Bio-catalysts and catalysts based on ruthenium(II) polypyridyl complexes imparting diphenyl-(2-pyridyl)-phosphine as a co-ligand

Article abstract of DOI:10.1016/j.jorganchem.2011.06.031

Reactions of the ruthenium complexes [Ru(κ³-tpy)(PPh ₃)Cl₂, [Ru(κ³-tptz)(PPh ₃)Cl₂ and [Ru(κ³-tpy)Cl₃ [tpy = 2,2′:6′,2′′-terpyridine; tptz = 2,4,6-tris(2-pyridyl)- 1,3,5-triazine with diphenyl-(2-pyridyl)-phosphine (PPh₂Py) have been investigated. The complexes [Ru(κ³-tpy)(PPh ₃)Cl₂ and [Ru(κ³-tptz)(PPh ₃)Cl₂ reacted with PPh₂Py to afford [Ru(κ³-tpy)(κ¹-P-PPh₂Py) ₂Cl⁺ (1) and [Ru(κ³-tptz) (κ¹-P-PPh₂Py)₂Cl⁺ (2), which were isolated as their tetrafluoroborate salts. Under analogous conditions, [Ru(κ³-tpy)Cl₃ gave a neutral complex [Ru(κ³-tpy)(κ¹-PPh₂Py)Cl ₂ (3). Upon treatment with an excess of NH₄PF₆ in methanol, 1 and 2 gave [Ru(κ³-tpy)(κ¹-P- PPh₂Py)(κ²-P,N-PPh₂Py)(PF ₆)₂ (4) and [Ru(κ³-tptz) (κ¹-P-PPh₂Py)(κ²-P,N-PPh ₂Py)(PF₆)₂ (5) containing both monodentate and chelated PPh₂Py. Further, 4 and 5 reacted with an excess of NaCN and CH₃CN to afford [Ru(κ³-tpy)(κ¹-P- PPh₂Py)₂(CN)(PF₆) (6), [Ru(κ³- tpy)(κ¹-P-PPh₂Py)₂(NCCH ₃)(PF₆)₂ (7), [Ru(κ³-tptz) (κ¹-P-PPh₂Py)₂(CN)PF₆ (8) and [Ru(κ³-tptz)(κ¹-P-PPh₂Py) ₂(NCCH₃)(PF₆)₂ (9) supporting hemi labile nature of the coordinated PPh₂Py. The complexes have been characterized by elemental analyses, spectral (IR, NMR, electronic absorption, FAB-MS), electrochemical studies and structures of 1, 2 and 3 determined by X-ray single crystal analyses. At higher concentration level (40 μM) the complexes under investigation exhibit inhibitory activity against DNA-Topo II of the filarial parasite S. cervi and 3 catalyses rearrangement of aldoximes to amide under aerobic conditions.

Full text of DOI:10.1016/j.jorganchem.2011.06.031

Journal of Organometallic Chemistry 696 (2011) 3454e3464
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Bio-catalysts and catalysts based on ruthenium(II) polypyridyl complexes
imparting diphenyl-(2-pyridyl)-phosphine as a co-ligand
*
Prashant Kumar, Ashish Kumar Singh, Rampal Pandey, Daya Shankar Pandey
Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi, U.P. 221 005, India
a r t i c l e i n f o
a b s t r a c t
Reactions of the ruthenium complexes [Ru(k k k
3-tpy)(PPh3)Cl2], [Ru( 3-tptz)(PPh3)Cl2] and [Ru( 3-tpy)Cl3]
Article history:
[tpy ¼ 2,20:60,200-terpyridine; tptz ¼ 2,4,6-tris(2-pyridyl)-1,3,5-triazine] with diphenyl-(2-pyridyl)-phos-
Received 14 February 2011
Received in revised form
7 June 2011
phine (PPh2Py) have been investigated. The complexes [Ru(k k
3-tpy)(PPh3)Cl2] and [Ru( 3-tptz)(PPh3)Cl2]
reacted with PPh2Py to afford [Ru(
which were isolated as their tetrafluoroborate salts. Under analogous conditions, [Ru(
a neutral complex [Ru(
3-tpy)( 1-PPh2Py)Cl2] (3). Upon treatment with an excess of NH4PF6 in methanol,
1 and 2 gave [Ru(
3-tpy)( 1-P-PPh2Py)( 2-P,N-PPh2Py)](PF6)2 (4) and [Ru( 3-tptz)( 1-P-PPh2Py)( 2-P,N-
PPh2Py)](PF6)2 (5) containing both monodentate and chelated PPh2Py. Further, 4 and 5 reacted with an
excess of NaCN and CH3CN to afford [Ru(
3-tpy)( 1-P-PPh2Py)2(CN)](PF6) (6), [Ru( 3-tpy)( 1-P-
PPh2Py)2(NCCH3)](PF6)2 (7), [Ru(
3-tptz)( 1-P-PPh2Py)2(CN)]PF6 (8) and [Ru( 3-tptz)( 1-P-PPh2
k
3-tpy)(
k
1-P-PPh2Py)2Cl]þ (1) and [Ru(
k
3-tptz)(
k
1-P-PPh2Py)2Cl]þ (2),
3-tpy)Cl3] gave
Accepted 28 June 2011
k
k
k
Keywords:
k
k
k
k
k
k
Polypyridyl ruthenium complex
Topo II isomerase inhibition
DNA binding
k
k
k
k
k
k
k
k
Catalysis
Py)2(NCCH3)](PF6)2 (9) supporting hemi labile nature of the coordinated PPh2Py. The complexes have
been characterized by elemental analyses, spectral (IR, NMR, electronic absorption, FAB-MS), electro-
chemical studies and structures of 1, 2 and 3 determined by X-ray single crystal analyses. At higher
Diphenylphosphinopyridine
concentration level (40 mM) the complexes under investigation exhibit inhibitory activity against DNA-
Topo II of the filarial parasite S. cervi and 3 catalyses rearrangement of aldoximes to amide under
aerobic conditions.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
about a variety of potential applications. DNA-topoisomerases,
which are intricately involved in maintaining the topographic
Considerable current interest has arisen in ruthenium(II) poly-
pyridyl complexes because of their interesting photochemical
properties and potential application in diverse areas [1e6]. The
cationic complexes based on Pt, Ru, Rh, Co and Zn containing pol-
ypyridyl ligands display intense metal-to-ligand charge transfer
(MLCT) and strong luminescence in the visible region and have the
potential to serve as an excellent probe for various micro-
environments [7,8]. The polypyridyl ligands present in complexes
play an important role in determining and improving their light
emitting and electron transfer performances [9e11]. Study of
kinetically inert octahedral Ru(II) complexes as chiral probes for
DNA has elicited intense investigation in recent years. The Ru(II)
complexes may bind DNA either through non-covalent interactions
such as electrostatic, groove binding and intercalation, or a combi-
nation of these depending upon its structure [12,13]. An under-
standing of how the metal complexes bind DNA will not only pave
the way to understand fundamentals of these interactions but, also,
structure of DNA transcription and mitosis, have been identified as
an important biochemical target in cancer chemotherapy, microbial
infection, and development of antifilarial compounds [14e16]. In
our earlier work we have shown that octahedral ruthenium
complexes containing both the phosphine and polypyridyl/pyr-
idylazine ligands behave as Topo II inhibitors and inhibition
percentage largely depends on the nature of complexes and
number of uncoordinated N-donor sites of the polypyridyl ligand
[14e17].
The hetero difunctional ligand diphenyl-(2-pyridyl)-phosphine
(PPh2Py) may coordinate metal center in monodentate, chelating or
bridging manner depending on requirements (Scheme 1) [18e23].
PPh2Py, in its chelating mode forms four membered rings which are
strained, relatively unstable, and plays crucial role in catalysis
[24e33]. While a few reports dealing with ruthenium complexes
based on PPh2Py are available in the literature complexes con-
taining both the PPh2Py and polypyridyl ligands are rather scarce
[18e23].
Transition metal-catalyzed transfer hydrogenations have been
successfully employed in the transformation of alcohol and
* Corresponding author. Tel.: þ91 542 6702480; fax: þ91 542 2368174.
