Synthesis, characterization, DNA binding and cleavage studies of Ru(II) complexes containing oxime ligands

Article abstract of DOI:10.1016/j.molstruc.2010.09.004

The Ru(II) precursors, [RuHCl(CO)(EPh₃)₃] (E = P or As) when reacted with some well known monoxime and dioxime ligands in ethanolic solution afforded the new complexes of the types [RuCl(CO)(EPh₃) ₂L1], [RuH(CO)(EPh₃)₂L2] and [RuCl(CO)(EPh ₃)₂L3] ((H₁L1) = diacetylmonoxime, (H ₁L2) = dimethylglyoxime and (H₂L3) = benzoiloxime). The ligands coordinated in a bidentate chelate mode forming a five membered chelate ring. The molecular structures of two of the complexes have been determined by single crystal X-ray diffraction study. The structural determination confirms the deprotonation of the oxime function. Examination of all the complexes by cyclic voltammetry showed the occurrence of some quasi-reversible redox reactions owing to changes in the oxidation state of the central metal atoms. Structural assignments are supported by combination of IR, UV-Vis, ¹H NMR and elemental analyses. In addition, the DNA binding properties and cleavage efficiency of new complexes have been tested.

Full text of DOI:10.1016/j.molstruc.2010.09.004

Journal of Molecular Structure 984 (2010) 30–38
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, characterization, DNA binding and cleavage studies of Ru(II)
complexes containing oxime ligands
Nataraj Chitrapriya a, Viswanathan Mahalingam b, Matthias Zeller c, Hyosun Lee a,
Karuppannan Natarajan b,
⇑
a Department of Chemistry, Kyungpook National University, 1370 Sankyuk-dong, Buk-gu, Deagu-city 702-701, Republic of Korea
b Department of Chemistry, Bharathiar University, Coimbatore 641 046, India
c Department of Chemistry, Youngstown State University, Youngstown, OH 44555-3663, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 9 June 2010
Received in revised form 27 August 2010
Accepted 1 September 2010
Available online 24 September 2010
The Ru(II) precursors, [RuHCl(CO)(EPh3)3] (E = P or As) when reacted with some well known monoxime
and dioxime ligands in ethanolic solution afforded the new complexes of the types [RuCl(CO)(EPh3)2L1],
[RuH(CO)(EPh3)2L2] and [RuCl(CO)(EPh3)2L3] ((H1L1) = diacetylmonoxime, (H1L2) = dimethylglyoxime
and (H2L3) = benzoiloxime). The ligands coordinated in a bidentate chelate mode forming a five mem-
bered chelate ring. The molecular structures of two of the complexes have been determined by single
crystal X-ray diffraction study. The structural determination confirms the deprotonation of the oxime
function. Examination of all the complexes by cyclic voltammetry showed the occurrence of some
quasi-reversible redox reactions owing to changes in the oxidation state of the central metal atoms.
Structural assignments are supported by combination of IR, UV–Vis, 1H NMR and elemental analyses.
In addition, the DNA binding properties and cleavage efficiency of new complexes have been tested.
Ó 2010 Elsevier B.V. All rights reserved.
Keywords:
Ru(II) oxime complexes
Oximato oxygen
X-ray crystal structures
Electrochemistry
DNA binding and cleavage
1. Introduction
functions and the fact that the oxime bridges were established to
mediate exchange interactions between paramagnetic centers very
Organometallic and coordination chemistries of oximes consti-
tute an active area of research, with efforts in particular being di-
rected toward unusual reactivity modes of oximes and their
complexes [1–3]. One potential advantage to the use of oximes is
the possibility of greater tunability by facile variation of the sub-
stituents [4]. The presence of mild acidic hydroxyl groups and
slightly basic nitrogen atoms makes oximes amphoteric ligands
[5–8]. Nitrogen coordination of the oxime group to a metal ion
leads to a dramatic increase in its acidic character and formation
of an oximato ligand is favored [9]. The binding mode of the oxime
group depends to a great extent not only on the nature of the metal
ion but on the presence of a neighboring donor group in the same
ligand. The combination of these two moieties results in stable
chelate rings upon coordination to a metal ion [10]. Traditionally,
oximes have been extensively used in analytical chemistry and
metallurgy as very effective complexing agents for the purposes
of isolation, separation and extraction of different metal ions.
Molecular design of multidonor ligands containing other strong
donor groups along with the oxime function may lead to new, very
effective chelating agents [11]. The capacity of the oximato group
to coordinate additional metal ions via the bridging N and O
effectively provoked the start of a wide usage of oxime ligands in
molecular magnetism for the design and synthesis of polynuclear
assemblies [12,13].
Oximes and their metal complexes are of current interest for
their rich physicochemical properties, reactivity patterns and po-
tential applications in many important chemical processes in the
areas of medicine [14–16], bioorganic systems [17,18], catalysis
[19], electrochemical [20] and electro optical sensors [21,22]. The
investigations of the redox properties of these types of complexes
are also of great interest in terms of their various technological
applications [23–25]. The interest in oxime containing coordina-
tion compounds is constantly increasing in connection with the
biological implication of oximes (especially, as intermediates in
the biosynthesis of nitrogen oxide) and the marked and versatile
bioactivity indicated by different oximes and their metal com-
plexes [26]. It is important to note that the realization of the bio-
logical function of oximes and the mechanism of their
metabolism in living systems are evidently connected with their
chelation by metal ions [27]. Ruthenium(II) complexes have shown
to act not only as good catalysts for many industrially important
reactions but also have shown promising biological activities
including anticancer activities [14]. Hence, there is a need for the
synthesis of oxime complexes of ruthenium(II) and to study their
reactivities. Herein, we report the synthesis, characterization,
⇑
Corresponding author. Tel.: +91 422 2428311; fax: +91 422 2422387.
E-mail address: k_natraj6@yahoo.com (K. Natarajan).
0022-2860/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2010.09.004

N. Chitrapriya et al. / Journal of Molecular Structure 984 (2010) 30–38
31
electron transfer and DNA binding properties of Ru(II) oxime com-
plexes. Also the DNA cleavage properties have been studied using
pBR322 super coiled plasmid DNA.
1:1 ratio with ramp rate of 0.1 °C/min. The viscosity measurement
was carried out using an Ubbelodhe viscometer immersed in a
thermostatic water bath maintained at 16( 0.l) °C. DNA samples
with approximately 200 base pairs in length were prepared by son-
ication in order to minimize complexities arising from DNA flexi-
bility. Flow times were measured with a digital stopwatch; each
sample was measured three times, and an average flow time was
calculated. Relative viscosities for HS-DNA in the presence and ab-
2. Experimental
2.1. Materials and methods
sence of the complex were calculated from the relation
t0, where t is the observed flow time of DNA-containing solution
g
= (t ꢀ t0)/
All chemicals were of reagent grade and were used without fur-
ther purification. Solvents were purified and dried according to
standard procedures [28]. The ruthenium(II) precursor complexes
[RuHCl(CO)(PPh3)3] and [RuHCl(CO)(AsPh3)3] were prepared by re-
ported literature methods [29,30]. All the ligands are obtained
from commercial suppliers and were used as received. Protein free
Herring Sperm ds DNA obtained from SRL chemicals was stored at
0–4 °C and its purity was checked by measuring the optical density
before use. The pBR322 plasmid DNA was purchased from Amer-
and t0 is the flow time of Tris–HCl buffer alone. Data are presented
as (
in the presence of complex and
For the gel electrophoresis experiment, supercoiled pBR322 DNA
(0.1 g) was treated with the Ru(II) complexes in the presence of
g
/g0)
1/3 versus binding ratio, where
g
is the viscosity of HS-DNA
g0 is the viscosity of HS-DNA alone.
