Ruthenium(II) complexes containing quinone based ligands: Synthesis, characterization, catalytic applications and DNA interaction

Article abstract of DOI:10.1016/j.saa.2012.09.019

1,2-Naphthaquinone reacts with amines such as semicarbazide, isonicotinylhydrazide and thiosemicarbazide in high yield procedure with the formation of tridentate ligands HL_n (n = 1-3). By reaction of ruthenium(II) starting complexes and quinone based ligands HL_n (n = 1-3), a series of ruthenium complexes were synthesized and characterized by elemental and spectroscopic methods (FT-IR, electronic, ¹H, ¹³C, ³¹P NMR and ESI-MS). The ligands were coordinated to ruthenium through quinone oxygen, imine nitrogen and enolate oxygen/thiolato sulfur. On the basis of spectral studies an octahedral geometry may be assigned for all the complexes. Further, the catalytic oxidation of primary, secondary alcohol and transfer hydrogenation of ketone was carried out. The DNA cleavage efficiency of new complexes has also been tested.

Full text of DOI:10.1016/j.saa.2012.09.019

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Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 99 (2012) 174–180
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Ruthenium(II) complexes containing quinone based ligands: Synthesis,
characterization, catalytic applications and DNA interaction
P. Anitha a, R. Manikandan a, A. Endo b, T. Hashimoto b, P. Viswanathamurthi a,
⇑
a Department of Chemistry, Periyar University, Salem 636 011, India
b Department of Materials and Life Sciences, Sophia University, Tokyo 102-8554, Japan
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
Ruthenium(II) complexes containing 1,2-naphthaquinone semicarbazone/isonicotinylhydrazone/thio-
semicarbazone were synthesized and characterized. They have been assigned an octahedral structure.
The new complexes were found to be efficient catalyst for oxidation and transfer hydrogenation reac-
tions. The complexes also successfully cleaved the DNA.
"
"
"
A new series of ruthenium(II)
complexes were synthesized.
Analytical and spectral data confirm
the structure of the complexes.
The complexes used as catalysts in
the oxidation and transfer
hydrogenation reaction.
"
The obtained complexes are potent
DNA cleaving agents.
a r t i c l e i n f o
a b s t r a c t
Article history:
1,2-Naphthaquinone reacts with amines such as semicarbazide, isonicotinylhydrazide and thiosemicar-
bazide in high yield procedure with the formation of tridentate ligands HLn (n = 1–3). By reaction of
ruthenium(II) starting complexes and quinone based ligands HLn (n = 1–3), a series of ruthenium com-
plexes were synthesized and characterized by elemental and spectroscopic methods (FT-IR, electronic,
1H, 13C, 31P NMR and ESI-MS). The ligands were coordinated to ruthenium through quinone oxygen, imine
nitrogen and enolate oxygen/thiolato sulfur. On the basis of spectral studies an octahedral geometry may
be assigned for all the complexes. Further, the catalytic oxidation of primary, secondary alcohol and
transfer hydrogenation of ketone was carried out. The DNA cleavage efficiency of new complexes has also
been tested.
Received 6 August 2012
Accepted 9 September 2012
Available online 16 September 2012
Keywords:
Quinone based ligands
Ruthenium(II) complexes
Catalytic oxidation
Catalytic transfer hydrogenation
DNA cleavage
Ó 2012 Elsevier B.V. All rights reserved.
Introduction
bered chelate rings at the metal center [3]. The structural peculiar-
ities of coordination compounds of 1,2-benzoquinone ligands have
Thiosemicarbazones usually react as chelating ligands with
transition metal ions by bonding through the sulfur and the azo-
methine nitrogen atoms and in some cases they behave as triden-
tate ligands and bond through the sulfur and two nitrogen atoms
[1]. Particularly, thiosemicarbazones have emerged as an impor-
tant class of sulfur donor ligands for transition metal ions because
of their mixed hard–soft donor character and versatile coordina-
tion behavior [2]. Thiosemicarbazones and semicarbazones of aro-
matic aldehydes or ketones are known to act as tridentate ligands
can yield cyclometallated complexes having two fused five-mem-
been studied by several workers [4–7] and comprehensively re-
viewed by Pierpont and coworkers [8]. Surprisingly analogous
1,2-naphthaquinone ligands have remained marginally investi-
gated. Some of these like beta-lapachone, exhibit remarkable anti-
proliferative activities against a variety of tumor cell lines [9].
Recently the structural and biological properties of 1,2-naphtha-
quinone ligands appended with thiosemicarbazone/semicarbazone
along with their transition metal complexes have been studied
[10–15]. However the catalytic activity of these complexes has
been omitted.
