) 2655.
[8] M.I.J. Polson, E.A. Medlycott, G.S. Hanan, L. Mikelsons, N.J. Taylor, M. Watanabe,
Y. Tanaka, F. Loiseau, R. Passalacqua, S. Campagna, Chem. Eur. J. 10 (2004)
3640.
spectrophotometrically .[48,49]. The UV absorbance ratio A295
/
A260 was monitored for conformational change in the DNA helix
from B–Z DNA. Condensation of DNA was monitored by following
the increase in the value of absorbance at 320 nm against different
complex/DNA ratios, according to the method of Basu and Marton
[50].
[9] C.M. Metcalfe, S. Spey, H. Adams, J.A.J. Thomas, Chem. Soc., Dalton Trans.
(2002) 4732.
3.5. Heme polymerase assay
[10] A. Amboise, B.J. Maiya, Inorg. Chem. 39 (2000) 4256.
[11] X.-J. Yang, F. Drepper, B. Wu, W. Sun, W. Haehnel, C. Janiak, Dalton Trans.
(2005) 256.
[12] K. Karidi, A. Garoufis, N. Hadjiliadis, J. Reedijik, Dalton Trans. (2005) 256.
[13] F. Gao, H. Chao, L.N. Ji, Chem. Biodiv. Rev. 5 (2008) 1962.
[14] A. Sitlani, C.M. Dupureur, J.K. Barton, J. Am. Chem. Soc. 115 (1993) 12589.
[15] K. Weise, Angew. Chem., Int. Ed. 36 (2003) 2592.
Inhibition of P. yoelii lysate heme polymerase activity by mono-
nuclear ruthenium complexes was studied by measuring the beta
hematin formation as reported previously [52]. For determining
the inhibition percentage of anti-malarial activity, the reaction
mixture (1 ml) contained 100
20 l of hemin (1.2 mg/ml), and 25
volume was made up with triple-distilled water. A total of 20
l
l of 1 M sodium phosphate buffer,
[16] G. Ciancaleoni, I.D. Maio, D. Zuccaccia, A. Macchioni, Organometallics 26
(2007) 489.
l
ll of P. yoelii enzyme, and the
[17] M.L. Gonzalez, J.M. Tercero, A. Matilla, J. Niclos-Gutirrez, M.T. Fernandez, M.C.
Lopez, C. Alonso, S. Gonalez, Inorg. Chem. 36 (1997) 1806.
[18] A. Matilla, J.M. Tercero, N.H. Dung, B. Viossat, J.M. Perez, C. Alonso, J.D. Martin-
Ramos, J. Niclos-Gutirrez, J. Inorg. Biochem. 55 (1994) 235.
[19] T.G. Appleton, Coord. Chem. Rev. 166 (1997) 313.
[20] H. Kozlowski, L.D. Pettit, F.R. Hartley (Eds.), Chemistry of Platinum Group
Metals: Recent Developments, Elsevier, Amsterdam, 1991, p. 530.
[21] L.J.K. Boerner, J.M. Zaleski, Curr. Opin. Chem. Biol. 9 (2005) 135.
[22] R.L. William, H.N. Toft, B. Winkel, K.J. Brewer, Inorg.Chem. 42 (2003) 4394.
[23] M. Sironi, Mol. Biochem. Parasitol. 74 (1995) 223.
[24] S.K. Singh, S. Sharma, M. Chandra, D.S. Pandey, J. Organomet. Chem. 690 (2005)
3130.
lg
of the complexes were added in the reaction mixture and incu-
bated for 16 h at 37 °C in an incubator shaker at the speed of
174 rpm. After incubation, the reaction mixture was centrifuged
at 10 000 rpm for 15 min and the pellet obtained was washed three
times with 10 ml of buffer containing 0.1 M Tris–HCl buffer, pH 7.5,
and 2.5% SDS and then with buffer 2 (0.1 M sodium bicarbonate
buffer, pH 9.2, and 2.5% SDS), followed by distilled water. The
semi-dried pellets were suspended in 50 ll of 0.2 N NaOH and
the volume was adjusted to 1 ml with distilled water. The optical
density was measured at 400 nm and the percent inhibition was
calculated using the following formula:
[25] P. Paul, B. Tyagi, A.K. Bilakhiya, P. Dastidar, E. Suresh, Inorg. Chem. 39 (2000)
14.
[26] S. Sharma, S.K. Singh, D.S. Pandey, Inorg. Chem. 47 (2008) 1179.
[27] C. Djordjevic, N. Vuletic, B.A. Jacobs, M. Lee-Reenslo, E. Sinn, Inorg. Chem.