l
oxygen and sodium ascorbate (1 mM) in Tris–HCl buffer (50 mM)
with 0.1 M NaCl (pH, 7.1) followed by dilution with the Tris–HCl
buffer to a total volume of 20
24 h at 37 °C. A loading buffer containing 25% bromophenol blue,
0.25% xylene cyanol, 30% glycerol (3 l) was added and electropho-
resis performed at 100 V for 2 h in Tris–Acetate–EDTA (TAE) buffer
using 1% agarose gel containing 1.0 g/ml ethidium bromide. Aga-
ll. The samples were incubated for
sham–Pharmacia Biotech. Ultra-pure MilliQ water (18.2 mX) was
used in experiments. The Tris-buffer solution was prepared with
double-distilled water and its pH was adjusted to 7.1 using 0.1 M
NaOH solution. DNA stock solutions were freshly prepared with
this buffer solution before use. Distilled dimethyl sulphoxide
(DMSO) was used for the preparation of solutions of complexes
for DNA-binding studies. Commercially available TBAP (tetra butyl
ammonium perchlorate) was properly dried and used as support-
ing electrolyte for recording cyclic voltammograms of the
complexes (except for DNA-binding studies). FT-IR spectra
(4000–400 cmꢀ1) of the complexes and the free ligands were re-
corded as KBr pellets with a Nicolet Avatar Model FT-IR spectro-
photometer. UV–Vis spectra (800–250 nm) of the complexes
were obtained on a Systronics 119 UV–Vis spectrophotometer. 1H
NMR spectra of the complexes were recorded using a Varian-
Australia AMX-400 spectrometer. Micro analyses (C, H & N) were
performed on a Vario EL III Elementar analyzer. Cyclic voltammo-
grams were recorded on CHI 1120A electrochemical analyzer with
a three electrode compartment consisting of a platinum disc work-
ing electrode, platinum wire counter electrode and Ag/Ag+ refer-
ence electrode.
l
l
rose gel electrophoresis of plasmid DNA was visualized by photo-
graphing the fluorescence of intercalated ethidium bromide
under a UV illuminator. The cleavage efficiency was measured by
determining the ability of the complex to convert the supercoiled
DNA (SC) to nicked circular form (NC) and linear form.
2.4. Synthesis of new Ru(II) oxime complexes
All the complexes were synthesized by the following general
method. To
a suspension of the appropriate oxime ligand
(0.1 mmol) in ethanol (30 cm3) was added the respective Ru(II)
starting complex (0.1 mmol). The resulting solution was refluxed
for 10 h. On slow evaporation at room temperature, the product
got separated which was filtered and washed with diethyl ether
and cold ethanol.
2.4.1. [RuCl(CO)(PPh3)2(L1)] (1)
It was prepared from [RuHCl(CO)(PPh3)3] (0.1 g, 0.105 mmol)
and diacetylmonoxime (0.0105 g, 0.105 mmol) as an orange crys-
talline product. Yield: 48 mg (68%). Anal. Calc. for C41H36O3N1-
RuClP2: C, 62.39; H, 4.59; N, 1.77. Found: C, 62.31; H, 4.53; N,
2.2. X-ray crystallography
X-ray diffraction measurements were performed on a Bruker
AXS SMART APEX CCD diffractometer with graphite monochroma-
tized Mo Ka radiation. The unit cell was determined using SMART
1.75%. IR (KBr, cmꢀ1):
m(C@O) 1642, m(C@N) 1577, m(N–O) 974.
1H NMR (400 MHz, CDCl3, d, ppm; s, singlet; m, multiplet): 1.65
(s, 3H, CH3), 1.70 (s, 3H, CH3), 7.26–7.68 (m, aromatic). UV–Vis k
[31], SAINT+ [32] and the data were corrected for absorption using
SADABS [33]. The structure was solved by direct methods and
refinements were carried out by full-matrix least-square tech-
niques. The hydrogen atoms were treated by a mixture of indepen-
dent and constrained refinement. The computer program SHELXTL
6.14 [34] was used for structure solution, refinement and molecu-
lar graphics. Refinement of an extinction coefficient was found to
be insignificant. All non-hydrogen atoms were refined
anisotropically.
(nm) (e
, molꢀ1 cmꢀ1 L): 229(29,649), 259(19,115), 416(1509).
2.4.2. [RuH(CO)(PPh3)2(HL2)] (2)
It was prepared from [RuHCl(CO)(PPh3)3] (0.1 g, 0.105 mmol)
and dimethylglyoxime (0.0121 g, 0.105 mmol) as an yellow crys-
talline product. Yield: 51 mg (70%). Anal. Calc. for C41H38O3N2RuP2:
C, 63.97; H, 4.97; N, 3.63. Found: C, 63.58; H, 4.58; N, 3.68%. IR
(KBr, cmꢀ1): (N–O) 930. 1H NMR(400 MHz, CDCl3,
m(C@N) 1625, m
d, ppm; s, singlet; m, multiplet): 2.85 (s, 3H, CH3), 2.95 (s, 3H,
2.3. DNA binding experiments
CH3), 7.24–7.71 (m, aromatic), 9.30 (s, 1H, N–OH). UV–Vis k (nm)
(e
, molꢀ1 cmꢀ1 L): 227(41,054), 228(41,955), 269(13,129).
The experiments were carried out in Tris–HCl buffer (50 mM,
pH 7.1) using a solution of Herring sperm DNA which gave a UV
absorbance at 260 and 280 nm in a 1.8:1 ratio indicating that the
DNA is sufficiently free from protein. No further effort was made
to purify the commercially obtained DNA. The concentration of
2.4.3. [RuCl(CO)(PPh3)2(L3)] (3)
It was prepared from [RuHCl(CO)(PPh3)3] (0.1 g, 0.105 mmol)
and benzoinoxime (0.0239 g, 0.105 mmol) as purple color product.
Yield: 62 mg (58%). Anal. Calc. for C51H41O3N1RuClP2: C, 66.99; H,
4.51; N, 1.53. Found: C, 66.79; H, 4.55; N, 1.59%. IR (KBr, cmꢀ1):
DNA was determined by absorption spectroscopy using the e value
of 6600 Mꢀ1 cmꢀ1 at 260 nm. DNA melting experiments were car-
ried out by monitoring the absorption (260 nm) of HS-DNA at var-
ious temperatures in the absence and presence of the complexes at
m(C@N) 1598,
m(C–O) 1375, m
(N–O) 932. 1H NMR (400 MHz, CDCl3,
d, ppm; s, singlet; m, multiplet): 6.8 (s, 1H, CH–), 7.20–7.70 (m,

32
N. Chitrapriya et al. / Journal of Molecular Structure 984 (2010) 30–38
aromatic). UV–Vis
263(8464), 552(694).