Among the different metal catalyzed hydrogenation reactions,
ruthenium-based catalytic systems are found to be effective in
the transfer hydrogenation of ketones [16] and imines [17]. The
⇑
Corresponding author. Fax: +91 427 2345124.
E-mail address: viswanathamurthi@rediffmail.com (P. Viswanathamurthi).
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.09.019

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175
ability of ruthenium complexes to dehydrogenate alcohols and de-
liver the hydrides to a ketone [18] or an ,b-unsaturated ketone
O
Y
C
l
O
O
q
i
a
a
i
j
a
j
k
k
m
n
N
h
N
C
h
p
b
b
c
N
NH2
N
has made them useful as transfer hydrogenation catalysts [19].
Also Ru-based oxidation catalysis is a powerful and extremely ver-
satile synthetic tool to afford selectively oxygenated products both
in homogeneous and in heterogeneous conversions [20,21]. DNA is
the primary target for most anticancer and antiviral therapies
according to cell biology. Investigation of the interaction of DNA
with small molecules is a basic study in the design of new type
of pharmaceutical molecules. When some kinds of metal com-
plexes [22] interact with DNA, they could induce the breakage of
DNA strands by appropriate ways. Thus, to cancer genes, after
DNA strand are cleaved by metal complexes and other cleaving
agents, the DNA double strand break. Based on the above facts,
syntheses of quinone based ligands and study of their coordination
behavior with ruthenium metal, catalytic and DNA interaction
properties gained importance. Hence, in this article, we describe
the synthesis and characterization of ruthenium(II) complexes
bearing 1,2-naphthaquinone binded with semicarbazone/ison-
icotinylhydrazone/thiosemicarbazone. Furthermore the catalytic
properties and DNA cleavage of the synthesized complexes have
been investigated.
l
g
g
c
H
H
N
e
e
d
o
f
d
f
(Y = O, HL1; Y = S, HL3)
(HL2)
Fig. 1. Structure of ligands.
ppm): 10.68 (s, 1Hk, NH), 8.36 (d, 2Ho,p, J = 6.6 Hz, CH), 8.10 (d,
2Hn,q, J = 6.6 Hz, CH), 7.54 (d, 1Ha, J = 7.2 Hz, CH), 7.58 (t, 2Hb,c
,
J = 7.3 Hz, CH), 7.90 (d, 1Hd, J = 7.2 Hz, CH), 7.02 (d, 1Hf, J = 7.2 Hz,
CH), 6.86 (d, 1Hg, J = 7.2 Hz, CH). 13C NMR (DMSO-d6, d, ppm):
176.48 (Ci, C@O), 161.20 (Ch, C@N), 164.72 (Cl, C@O), 150.25
(Co,p, CH), 140.28 (Cm, tert), 124.32 (Cn,q, CH), 129.02 (Ca, CH),
128.60 (Cb, CH), 134.22 (Cc, CH), 125.30 (Cd, CH), 135.98 (Ce, tert),
136.85 (Cf, CH), 123.20 (Cg, CH), 134.20 (Cj, tert). The structures
of the ligands used in this study are given in Fig. 1.
General procedure for synthesis of new ruthenium(II) complexes
All the new metal complexes were prepared according to the
following general procedure. To a solution of [RuHX(CO)(EPh3)2(B)]
(X@H or Cl, E = P or As, B = PPh3, AsPh3 or Py) (0.1 g, 0.1 mmol) in
benzene (20 cm3), the appropriate ligand (0.023–0.029 g,
0.1 mmol) was added in 1:1 M ratio. The mixture was heated under
reflux for 5 h on water bath. Then the resulting solution was con-
centrated to 3 cm3 and the product precipitated by the addition
of petroleum ether (60–80 °C) was recrystallised using CH2Cl2.The
compounds were dried under vacuum and the purity of the com-
plexes was checked by TLC.