E-mail addresses: dspbhu@bhu.ac.in, dspbhu@yahoo.co.in (D. S. Pandey).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.06.031

P. Kumar et al. / Journal of Organometallic Chemistry 696 (2011) 3454e3464
3455
M
N
Ph
M
M
Ph
M
N
M
P
P
Ph
Ph
Ph
N
P
Ph
N
P
Ph
Ph
N-monodentate
P-N bridge homo/heterobimetallic
P-monodentate
P-N chelate mode
Scheme 1.
carbonyl compounds [34e38]. Catalytic reduction of alkenes and
imines has also been achieved in presence of an alcohol as stoi-
chiometric reducing agent, as the conversion of alcohol into amine
using ruthenium catalysts [34e39]. The rearrangement of oxime to
amide is catalyzed by many reagents and generally in such reac-
tions R group anti- to the hydroxyl migrates to give the final
product (Scheme 2). Metal-catalyzed rearrangement of aldoximes
is well documented in the literature and it has been shown that
these reactions require relatively high catalyst loadings and
elevated temperature [34e38]. Recently, Williams et al., have
reported a catalyst based on ruthenium that effectively catalyses
rearrangement of aldoximes to amides [39]. This catalytic system
requires both a chelating phosphine and p-toluene sulfonic acid as
an additive and can form a mixture of amide and nitrile.
water. Topoisomerase II (Topo II) was isolated from the filarial
parasite S. cervi and partially purified by literature procedures
[50,51].
2.2. Instrumentation
Elemental analyses for C, H and N were performed on an Exeter
CE-440 elemental analyzer. Infra red spectra in nujol mull and
electronic spectra in dichloromethane were acquired on a Varian
3300 FT-IR and Shimadzu UV-1601 spectrophotometers, respec-
tively. 1H and 31P NMR spectra were obtained at room temperature
on a JEOL AL 300 FT-NMR using CDCl3 as a solvent and TMS as an
internal reference for 1H and 85% H3PO4 for 31P NMR. FAB mass
spectra (FAB-MS) were recorded on a JOEL SX 102/DA-6000 Mass
Spectrometer using Xenon as the FAB gas (6 kV, 10 mA). Acceler-
ating voltage was 10 kV and spectra were recorded at room
temperature using m-nitrobenzyl alcohol as the matrix. Cyclic
voltammetric measurements were performed on a CHI 620c elec-
trochemical analyzer. A platinum working electrode, platinum wire
auxiliary electrode, and Ag/Agþ reference electrode were used in
a standard three electrode configuration. Tetrabutylammonium
perchlorate (TBAP) was used as the supporting electrolyte and
It is noteworthy that the ligand tpy is indispensable in coordi-
nation chemistry and molecular recognition, complexes based on it
has seldom been employed in organometallic catalysis [40e47]. In
this direction, an attempt has been made to develop bio-catalysts
and catalysts based on ruthenium complexes containing both
PPh2Py and polypyridyl ligands tpy or tptz. The present work deals
with synthesis and characterization of cationic ruthenium(II)
complexes of the formulations [Ru(
or tptz), [Ru(
3-L)( 1-P-PPh2Py)(
complex [Ru(
3-tpy)(
[Ru(
3-tpy)-( 1-P-PPh2Py)2Cl]BF4 (1), [Ru(
Cl]BF4 (2), and [Ru(
3-tpy)( 1-PPh2Py)-Cl2] (3). We also report
herein, inhibitory effect of 1e5 on DNA-Topoisomerase (Topo II)
activity of the filarial parasite Setaria. cervi, -hematin/hemozoin
k
k
3-L)(
k
1-P-PPh2Py)2Cl]þ (L ¼ tpy
2-P,N-PPh2Py)]2þ
,
a
neutral
solution concentration was ca. 10ꢀ3
.
k
k
k
k
1-PPh2Py)Cl2] and crystal structures of
k
k
k
3-tptz)( 1-P-PPh2Py)2
k
2.3. Synthesis
k
k
2.3.1. Synthesis of [Ru(
k
3-tpy)(
k
1-P-PPh2Py)2Cl]BF4 (1)
To a suspension of [Ru(
k
3-tpy)(PPh3)Cl2] (0.667 g, 1.0 mmol) in
b
formation in presence of Plasmodium yoelii lysate and application of
3 in the rearrangement of aldoximes to amide under aerobic
conditions.
methanol (25 mL) PPh2Py (0.526 g, 2.0 mmol) was added and
contents of the flask were heated under reflux for 07 h. Resulting
dark red solution was cooled to room temperature and filtered to
remove any solid residue. The filtrate was concentrated to one
fourth of its volume under reduced pressure and a saturated
solution of ammonium tetrafluoroborate dissolved in methanol
added to it. Slowly, microcrystalline product separated which was
filtered washed with diethyl ether and dried under vacuo. Yield:
0.339 g (77%). Microanalytical data BC49F4H39N5P2RuCl requires: C,
55.01; H, 3.67; N, 6.55%. Found: C, 55.15; H, 3.59; N, 6.44%. FAB-MS
[m/z, calcd. (obs.)]: 983.1 (983) [Ru(tpy)(PPh2Py)2Cl)](BF4); 896.3
2. Experimental section
2.1. General
Analytical grade reagents were used throughout. The solvents
were dried and distilled following standard literature procedures
[48]. Hydrated ruthenium(III) chloride, diphenyl-(2-pyridyl)-phos-
phine, 2,20:60,200-terpyridine, 2,4,6-tris(2-pyridyl)-1,3,5-triazine,
(896) [Ru(tpy)(PPh2Py)2Cl)]þ; 860.8 (860) [Ru(tpy)-(PPh2Py)2]2þ
597.8 (597) [Ru(tpy)(PPh2Py)]2þ 1H NMR (
ppm): 8.91 (d, 2H,
;
.
d
ammonium
tetrafluoroborate
and
ammonium
hexa-
J ¼ 5.1 Hz, tpy), 8.69 (d, 2H, J ¼ 5.4 Hz; Py, PPh2Py), 8.47 (d, 2H,
J ¼ 6.3 Hz, tpy), 8.13 (d, 2H, J ¼ 6.9 Hz; Py, PPh2Py), 7.94 (d, 3H,
J ¼ 7.8 Hz; Py, PPh2Py þ tpy), 7.71 (d, 4H, J ¼ 6.0 Hz, tpy), 7.45 (d, 2H,
J ¼ 4.8 Hz, tpy), 7.26e6.92 (br. m, 20H, PPh2Py), 6.45 (d, 2H,
fluorophosphate were procured from Aldrich and used without
further purifications. Calf thymus (CT) and supercoiled pBR322 DNA
were procured from Sigma Chemical Co., St. Louis, MO. The
complexes [Ru(
[Ru(
3-tpy)Cl3] were prepared following literature procedures
[17,49]. Various buffers were prepared in triply distilled deionized
k k
3-tpy)Cl2(PPh3)], [Ru( 3-tptz)Cl2(PPh3)] and
J ¼ 6.3 Hz; Py, PPh2Py). 31P{1H} NMR (
d ppm): 36.02 (s). IR (nujol,
k
cmꢀ1): 1626 (s), 1440 (s), 1394 (m), 1102 (m), 758 (s), 698 (s), 1056
(br, BeF, BFꢀ4 ). UVevis [lmax, nm;
3
, Mꢀ1 cmꢀ1]: 554 (10800), 485
(21000), 345 (19400), 286 (39500).
O
HO
R
Rearrangment
2.3.2. Synthesis of [Ru(k k
3-tptz)( 1-P-PPh2Py)2Cl]BF4 (2)
N
R'
It was prepared following the above procedure for 1 using
R
N
[Ru(
k
3-tptz)Cl2(PPh3)] in place of [Ru( 3-tpy)(PPh3)Cl2]. Yield:
k
R'
H
0.524 g (70%). Microanalytical data BC52F4H40N8P2O2ClRu requires:
C, 57.08; H, 3.68; N, 10.24%. Found: C, 56.98; H, 3.71; N, 10.22%. FAB-
Scheme 2. Beckmann rearrangement of oximes to amides.