k
(nm)
(
e,
molꢀ1 cmꢀ1 L): 223(25,770),
the complexes. In the spectra of complexes (1) and (4), the
(C@O) band is shifted to lower frequencies by about 30 cmꢀ1
m
compared to free ligands, indicating the coordination of oxygen
atom of the carbonyl moiety to Ru(II) ion. In the spectra of (2)
2.4.4. [RuCl(CO)(AsPh3)2(L1)] (4)
and (5), the band due to m
(OH) appeared around 2500 cmꢀ1 instead
It was prepared from [RuHCl(CO)(AsPh3)3] (0.1 g, 0.107 mmol)
and diacetylmonoxime (0.0107 g, 0.107 mmol) as red color prod-
uct. Yield: 53 mg (67 %). Anal. Calc. for C41H36O3N1RuClAs2: C,
56.14; H, 4.13; N, 1.59. Found: C, 56.21; H, 4.32; N, 1.59%. IR
of around 3200 cmꢀ1 indicating the hydrogen bonding between
the hydroxyl group and the oxygen atom of DMF molecule. Nor-
mally hydrogen bonded hydroxyl groups are found to absorb at
lower energy depending on the extent of hydrogen bonding. The
presence of hydrogen bonding has also been reflected from the de-
(KBr, cmꢀ1):
m(C@O) 1639, m(C@N) 1577, m
(N–O) 987. 1H NMR
(400 MHz, CDCl3, d, ppm; s, singlet; m, multiplet): 1.60 (s, 3H,
crease in
m(N–O) frequency observed in the IR spectra of com-
CH3), 1.75 (s, 3H, CH3), 7.26–7.56 (m, aromatic). UV–Vis k (nm)
(e,
molꢀ1 cmꢀ1 L):
425(1024).
228(20,198),
260(18,911),
303(3754),
plexes. This is also confirmed by the shift in N–O absorbance to
lower energy. This decrease is consistent with protonation occur-
ring at a hydrogen bonded oxime oxygen atom, in that such a pro-
tonation would be expected to result in a removal of electron
density from the N–O bond and a corresponding increase in the
N–O bond length and a decrease in N–O stretching frequency.
The expected increase of an N–O bond length upon the formation
of a covalent O–H bond associated with oxime oxygen has been
confirmed by X-ray structural determination of complex (2). The
absorption band which appeared at 2020 cmꢀ1 has been assigned
2.4.5. [RuH(CO)(AsPh3)2(HL2)] (5)
It was prepared from [RuHCl(CO)(AsPh3)3] (0.1 g, 0.107 mmol)
and dimethylglyoxime (0.0124 g, 0.107 mmol) as an yellow prod-
uct. Yield: 49 mg (61%). Anal. Calc. for C41H38O3N2RuAs2: C,
57.41; H, 4.46; N, 3.26. Found: C, 57.86; H, 4.64; N, 3.38%. IR
(KBr, cmꢀ1): (N–O) 923. 1H NMR 400 MHz, CDCl3,
m(C@N) 1617, m
d, ppm; s, singlet; m, multiplet): 2.85 (s, 3H, CH3), 2.95 (s, 3H,
to m(Ru–H) for the hydrido complexes (2 and 5). However, this
CH3), 7.00–7.70 (m, aromatic), 9.60 (s, 1H, N–OH). UV–Vis k (nm)
(e
, molꢀ1 cmꢀ1 L): 230(9833), 245(9649), 256(28,275), 379(1358).
band was not observed for the other complexes (1, 3, 4 and 6).
The IR spectrum of benzoiloxime showed a band at 1388 cmꢀ1
and band at 3480 cmꢀ1 due to
m(C–O) and m(OH) respectively. In
2.4.6. [RuCl(CO)(AsPh3)2(L3)] (6)
the spectra of (3) and (6), the band at 3480 cmꢀ1 has completely
disappeared indicating the deprotonation of –OH prior to coordina-
tion. This coordination by oxygen atom has been further confirmed
It was prepared from [RuHCl(CO)(AsPh3)3] (0.1 g, 0.107 mmol)
and benzoinoxime (0.0249 g, 0.107 mmol) as purple product.
Yield: 76 mg (67%). Anal. Calc. for C51H41O3N1RuClAs2: C, 61.11;
H, 4.12; N, 1.39. Found: C, 61.17; H, 4.14; N, 1.38%. IR (KBr,
by the reduction in
band for (OH) of (N–OH) group is absent in the spectra of all
m
(C–O) to around 1375 cmꢀ1. Characteristic
m
cmꢀ1):
m(C@N) 1605,
m(C–O) 1381 m
(N–O) 932. 1H NMR
the complexes indicating the deprotonation of N–OH group.
(400 MHz, CDCl3, d, ppm; s, singlet; m, multiplet): 6.8 (s, 1H, CH–
), 7.20–7.80 (m, aromatic). UV–Vis k (nm) (e
, molꢀ1 cmꢀ1 L):
3.2. Electronic spectra
227(13,726), 267(7048), 536(880).
The electronic spectra of all the new complexes have been re-
corded in CHCl3 solution. The spectral data are given in the exper-
imental section. The low spin d6 complexes are generally
dominated by metal to ligand charge transfer in the visible region
[36,37]. All the complexes display three to four absorptions, one of
which appears in the visible region while the others extended into
the UV region. The bands in the region 379–552 nm have been as-
signed to the metal–ligand charge transfer transition on the basis
of high extinction coefficient values. Two to three high energy
bands which appeared around 223–303 nm in all the complexes
3. Results and discussion
The starting complexes of general formula [RuHCl(CO)(EPh3)3]
(where E = As or P) were reacted with three oxime ligands
[(H1L1) = diacetylmonoxime, (H2L2) = dimethylglyoxime and
(H2L3) = benzoinoxime]. The primary intension of the present
study has been to see how the oxime ligands interact with Ru(II)
complexes. Three types of complexes have been obtained (Scheme
1) and they have been characterized by spectroscopic techniques.
The elemental analyses data confirm the molecular formulae of
the complexes. The oxime ligands coordinate to ruthenium ion as
a bidentate donor forming a five membered chelate ring leaving
the oximato oxygen atom uncoordinated. All the six complexes
synthesized are diamagnetic. Structures of two of the complexes
have been determined by single crystal X-ray crystallography.
are attributed tintraligand (oxime)
p ?
pꢁ transition [38].
3.3. 1H NMR spectra
1H NMR spectra of complexes were recorded in CDCl3, and their
assignments are given in the experimental section. The spectra of
the complexes (1) and (4) showed two singlet, one at d 1.60–
1.63 ppm and the other at d 1.70–1.75 ppm, attributed to the
resonance of the two magnetically different methyl groups. The
complexes (2) and (5) displayed two singlets at d 2.85 and d
2.95 ppm, which are assigned to the two different methyl protons
of the ligand (H2L2). The methyl groups in (H2L2) are known to be
non equivalent [39,40]. For the complexes (2) and (5), a singlet at d
9.2 and d 9.4 ppm have been observed respectively for the N–OH
proton. However, the spectra of the complexes 1, 3, 4 and 6 did
not show any signal for N–OH indicating the deprotonation of
oxime proton leaving oximato oxygen uncoordinated (crystal
structure will be discussed later). The metal hydride signal corre-
sponding to Ru–H has been detected as a singlet at d ꢀ12.3 ppm
for the complexes (2 and 5). However, this peak was not observed
for the complexes (1, 3, 4 and 6). The >CH proton of >CHOH which
appeared at d 5.6 ppm for benzoinoxime ligand (H2L3) has been
3.1. IR spectra
The IR spectral data are given experimental section and are dis-
cussed below in terms of the pertinent regions of the spectrum.