Experimental
Materials and methods
All the reagents used were chemically pure and AR grade. The
solvents were purified and dried according to standard procedures
[23]. RuCl3ÁH2O was purchased from Loba Chemie Pvt. Ltd. Micro-
analysis of carbon, hydrogen and nitrogen was carried out using
Vario EL III Elemental analyzer at SAIF – Cochin India. The IR spec-
tra of the ligand and their complexes were recorded as KBr pellets
on a Nicolet Avatar model spectrophotometer in 4000–400 cmÀ1
range. Electronic spectra of the ligand and their complexes have
been recorded in dichloromethane using a Shimadzu UV – 1650
PC spectrophotometer in 800–200 nm range. 1H, 13C and 31P
NMR spectra were recorded in Jeol GSX – 400 instrument using
DMSO as the solvent. 1H NMR and 13C NMR spectra were obtained
at room temperature using TMS as the internal standard. 31P NMR
spectra of the complexes were obtained at room temperature using
ortho phosphoric acid as a reference. The ESI-MS spectra were re-
corded by using LC–MS Q–ToF Micro Analyzer (Shimadzu) in the
SAIF, Panjab University, Chandigarh. Melting points were recorded
on a Technico micro heating table and are uncorrected. The cata-
lytic yields were determined using ACME 6000 series GC–FID with
[RuCl(CO)(PPh3)(L1)]
Yield 79%, Brown solid, m.p. 210 °C, Anal. Found: C 56.08, H
3.46, N 6.16. Calcd for C30H23ClN3O3PRu: C 56.21, H 3.62, N 6.56.
IR (KBr, cmÀ1): 1964 (Cr„O), 1188 (ClAO), 1620 (Ci@O), 1536 (Ch-
@N). UV kmax: 620, 380, 262. 1H NMR (DMSO-d6, d, ppm): 8.92 &
8.66 (s, 2H, NH2), 7.20 (d, 1Ha, J = 7.2 Hz, CH), 7.28 (t, 2Hb,c
,
J = 7.3 Hz, CH), 7.48 (d, 1Hd, J = 7.2 Hz, CH), 6.94 (d, 1Hf,
J = 7.2 Hz, CH), 6.80 (d, 1Hg, J = 7.2 Hz, CH), 7.92–7.56 (m, 15H,
PPh3). 13C NMR (DMSO-d6, d, ppm): 204.82 (Cr, C„O), 180.62 (Ci,
C@O), 163.04 (Ch, C@N), 168.50 (Cl, CAO), 130.68 (Ca, CH), 129.76
(Cb, CH), 134.28 (Cc, CH), 124.96 (Cd, CH), 136.72 (Ce, tert),
135.88 (Cf, CH), 124.78 (Cg, CH), 134.66 (Cj, tert), 138.02, 136.28,
128.67, 126.78 (PPh3). 31P NMR (CDCl3, d, ppm): 28.87. MS (ESI),
m/z = 641.10 [M+].
DP-5 column of 30 m length, 0.53 mm diameter and 5.00 lm film
thickness. DNA cleavage studies were carried out at Biogenics,
Hubli. The starting complexes [RuHCl(CO)(PPh3)3] [24],
[RuHCl(CO)(Py)(PPh3)2] [25], [RuHCl(CO)(AsPh3)3] [26], [RuH2(CO)
(PPh3)3] [24] and ligands HL1, HL3 [15] were prepared according to
literature procedures.
[RuCl(CO)(PPh3)(L2)]
Yield 78%, Green solid, m.p. 210 °C, Anal. Found: C 59.38, H 3.32,
N 5.36. Calcd for C35H25ClN3O3PRu: C 59.79, H 3.58, N 5.98. IR (KBr,
cmÀ1): 1950 (Cr„O), 1182 (ClAO), 1590 (Ci@O), 1550 (Ch@N). UV
kmax: 517, 327, 262, 244. 1H NMR (DMSO-d6, d, ppm): 8.42 (d,
2Ho,p, J = 6.6 Hz, CH), 8.20 (d, 2Hn,q, J = 6.6 Hz, CH), 7.42 (d, 1Ha,
Preparation of naphthaquinone isonicotinylhydrazone (HL2)
Isonicotinyl hydrazide (0.14 g, 1.0 mmol) dissolved in hot dis-
tilled water (3.0 cm3) was added to a hot ethanolic suspension
(50 cm3) of 1,2-naphthaquinone (0.16 g, 1.0 mmol) resulting in a
clear brown solution which was refluxed on a water bath for 3 h.
The precipitate formed upon cooling the reaction mixture to room
temperature was filtered off, washed several times with cold etha-
nol and dried in vacuo. Yield 76%, Brown solid, m.p. 170 °C, Anal.