3456
P. Kumar et al. / Journal of Organometallic Chemistry 696 (2011) 3454e3464
MS [m/z, calcd. (obs.)]: 1007.4 (1008) [Ru(tptz)(PPh2Py)2Cl]þ;
[Ru(tptz)(PPh2Py)(PPh2Py)]þ; 821 [Ru(tptz)(PPh2Py)]þ. 1H NMR (
d
744.14 (745) [Ru(tptz)(PPh2Py)Cl]þ; 480.8 (481) [Ru(tptz)Cl]þ. 1H
ppm): 9.02 (d, 2H, J ¼ 6.1 Hz, tptz), 8.79 (d, 1H, J ¼ 6.3 Hz; Py, k2
-
NMR (
d
ppm): 9.20 (d, 2H, J ¼ 3.9 Hz, tptz), 8.84 (d, 1H, J ¼ 7.8 Hz,
PPh2Py), 8.65 (d, 1H, J ¼ 4.2 Hz; Py,
k
1-PPh2Py), 8.43 (d, 2H,
tptz), 8.78 (d, 2H, J ¼ 6.3 Hz; Py, PPh2Py), 8.74 (d, 2H, J ¼ 11.7 Hz; Py,
PPh2Py), 8.60 (d, 3H, J ¼ 6.0 Hz, tptz), 8.43 (d, 2H, J ¼ 5.1 Hz, tptz),
8.17 (d, 2H, J ¼ 5.1 Hz, tptz), 7.85 (d, 2H, J ¼ 6.3 Hz; Py, PPh2Py), 7.65
(d, 2H, J ¼ 4.8 Hz, tptz), 7.08e7.40 (br. m, 20H, PPh2Py), 6.37 (d, 2H,
J ¼ 5.4 Hz, tptz), 7.97 (d, 6H, J ¼ 4.8 Hz; Py, PPh2Py þ tptz), 7.90 (d,
2H, J ¼ 6.9 Hz; Py, PPh2Py), 7.85 (d, 4H, J ¼ 6.3 Hz, tptz), 6.97e7.36
(br. m, 20H, PPh2Py), 6.35 (d, 2H, J ¼ 7.5 Hz; Py, PPh2Py). 31P{1H}
NMR (
d
ppm): ꢀ12.30 (s), 38.48 (s). IR (nujol, cmꢀ1): 1598 (s), 1439
J ¼ 7.5 Hz; Py, PPh2Py). 31P{1H} NMR (
d
ppm): 40.40 (s). IR (nujol,
(s), 1388 (m), 1112 (m), 758 (s), 698 (s), 845 (s, PFꢀ6 ). UVevis. [lmax
,
cmꢀ1): 1596 (s), 1436 (s), 1390 (m), 1108 (m), 748 (s), 692 (s), 1054
nm; 3
, Mꢀ1 cmꢀ1]: 538 (6479), 495 (11900), 358 (10300), 279
(br, BFꢀ4 ). UVevis. [lmax, nm;
3
, Mꢀ1 cmꢀ1]: 536 (7940), 481 (11900),
(34400), 239 (35300).
346 (24100), 241 (38400).
2.3.6. Synthesis of [Ru(k k
3-tpy)( 1-P-PPh2Py)2(CN)]PF6 (6)
2.3.3. Synthesis of [Ru(
k
3-tpy)(
k
1-P-PPh2Py)Cl2] (3)
NaCN (0.52 g, 8.0 mmol) was added to a suspension of 2 (0.1 g,
0.086 mmol) in methanol (40 mL) and contents of the flask heated
under reflux for 10 h. Resulting solution was concentrated to
dryness under reduced pressure and the residue extracted with
dichloromethane (40 mL). After filteration through celite, the
filtrate was saturated with diethyl ether. It gave a red solid which
was filtered, washed with diethyl ether and dried in air. Yield:
0.670 g (64%). Microanalytical data C50H39N6P3F6Ru, requires: C,
58.20; H, 3.81; N, 8.14%. Found: C, 58.42; H, 4.13; N, 8.04%. 1H NMR
PPh2Py (0.263 g, 1.0 mmol) was added to a suspension of [Ru(k3
-
tpy)Cl3] (0.439 g, 1.00 mmol) in methanol (25 mL) and heated
under reflux for 07 h. Resulting solution was cooled to room
temperature and filtered to remove any solid residue. The filtrate
was concentrated under reduced pressure to one fourth of its
volume and left undisturbed for slow crystallization. Slowly,
a microcrystalline product separated which was filtered washed
with diethyl ether and dried under vacuo. Its crystal contained one
CH2Cl2 molecule. Yield: 0.169 g (64%). Microanalytical data
C33H27N4PCl4Ru requires: C, 52.61; H, 3.61; N, 7.44%. Found: C,
52.54; H, 3.56; N, 7.42%. FAB-MS [m/z, obs. (calcd.)]: 668 [Ru(t-
(
d
ppm): 8.45 (d, 2H, J ¼ 4.2 Hz, tpy), 7.86 (d, 2H, J ¼ 7.2 Hz; Py,
PPh2Py), 7.74 (m, 5H; Py, PPh2Py þ tpy), 7.64 (t, 4H, J ¼ 8.1 Hz, tpy),
7.48 (t, 4H, J ¼ 8.1 Hz; Py, PPh2Py þ tpy), 7.36e6.94 (br. m, 20H,
py)(PPh2Py)Cl2)]; 405 [Ru(tpy)Cl2)]. 1H NMR (
d
ppm): 9.18 (d, 2H,
PPh2Py), 6.87 (t, 2H, J ¼ 6.3 Hz; Py, PPh2Py). 31P{1H} NMR (
d ppm):
J ¼ 3.9 Hz, tpy), 8.93 (d, 1H, J ¼ 4.2 Hz; Py, PPh2Py), 8.71 (d, 2H,
J ¼ 6.9 Hz, tpy), 8.45 (d, 1H, J ¼ 5.7 Hz; Py, PPh2Py), 8.01 (t, 3H,
J ¼ 6.7 Hz; Py, PPh2Py þ tpy), 7.82 (dd, 3H, J ¼ 3.9 Hz, tpy), 7.62 (t,
2H, J ¼ 6.1 Hz, tpy), 6.99e7.45 (br. m, 10H, PPh2Py), 6.34 (t, 1H,
36.72 (s). IR (nujol, cmꢀ1): 2224 {s,
n(C^N)}, 1625 (s), 1441 (s), 1393
(m), 1102 (m), 756 (s), 698 (s), 844 (s, PFꢀ6 ).
2.3.7. Synthesis of [Ru(
k
3-tpy)( 1-P-PPh2Py)2(NCCH3)](PF6)2 (7)
k
J ¼ 6.3 Hz; Py, PPh2Py). 31P{1H} NMR (
d
ppm): 42.87 (s). IR (nujol,
It was prepared following the above procedure for 6 except that
an excess of CH3CN was used in place of NaCN. Yield: 0.882 g, 74%.
Microanalytical data: C51H42N6P4F12Ru requires: C, 51.39; H, 3.55;
cmꢀ1): 1624 (s), 1436 (s), 1396 (m), 1116 (m), 752 (s), 688 (s).
UVevis. [lmax, nm; 3
, Mꢀ1 cmꢀ1]: 548 (5520), 496 (9870), 354
(96300), 275 (27100).
N, 7.05%. Found: C, 51.36; H, 3.44; N, 7.03%. 1H NMR (
d ppm): 8.44
(d, 2H, J ¼ 4.3 Hz, tpy), 7.84 (d, 4H, J ¼ 7.5 Hz; Py, PPh2Py), 7.72 (m,
7H; Py, PPh2Py þ tpy), 7.60 (t, 2H, J ¼ 7.5 Hz, tpy), 7.48 (t, 2H,
J ¼ 7.8 Hz, tpy), 7.26e7.04 (br. m, 20H, PPh2Py), 6.87 (t, 2H,
2.3.4. Synthesis of [Ru(k k k
3-tpy)( 1-P-PPh2Py)( 2-P,N-PPh2Py)](PF6)2
(4)
NH4PF6 (0.354 g, 2.0 mmol) was added to suspension of 1
(1.069 g, 1.0 mmol) in methanol (15 mL) and stirred at room
temperature for 08 h. It gave a clear red solution which was
concentrated to dryness on a rotatory evaporator, extracted with
dichloromethane and filtered. The filtrate was saturated with
petroleum ether and left undisturbed for slow crystallization.