Generally oximes are characterized by three IR absorption bands
due to
IR spectra of all the ligands exhibit a broad medium intensity band
around 3250 cmꢀ1, which is assigned to
(O–H) of the oxime
group. The bands in the region 976–1018 cmꢀ1 and 1590–
1641 cmꢀ1 are due to
(N–O) and (C@N) respectively. In case of
HL1 alone, a strong peak at 1671 cmꢀ1 due to
(C@O) moiety has
been observed. The striking feature common in all the spectra of
the complexes are the noticeable shift of (N–O) and (C@N)
m(O–H), m(C@N) and m(N–O) stretching vibrations [35]. The
m
m
m
m
m
m
stretching vibrations relative to the free ligands. This suggests
the coordination of the oxime group through nitrogen atom in all

N. Chitrapriya et al. / Journal of Molecular Structure 984 (2010) 30–38
33
O
N
Ph3E
OH
C
C
Cl
C
C
N
O
Ethanol
Reflux 10 h
[RuHClCO(EPh3)3]
[RuHClCO(EPh3)3]
[RuHClCO(EPh3)3]
Ru
OC
O
EPh3
OH
N
Ph3E
OH
C
H
C
C
N
N
Ethanol
Ru
Reflux 10 h
OC
N
O
C
EPh3
OH
Ph
Ph3E
Ph
Ph
O
CH
C
Cl
CH OH
Ethanol
Reflux 10 h
Ru
C
N
OC
N
O
EPh3
OH
Ph
E = P or As
Scheme 1.
shifted to d 6.8 ppm in the complexes (3) and (6) indicating its
deshielding due to the coordination of oxygen to the metal ion.
The aromatic protons appeared as a multiplet in the region d
6.9–8.0 ppm in all the complexes.
3.4. X-ray structure determination
The molecular structures of (1) and (2) are illustrated in Figs. 1
and 2 respectively and their pertinent crystallographic data are
listed in Table 1. The significant bond distance and angles of the
complexes are given in Table 2. In (1), Ru(II) ion is coordinated to
carbonyl oxygen and oxime nitrogen of the ligand (H1L1) forming
a five membered chelate ring with a bite angle of 78.25(5)°. The
ruthenium atom is hexacoordinated with slightly distorted octahe-
dral geometry. The two P atoms from triphenylphosphine occupy
the apical position while one chloride, carbon atom from carbonyl
group and oxygen and nitrogen atoms of the ligand occupy basal
plane of the octahedron. The bond distances Ru1–N1 and Ru1–
O1 therein are 2.0100(14) Å and 2.1041(12) Å respectively, which
are about the same length as those found in related Ru(II)
complexes [41–43]. The Ru–Cl, Ru–C and Ru–P distances are all
normal and they are similar to what have been observed in struc-
turally characterized Ru(II) complexes containing these bonds
[42,44,45]. The geometrical parameters of the present ligand are
similar to those observed for other ligands having deprotonated
oxime group [41,42]. The distance N1–O1 of 1.2577(19) Å and
N1–C3 of 1.362(2) Å are close to reported values of nitrogen coor-
dinated deprotonated oxime group [41,46,47]. Loss of the N–OH
hydrogen and coordination of the oxime nitrogen results in signif-
icant decreases in the N1–O1 bond distance compared to the pro-
tonated N–O bond distance found in reported oxime complexes
[41,48]. The bond distances of C3–C4 and C3–C2 have been found
Fig. 1. Labeled ORTEP diagram of (1) with thermal probability. Hydrogen atoms are
omitted for clarity.
to be shorter due to deprotonation of oxime OH. It has been noted
that N–O distances in oxime complexes are sensitive indicators of

34
N. Chitrapriya et al. / Journal of Molecular Structure 984 (2010) 30–38
Fig. 2. Labeled ORTEP diagram of (2) with thermal probability. Hydrogen atoms are omitted for clarity.
Table 1
Crystal data for (1) and (2).
Table 2
0
Selected bond lengths (ÅA) and bond angles (°) for (1) and (2).
Crystal data
(1)
(2)
(1)
(2)
Empirical formula
Formula weight
Crystal color, Habit
Crystal dimensions
Crystal system
Lattice type
C
41H36ClNO3P2Ru
C46H51N4O6P2Ru
918.92
Yellow, Block
0.45 ꢂ 0.35 ꢂ 0.22mm
Triclinic
Primitive
P-1
10.6021(4)
Ru1–C5
Ru1–N1
Ru1–O1
Ru1–Cl1
Ru1–P1
Ru1–P2
1.8668(19)
2.0100(14)
2.1041(12)
2.4384(4)
2.3943(4)
2.3819(4)
96.43(5)
94.48(7)
172.72(6)
91.11(5)
89.15(5)
168.98 (4)
78.25(5)
89.93(4)
90.85(3)
Ru1–C41
Ru1–N1
Ru1–N2
Ru1–H1A
Ru1–P1
Ru1–P2
1.8484(19
2.1001(15)
2.1602(15)
1.84(2)
2.3461(5)
2.3678(5)
95.2(2)
170.9(4)
100.7(3)
92.4(4)
87.5(4)
78.1(4)
163.8(2)
90.98(18)
89.1(7)
789.17
Orange, Block
0.37 ꢂ 0.36 ꢂ 0.34mm
Monoclinic
Primitive
Space group
A
P2(1)/n
C5–Ru1–Cl1
C5–Ru1–N1
C5–Ru1–O1
C5–Ru1–P1
C5–Ru1–P2
N1–Ru1–Cl1
N1–Ru1–O1
N1–Ru1–P1
N1–Ru1–P2
O1–Ru1–Cl1
O1–Ru1–P1
O1–Ru1–P2
P2–Ru1–Cl1
P2–Ru1–P1
P1–Ru1–P2
C51–Ru1–C50
C51–Ru1–N3
C51–Ru1–O2
C51–Ru1–P1
C51–Ru1–P2
C50–Ru1–N3
C50–Ru1–O2
C50–Ru1–P1
C50–Ru1–P2
N3–Ru1–O2
N3–Ru1–P1
N3–Ru1–P2
O2–Ru1–P1
O2–Ru1–P2
P1–Ru–P2
0
9.9789(7) ÅA
0
B
C
12.5182(5)
17.3708(7)
16.1803 (11) ÅA
0
22.6705 (15) ÅA
90°
95.6050 (16)°
90°
3642.9 (4) ÅA3
a
b
c
V
83.1850(10)
89.0220(10)
69.8710(10)
2148.63(15)
0
90.84(4)
89.01(3)
90.85(3)
87.663(14)
179.064(15)
91.413(14)
85.8(4)
87.8(4)
92.4(4)
91.28(18)
88.73(18)
179.81(4)
Z
4
2
Reflections collected
Unique reflections
30070
8902
8352
22527
10633
9594
0.0343
0.0920
1.420
954
0.493
0.0181
1.043
30.54
Reflections [I > 2
r(I)]
R [F2 > 2
wR [F2]
Dcalc
r
(F2)]
0.0290
0.0734
1.439 Mg mꢀ3
1616
F000
l
(Mo K
a
)
0.631 mmꢀ1
0.0216
1.056
The coordination geometry of (2) is best described as distorted
octahedron with two nitrogen atoms from chelating ligand, C atom
from CO and hydride ion occupying the four equatorial positions
and two PPh3 molecules filling the axial sites. The structure shows
that the ligand (H2L2) is coordinated to ruthenium through the
two oxime nitrogen atoms, forming a five membered chelate ring
with a bite angle of N1–Ru1–N2 = 74.81(16)°. The two trans PPh3 li-
gands have been found to bent away from the coordinated H2L2 li-
gand [P1–Ru1–P2 = 172.26(17) Å] due to steric bulk of the chelated
H2L2. This has resulted in lowering of angle for P2–Ru1–C41 =
Rint
Goodness of fit (S)
hmax (°)
30.53
the deprotonation of the hydrogen atom and position of the hydro-
gen atom (covalently or hydrogen bonded). The observation of
shorter N–O bond length and larger C–N–O angles definitively rule
out the possibility of oxime protons being present in the
complexes.