Found: C 69.66, H 3.58, N 15.01. Calcd for C16H11N3O2: C 69.31, H
4.00, N 15.15. IR (KBr, cmÀ1): 3165 (NkAH), 1676 (Cl@O), 1651 (Ci-
@O), 1599 (Ch@N). UV kmax: 305, 291, 248. 1H NMR (DMSO-d6, d,
,
J = 7.2 Hz, CH), 7.50 (t, 2Hb,c J = 7.3 Hz, CH), 7.82 (d, 1Hd,
J = 7.2 Hz, CH), 6.78 (d, 1Hf, J = 7.2 Hz, CH), 6.71 (d, 1Hg, J = 7.2 Hz,
CH), 8.02–7.84 (m, 15H, PPh3). 13C NMR (DMSO-d6, d, ppm):
204.52 (Cr, C„O), 183.80 (Ci, C@O), 162.24 (Ch, C@N), 171.72 (Cl,
CAO), 152.40(Co,p, CH), 143.86(Cm, tert), 126.68 (Cn,q, CH), 129.44
(Ca, CH), 128.82 (Cb, CH), 134.48 (Cc, CH), 125.64 (Cd, CH), 136.66
(Ce, tert), 137.02 (Cf, CH), 123.42 (Cg, CH), 134.62 (Cj, tert),
138.21, 134.72, 130.05, 128.46 (PPh3). 31P NMR (CDCl3, d, ppm):
30.02.

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[RuCl(CO)(PPh3)(L3)]
127.42 (Cb, CH), 135.84 (Cc, CH), 126.30 (Cd, CH), 136.08 (Ce, tert),
137.26 (Cf, CH), 124.96 (Cg, CH), 134.96 (Cj, tert), 137.63, 132.21,
128.43, 126.72 (AsPh3).
Yield 80%, Green solid, m.p. 203 °C, Anal. Found: C 54.45, H 3.19,
N 6.11, S 4.62. Calcd for C30H23ClN3O2PSRu: C 54.84, H 3.53, N 6.39,
S 4.88. IR (KBr, cmÀ1): 1936 (Cr„O), 760 (ClAS), 1575 (Ci@O), 1531
(Ch@N). UV kmax: 600, 454, 275. 1H NMR (DMSO-d6, d, ppm): 8.68 &
[RuCl(CO)(AsPh3)(L2)]
8.26 (s, 2H, NH2), 7.32 (d, 1Ha, J = 7.2 Hz, CH), 7.48 (t, 2Hb,c
,
Yield 77%, Green solid, m.p. 200 °C, Anal. Found: C 55.88, H 3.55,
N 5.21. Calcd for C35H25ClN3O3AsRu: C 56.27, H 3.37, N 5.62. IR
(KBr, cmÀ1): 1955 (Cr„O), 1186 (ClAO), 1620 (Ci@O), 1500 (Ch@N).
UV kmax: 582, 436, 318, 242. 1H NMR (DMSO-d6, d, ppm): 8.31(d,
2Ho,p, J = 6.6 Hz, CH), 8.12 (d, 2Hn,q, J = 6.6 Hz, CH), 7.36 (d, 1Ha,
J = 7.3 Hz, CH), 7.70 (d, 1Hd, J = 7.2 Hz, CH), 6.78 (d, 1Hf, J = 7.2 Hz,
CH), 6.90 (d, 1Hg, J = 7.2 Hz, CH), 8.18–7.76 (m, 15H, PPh3). 13C
NMR (DMSO-d6, d, ppm): 204.28 (Cr, C„O), 183.42 (Ci, C@O),
162.94 (Ch, C@N), 171.86 (Cl, CAS), 128.30 (Ca, CH), 127.96 (Cb,
CH), 136.02 (Cc, CH), 125.88 (Cd, CH), 138.10 (Ce, tert), 136.74 (Cf,
CH), 125.76 (Cg, CH), 135.06 (Cj, tert), 138.74, 135.03, 129.72,
128.20 (PPh3). 31P NMR (CDCl3, d, ppm): 29.02.
,
J = 7.2 Hz, CH), 7.48 (t, 2Hb,c J = 7.3 Hz, CH), 7.82 (d, 1Hd,
J = 7.2 Hz, CH), 7.02 (d, 1Hf, J = 7.2 Hz, CH), 6.90 (d, 1Hg, J = 7.2 Hz,
CH), 8.12–7.86 (m, 15H, AsPh3). 13C NMR (DMSO-d6, d, ppm):
204.06 (Cr, C„O), 181.83 (Ci, C@O), 162.78 (Ch, C@N), 170.23 (Cl,
CAO), 154.28 (Co,p, CH), 143.60 (Cm, tert), 126.72 (Cn,q, CH),
129.35 (Ca, CH), 128.23 (Cb, CH), 136.18 (Cc, CH), 127.56 (Cd, CH),
138.01 (Ce, tert), 137.37 (Cf, CH), 126.78 (Cg, CH), 135.40 (Cj, tert),
138.24, 132.73, 129.46, 126.02 (AsPh3).
[RuCl(CO)(Py)(L1)]
Yield 74%, Violet solid, m.p. 270 °C, Anal. Found: C 44.48, H 2.41,
N 12.40. Calcd for C17H13ClN4O3Ru: C 44.60, H 2.86, N 12.24. IR
(KBr, cmÀ1): 1954 (Cr„O), 1192 (ClAO), 1609 (Ci@O), 1523 (Ch@N).