(1997) 36.
[28] J. Goubean, W.Z. Bues, Anorg. Allg. Chem. 268 (1952) 221.
% inhibition ¼ ð1 ꢂ o:d of controlÞ=o:d of experimental ꢄ 100

P. Kumar et al. / Journal of Organometallic Chemistry 694 (2009) 3570–3579
3579
[29] N.N. Greenwood, J. Chem. Soc. (1959) 3811.
[30] S. Chirayil, V. Hegde, Y. Jahng, R.P. Thummel, Inorg. Chem. 30 (1991)
2821.
[31] K. Majumder, R.J. Butcher, S. Bhattacharya, Inorg. Chem. 41 (2002) 4605.
[32] C. Metcalfe, S.D. Spey, H. Adam, J.A. Thomas, Dalton Trans. (2002) 4732.
[33] M.H.V. Huynh, D.G. Lee, P.S. White, T.J. Mayer, Inorg. Chem. 40 (2001)
3842.
[34] D. Braga, F. Grepioni, E. Tedesco, Organometallics 17 (1998) 2669.
[35] J.H.K.K. Hirschberg, L. Brunsveld, A. Ramzi, J.A.J.M. Vekemans, R.P. Sijbesma,
E.W. Meijer, Nature 407 (2000) 167.
[44] W.H. Ang, P.J. Dyson, J. Eur. Inorg. Chem. (2006) 4003.
[45] D.V. Deubel, J.K.C. Lau, Chem. Commun. (2006) 2451.
[46] C. Scalaro, A. Bergamo, L. Brescacin, G. Sava, P.J. Dyson, J. Med. Chem. 48 (2005)
4161.
[47] B. Serli, E. Zangrando, T. Gianferrara, C. Scalaro, P.J. Dyson, A. Bergamo, E.
Alessio, J. Eur. Inorg. Chem. (2005) 3423.
[48] E.M. Pohl, T.M. Jovin, J. Mol. Biol. 67 (1972) 375.
[49] J.B. Chaires, J. Biol. Chem. 261 (1986) 8899. and references therein.
[50] H.S. Basu, L.J. Marton, Biochem. J. 244 (1987) 243.
[51] T.J. Thomas, R.P.J. Messner, Mol. Biol. 201 (1988) 463.
[52] A.V. Pandey, N. Singh, B.L. Takwani, S.K. Puri, V.S. Chauhan, J. Pharma. Biomed.
Anal. 20 (1999) 203.
[36] H. Yin, G.I. Lee, H.S. Park, G.A. Payne, J.M. Rodriguez, S.M. Sebti, A.D. Hamilton,
Angew. Chem., Int. Ed. 44 (2005) 2704.
[37] G.A. Jeffrey, An Introduction to Hydrogen Bonding, Oxford University Press,
Oxford, UK, 1997. p. 160.
[53] D.D. Perrin, W.L.F. Armango, D.R. Perrin, Purification of Laboratory Chemicals,
Pergamon, Oxford, UK, 1986.
[38] K. Liu, M.G. Brown, C. Carter, R.J. Saykally, J.K. Gregory, D.C. Clary, Nature 381
(1996) 501.
[39] M. Matsumoto, S. Saito, I. Ohmine, Nature 416 (2002) 409.
[40] U. Pandya, J.K. Saxena, S.M. Kaul, P.K. Murthy, R.K. Chatterjee, R.P. Tripathi, A.P.
Bhaduri, O.P. Shukla, Med. Sci. Res. 27 (1999) 103.
[54] B.P. Sullivan, M.C. Jaffrey, T.J. Meyer, Inorg. Chem. 19 (1980) 1404.
[55] G.R. Desiraju, T. Steiner, Weak Hydrogen Bonds in Structural Chemistry and
Biology, Oxford University Press, Oxford, UK, 1999.
[56] T. Steiner, Angew. Chem., Int. Ed. 41 (2002) 48.
[57] G.M. Sheldrick, SHELX-97: Programme for the Solution and Refinement of
Crystal Structures, University of Göttingen, Germany, 1997.
[58] A.L. Spek, Acta Crystallogr. 46 (1990) C31.
[41] D.A. Burden, N. Osheroff, Biochim. Biophys. Acta 1400 (1998) 139.
[42] J.C. Wang, J. Biol. Chem. 266 (1991) 6659.
[43] R.E. Morris, R.E. Aird, P. del S.Murdoch, H. Chen, J. Cummings, N.D. Hughes, S.
Parsons, A. Parkin, G. Boyd, D.I. Jodrell, P.J. Sadler, J. Med. Chem. 44 (2001)
3616.