N. Chitrapriya et al. / Journal of Molecular Structure 984 (2010) 30–38
35
Table 4
89.23(6)° and P1–Ru1–H1A = 82.0(7)° compared P1–Ru1–N1 =
Cyclic voltammetry data for Ru(II) complexes.
91.00(4)° and P2–Ru1–N2 = 89.12(4)° angles. The Ru–P, Ru–H, Ru–
C bond lengths are quite normal and they are comparable with
the values reported for other complexes [49–51]. It is interesting
to note that though the ligand (H2L2) consists of two dissociable
oxime protons, only one of the oxime protons is deprotonated dur-
ing complexation. The Ru1–N1 bond length 2.1001(15) Å is shorter
than Ru1–N2 [2.1602(15) Å] length. Generally, the M–N(oxime) dis-
tances are related to the N–O bond distances, which are in turn,
allied to the protonation or nonprotonation of oxygen. The Ru–N
length on the protonated side of glyoxime is significantly shorter
than those on the deprotonated side. In support of the above conclu-
sion, we note that the two N–O distances are significantly different
(they are being 1.3914(19) Å and 1.3299(19) Å for N1–O1 and N2–
O2 respectively), the longer N–O distance is associated with the
oxygen atom which is covalently bound to the hydrogen atom.
The bond distances of C@N and C–CH3 also show the effect of the
deprotonation. The C2–N2 bond length is 1.302(2) Å, which is an
intermediate value between single and double bond lengths and
C2–C3 distance of 1.320 Å is significantly shorter. These are in sharp
contrasts to what was found for protonated side and free glyoxime
Complex
Ru(III)/Ru(II)a E1/2/V(
D
Ep/mV)
Ligand reduction
(1)
(2)
(3)
(4)
(5)
(6)
1.4b
1.07(160)
0.82(540)
1.48b
1.09(80)
1.06(110)
ꢀ1.27(390)
ꢀ1.19(50)
ꢀ1.5c
ꢀ1.5c
ꢀ1.51c
ꢀ1.5c
ꢀ1.5c
ꢀ1.45c
ꢀ1.21(230)
ꢀ1.28(370)
ꢀ1.22(110)
ꢀ1.18(170)
a
b
c
Oxidation couple.
Irreversible, Epa value.
irreversible, Epc value.
ligand. The above facts suggest a delocalization of the
p electron
density on deprotonated side of the glyoxime (O2–N2–C2–C3) moi-
ety. The observed distances of C1–N1 = (1.298(2) Å) and C1–
C4 = (1.502(3) Å) are in agreement with those distances found in
the free ligand [52]. The shortening of the N–O distance and length-
ening of the C–N distance in the oxime group are characteristic of
oxime donor ligands and were observed earlier in the relevant
structures [53,54]. The structure is additionally stabilized by the
formation of hydrogen bonding. One of the oxygen bound acidic
hydrogen atom is lost from the ligand during complex formation
and remaining hydroxyl group of the ligand is involved in hydrogen
bonding to the oxygen (O4) atom from the DMF of crystallization.
Both hydrogen atoms of the water molecule are participating in
hydrogen bonding (Table 3). Atom O2 forms a bifurcated hydrogen
bond, with H6A and H6B of water molecule. In addition to that, the
free ligand (H2L2) present in the crystal lattice is also found to par-
ticipate in the intermolecular hydrogen bonding. The hydrogen
bond is formed between O5 of the free ligand and O6 of solvent
water.
Fig. 3. Cyclic voltammogram of complex (1).
3.6. DNA-binding studies
3.6.1. Absorption spectroscopic studies
DNA-binding studies are important for the rational design and
construction of new and more efficient drugs targeted to DNA.
Electronic absorption spectroscopy is often employed to ascertain
the binding of complexes with DNA. The spectral change reflects
the corresponding changes in DNA in its conformation and struc-
tures after the drug bound to DNA. The extent of spectral change
is related to the strength of binding [55,56]. Hypochromism results
from the contraction of DNA in the helix axis, as well as from the
change in conformation in DNA, in contrast hyperchromism de-
rives from damage to the DNA double helix structure [57,58].
The spectra of all complexes consist of two to three resolved bands.
The MLCT band of complexes (1) and (4) at 438 and 442 nm
respectively showed clearly that the progressive addition of DNA
to the complexes leads to strong hyperchromism, accompanied
the slight red shifts of 3 nm and 1 nm respectively The extent of
hyperchromism (53%) in (1) is higher at saturation point than that
observed for (4). A strong hyperchromic effect with significant red
shift was observed for (1), suggesting that this complex possesses a
higher propensity for DNA binding. The other bands at 261 and
259 nm experience a slight blue shift, a change in band shape
and hyperchromism. The hyperchromism of the complexes implies
that the binding mode is non-intercalative in nature. With increas-
ing concentration of DNA, the absorption bands of (2) and (5) are
affected, resulting in the obvious tendency of hyperchromism
and blue shift. The intraligand transition band of the complexes
(2 and 5) at 293 and 300 nm exhibit hyperchromism of about
50% and 47% with blue shifts of 6 and 10 nm at a ratio of [com-
plex]/[DNA] of 5 respectively. The strong hyperchromism and
spectral broadening in absorption intensity indicate interaction
of DNA with complexes. For (3) and (6), the low energy absorption
3.5. Cyclic voltammetry
Electrochemical properties of the complexes have been studied
by cyclic voltammetry. Voltammetric data are presented in Table 4
and a representative voltammogram is displayed in Fig. 3. Each
complex shows one oxidative and two reductive responses. The
cyclic voltammograms of all the complexes are dominated by the
Ru(II)–Ru(III) redox couple. The complexes (1) and (4) showed irre-
versible redox behaviour, whereas (2), (3), (5) and (6) showed
reversible redox behaviour with peak to peak separation in the
range 70–80 mV. Comparison of the peak potential of the ligands
with those of the complexes reveals that the two reductive re-
sponses are ligand centered reduction. From the electrochemical
data, it is inferred that the present ligand system is ideally suitable
for stabilizing the Ru(II) ion.
Table 3
Hydrogen bonding geometry for (2).