UV kmax: 461, 323, 275, 231. 1H NMR (DMSO-d6, d, ppm): 8.62 &
8.30 (s, 2H, NH2), 7.24 (d, 1Ha, J = 7.2 Hz, CH), 7.60 (t, 2Hb,c
,
[RuCl(CO)(AsPh3)(L3)]
J = 7.3 Hz, CH), 7.72 (d, 1Hd, J = 7.2 Hz, CH), 6.93 (d, 1Hf,
J = 7.2 Hz, CH), 6.80 (d, 1Hg, J = 7.2 Hz, CH), 8.26–7.78 (m, 5H, Py).
13C NMR (DMSO-d6, d, ppm): 204.66 (Cr, C„O), 180.82 (Ci, C@O),
163.04 (Ch, C@N), 169.01 (Cl, CAO), 129.27 (Ca, CH), 127.08 (Cb,
CH), 135.03 (Cc, CH), 126.98 (Cd, CH), 134.98 (Ce, tert), 135.07 (Cf,
CH), 124.40 (Cg, CH), 133.76 (Cj, tert), 137.90, 133.46, 129.26 (Py).
Yield 78%, Green solid, m.p. 220 °C, Anal. Found: C 50.96, H 3.12,
N 5.81, S 4.32. Calcd for C30H23ClN3O2AsSRu: C 51.40, H 3.31, N
5.99, S 4.57. IR (KBr, cmÀ1): 1955 (Cr„O), 768 (ClAS), 1610 (Ci@O),
1538 (Ch@N). UV kmax: 417, 270. 1H NMR (DMSO-d6, d, ppm): 9.16
& 8.62 (s, 2H, NH2), 7.42 (d, 1Ha, J = 7.2 Hz, CH), 7.58 (t, 2Hb,c
,
J = 7.3 Hz, CH), 7.72 (d, 1Hd, J = 7.2 Hz, CH), 6.98 (d, 1Hf,
J = 7.2 Hz, CH), 6.96 (d, 1Hg, J = 7.2 Hz, CH), 7.98–7.74 (m, 15H,
AsPh3). 13C NMR (DMSO-d6, d, ppm): 203.94 (Cr, C„O), 182.70
(Ci, C@O), 163.01 (Ch, C@N), 171.66 (Cl, CAS), 129.30 (Ca, CH),
128.60 (Cb, CH), 135.02 (Cc, CH), 126.20 (Cd, CH), 137.41 (Ce, tert),
135.90 (Cf, CH), 127.12 (Cg, CH), 135.51 (Cj, tert), 137.16, 132.24,
129.48, 128.30 (AsPh3).
[RuCl(CO)(Py)(L2)]
Yield 73%, Brown solid, m.p. 235 °C, Anal. Found: C 50.53, H
2.54, N 10.62. Calcd for C22H15ClN4O3Ru: C 50.82, H 2.91, N
10.78. IR (KBr, cmÀ1): 1950 (Cr„O), 1178 (ClAO), 1600 (Ci@O),
1558 (Ch@N). UV kmax: 680, 327, 259, 245. 1H NMR (DMSO-d6, d,
ppm): 8.38 (d, 2Ho,p, J = 6.6 Hz, CH), 8.16 (d, 2Hn,q, J = 6.6 Hz, CH),
7.22 (d, 1Ha, J = 7.2 Hz, CH), 7.36 (t, 2Hb,c, J = 7.3 Hz, CH), 7.86 (d,
1Hd, J = 7.2 Hz, CH), 6.98 (d, 1Hf, J = 7.2 Hz, CH), 6.82 (d, 1Hg,
J = 7.2 Hz, CH), 8.08–7.90 (m, 5H, Py). 13C NMR (DMSO-d6, d,
ppm): 202.78 (Cr, C„O), 178.02 (Ci, C@O), 162.48 (Ch, C@N),
[RuH(CO)(PPh3)(L1)]
Yield 73%, Brown solid, m.p. 230 °C, Anal. Found: C 59.62, H
3.72, N 6.35. Calcd for C30H24N3O3PRu: C 59.40, H 3.99, N 6.93. IR
(KBr, cmÀ1): 1946 (Cr„O), 1176 (ClAO), 1610 (Ci@O), 1552 (Ch@N).