Slowly, microcrystalline solid separated which was filtered, washed
with diethyl ether and dried in vacuo Yield 0.664 g (57%). Micro-
analytical data C49F12H39N5P4Ru requires: C, 51.14; H, 3.42; N,
6.09%. Found: C, 51.11; H, 3.44; N, 6.12%. FAB-MS [m/z, calcd. (obs.)]:
J ¼ 6.3 Hz; Py, PPh2Py), 2.18 (s, 3H, CH3). 31P{1H} NMR (
d ppm):
36.72 (s). IR (nujol, cmꢀ1): 2100 {s,
n
(C^N), 1628 {s,
n(C¼N)}, 1439
(s), 1396 (m), 1100 (m), 756 (s), 698 (s), 842 (s, PFꢀ6 ).
2.3.8. Synthesis of [Ru(
k
3-tptz)( 1-P-PPh2Py)2(CN)]PF6 (8)
k
NaCN (0.39 g, 8.0 mmol) was added to a suspension of 4 (0.1 g,
0.081 mmol) in methanol (40 mL) and refluxed for 10 h. Resulting
solution was concentrated to dryness under reduced pressure and
residue extracted with dichloromethane (40 mL). After filtration
through celite the filtrate was saturated with diethyl ether. It gave
a brow red solid which was filtered, washed with diethyl ether and
dried in air. Yield: 0.810 g, 72%. Microanalytical data:
C54H44N9P3F6Ru, requires: C, 57.55; H, 3.94; N, 11.19%. Found: C,
860.9
(860)
[Ru(tpy)(PPh2Py)(PPh2Py)]2þ
;
597.6
(597)
[Ru(tpy)(PPh2Py)]2þ. 1H NMR (
d
ppm): 8.74 (d, 2H, J ¼ 4.8 Hz, tpy),
8.26 (d, 1H, J ¼ 6.0 Hz; Py,
k
2-PPh2Py), 8.10 (d, 3H, J ¼ 7.8 Hz; Py, k1
-
PPh2Py þ tpy), 7.91 (t, 3H, J ¼ 7.6 Hz; Py, PPh2Py þ tpy), 7.84 (d, 2H,
J ¼ 7.8 Hz, tpy), 7.61 (d, 4H, J ¼ 3.9 Hz; Py, PPh2Py þ tpy), 7.49 (d, 2H,
J ¼ 4.2 Hz, tpy), 7.08e7.33 (br. m, 20H, PPh2Py), 6.80 (q, 1H,
J ¼ 6.3 Hz; Py, PPh2Py), 6.45 (t, 1H, J ¼ 6.3 Hz; Py, PPh2Py). 31P{1H}
57.46; H, 3.76; N, 11.11%. 1H NMR (
d
ppm): 8.96 (d, 2H, J ¼ 2.6 Hz,
tptz), 8.78 (d, 1H, J ¼ 6.4 Hz, tptz), 8.72 (d, 2H, J ¼ 6.0 Hz; Py,
PPh2Py), 8.68 (d, 2H, J ¼ 9.8 Hz; Py, PPh2Py), 8.54 (d, 3H, J ¼ 6.2 Hz,
tptz), 8.48 (d, 2H, J ¼ 5.0 Hz, tptz), 8.20 (d, 2H, J ¼ 4.8 Hz, tptz), 7.80
(d, 2H, J ¼ 5.8 Hz; Py, PPh2Py), 7.52 (d, 2H, J ¼ 3.8 Hz, tptz),
7.12e7.36 (br. m, 20H, PPh2Py), 6.48 (d, 2H, J ¼ 5.6 Hz; Py, PPh2Py).
NMR (
d
ppm): 36.42 (s), ꢀ10.30 (s). IR (nujol, cmꢀ1): 1620 (s), 1439
(s), 1393 (m), 1100 (m), 768 (s), 694 (s), 840 (s, PFꢀ6 ). UVevis. [lmax
,
nm;
3
, Mꢀ1 cmꢀ1]: 539 (9270), 484 (17800), 341 (15700), 243
31P{1H} NMR ( ppm): 42.54 (s). IR (nujol, cmꢀ1): 2221 {s,
d n(C^N)},
(38700).
1594 {s, n(C]N)}, 1439 (s), 1390 (m), 1115 (m), 758 (s), 712 (s), 846
(s, PeF, PFꢀ6 ). UVevis. [lmax, nm; , Mꢀ1 cmꢀ1]: 516 (9600), 355
3
2.3.5. Synthesis of [Ru(
k
3-tptz)(
k
1-P-PPh2Py)(
k
2-P,N-PPh2Py)](PF6)2
(15200), 274 (30100).
(5)
It was prepared following the above procedure for 2 using
2.3.9. Synthesis of [Ru(k k
3-tptz)( 1-P-PPh2Py)2(CH3CN)](PF6)2 (9)
[Ru(
[Ru(
k
3-tptz)(
3-tpy)(
k
1-P-PPh2Py)2Cl]BF4 (1.094 g, 1.00 mmol) in place of
1-P-PPh2Py)2Cl]BF4. Yield: 0.750 g (68%). Microana-
It was prepared following the above procedure for 8 except that
an excess CH3CN was used in place of NaCN. Yield: 0.876 g, 69%.
Microanalytical data: C54H43N9P4F12Ru requires: C, 51.03; H, 3.41;
k
k
lytical data C52H40N8P4F12Ru requires: C, 50.78; H, 3.28; N, 9.11%.
Found: C, 50.74; H, 3.26; N, 9.14%. FAB-MS [m/z, obs. (calcd.)]: 1084
N, 9.92%. Found: C, 50.97; H, 3.32; N, 9.76%. 1H NMR (
d ppm): 9.08

P. Kumar et al. / Journal of Organometallic Chemistry 696 (2011) 3454e3464
3457
(d, 2H, J ¼ 3.6 Hz, tptz), 8.92 (d, 1H, J ¼ 6.4 Hz, tptz), 8.70 (d, 2H,
ATP, 0.1 mM EDTA, 0.5 mM DTT, 30
Supercoiled pBR322 DNA (0.25
reaction mixture was incubated for 30 min at 37 ꢁC and quenched
by adding 5 L of the loading dye (buffer containing 0.25% bro-
mophenol blue, 1 M sucrose, 1 mM EDTA, and 0.5% SDS). Samples
were applied on horizontal 1% agarose gel in 40 mM Triseacetate
buffer, pH 8.3, and 1 mm EDTA and run for 10 h at room tempera-
m
g/ml BSA and enzyme protein.
J ¼ 5.8 Hz; Py, PPh2Py), 8.66 (d, 2H, J ¼ 8.6 Hz; Py, PPh2Py), 8.60 (d,
3H, J ¼ 5.2 Hz, tptz), 8.38 (d, 2H, J ¼ 4.8 Hz, tptz), 8.08 (d, 2H,
J ¼ 4.2 Hz, tptz), 7.76 (d, 2H, J ¼ 5.8 Hz; Py, PPh2Py), 7.55 (d, 2H,
J ¼ 3.6 Hz, tptz), 7.04e7.30 (br. m, 20H, PPh2Py), 6.38 (d, 2H,
mM) was used as substrate. The
m
J ¼ 6.6 Hz; Py, PPh2Py), 2.21 (s, 3H, CH3). 31P{1H} NMR (
d ppm):
39.82 (s). IR (nujol, cmꢀ1): 2112 {s,
n(C^N)}, 1600 (s), 1436 (s), 1392
(m), 1108 (m), 752(s), 694 (s), 840 (s, PFꢀ6 ). UVevis. [lmax, nm;
ꢀ1 cmꢀ1]: 544 (9450), 374 (18770), 282 (23700).
3,
ture at 20 V. The gel was stained with ethidium bromide (0.10 mg/
M
mL) and photographed in a GDS 7500 UVP (Ultra Violet Product,
Cambridge, UK) transilluminator. One unit of topoisomerase
activity is defined as the amount of enzyme required to relax 50% of
the supercoiled DNA under standard assay conditions.
2.4. Catalytic activity
Mixture of the oxime (2.0 mmol) and the catalyst [Ru(k3
-
The BeZ conformational transitions of CT-DNA in presence of 1,
2, 3 and 5 were followed spectrophotometrically [56,57]. The
absorbance ratio A295/A260 was monitored for conformational
changes in the DNA helix. Condensation of the DNA was monitored
by following the increase in absorbance at 320 nm against different
complex/DNA ratios [58e61].
tpy)(k
1-P-PPh2Py)Cl2)] (3) (13.3 mg, 0.02 mmol) was refluxed in
toluene (1 mL) for appropriate time (Table 1). After completion of
the reaction CH2Cl2 was added to reaction mixture and resulting
solution was filtered through celite. The crude product was purified
by column chromatography (silica gel, MeOH/CH2Cl2). After work-
up amides were obtained in good yield (Table 1).