D–Hꢃ ꢃ ꢃA
D–H
Hꢃ ꢃ ꢃA
Dꢃ ꢃ ꢃA
D–Hꢃ ꢃ ꢃA
(1)
O1 H1 O4
O5 H5 O6
O6 H6AO2
O6 H6BO2
0.84
0.84
0.833
0.813
1.81
1.85
2.028
1.921
2.602(3)
2.686(2)
2.8494(19)
2.7320(19)
156(1)
175(5)
169(3)
176(3)

36
N. Chitrapriya et al. / Journal of Molecular Structure 984 (2010) 30–38
band at 542 and 537 nm respectively, assigned to metal to ligand
charge transfer (MLCT) transition disappeared gradually upon
addition of DNA. The initial increase in absorption intensity
(hyperchromism 19 and 23%) with a slight blue shift (3 and
6 nm, respectively) is due to electrostatic interaction between
DNA and metal complexes. The continuous increase in hyper-
chromicity of intraligand transition at 296 and 298 nm respectively
associated with a spectral shift of 3 and 4 nm to blue shift is typical
for an exclusive electrostatic interaction between the complexes
and helix surface. For complex 3, the hyperchromicity approxi-
mately attains as high as about 10.2% at the same ratio as complex
6. The absorption spectrum of all complexes upon titration with
DNA did not show any wavelength shift in absorption maxima at
236 nm. However, the addition of DNA clearly yielded an absor-
bance hyperchromism. There is no special pattern changes in the
absorption spectra of the complexes in the presence of DNA have
been detected, except increases in hyperchromism for the absorp-
tion spectra. This suggests that the interaction between the com-
plexes and DNA should be a weak one between the molecules.
Fig. 4. Thermal denaturation of HS-DNA in the absence and presence of complexes.
3.6.4. Viscosity measurements
The relative change in viscosity was measured using sonicated
herring sperm DNA with increasing concentrations of ruthenium
compounds. Hydrodynamic measurements sensitive to length
change (i.e. viscosity and sedimentation) are regarded as the least
ambiguous and most critical tests of a binding mode in solution in
the absence of crystallographic structural data [62–64]. The meth-
od is based on the well-known fact that intercalation of molecules
between DNA bases causes a change in the relative viscosity of
solutions due to the unwinding and elongation of the double helix
[64–66]. No significant change was observed in the viscosity of
DNA for almost all our ruthenium complexes (Fig. 5). From this
observation, we can conclude that the complexes may be electro
statically bound to the phosphate group of DNA backbone.
3.6.2. Cyclic voltammetric studies
The cyclic voltammetry is also a useful technique for studying
and understanding the binding nature of the metal complexes with
DNA. Binding of the complex to the slowly diffusing nucleic acid
strand results in decrease in current which is a direct reflection
of the concentration of free and bound complex. The decrease of
peak current in the presence of DNA implies the interaction of
the complexes with DNA. It has already been observed that the
new complexes were irreversibly reduced in the range ꢀ0.52 to
ꢀ0.55 V. But, after adding DNA into the complexes, the peak cur-
rent of the cyclic voltammetric waves diminished regularly, but
no palpable change in the peak potential were observed for com-
plexes (1), (2) and (4). However, it can be seen that the cathode
peak currents decreased in the presence of DNA. The decrease in
current may be attributed to the slow diffusion of an equilibrium
mixture of the free and DNA bound complexes to the electrode sur-
face [59]. The decrease in the peak current generally is ascribed to
the stronger binding between the complexes and DNA. In contrast,
the irregular changes in peak current were observed for the com-
plexes (3), (5) and (6). This indicates the different binding affinity
of the complexes with DNA.
3.7. Chemical nuclease activity
There is substantial and continuing interest in DNA endonucleo-
lytic cleavage reactions that are activated by metal ions [67–69].
Redox-active complexes are expected to show good chemical
nuclease activity in the presence of metal-based redox couple(s).
The cleavage reaction on plasmid DNA can be monitored by aga-
rose gel electrophoresis. When circular plasmid DNA is subjected
to electrophoresis, relatively fast migration will be observed for
the intact supercoil form (Form I). If scission occurs on one strand
(nicking), the supercoil will relax to generate a slower-moving
open circular form (Form II). If both strands are cleaved, a linear
3.6.3. Thermal denaturation studies
According to the literature [60,61], the intercalation of natural
or synthesized organic- and metallointercalators generally results
in a considerable increase in the melting temperature (Tm). The
thermal behaviour of DNA in the presence of complexes can give
insight into the conformation change as the temperature is raised.
The melting temperature Tm of DNA solution, which is defined as
the temperature where half of the total base pairs is unbonded, is
usually introduced to study the interaction of transition metal
complexes with nucleic acid. Generally, the melting temperature
of DNA increases when metal complexes bind to DNA by intercala-
tion, as intercalation of the complexes between DNA base pairs
causes stabilization of base stacking and hence raises the melting
temperature of double-stranded DNA. The melting curves of
HS-DNA in the absence and presence of complex are presented in
Fig. 4. In the absence of any added complexes, the thermal denatur-
ation carried out for DNA gave a Tm of 60 2 °C under our
experimental conditions. We have observed only a minor increase
(1–3 °C) in the DNA melting temperature of HS-DNA in the
presence of complexes 1–6, indicating the groove and/or electro-
static binding nature of the complexes. This reveals that the DNA
interaction of the present Ru(II) complexes with the double-
stranded DNA is relatively weak.
Fig. 5. Effect of increasing amount of the complexes(1–6) on the relative viscosity
of HS-DNA at 16( 0.l) °C.

N. Chitrapriya et al. / Journal of Molecular Structure 984 (2010) 30–38
37
Fig. 6. Cleavage of supercoiled pBR322 DNA by the Ru(II) complexes in Tris–HCl buffer in the presence of sodium ascorbate (1 mM); in TAE buffer at 37 °C. Lane 1, DNA
control; lane 2, DNA + sodium ascorbatelane 3, DNA + complex 1 (25 m); lane 4, DNA + complex 2 (25 m); lane 5, DNA + complex 3 (25 m); lane 6, DNA + complex 4
m); lane 8, DNA + complex 6 (25 m); lane 9, DNA + complex 1 (100 m); lane 10, DNA + complex 2 (100 m); lane 11,
m); lane 13, DNA + complex 5 (100 m); lane 14, DNA + complex 6 (100 m). SC = supercoiled, NC = nicked
l
l
l
(25
lm); lane 7, DNA + complex 5 (25
l
l
l
l
DNA + complex 3 (100
lm); lane 12, DNA + complex 4 (100
l
l
l
circular DNA.
Fig. 7. Cleavage of supercoiled pBR322 DNA by the Ru(II) complexes in Tris–HCl buffer in the presence of sodium ascorbate (1 mM) in TAE buffer at 37 °C. Lane 1, DNA
control; lane 2, DNA + sodium ascorbate; lane 3, DNA + complex 3 (20 m); lane 4, DNA + complex 3 (40 m); lane 5, DNA + complex 3 (60 m); lane 6, DNA + complex 3
(80 m); lane 7, DNA + complex 3 (100 m); lane 8, DNA + complex 6 (20 m); lane 9, DNA + complex 6 (40 m); lane 10, DNA + complex 6 (60 m); lane 11, DNA + complex
6 (80 m); lane 12, DNA + complex 6 (100 m).
l
l
l
l
l
l
l
l
l
l
Fig. 8. Cleavage of supercoiled pBR322 DNA by the 40
lm of complex (3 or 6) in the presence of sodium ascorbate (1 mM) and potential inhibitors agents. Lane 1, DNA
control; lane 2, DNA + complex 3 (40 m); lane 3, DNA + complex 3 + ethanol (2 mM); lane 4, DNA + complex 3 + NaN3 (1 mM); lane 5, DNA + complex 3 + tiron (2 mM); lane
l
6, DNA + complex 3 + KI (5 mM); lane 7, DNA + complex 6; lane 8, DNA + complex 6 + ethanol (2 mM); lane 9, DNA + complex 6 + NaN3 (1 mM); 10, DNA + complex 6 + tiron
(2 mM); 11, DNA + complex 6 + KI (5 mM).
