Synthesis, structure and reactivity of azosalophen complexes of vanadium(IV): Studies on cytotoxic properties

Article abstract of DOI:10.1039/b903352a

The free ligands, 2-{(o-hydroxyaryl)azo}-1-N-salicylidene phenylamine, H₂L [where H₂L = RC₆H₄NNC ₆H₄NCH-C₆H₄OHR = p-H for H ₂L¹, p-Me for H₂L² and p-Cl for H₂L³], were prepared by the condensation of salicylaldehyde with 2-{(o-hydroxy aryl)azo} aniline. Reaction of H₂L with VOSO₄ afforded the oxovanadium complex, (L)V(O)(H ₂O). The (L¹)V(O)(H₂O) complex displays two reversible responses at 0.7 V and -0.65 V vs. SCE in cyclic voltammetry. Catalytic activity of (L¹)V(O)(H₂O) toward H ₂O₂ induced oxidation of organic thioethers to sulfoxide and sulfones have been examined. The cytotoxicity of (L¹)V(O)(H ₂O) has also been examined on human lung cancer cells. The Royal Society of Chemistry 2009.

Full text of DOI:10.1039/b903352a

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Synthesis, structure and reactivity of azosalophen complexes of vanadium(IV):
studies on cytotoxic properties†
Poulami Pattanayak,a Jahar Lal Pratihar,a Debprasad Patra,a Soham Mitra,b Arindam Bhattacharyya,‡c
Hon Man Leed and Surajit Chattopadhyay*a
Received 17th February 2009, Accepted 6th May 2009
First published as an Advance Article on the web 23rd June 2009
DOI: 10.1039/b903352a
The free ligands, 2-{(o-hydroxyaryl)azo}-1-N-salicylidene phenylamine, H2L [where H2L =
1
2
3
=
=
RC6H4N NC6H4N CH-C6H4OHR = p-H for H2L , p-Me for H2L and p-Cl for H2L ], were prepared
by the condensation of salicylaldehyde with 2-{(o-hydroxy aryl)azo} aniline. Reaction of H2L with
VOSO4 afforded the oxovanadium complex, (L)V(O)(H2O). The (L1)V(O)(H2O) complex displays two
reversible responses at 0.7 V and -0.65 V vs. SCE in cyclic voltammetry. Catalytic activity of
(L1)V(O)(H2O) toward H2O2 induced oxidation of organic thioethers to sulfoxide and sulfones have
been examined. The cytotoxicity of (L1)V(O)(H2O) has also been examined on human lung cancer cells.
Introduction
Synthesis of target molecules via metal assisted routes is an
important area of current chemical research.1 Interest on the
chemistry of transition metal complexes incorporating salen type
of ligands, 1, has accelerated during the last few years due to
the discovery of their catalytic properties and towards alkene
epoxidation in particular.2,3
Studies on tuning the catalytic activity of such complexes
of organic substrates.5 The oxovanadium complexes of tetraden-
by modifying the ligand backbone have been ongoing. As a
consequence developments in the area of asymmetric epoxidation
of unfunctionalised alkenes are remarkable.3
tate (O, N, N, O) salen ligands bearing electron withdrawing
substituents catalyse the epoxidation of cyclohexene.6 Thus it
was expected that the azosalophen complexes of [VO]2+ may be
an interesting alternative catalyst for oxygenation reactions since
Recently we have reported the synthesis and properties of Ni(II)
complexes incorporating new azosalophen ligands, 2.4 The Ni(II)–
azosalophen complexes could be prepared by O-insertion into the
Ni–C(aryl) bond with peroxo reagents.4 The azosalophen ligands
are new salen like ligands in terms of coordination mode (O, N, N,
O) and charge (i.e. -2 after dissociation of two phenolic protons).
Isolation or syntheses of free authentic azosalophen ligands,
H2L, were necessary to explore the possibility of preparing new
complexes with the potential to exhibit new and interesting
properties. Therefore we intended to isolate the free H2L ligands
and the chemistry of corresponding vanadium complexes. Several
V(IV) and V(V) complexes were used as catalysts for oxygenation
=
coordinated diazo (-N N-) nitrogen possesses considerable p acid
character.4,7
Further, the oxidative properties of salen complexes have
attracted biological chemists to search for a novel class of agents
that are capable of triggering apoptosis in human cells.8c As
a result, we were encouraged to examine the cytotoxity for
the resultant vanadium complexes of azosalophen ligands. It is
important to mention that several studies have been reported
where the Fe(II) and Fe(III), Mn(III) and Ni(II) salen complexes
have been examined towards in vitro DNA damage and human
cell cytotoxicity.8
Herein we report the synthesis and characterization of azosa-
lophen complexes of V(IV). The electrochemical properties, cat-
alytic properties toward oxidation of thioethers and cytotoxicity
on human lung cancer cells have been described.
aDepartment of Chemistry, University of Kalyani, Kalyani, 741235, India.