UV kmax: 401, 272, 244. 1H NMR (DMSO-d6, d, ppm): 8.94 & 8.18 (s,
2H, NH2), 7.34 (d, 1Ha, J = 7.2 Hz, CH), 7.47 (t, 2Hb,c, J = 7.3 Hz, CH),
7.66 (d, 1Hd, J = 7.2 Hz, CH), 7.68 (d, 1Hf, J = 7.2 Hz, CH), 6.52 (d,
1Hg, J = 7.2 Hz, CH), 7.83–7.72 (m, 15H, PPh3), À8.13 (s, 1H, Ru-
H). 13C NMR (DMSO-d6, d, ppm): 203.16 (Cr, C„O), 181.78 (Ci,
C@O), 162.98 (Ch, C@N), 168.76 (Cl, CAO), 131.20 (Ca, CH), 128.48
(Cb, CH), 134.76 (Cc, CH), 125.56 (Cd, CH), 136.11 (Ce, tert),
135.26 (Cf, CH), 125.16 (Cg, CH), 134.18 (Cj, tert), 139.22, 137.03,
128.40, 125.42 (PPh3). 31P NMR (CDCl3, d, ppm): 28.04.
169.24 (Cl, CAO), 150.90 (Co,p, CH), 141.28 (Cm, tert), 129.88 (Cn,q
,
CH), 128.42 (Ca, CH), 127.86 (Cb, CH), 133.22 (Cc, CH), 126.71 (Cd,
CH), 135.24 (Ce, tert), 135.48 (Cf, CH), 124.32 (Cg, CH), 133.40 (Cj,
tert), 136.48, 133.26, 130.63 (Py).
[RuCl(CO)(Py)(L3)]
Yield 72%, Violet solid, m.p. 218 °C, Anal. Found: C 43.37, H 2.60,
N 11.96, S 6.63. Calcd for C17H13ClN4O2SRu: C 43.09, H 2.76, N
11.82, S 6.77. IR (KBr, cmÀ1): 1952 (Cr„O), 782 (ClAS), 1587 (Ci-
@O), 1535 (Ch@N). UV kmax: 612, 528, 385, 254. 1H NMR (DMSO-
d6, d, ppm): 8.64 & 8.41 (s, 2H, NH2), 7.28 (d, 1Ha, J = 7.2 Hz, CH),
7.40 (t, 2Hb,c, J = 7.3 Hz, CH), 7.75 (d, 1Hd, J = 7.2 Hz, CH), 6.84 (d,
1Hf, J = 7.2 Hz, CH), 6.73 (d, 1Hg, J = 7.2 Hz, CH), 8.34–7.82 (m, 5H,
Py). 13C NMR (DMSO-d6, d, ppm): 205.32 (Cr, C„O), 182.54 (Ci,
C@O), 162.78 (Ch, C@N), 171.22 (Cl, CAS), 128.92 (Ca, CH), 127.41
(Cb, CH), 135.48 (Cc, CH), 126.86 (Cd, CH), 137.48 (Ce, tert),
136.22 (Cf, CH), 124.86 (Cg, CH), 134.40 (Cj, tert), 138.43, 133.22,
130.08 (Py).
[RuH(CO)(PPh3)(L2)]
Yield 74%, Brown solid, m.p. 248 °C, Anal. Found: C 62.36, H
3.32, N 5.81. Calcd for C35H26N3O3PRu: C 62.87, H 3.92, N 6.28. IR
(KBr, cmÀ1): 1944 (Cr„O), 1174 (ClAO), 1624 (Ci@O), 1553 (Ch@N).
UV kmax: 406, 217. 1H NMR (DMSO-d6, d, ppm): 8.56 (d, 2Ho,p
,
J = 6.6 Hz, CH), 8.26 (d, 2Hn,q
,
J = 6.6 Hz, CH), 7.46 (d, 1Ha,
J = 7.2 Hz, CH), 7.60 (t, 2Hb,c, J = 7.3 Hz, CH), 7.7 (d, 1Hd, J = 7.2 Hz,
CH), 7.26 (d, 1Hf, J = 7.2 Hz, CH), 6.98 (d, 1Hg, J = 7.2 Hz, CH),
7.80–7.66 (m, 15H, PPh3), À8.30 (s, 1H, Ru-H). 13C NMR (DMSO-
d6, d, ppm): 204.26 (Cr, C„O), 180.44 (Ci, C@O), 162.25 (Ch,
C@N), 169.98 (Cl, CAO), 151.26 (Co,p, CH), 142.48 (Cm, tert),
127.83 (Cn,q, CH), 129.40 (Ca, CH), 128.66 (Cb, CH), 136.72 (Cc,
CH), 127.44 (Cd, CH), 138.46 (Ce, tert), 137.92 (Cf, CH), 126.08 (Cg,
CH), 135.26 (Cj, tert), 136.22, 133.40, 131.02, 129.47 (PPh3). 31P
NMR (CDCl3, d, ppm): 29.48.