form (Form III) that migrates between Form I and Form II will be
generated [70]. The tests were performed under aerobic conditions
with sodium ascorbate (1 mM) as a reducing agent. No cleavage
occurs in the absence of sodium ascorbate or with uncomplexed
Ru atoms (not shown). As shown in Fig. 6, no obvious DNA cleavage
was observed for the control in which metal complex was absent
(DNA alone), or incubation of the plasmid with sodium ascorbate
alone. The complexes 3 and 6 can effectively cleave DNA but other
complexes do not show any significant chemical nuclease activity,
cleavage mode is not involved. In order to establish the reactive
species responsible for the cleavage of the plasmid, the following
experiments were carried out. The cleavage activity of 3 and 6 in
the presence of different inhibitors are shown in Fig. 8. Complete
inhibition of DNA cleavage was observed in the presence of perox-
ide scavenger such as KI or catalase, which suggests that the perox-
ide is likely to be the reactive species responsible for the cleavage
reaction. Moreover, the cleavage was weakly inhibited by hydroxyl
radical scavengers such as ethanol or mannitol. This indicates that
OHÅ may also be the reactive species. However, the cleavage is not
even at a concentration as high as 100 lM. It can be concluded that
complexes 3 and 6 are the most efficient nuclease in the series.
Fig. 7 (lanes 3–8) shows the gel electrophoretic separations of plas-
mid pBR322 DNA after incubation 24 h in the presence of varying
concentrations of complexes 3 and 6 with sodium ascorbate
(1 mM). It can be seen that with increasing the concentration of
complex, Form II (nicked circular DNA) increase gradually, while
Form I (supercoiled circular pBR 322 DNA) diminish gradually,
but the Form III (linear DNA) do not occur. It is suggested that these
Ru(II) complexes present weak nuclease activity. It is clear that the
degradation of pBR 322 DNA is highly dependent on the concentra-
tion of complex used. The percentage of Form II demonstrates a lin-
ear correlation with concentration. Hence, it is evident that the
complexes 3 and 6 in the presence of ascorbate show nuclease
activity. The nuclease activity of the 3 and 6 may be related to their
different structural features as compared to other complexes.
Reactions in the absence of dioxygen and/or hydrogen peroxide
were performed simultaneously. DNA was not cleaved by 3 and 6
under such conditions (not shown). The results indicated molecu-
lar oxygen is an essential cofactor for DNA scission and a hydrolytic
inhibited by the singlet oxygen (1O2) and superoxide dismutase
Åꢀ
quenchers, suggesting that 1O2 and O are not the reactive species.
2
Oxidation of the complexes by molecular oxygen is expected to
proceed in a manner analogous to that observed for some ruthe-
nium complexes [71]. The chemical nuclease mechanism of ruthe-
nium complexes was reported rather rarely. A mechanism has
been suggested [72,73] involving a simple bimolecular, outer
sphere oxidation of the metal ion to generate superoxide, followed
by a second single-electron transfer from Ru(II) to yield HOꢀ2 . In
this mechanism the HOÅ radical produced ultimately is thought
to abstract a hydrogen atom from deoxyribose, and lead to sugar
fragmentation, base release and then DNA cleavage [74,75].
4. Conclusion
The spectroscopic data and crystal structure of the complexes
have been of great help to understanding the uncoordinated oxi-
mato oxygen atom. The deprotonation of the oxime OH group leads

38
N. Chitrapriya et al. / Journal of Molecular Structure 984 (2010) 30–38
[26] D. Mansuy, P. Battioni, J.-P. Battioni, Eur. J. Biochem. 184 (1989) 267.
[27] J. Custot, J.-L. Boucher, S. Vadon, C. Guedes, S. Dijols, M. Delaforge, D. Mansuy, J.
Biol. Inorg. Chem. 1 (1995) 73.
[28] A.I. Vogel, Text Book of Practical Organic Chemistry, 5th ed., Longman, London,
1989.
[29] N. Ahmed, J.J. Lewison, S.D. Robinson, M.F. Uttley, Inorg. Synth. 15 (1974) 48.
[30] R.A.S. Pelgado, W.Y. Lee, S.R. Choi, Y. Cho, M.J. Jun, Trans. Met. Chem. 16 (1991)
241.
[31] Bruker Advanced X-ray Solutions SMART for WNT/2000, Version 5.628, Bruker
AXS Inc., Madison, Wisconsin, USA, 1997–2002.
[32] Bruker Advanced X-ray Solutions SAINT, Version 6.45, Bruker AXS Inc.,
Madison, Wisconsin, USA, 1997–2003.
[33] Bruker Advanced X-ray Solutions SADABS in SAINT, Version 6.45, Bruker AXS
Inc., Madison, Wisconsin, USA, 1997-2003.
[34] G.M. Sheldrick, SHELXTL, Version 6.14, Bruker AXS, Inc, Madison, WI, 2003.
[35] S.C. Jakels, F. Farmery, E.K. Barfield N.J. Rose, D.H. Busch, Inorg. Chem. 11
(1972) 289.
[36] M.A. Greaney, C.L. Coyle, M.A. Harmer, A. Jordan, E.I. Stifel, Inorg. Chem. 28
(1989) 912.
to a rearrangement of the electron density from the oxime oxygen
to the oxime nitrogen making the latter donor very efficient in me-
tal ion coordination. In addition, the interaction of the complexes
with DNA was investigated by absorption spectroscopy, cyclic vol-
tammetry and thermal denaturation measurements. The results
indicate that the complexes do not intercalate between the DNA
base pairs. Most probably, the interaction of the complexes is
mainly electrostatic through the phosphate backbone of the DNA.
These results further supported by viscosity measurement. The
poor DNA-binding propensity of the complexes could be due to
the presence of triphenylphophine as a steric protector ligand.
DNA cleavage studies carried out with the complexes demonstrate
that the complexes are less efficient in promoting the cleavage of
plasmid DNA even in the presence sodium ascorbate. At high con-
centration, complexes 3 and 6 can effectively cleave the DNA in
presence of activating agent.
[37] E.S. Dodsworth, A.B.P. Lever, Chem. Phys. Lett. 124 (1986) 152.
[38] A. Cukurovali, E. Tas, Synth. React. Inorg. Met. – Org. Chem. 28 (3) (1998) 449.
[39] L.A. Epps, L.G. Marzilli, Inorg. Chem. 12 (1973) 1514.
[40] A.L. Crumbliss, P.L. Gaus, Inorg. Chem. 14 (11) (1975) 2745.
[41] L.F. Szczepura, J.G. Muller, C.A. Bessel, R.F. See, T.S. Janik, M.R. Churchill, K.J.
Takeuchi, Inorg. Chem. 31 (1992) 859.
Supplementary material
[42] N. Chitrapriya, V. Mahalingam, L.C. Channels, M. Zeller, F.R. Fronczek, K.
Natarajan, Inorg. Chim. Acta 361 (2008) 2841.
[43] R. Raveendran, S. Pal, Polyhedron 24 (2005) 57.
[44] M. Maji, M. Chatterjee, S. Ghosh, S.K. Chattopadhyay, B.-M. Wu, T.C.W. Mak, J.
Chem. Soc. Dalton Trans. 135 (1999).
[45] N. Chitrapriya, V. Mahalingam, M. Zeller, K. Natarajan, Polyhedron 27 (2008)
1573.
[46] E. Bermejo, A. Castineiras, D.X. West, Z. Naturforsch. 56B (2001) 369.