2.8. Heme polymerase assay
2.5. X-ray structural analysis
Antimalarial activity of 1e5 was investigated by examining their
inhibition percentage against
tion mixture (1 mL) contained 100
buffer, 20 L of hemin (1.2 mg/mL), and 25
triple distilled water. It was treated with 20
b
-hematin formation [62]. The reac-
L of 1 M sodium phosphate
L of P. yoelii enzyme in
g complexes followed
Crystals suitable for single crystal X-ray diffraction analyses for
1, 2 and 3 were obtained by slow diffusion of petroleum ether
(40e60 ꢁC) to the solution of respective complexes in CH2Cl2 at
room temperature. Preliminary data on the space group and unit
cell dimensions as well as intensity data were collected on Oxford
Diffration X CALIBUR-S and Bruker Smart APEX II diffractometer
m
m
m
m
by incubation for 16 h at 37 ꢁC in an incubator shaker at a speed of
174 rpm. After incubation the reaction mixture was centrifuged at
10,000 rpm for 15 min and the pellets obtained were washed thrice
with 10 mL of buffer (containing 0.1 M TriseHCl, pH 7.5, and 2.5%
SDS) and then with buffer 2 (containing 0.1 M sodium bicarbonate,
pH 9.2, and 2.5% SDS), followed by distilled water. Semi dried
using graphite monochromatized Mo-Ka radiation. Structures were
solved by direct methods and refined using SHELX-97 [52]. The
non-hydrogen atoms were refined with anisotropic thermal
parameters. Hydrogen atoms were geometrically fixed and allowed
to refine using riding model. Computer program PLATON was used
for analyzing interaction and stacking distances [53].
pellets were suspended in 50 mL of 0.2 N NaOH and volume
adjusted to 1 mL with distilled water. The optical density was
measured at 400 nm and percent inhibition was calculated using
the formula:
experimental} ꢂ 100.
%
inhibition ¼ {(1 ꢀ O.D of the control)/O.D
2.6. Absorption titration
Absorption titration studies were performed using a constant
concentration of CT-DNA (20 mM) in aqueous tris buffer (5 mM
3. Results and discussion
3-L)(PPh3)Cl2] (L ¼ tpy and
TriseHCl, 50 mM NaCl: 7.1 pH) and varying the concentration of
complexes in spectral region 340e250 nm.
Reactions of the complexes [Ru(
tptz) with hetero difunctional phosphine PPh2Py (1:2 molar ratio)
k
in methanol under refluxing conditions gave P-coordinated cationic
complexes [Ru(k k k -
3-tpy)( 1-P-PPh2Py)2Cl]þ (1) and [Ru( 3-tptz)(k1
2.7. Gel mobility shift assay
P-PPh2Py)2Cl]þ (2), which were isolated as their tetrafluoroborate
The interaction of complexes with DNA-Topo II was followed by
enzyme-mediated supercoiled pBR322 relaxation [54,55]. For
activity measurement the reactions were performed in a mixture
containing 50 mM TriseHCl, pH 7.5, 50 mM KCl, 1 mM MgCl2 1 mM
salts. Upon treatment with an excess of NH4PF6 in methanol at
room temperature the complexes 1 and 2 afforded [Ru(
k
3-tpy)(k1
-
-
P-PPh2Py)(k k k
2-P,N-PPh2Py)]2þ (4) and [Ru( 3-tptz)( 1-P-PPh2Py)(k2
P,N-PPh2Py)]2þ (5), wherein one of the coordinated PPh2Py forms
a P,N-chelated four membered ring (Schemes 3 and 4).
On the other hand, reaction of [Ru(k
3-tpy)Cl3] with PPh2Py in
1:1 molar ratio gave the neutral complex [Ru(k k
3-tpy)( 1-P-PPh2Py)
Table 1
Rearrangement of various oximes into amides.a
Cl2] (3) in reasonably good yield (Scheme 5).
The hemi labile nature of coordinated PPh2Py in these
complexes has been established by reacting representative
complexes 4 and 5 with an excess of NaCN and CH3CN in methanol
under refluxing conditions. As expected, it gave cationic complexes
OH
H
O
TerpyRu(II)(5)
N
R
NH2
toulene, 10 h, reflux
R
[Ru(
(NCCH3)](PF6)2 (7), [Ru(
[Ru(
3-tptz)( 1-P-PPh2Py)2(NCCH3)](PF6)2 (9) in good yield, which
k
3-tpy)(
k
1-P-PPh2Py)2(CN)]PF6 (6), [Ru(
k
k
3-tpy)( 1-P-PPh2Py)2
k
3-tptz)(
k
1-P-PPh2Py)2(CN)]PF6 (8) and
Entry
R
Time (h)
Yieldb%
k
k
1
2
4
(4-NO2)C6H4
(4-OCH3)C6H4
(4-CN)C6H4
10
10
12
82
80
80
were isolated as their hexafluorophosphate salt (Schemes 3 and 4).
The complexes under study are air stable, non hygroscopic,
crystalline solids, soluble in polar solvents such as chloroform,
dichloromethane and insoluble in benzene, hexane and n-pentane,
diethyl ether and petroleum ether. All the complexes have been
2.00 mmol of oxime, [Ru(k
3-tpy)(PPh2Py)Cl2] (1 mol%), and toluene (1 ml) were
refluxed for the specified amount of time.
a
b
Isolated yields after column chromatography.

3458
P. Kumar et al. / Journal of Organometallic Chemistry 696 (2011) 3454e3464
+
N
N
PPh2Py
N
N
N
N
Cl
Ru
Cl
MeOH,
Ru
Cl
P
P
Ph3P
N
N
(1) 77%
NH4PF6,
MeOH
2+
2+
+
N
CH3CN (excess)
MeOH,
N
NaCN (excess)
MeOH,
N
N
N
N
N
N
P
N
Ru
N
Ru
Ru
P
P
P
P
P
N
N
N
CN
N
N
NCMe
(7) 74%
(6) 64 %
(4) 57%
Scheme 3. Synthesis 1, 4, 6 and 7.
characterized by satisfactory elemental analyses, spectral and
electrochemical studies. Analytical data of 1e9 conformed well to
their respective formulations. Information about the composition
of complexes has also been obtained by FAB-MS spectral studies.
The MS spectra of 1e5 are depicted in Figure S1eS5 (Supporting
Information) and resulting data along with their assignments are
summarized in the experimental section. The position of various
peaks and overall fragmentation pattern strongly supported
proposed formulation of the respective complexes.
3.1. NMR spectral studies
1H and 31P NMR spectral data summarized in experimental
section strongly supported formation of the complexes. Shift in the
position of signals associated with tptz and tpy protons relative to
these in precursor complexes suggested coordination of PPh2Py to
ruthenium in monodentate/chelating mode. 31P{1H} NMR spectra
provided valuable information about coordination mode of the
PPh2Py in respective complexes. In its 31P{1H} NMR spectra 1 and 2
+
N
N
N
N
N
N
PPh2Py
MeOH,
N
N
N
N
N
N
Ru
Ru
P
P
Ph3P
Cl
N
N
Cl
Cl
(2) 70%
NH4PF6,
MeOH
+
2+
2+
N
N
N
N
N
N
N
N
N
CH3CN (excess)
MeOH,
N
N
NaCN (excess)
MeOH,
N
N
N
N
N
N
N
Ru
Ru
Ru
P
P
P
P
P
P
N
N
N
N
N
CN
N
NCMe
(8) 72%
(5)
68%
(9) 69%
P
N =diphenylphosphinopyridine
Scheme 4. Synthesis 2, 5, 8 and 9.