E-mail: scha8@rediffmail.com; Fax: +91 33 25828282; Tel: +91 33
24149725
bDepartment of Environmental Science, University of Kalyani, Kalyani
741235, India
cDepartment of Zoology, University of Calcutta, Kolkata, India
dDepartment of Chemistry, National Changhua University of Education,
Changhua 50058, Taiwan
Results and discussion
Preparation of authentic H2L ligand and new V(IV)-azosalophen
complexes
† Electronic supplementary information (ESI) available: Fig. S1–S5,
UV/Vis, 1H NMR of H2L ligands, Fig. S6–S7, UV/Vis of (L)V(O)(H2O)
complexes, Fig. S8–S13 all the IR spectra of H2L ligands and
(L)V(O)(H2O) complexes and Fig. S14 mass spectrum for complex
(L1)V(O)(H2O). CCDC reference number 671690 for 6. For ESI and
crystallographic data in CIF or other electronic format see DOI:
10.1039/b903352a
The 2-{(2-hydroxyaryl)azo}aniline, 3, were prepared following
Ni(II) assisted route as described earlier (Scheme 1).4 The con-
densation of 3a, 3b and 3c with salicylaldehyde in refluxing diethyl
ether afforded H2L1(4a), H2L2(4b) and H2L3 (4c) respectively in
‡ Collaborator for experiments related to cytotoxicity.
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Scheme 1
good yield (eqn (1)). The H2L ligands displayed characteristic
UV/Vis spectra.
1H NMR spectra of the H2L ligands exhibited two singlets at
d = 12.88 and d = 12.77 ppm, respectively which are characteristic
=
of two phenolic protons. Azomethine (-N CH-) proton resonance
appeared near d 8.62. Other aromatic proton signals are consistent
with the structure. The spectra are given in Fig. S3–S5† and the
data are collected in the Experimental section.
Reaction of H2L with VOSO4·5H2O in refluxing aqueous
methanol afforded the complex of composition (L)V(O)(H2O),
(eqn (1)). The (L)V(O)(H2O) complexes displayed character-
istic UV/Vis spectra in dichloromethane solution where five
absorption bands appeared within the range of 494–244 nm.
A representative UV/Vis spectrum of (L1)V(O)(H2O) has been
shown in Fig. 1. The other two spectra are given in Fig. S6 and
(1)
A representative UV/Vis spectrum of H2L1 (4a) has been given
in Fig. 1. The other two spectra are given in Fig. S1 and Fig. S2
(see ESI†) for H2L2 (4b) and H2L3 (4c) respectively and the data
are collected in the Experimental section.
Fig. 1 UV/Vis spectra of H2L1 (- - -) and (L1)V(O)(H2O) (—). The arrows indicate scales of the corresponding spectra.
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Fig. S7† for (L2)V(O)(H2O) and (L3)V(O)(H2O) respectively and
data are collected in the Experimental section.
ESI-MS spectrum of (L1)V(O)(H2O) was recorded as repre-
sentative for characterization. The molecular ion peak [M + H]+
(without water molecule) appeared at m/z 383.2282.10
IR spectra of H2L ligands exhibited nO–H, nC= and nN= near
N
N
3375, 1612 and 1473 cm-1 respectively. Whereas in the case of
(L)V(O)(H2O) complexes, nO–H is absent indicating the binding of
phenoxide oxygen. The nC= and nN= of (L)V(O)(H2O) shifted
X-Ray structure of (L1)V(O)(H2O)
N
N
The X-ray structure of (L1)V(O)(H2O), has been determined.