[47] J.D. Martin, K.A. Abboud, K.-H. Dahmen, Inorg. Chem. 37 (1998) 5811.
[48] S. Ganguly, V. Manivannan, A. Chakravorty, J. Chem. Soc. Dalton Trans. 146
(1998).
[49] S.A. Serron, C.M. Haar, S.P. Nolan, Organometallics 16 (1997) 5120.
[50] M. Poyatos, J.A. Mata, E. Falomir, R.H. Crabtree, E. Peris, Organometallics 22
(2003) 1110.
[51] M.A. Rankin, R. McDonald, M.J. Ferguson, M. Stradiotto, Angew. Chem. Int. Ed.
44 (2005) 3603.
[52] M. Calleri, G. Ferreris, D. Viterbo, Acta Crystallogr. 20 (1966) 73.
[53] L.E. Sutton, Spec. Publ. – Chem. Soc. 18 (1965).
CCDC 663251 and 632083 contain the supplementary crystallo-
graphic data for 1 and 2. These data can be obtained free of charge
from via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from
the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336 033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this article
can be found in the online version.
References
[1] V.Y. Kukushkin, D. Tudela, A.J.L. Pombeiro, Coord. Chem. Rev. 156 (1996) 333.
[2] V.Y. Kukushkin, A.J.L. Pombeiro, Coord. Chem. Rev. 181 (1999) 147.
[3] S. Ganguly, S. Karmakar, C.K. Pal, A. Chakravorty, Inorg. Chem. 38 (1999) 5984.
[4] E.A. Bruton, L. Brammer, F.C. Pigge, C.B. Aakeroy, D.S. Leinend, New J. Chem. 27
(2003) 1084.
[54] S.M. Morehouse, A. Polychronopoulou, G.J.B. Williams, Inorg. Chem. 19 (1980)
3558.
[5] M. Kurtoglu, S. Serin, Synth. React. Inorg. Met. – Org. Chem. 32 (2002) 629.
[6] M. Ertas, V. Ahsen, A. Gul, O. Bekarogelu, J. Organomet. Chem. 335 (1987) 105.
[7] Y. Gok, H. Kantekin, New J. Chem. 19 (1995) 461.
[8] D.C. Bradley, R.C. Mehrotra, I.P. Rothwell, A. Sing, Alkoxo and Aryloxo
Derivatives Metals, Academic Press, London, 2001.
[55] Z.D. Xu, H. Liu, S.L. Xiao, M. Yang, X.H. Bu, J. Inorg. Biochem. 90 (2002) 83.
[56] Y. Wang, Z.-Y. Yang, Trans. Met. Chem. 30 (2005) 902.
[57] C.-Y. Zhou, J. Zhao, Y.-B. Wu, C.-X. Yin, P. Yang, J. Inorg. Biochem. 101 (2007) 10.
[58] Q.S. Li, P. Yang, H.F. Wang, M.L. Guo, J. Inorg. Biochem. 64 (1996) 181.
[59] J. Liu, T. Zhang, T. Lu, L. Qu, H. Zhou, Q. Zhang, L. Ji, J. Inorg. Biochem. 91 (2002)
269.
[60] M.J. Waring, J. Mol. Biol. 13 (1965) 269.
[61] G.A. Neyhart, N. Grover, S.R. Smith, W.A. Kalsbeck, T.A. Fairly, M. Cory, H.H.
Thorp, J. Am. Chem. Soc. 115 (1993) 4423.
[9] A. Chakravorty, Coord. Chem. Rev. 13 (1974) 1.
[10] A.M. Duda, A. Karaczyn, H. Kozlowski, I.O. Fritsky, T. Glowiak, E.V. Prisyazhnaya,
T.Y. Sliva, J.S. Kozlowskac, J. Chem. Soc. Dalton Trans. 3853 (1997).
[11] B. Kurzak, H. Kozlowski, E. Farkas, Coord. Chem. Rev. 114 (1992) 169.
[12] B. Cervera, R. Ruiz, F. Lloret, M. Julve, J. Faus, M.C. Munoz, Y. Journaux, Inorg.
Chim. Acta 288 (1999) 57.
[62] X. Xiaoli, Y. Manman, Z. Chengyong, Z. Jing, Y. Pin, Chin. Sci. Bull. 51 (19) (2006)
2322.
[13] R. Ruiz, J. Sanz, B. Cervera, F. Lloret, M. Julve, C. Bois, J. Faus, M. Carmen Munoz,
J. Chem. Soc. Dalton Trans. 1623 (1993).
[63] D.S. Sigman, A. Mazumder, D.M. Perrin, Chem. Rev. 93 (1993) 2295.
[64] S. Satyanarayana, J.C. Dabrowiak, J.B. Chaires, Biochem. 31 (1992) 9319.
[65] J.B. Suh, Chaires, Bioorg. Med. Chem. 3 (6) (1995) 723.
[66] J.D. Aguirre, A.M. Angeles-Boza, A. Chouai, C. Turro, J. Pellois, K.R. Dunbar,
Dalton Trans. (2009) 10806.
[14] M. Kandaz, I. Yylmaz, S. Keskin, A. Koca, Polyhedron 21 (2002) 825.
[15] J.R. Dilworth, S.J. Parrott, Chem. Soc. Rev. 27 (1998) 43.
[16] P.J. Blower, Trans. Met. Chem. 23 (1998) 109.
[17] W.A. Wolkert, T.J. Hoffman, Chem. Rev. 99 (1999) 2269.
[18] K. Ohta, R. Higashi, M. Ikejima, I. Yamamoto, N. Kobayashi, J. Mater. Chem. 8
(1998) 1979.
[67] D.S. Sigman, Acc. Chem. Res. 19 (1986) 180.
[68] B. Armitage, Chem. Rev. 98 (1998) 1171.
[19] B.G. Malmstrom, Acc. Chem. Res. 26 (1993) 332.
[69] A. Sitlani, E.C. Long, A.M. Pyle, J.K. Barton, J. Am. Chem. Soc. 114 (1992) 2303.
[70] J.K. Barton, A.L. Raphael, J. Am. Chem. Soc. 106 (1984) 2466.
[71] D. Stanbury, O. Haas, H. Taube, Inorg. Chem. 19 (1980) 518.
[72] P. Uma Maheswari, M. Palaniandavar, J. Inorg. Biochem. 98 (2004) 219.
[73] P. Uma Maheswari, M. Palaniandavar, Inorg. Chim. Acta 357 (2004) 901.
[74] R.P. Hertzberg, P.B. Dervan, J. Am. Chem. Soc. 104 (1982) 313.
[75] R.P. Hertzberg, P.B. Dervan, Biochemistry 23 (1984) 3934.
[20] M.C.M. Laranleira, R.A. Marusak, A.G. Lappin, Inorg. Chim. Acta 186 (2000) 300.
[21] M. Bakir, J. Electroanal. Chem. 466 (1999) 60.
[22] M. Bakir, J.A.M. McKenzie, J. Chem. Soc. Dalton Trans. 3571 (1997).
[23] A.R. Ozkaya, A. Gurek, A. Gul, O. Bekaroglu, Polyhedron 16 (1997) 1877.
[24] A.R. Ozkaya, I. Yilmaz, O. Bekaroglu, J. Porphyrins, Phthalocyanines 2 (1998)
483.
[25] A.R. Ozkaya, E. Hamuryudan, Z. Altuntasß Bayyr, O. Bekaroglu, J. Porphyrins
Phthalocyanines 4 (2000) 689.