P. Kumar et al. / Journal of Organometallic Chemistry 696 (2011) 3454e3464
3459
p
/
p
*/n /
PPh2Py in chelating mode leads to a blue shift in the position of
MLCT transition. It may be attributed to enhanced -back bonding
p* transitions [64,65]. Notably, the coordination of
N
PPh2Py
MeOH,
N
p
N
N
N
N
resulting from coordination of one PPh2Py in chelating mode
through both the P and N-donor sites. Further, complexes con-
taining tpy displayed a red shift in the position of lowest energy
transitions (w554 nm, 1; 548 nm, 3; 539 nm, 4) in comparison to
tptz complexes (536 nm, 2; 538 nm, 5). It may be attributed to
Ru
Cl
Ru
P
Cl
Cl
Cl
N
Cl
(3) 64%
greater stabilization of the
p* orbitals on tpy relative to tptz.
Scheme 5. Synthesis of 3.
However, introduction of anionic (CNꢀ) or neutral (NCCH3) ligands
in complex 4 and 5 has little influence on the MLCT bands.
displayed singlets at d
36.02 and 40.04 ppm, assignable to 31P nuclei
of the coordinated PPh2Py. The presence of only one signal indi-
cated that both the 31P nuclei are chemically equivalent and are
trans-disposed. On the other hand, 4 and 5 displayed singlets in the
3.3. Electrochemistry
Electrochemical properties of 1e5 in acetonitrile have been
followed by cyclic voltammetry using 0.1 M tertabutylammonium
perchlorate (TBAP) as supporting electrolyte. Resulting data is
summarized in Table 2 and cyclic voltammograms of 1, 4 and 5 are
shown in Figure S6eS8. The potential of Fc/Fcþ couple under
experimental conditions was 0.10 V (80 mV) vs Ag/Agþ. The
complexes displayed an oxidative wave in the range 0.39e1.15 V
[0.62 (90), 1; 1.15 (92), 2; 1.10 (74) V, 3; 0.51 (69), 4; 0.39 (75), 5]
assignable to Ru(II)/Ru(III) oxidation. The peak-to-peak separation
(Δ Ep) of w69 mV and equivalence of the anodic peak current to
cathodic peak current (ipc) in 4 and other complexes suggested
a reversible electron transfer process. The magnitude of oxidation
potential indicated that the bivalent state of ruthenium is
comfortable in the P,N coordination mode. Further, it has been
observed that Ru(II)/Ru(III) oxidation potential in complexes 4 and
5 are lower in comparison to those of 1 and 2. It suggested that
high field side at
in low field side at
d
ꢀ10.30 and ꢀ12.30 ppm, along with the signals
d
36.42 and 38.48 ppm. The presence of reso-
nances both in the high and low field side suggested coordination
of PPh2Py to ruthenium in two different modes. Accordingly the
signals in high field side have been assigned to 31P nuclei of
chelated k k
2-P,N-PPh2Py, while the one in down field side to 1-P-
bonded PPh2Py. It is interesting to note that in these complexes the
31P nuclei of PPh2Py exhibited an upfield shift in comparison to the
free ligand (
d
ꢀ3.9 ppm). The upfield shift may be attributed to high
electron density on the metal center resulting from coordination of
two bulky PPh2Py ligands. Owing to high electron density on the
metal center one can expect enhanced metal-to-ligand d
bonding interactions.
pepp back
PPh2Py is a better stabilizer of the trivalent state of ruthenium in k2
chelating mode in comparison to mondentate
1-mode in 1 and 2. It
may be due to high electron density on the metal center arising
from back bonding between metal and ligand through p ed
-
3.2. UVevis spectroscopy
k
Electronic spectral data of the complexes is summarized in the
experimental section and spectra of 1e5 depicted in Fig. 1. Ruthe-
nium polypyridyl complexes usually exhibit intense peaks in ultra
p
p
interactions. The complexes displayed successive three electron
reductions at w (ꢀ) 0.60e1.69 (tptz, complexes), w (ꢀ) 0.29e1.19 V
(tpy, complexes). As the ligand becomes more electron deficient
there is concomitant lowering of the ligand LUMO, resulting in an
violet region attributable to ligand based
p / p* transitions with
overlapping MLCT transitions in the visible region [17,63]. Elec-
tronic absorption spectra of 1e5 displayed bands at w554e536,
495e484, w345e341 and w286e243 nm. On the basis of its
position and intensity the lowest energy transitions in visible
enhanced p
- acceptance and more anodic RuIII/II oxidation couples.
region at w554e539 nm have been assigned to dp(Ru)
tpy) MLCT transitions and the bands at w495e484 to dp(Ru)
/ p* (tptz/
3.4. X-ray crystallography
/ p*
(PPh2Py). High energy transitions at w345e341 and
w286e243 nm have been assigned to intra-ligand charge transfer
Molecular structures of 1, 2 and 3 have been determined crys-
tallographically. ORTEP views at 30% thermal ellipsoid probability
along with the atom numbering scheme is shown in Fig. 2e4.
Details about data collection, solution and refinement are
summarized in Table 3 and important geometrical parameters in
Table 4. A common structural feature of 1, 2 and 3 is k
1-P-PPh2Py
coordination of PPh2Py to the metal center ruthenium. The coor-
dination geometry about ruthenium in these complexes is distorted
octahedral. The bond angles N1eRueN2 and N2eRueN3 are
almost equal [79.68(2) and 79.47(2)ꢁ, 1; 78.72(2) and 78.37(2)ꢁ, 2;
79.14(2), 79.65(2)ꢁ, 3]. It suggested an octahedral distortion due to
inward bending of the coordinated pyridyl rings in tptz as well as
Table 2
Electrochemical data of 1e5 in acetonitrile solution at (rt), scan rate 100 mV/s.
E1/2 (V)
Ep (V)
Complex
Ru II/III
Ligand centered
1
2
3
4
5
0.62(90)
1.10(92)
1.15(74)
0.51(69)
0.39(75)
ꢀ0.69, ꢀ1.08, ꢀ1.36
ꢀ0.72, ꢀ1.06, ꢀ1.69
ꢀ0.29, ꢀ1.70, ꢀ1.99
ꢀ0.69, ꢀ1.03, ꢀ1.28
ꢀ0.71, ꢀ1.11, ꢀ1.49
Fig. 1. UVevis spectra of 1e5 in dichloromethane.

3460
P. Kumar et al. / Journal of Organometallic Chemistry 696 (2011) 3454e3464
Fig. 2. Crystal structure of 1.
tpy complexes. The distortion from regular octahedral geometry is
further evidenced from intra-ligand trans angles N1eRueN3,
which are 158.9(15), 157.13(16) and 157.84(17)ꢁ, respectively in 1, 2
and 3. Other intra-ligand trans angles also, supported distorted
octahedral geometry about the metal center ruthenium. In complex
3, the Cl2eRu1eCl1 angle [87.50(4)ꢁ] suggested that coordinated
chloro-groups are cis disposed. The RueCl and RueP bond
distances are normal and close to the one reported in other related
complexes [49,66]. In compound 1, the BFꢀ4 anion is disordered over
two positions with equal S.O.Fs.
Fig. 4. Crystal structure of 3.
Structural studies on 1, 2 and 3 revealed the presence of
extensive intra- and intermolecular CeH/X (X ¼ N, Cl, and F) and
CeH/
p interactions. Various interaction distances fall in the
normal range [69e71]. Matrices for the weak bonding interactions
in 1, 2 and 3 are given in Table S1 (Supporting Information) and
some interesting motifs are shown in Figures S9eS13.
The RueN bond lengths in 1, 2 and 3 are normal and consistent
with
3.5. Absorption titration studies
k
3-coordination of tptz/tpy to ruthenium [49,66e71]. The
uncoordinated pyridyl rings in 1 and 2 are inclined from the central
triazine ring plane by 18.14 and 18.6ꢁ, respectively. The RueCl1
bond distances in 1 and 2 are indistinguishable (w2.41 Å) and close
to reported values whereas in 3 the RueCl1 and RueCl2 distances
are slightly longer [(2.44(1) and 2.45(1) Å)] but in the range of
RueCl bond distances [67]. The RueP bond distances in 1, 2 and 3
are comparable to the values reported in literature [68].