Fig. 3 shows the perspective view of the molecule in which
the octahedral vanadium centre is equatorially coordinated by
tetradentate (O, N, N, O) dianionic (L1)2- ligand. The oxo (O) and
aqua (H2O) ligands bind axially completing the hexacoordination
about V(IV). Selected bond distances and angles are collected in
Table 1.
to lower energy (1601 and 1384 cm-1 respectively) than the
=
corresponding ligands signifying the coordination of azo (-N N-)
4,7
=
and imine (-CH N-) nitrogens. The IR spectra of ligands and
complexes are given in Fig. S8–S13.† The absorption near 984 cm-1
for all the complexes is characteristic of nVO consistent with a
vanadyl, [VO]2+, centre.9
The magnetic susceptibility measurements indicated that the
moment (m ª1.68 BM) is consistent with one unpaired electron
and the EPR spectrum of (L1)V(O)(H2O) exhibited eight lines
(Fig. 2) for I = 7/2 confirming the tetrapositive oxidation state of
vanadium having d1 configuration.
9
˚
=
V O (1.573(8) A) bond length is typical, whereas the V–O
(H2O) distance is longer compared to other aqua complexes of
VO2+ where H2O is trans to oxo ligand.11 The coordinated (L1)2-
ligand backbone is planar (mean deviation 0.086 A). The vana-
˚
˚
dium centre is displaced toward the oxo ligand by 0.313 A from the
least square plane of (O, N, N, O) the coordination sphere of (L1)2-.
Two molecules of (L1)V(O)(H2O) exhibit dimeric association in the
crystal lattice through hydrogen bond interactions of coordinated
H2O as shown in Fig. 4.
Electrochemistry of (L1)V(O)(H2O)
The redox property of (L1)V(O)(H2O) complex has been stud-
ied by cyclic voltammetry. The cyclic voltammogram (Fig. 5)
displays two reversible responses at 0.7 V and -0.65 V vs SCE
in dichloromethane–acetonitrile mixed solvent. The oxidative
response at 0.7 V was assignable to the [VVO(L)]+/[VIVO(L)]
redox process12 while the reductive response may be assigned
to either [VIVO(salen)]/[VIIIO(salen)]- redox couple or for the
ligand centered redox process. Though the reductive process,
[VIVO(salen)]/[VIIIO(salen)]-, has never been reported for similar
(VO)2+ (salen) complexes, but these types of redox couples were
reported in some other kind of vanadium complexes.11 However,
the possibility of the involvement of a delocalized metal–ligand
mixed redox orbital could not be ruled out unequivocally.
Fig. 2 EPR spectrum of (L1)V(O)(H2O) in dichloromethane at 298 K.
Fig. 3 Perspective view of molecular structure of (L1)V(O)(H2O) with atom numbering scheme. The hydrogen atoms except on O3 have been omitted
for clarity.
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◦
˚
Table 1 Selected bond distances (A) and angles ( ) for compound
(L1)V(O)(H2O)
Bond distances
V–O1
V–O2
V–O3
V–O4
V–N2
V–N3
O1–C19
C2–O2
O3–H1B
O3–H1A
N1–C1
1.9451(17)
1.9499(15)
2.3536(19)
1.6112(16)
2.069(2)
2.0673(18)
1.320(3)
1.308(3)
0.78(4)
0.86(4)
1.389(3)
N2–C7
N1–N2
N3–C13
C1–C2
C2–C3
C4–C5
C1–C6
C8–C9
C3–C4
C5–C6
C7–C8
1.433(3)
1.271(3)
1.296(3)
1.439(3)
1.414(3)
1.406(3)
1.411(3)
1.376(3)
1.364(3)
1.366(3)
1.389(3)
Fig. 5 Cyclic voltammogram of (L1)V(O)(H2O) in CH2Cl2–CH3CN and
TEAP (0.1 M).
Bond angles
while the LUMO has considerable ligand character. Thus, from the
DFT results, the oxidative and reductive couples may be inferred
to be a metal centred oxidation (VIV/VV) and ligand reduction
respectively.