[RuCl(CO)(AsPh3)(L1)]
Yield 77%, Brown solid, m.p. 242 °C, Anal. Found: C 52.97, H
2.96, N 5.89. Calcd for C30H23ClN3O3AsRu: C 52.61, H 3.38, N
6.13. IR (KBr, cmÀ1): 1944 (Cr„O), 1190 (ClAO), 1616 (Ci@O),
1583 (Ch@N). UV kmax: 440, 319, 271, 230. 1H NMR (DMSO-d6, d,
ppm): 8.92 & 8.36 (s, 2H, NH2), 7.40 (d, 1Ha, J = 7.2 Hz, CH), 7.42
(t, 2Hb,c, J = 7.3 Hz, CH), 7.70 (d, 1Hd, J = 7.2 Hz, CH), 6.76 (d, 1Hf,
J = 7.2 Hz, CH), 6.48 (d, 1Hg, J = 7.2 Hz, CH), 7.90–7.62 (m, 15H,
AsPh3). 13C NMR (DMSO-d6, d, ppm): 203.68 (Cr, C„O), 183.98
(Ci, C@O), 163.09 (Ch, C@N), 169.96 (Cl, CAO), 128.74 (Ca, CH),
[RuH(CO)(PPh3)(L3)]
Yield 77%, Violet solid, m.p. 245 °C, Anal. Found: C 57.62, H 3.72,
N 6.95, S 4.88. Calcd for C30H24N3O2PSRu: C 57.87, H 3.89, N 6.75, S

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P. Anitha et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 99 (2012) 174–180
177
5.15. IR (KBr, cmÀ1): 1945 (Cr„O), 776 (ClAS), 1600 (Ci@O), 1540
(Ch@N). UV kmax: 520, 354, 280, 224. 1H NMR (DMSO-d6, d, ppm):
8.83 & 8.10 (s, 2H, NH2), 7.26 (d, 1Ha, J = 7.2 Hz, CH), 7.46 (t,
2Hb,c, J = 7.3 Hz, CH), 7.82 (d, 1Hd, J = 7.2 Hz, CH), 6.83 (d, 1Hf,
J = 7.2 Hz, CH), 6.60 (d, 1Hg, J = 7.2 Hz, CH), 7.98–7.84 (m, 15H,
PPh3), À8.35 (s, 1H, Ru-H). 13C NMR (DMSO-d6, d, ppm): 204.98
(Cr, C„O), 182.66 (Ci, C@O), 163.04 (Ch, C@N), 172.78 (Cl, CAS),
129.36 (Ca, CH), 128.48 (Cb, CH), 135.43 (Cc, CH), 126.98 (Cd, CH),
137.92 (Ce, tert), 136.88 (Cf, CH), 126.70 (Cg, CH), 135.02 (Cj, tert),
138.92, 133.66, 130.04, 128.62 (PPh3). 31P NMR (CDCl3, d, ppm):
28.64.
B
r
B
Ru
N
r
X
CO
X
CO
Ru
O
O
C m
O
Y
C
q
o
a
i
k
j
a
i
N
h
j
p
k
b
c
h
b
c
N
l
N
NH2
l
g
N
g
n
e
e
d
f
d
f
(a)
(b)
(B = PPh3, AsPh3 or Py; X = H or Cl; Y = O or S)
Catalytic oxidation
Fig. 2. Structure of complexes.
Catalytic oxidation of primary alcohols to corresponding alde-
hydes and secondary alcohols to ketones by ruthenium(II) com-
plexes were studied in the presence of N-methyl morpholine N-
oxide (NMO) as co-oxidant. In a typical reaction, ruthenium(II)
complexes as a catalyst and primary or secondary alcohol, as sub-
strates at 1:100 M ratios was described as follows. A solution of
ruthenium complexes (0.01 mmol) in CH2Cl2 (20 cm3) was added
to the mixture containing substrate (1 mmol), NMO (3 mmol)
and molecular sieves. The solution mixture was refluxed for 2 h
and the solvent was then evaporated from the mother liquor under
reduced pressure. The solid residue was extracted with petroleum
ether (60–80 °C) (20 cm3) concentrated to ꢀ1 ml and was analyzed
by GC. The oxidation products were identified by GC co-injection
with authentic samples.
served for the complex [RuCl(CO)(PPh3)(L1)] at m/z = 641.10
(Calcd. 641.03) confirms the stoichiometry of the complex (Fig. 2).