Absorption titration studies performed on 1 and 3 with calf
thymus (CT-DNA) indicated significant interaction between the
complexes and nucleic acid. Absorption titration spectra of 1 and 3
are shown in Figure S14e16. Titration of 1 and 3 (1e40
mM) with
a constant concentration of CT-DNA (20 M) shows a pronounced
m
increase in the absorption intensities (hyperchromism) at higher
concentrations (Figure S15e16). The hyperchromicity implies
interactions other than intercalation between the complexes and
DNA, because intercalation leads to a hypochromism. It suggested
that at higher concentration unwinding of DNA helix leads to an
increase in absorption intensity. Further, at lower concentration
(5 mM and 1 mM) it exhibited a decrease in the absorption intensity
(hypochromism) with respect to CT-DNA. At lower concentrations 1
and 3 displayed a pronounced hypochromism at their respective
metal-to-ligand charge transfer (MLCT) bands. It may arise from the
interaction between electronic state of intercalating chromophore
of tpy/tptz and that of DNA bases. The spectral changes at lower
concentration are consistent with intercalation of the complexes
into DNA base-stack.
3.6. BeZ conversion
Anomalous morphology of Z-DNA and its involvement in gene
expression and recombination have drawn extensive scientific
attention [57,58]. The BeZ-DNA transition in presence of the
complexes under study has been followed spectrophotometrically.
Change in the ratio A295/A260 is commonly taken as an evidence for
conformational changes in the DNA structure. The complexes 1e5
promoted an increase in A295/A260 ratio from 0.18 (for free DNA) to
0.77 (1), 0.66 (2), 0.56 (3), 0.72 (4) and 0.78 (5). The observed
alternation in UV absorption ratio in presence of complexes sug-
gested conformational changes in DNA structure. The BeZ equi-
librium may be influenced by two major factors, the ionic changes
Fig. 3. Crystal structure of 2.

P. Kumar et al. / Journal of Organometallic Chemistry 696 (2011) 3454e3464
3461
Table 3
Selected crystallographic data for 1, 2 and 3.
1
2
3
Empirical formula
Formula weight
Temperature (K)
Crystal system
C49H39BClF4N5P2Ru
983.12
150(2)
Triclinic
P-1
C52H40BClF4N8OP2Ru
1078.19
150(2)
Orthorhombic
Pbca
C33H27Cl4N4PRu
753.43
293(2)
Monoclinic
C2/c
space group
Wavelength (Å)
Unit cell dimensions
0.71073
0.71073
0.71073
a ¼ 11.2150(4) Å
b ¼ 11.6340(3) Å
c ¼ 19.5580(6) Å
a ¼ 15.4385(3) Å
b ¼ 20.1888(5) Å
c ¼ 31.0093(6) Å
a ¼ 20.931(2) Å
b ¼ 10.3381(10) Å
c ¼ 30.490(3) Å
a
b
g
¼ 73.770(3)ꢁ
¼ 85.968(3)ꢁ
¼ 70.778(3)ꢁ
b
¼ 108.914(3)ꢁ
Volume (Å3)
2312.88(12)
2, 1.412
9665.1(4)
8, 1.482
0.510
4384
0.28 ꢂ 0.26 ꢂ 0.18
3.11e25.00
ꢀ18 ꢃ h ꢃ 18
ꢀ21 ꢃ k ꢃ 24
ꢀ36 ꢃ l ꢃ 34
35207/8484
[R(int) ¼ 0.0478]
8484/12/659
1.034
6241.4(11)
4, 0.941
0.389
Z, Calculated density (g cm-3
)
m
(mm-1
F(000)
Crystal size (mm)
)
0.522
1000
1784
0.34 ꢂ 0.30 ꢂ 0.28
3.12e25.00 deg.
ꢀ13 ꢃ h ꢃ 12
ꢀ13 ꢃ k ꢃ 11
ꢀ22 ꢃ l ꢃ 23
17988/8116
[R(int) ¼ 0.0304]
8116/12/593
1.082
0.28 ꢂ 0.26 ꢂ 0.21
2.08e28.30
ꢀ27 ꢃ h ꢃ 24
ꢀ10 ꢃ k ꢃ 13
ꢀ40 ꢃ l ꢃ 39
19744/7687
[R(int) ¼ 0.0476]
7687/0/613
1.366
Theta range for data collection
Limiting indices
Reflections collected/unique
Data/restraints/parameters
GooF
Final R indices [I > 2
s
(I)]
R1 ¼ 0.0712
wR2 ¼ 0.2226
R1 ¼ 0.0927
wR2 ¼ 0.2360
R1 ¼ 0.0540,
wR2 ¼ 0.1453
R1 ¼ 0.0849
wR2 ¼ 0.1551
R1 ¼ 0.0599
wR2 ¼ 0.1645
R1 ¼ 0.0911
wR2 ¼ 0.2197
R indices (all data)
in solution and covalent modification [72,73]. Further, condensa-
tion of the calf thymus (CT-DNA) promoted by 1e5 was monitored
spectrophotometrically following the increase in absorption at
320 nm [59e62]. The complexes 1e5 exhibited condensation of
Alteration in the structure of DNA leads to retardation in migration
of supercoiled DNA and slight increase in mobility of the open
circular DNA. It has been shown that topo II is an essential enzyme
which plays an important role in DNA replication, repair and
transcription [74,75]. It is well known that non-covalent interaction
of the proteins with DNA is key step in Topo II catalytic cycle. Anti-
Topo II agents control the Topo II activity either by trapping Topo II-
DNA complex or acting as Topo II inhibitors [76e79]. The effect of
1e5 on Topo II activity of the filarial parasite S. cervi was followed
by enzyme-mediated supercoiled pBR322 relaxation assay [51,52].
Gel mobility assays of 1e5 were examined at different concentra-
tion levels. These complexes do not show DNA binding in absence
of enzyme Topo II (Figure S17eS18). However, in the presence of
Topo II an upward shift toward relaxed form of the plasmid DNA to
DNA at 20 mM concentration level, which is evident from
enhancement in the absorption at 320 nm [(A320/A260) from 0.075
for free DNA to 0.38 (1), 0.28 (2), 0.53 (3), 0.49 (4) and 0.45(5)]. It
was observed that 3, 4 and 5 are more effective in this regard in
comparison to 1 and 2.
3.7. Gel mobility assays
Direct DNAemetal interactions are evidenced by change in
electrophoretic mobility of the plasmid DNA on agarose gel [7,8].
Table 4
Selected geometrical parameters for 1, 2 and 3.
1
2
3
Ru(1)eN(2) 1.967(5)
Ru(1)eN(2) 1.931(4)
Ru(1)eN(2) 1.961(4)
Ru(1)eN(1) 2.085(5)
Ru(1)eN(3) 2.081(4)
Ru(1)eN(3) 2.070(4)
Ru(1)eN(3) 2.103(5)
Ru(1)eN(1) 2.114(4)
Ru(1)eN(1) 2.087(4)
Ru(1)eP(2) 2.3636(17)
Ru(1)eP(1) 2.3812(15)
Ru(1)eP(1) 2.3041(13)
Ru(1)eP(1) 2.3883(17)
Ru(1)eP(2) 2.3864(15)
Ru(1)eCl(1) 2.4431(13)
Ru(1)eCl(1) 2.4616(17)
Ru(1)eCl(1) 2.4345(13)
Ru(1)eCl(2) 2.4548(12)
N(2)eRu(1)eN(1) 79.8(15)
N(2)eRu(1)eN(3) 79.2(15)
N(1)eRu(1)eN(3) 158.9(15)
N(2)eRu(1)eP(2) 90.16(15)
N(1)eRu(1)eP(2) 90.05(16)
N(3)eRu(1)eP(2) 90.65(15)
N(2)eRu(1)eP(1) 91.20(15)
N(1)eRu(1)eP(1) 90.59(16)
N(3)eRu(1)eP(1) 89.22(15)
P(2)eRu(1)eP(1) 178.59(7)
N(2)eRu(1)eCl(1) 175.92(16)
N(1)eRu(1)eCl(1) 96.29(17)
N(3)eRu(1)eCl(1) 104.75(16)
P(1)eRu(1)eCl(1) 87.78(6)
P(2)eRu(1)eCl(1) 90.90(6)
N(2)eRu(1)eN(3) 78.39(16)
N(2)eRu(1)eN(1) 78.78(16)
N(3)eRu(1)eN(1) 157.13(16)
N(2)eRu(1)eP(1) 91.21(12)
N(3)eRu(1)eP(1) 89.71(13)
N(1)eRu(1)eP(1) 92.27(12)
N(2)eRu(1)eP(2) 91.19(12)
N(3)eRu(1)eP(2) 89.70(13)
N(1)eRu(1)eP(2) 89.27(12)
P(1)eRu(1)eP(2) 177.36(5)
N(2)eRu(1)eCl(1) 174.43(12)
N(3)eRu(1)eCl(1) 96.39(12)
N(1)eRu(1)eCl(1) 106.47(12)
P(1)eRu(1)eCl(1) 86.79(5)
P(2)eRu(1)eCl(1)e90.71(5)
N(2)eRu(1)eN(3) 79.65(17)
N(2)eRu(1)eN(1) 79.14(17)
N(3)eRu(1)eN(1) 157.84(17)
N(1)eRu(1)eP(1) 93.65(11)
N(3)eRu(1)eCl(1) 87.37(11)
N(2)eRu(1)eCl(1) 91.06(11)
N(1)eRu(1)eCl(1) 86.63(11)
N(3)eRu(1)eCl(2) 99.67(12)
N(2)eRu(1)eCl(2) 178.44(12)
N(1)eRu(1)eCl(2) 101.36(12)
P(1)eRu(1)eCl(1) 176.79(4)
P(1)eRu(1)eCl(2) 89.39(4)
Cl(1)eRu(1)eCl(2) 87.50(4)
N(2)eRu(1)eP(1) 92.14(11)
N(3)eRu(1)eP(1) 93.51(11)

3462
P. Kumar et al. / Journal of Organometallic Chemistry 696 (2011) 3454e3464
Fig. 5. Gel mobility shift assay of S. cervi topoisomerase II by the complexes 1, 2, 3, 4
and 5 (20 g, lane 3, 6, 7, 9 and 11; 40 g, lane 4, 5, 8, 10, and 12) Lane 1: Supercoiled
pBR322 (0.2
Fig. 7. Gel mobility shift assay of S. cervi topoisomerase II by the complex 2 (2
m
g, lane
g, lane 7). Lane 1: Supercoiled pBR322
g) alone; Lane 2: Supercoiled pBR322 þ S. cervi topo II.
m
m
3; 5
(0.2
mg, lane 4; 10 mg, lane 5; 20 mg, lane 6; 40 m
m
m
g) alone; Lane 2: Supercoiled pBR322 þ S. cervi topo II; Lane 3e4: 1; Lane
5e6: 4; lane 7e8: 2; lane 9e10: 5; and lane 11e12: 3.
coordinated PPh2Py interacted with metal center in a chelating
mode forming a four membered ring. The lower inhibition activity
of 3, 4 and 5 may be attributed to an increase in steric hindrance
resulting from the replacement of chloro group leading to the
formation of four membered chelate rings or introduction of
bulkier PPh2Py.
gel origin indicated that the complexes influence Topo II-DNA
activity by binding either to Topo II-DNA complex or the enzyme.
An appreciable effect on DNA activity has been observed by
substitution of the chloro group of precursor complexes [Ru(k3
-
tptz)Cl2(PPh3)], [Ru(
PPh2Py. Further, it was observed that complex 1 inhibited Topo II
activity at 40 M per reaction mixture in presence of the enzyme. At
the same concentration level (40 M) it exhibited strong complex
k k
3-tpy)(PPh3)Cl2] and [Ru( 3-tpy)Cl3] by
m
m
3.8. Heme polymerase activity
formation ability with DNA-Topo II complex as indicated by the
presence of DNA in gel lane (Figs. 5 and 6). On the other hand, 2
exhibited high Topo II inhibitory activity at 10, 20 and 40 mM levels
The complexes 1e5 also exhibited significant inhibitory effect
on heme polymerase activity of P. yoelii lysate, which was followed
by
b-hematin formation [63]. The parent complex [Ru(k
3-tptz)
(Figs. 5 and 7). It suggested that at higher concentration 1 and 2
inhibited relaxation of the supercoiled DNA, displaying a significant
inhibitory activity. Further, it was observed that 3, 4 and 5 are not
effective in this regard. This may result from structural changes and
ligands (tpy and tptz) involved in complex. It is observed that
inhibitory activity is dependent upon the number of coordinated
and uncoordinated nitrogen donor atoms. The complex 2 possesses
8 pyridyl nitrogens among which, only three are involved in coor-
dination and other five remains uncoordinated. On the other hand,
1 has only two uncoordinated pyridyl nitrogens. Higher inhibition
displayed by complex 2 in comparison to 1 strongly suggested that
inhibitory activity is determined by number of uncoordinated
nitrogen atoms. Ru(II) complexes used in the present study are
octahedral, wherein coordination geometry is completed by the
pyridyl nitrogen from ligands (tpy/tptz) along with two PPh2Py
lying trans to each other. An inspection of the single crystal X-ray
structure of 1 or 2 reveals that planar part of the ligand may stack
between base pairs of the DNA major groove. In 4 and 5 one of the
Cl2(PPh3)] shows 94% inhibition of heme polymerase activity, while
1e5 exhibited lower inhibition percentage (50, 1; 50, 2; 62, 3; 56, 4
and 54, 5). The above results could be attributed to an increase in
the steric hindrance resulting from replacement of the chloro group
in the complexes [Ru(k k
3-tpy)Cl2(PPh3)] and [Ru( 3-tptz)Cl2(PPh3)]
by bulkier PPh2Py ligand.
3.9. Catalytic applications of [Ru(k k
3-tpy)( 1-P-PPh2Py)Cl2] (3) in
the rearrangment of the aldoximes to amide
It is well known that the oximes are less amenable to reduction
in comparison to imines, although Beckmann rearrangement
catalytic pathways can be employed to convert alcohols into
hydroxylamines. In this study we have developed ruthenium pol-
ypyridyl complexes containing PPh2Py as a co-ligand, which
catalyses conversion of oximes to amide. The representative
complex 3 has been successfully employed as a catalyst for
conversion of oximes to amide (Scheme 6) in absence of an alcohol
or base. The optimized reaction conditions may be employed for
the conversion of a range of oximes into corresponding amides
(Table S4). Benzaldehyde oxime upon treatment with 3 (1 mol %) in
toluene under refluxing conditions (for 10 h, Scheme 6) gave ben-
zamide in 80% yield. The yields of isolated amides after simple
purification are consistently excellent (Table S4). Notably in this
reaction benzonitrile the product of abnormal Beckmann rear-
rangement sometimes seen in the transition metal-catalyzed
reactions was not observed [40,80e84]. Further, additional acid
O
OH
N
TerpyRu(II) (3)
NH2
H
Fig. 6. Gel mobility shift assay of S. cervi topoisomerase II by the complexes 1 and 4:
toulene, 10 h, reflux
(2
m
g, lane 3 and 10, 5
mg, lane 4 and 11, 10
mg, lane 5 and 12, 20
mg, lane 6 and 13,
40
mg, lane 7 and 14) Lane 1 and 8: Supercoiled pBR322 (0.2 mg) alone; Lane 2 and 9:
Supercoiled pBR322 þ S. cervi topo II; Lane 3e7: 1; Lane 10e14: 4.
Scheme 6. Rearrangement of benzaldoxime to benzamide.

P. Kumar et al. / Journal of Organometallic Chemistry 696 (2011) 3454e3464
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Acknowledgements
Financial support from the Department of Science and Tech-
nology, Ministry of Science and Technology, New Delhi, India (Grant
No. SR/SI/IC-15/2007) is gratefully acknowledged. We are also
thankful to Prof. P. Mathur, In-charge, National Single Crystal X-ray
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Appendix. Supporting information available
Supplementary data associated with this article can be found, in
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Abbreviations
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[49] D.D. Perrin, W.L.F. Armango, D.R. Perrin, Purification of Laboratory Chemicals.
Pergamon, Oxford, U.K, 1986.
tpy ¼ 2,20:60,200-terpyridine
tptz ¼ 2,4,6-tris(2-pyridyl)-1,3,5-triazine
PPh2Py ¼ diphenyl-2-pyridylphosphine
DNA-Topo II ¼ deoxyribose nucleic acid e Topo isomerease II
MLCT ¼ metal-to-ligand charge transfer
TBAP ¼ Tetrabutylammonium perchlorate
CT-DNA ¼ calf thymus DNA
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