Infrared spectroscopic analysis
In IR spectra, the free ligands display
t(C@O)/
t
(C@S) absorption
at 1688–1676 cmÀ1/863 cmÀ1. The absence of
t
(OAH)/ (SAH) in
t
the free ligand suggests that they are exist in the ketone/thione
form. The new band appeared around 1192–1174 cmÀ1 which cor-
responds to
complexes and the
icarbazone complexes. The IR spectra of the complexes did not
display (OAH)/
(SAH) at 3419–3409 cmÀ1/2585–2570 cmÀ1 sug-
t
(CAO) for semicarbazone and isonicotinylhydrazone
t
(CAS) appeared at 782–760 cmÀ1 in thiosem-
t
t
Catalytic transfer hydrogenation
gesting the deprotonation of the enol/thiol proton prior to coordi-
nation [28–31]. The bands assigned to azomethine (C@N) and
quinone carbonyl (C@O) appearing at 1600–1597 and 1672–
1637 cmÀ1 respectively in the spectra of free ligands are shifted
to lower wave numbers on complexation [32] indicates the other
coordination through imine nitrogen and quinone oxygen. The IR
spectrum of free ligands display two bands around 3450 and
3300 cmÀ1 due to tas and tsym of terminal NH2 group [33]. These
bands remain unaltered in the corresponding metal complexes
indicating the non-involvement of this group on complexation.
The existence of very strong band in the 1964–1936 cmÀ1 region
for all the complexes revealed the presence of terminally coordi-
nated carbon monoxide [34]. A medium intensity band is observed
in the region 1094–1091 cmÀ1 characteristic of the coordinated
pyridine [35]. Further the Ru-H absorption appeared around
2020–2010 cmÀ1 for complexes containing Ru-H coordination.
The peak around 480 cmÀ1 has been assigned to Ru-Cl vibrations
for complexes containing metal chloride bond [36]. In addition
other characteristic bands due to triphenylphosphine and triphen-
ylarsine are present around 1436–1432 cmÀ1, in the spectra of all
the complexes.
The catalytic transfer hydrogenation reactions were also stud-
ied using ruthenium(II) complexes as a catalyst, ketone as sub-
strate and KOH as base at 1:500:2.5 M ratios. The procedure was
described as follows. A mixture containing ketone (5 mmol), the
ruthenium complex (0.01 mmol) and KOH (0.025 mmol) was
heated to reflux in 10 cm3 of i-PrOH for 2 h. After completion of
reaction the catalyst was removed from the reaction mixture by
the addition of petroleum ether followed by filtration and subse-
quent neutralization with 1 M HCl. The ether layer was filtered
through a short path of silica gel by column chromatography.
The filtrate was subjected to GC analysis and the hydrogenated
product was identified and determined with authentic samples.
DNA cleavage experiments
DNA cleavage experiments were carried out according to re-
ported procedure [27]. For the gel electrophoresis experiment,
supercoiled DNA of Escherichia coli was treated with the ruthe-
nium(II) complexes in TAE buffer (10 mmol Tris acetate, 10 mmol
EDTA, pH 8.0) and the solution was then incubated at 37 °C for
2 h. The samples were analyzed by electrophoresis for 30 min at
50 V on a 0.8% agarose gel in TAE (4.84 g Tris–acetate, 0.5 mol
Electronic spectroscopic analysis
EDTA/1 l, pH 8.0). The gel was stained with 10 lg/ml ethidium bro-
mide and observe the bands under UV illuminator.
All the new ruthenium(II) complexes are diamagnetic indicating
the presence of ruthenium in the +2 oxidation state. The ground
1
state of ruthenium(II) is A1g arising from the t62g configuration in
Result and discussion
an octahedral environment. The excited state corresponding to
3
1
the t52g e1g configuration are T1g 3T2g 1T1g and T2g. Hence, four
, ,
All the complexes are stable in air at room temperature, brown
in color, non-hygroscopic in nature and highly soluble in common
organic solvents such as dichloromethane, benzene, acetonitrile,
chloroform and DMSO. The analytical data are in good agreement
with the general molecular formula proposed for all the complexes.
In addition, ESI-mass spectra was also used to check the composi-
tion of the complexes. For example the molecular ion peak ob-
bands corresponding to the transitions 1A1g ? 3T1g
,
1A1g ? 3T2g
,
1A1g ? 1T1g
,
1A1g ? 1T2g are possible in the order of increasing
energy.
The electronic spectra of ligands and the complexes in CH2Cl2
showed two to four bands in the region 680–217 nm. The bands
around 680–600 nm range have been assigned to the spin
allowed 1A1g ? 1T1g transition. The other high intensity bands