O1–V–O2
O1–V–O3
O1–V–O4
O1–V–N2
O1–V–N3
O2–V–O3
O2–V–O4
O2–V–N2
O3–V–O4
N2–C7–C8
N2–C7–C12
O4–V–N3
V–O1–C19
V–O3–H1A
V–O3–H1B
H1A–O3–H1B
93.07(6)
81.01(6)
104.26(8)
156.81(7)
90.56(7)
81.17(6)
103.93(7)
87.75(7)
172.28(8)
123.3(2)
115.7(2)
98.17(7)
127.64(14)
114(2)
N1–C1–C6
N1–C1–C2
C1–C2–C3
O2–C2–C3
O2–C2–C1
C2–C3–C4
C3–C4–C5
O2–V–N3
O3–V–N2
O3–V–N3
O4–V–N2
N2–V–N3
V–O2–C2
N1–N2–C7
N2–N1–C1
113.8(2)
126.7(2)
116.9(2)
118.7(2)
124.49(19)
121.7(2)
121.5(2)
155.95(7)
76.21(7)
75.93(7)
98.00(8)
79.81(8)
127.16(14)
115.68(19)
119.97(19)
Catalytic oxygenation of thioethers
Selective catalytic oxygenation of organic thioethers to sulfoxides
and sulfones (eqn (2)) is an efficient area in catalysis.14 Use of H2O2
as an oxidant has been extensively studied for this purpose.15
112(3)
116(4)
(2)
Meticulous experiments of spectroelectrochemistry may provide
clues to rationalise the reductive couple.13 To gain further insight,
single point DFT calculations were performed using the crys-
tallographic coordinates of (L1)V(O)(H2O). Two frontier orbitals
HOMO and LUMO, are shown in Fig. 6(a) and (b). From these
orbital diagrams it appears that the HOMO is metal centered
Oxidation of several organic sulfides with H2O2 in the presence
of (L1)V(O)(H2O) as catalyst was examined (Table 2). In most of
the cases, the conversion was calculated on the basis of isolated
yields where both the products (sulfoxide and sulfones) were
obtained. The oxidation of 1-benzylthio-2-(arylazo) benzene, 2 of
Table 2, afforded the sulfinyl derivative specifically. It was believed
Fig. 4 H-bonded dimer of (L1)V(O)(H2O). The dotted line represents a H-bond.
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Table 2 Oxidation of sulfides catalyzed by (L1)V(O)(H2O)
Timea
(h)
Yield (%)b
Sulfoxide
Entry
Sulfide
H2O2 (equiv)
Sulfone
(i)
1
2
3
4
5
5
5
5
5
5
0.5
2
2.5
3
35
60
40
37
30
45
—
48
40
35
(ii)
(iii)
(iv)
(v)
3
a Time required for optimal conversion. b Isolated yields.
Fig. 6 (a) HOMO of (L1)V(O)(H2O) and (b) LUMO of (L1)V(O)(H2O).
that the catalytic oxidation of thioethers went on according to the
proposed mechanism using analogous catalysts (Scheme 2).16
The reaction conditions and the results are collected in Table 2.
The products were isolated after separation and characterized by
we were encouraged to examine the effect of agents, which are able
to activate peroxide or superoxide, which here is (L1)V(O)(H2O)
on human cancer cells.
The effect of (L1)V(O)(H2O) in the human lung cancer cell line
A549 was assessed. These cells were exposed to (L1)V(O)(H2O),
within the dose range 5 to 25 mM. The Tryptan blue assay,
measured after 12 and 24 h, exhibited a time dependent reduction
in cell viability. The cell line was susceptible to the antiproliferative
effect after 24 h with the IC50 value of 15 mM (Fig. 7) though no
significant cell death was observed after 12 h.
monitoring the appearance and nature of nS= (for sulfoxides,
O
nS= ~ 1040–1060 cm-1; for sulfones, nS= ~1310–1350 and 1120–
O
O
1160 cm-1) in their IR spectra.
Cytotoxicity and death pattern of human cancer cell
The ability of the (L1)V(O)(H2O) complex to activate hydrogen
peroxide toward the catalytic oxygenation of thioethers has been
described (vide supra). In biology, the production of reactive
oxygen species (ROS) i.e. incremental in the oxidative stress in
the cell was identified as one of the putative mechanisms of
tumoricidal action of vanadium compounds.17 ROS is the various
reduced products of O2 (uptaken during respiration) within cells
which include peroxides and superoxides. This ROS i.e. peroxide
and superoxide, accumulation within the cell appears to be a
common event that occurs during cell death pathways.18 Therefore
Flow cytometric cell cycle analysis was carried out to determine
the DNA breakdown within the cell. The cell cycle phase distribu-
tion exhibited that the content of hypoploid DNA was increased
in A549 lung cancer cells upon treatment with (L1)V(O)(H2O) as
given in Fig. 8. This indicated the DNA damage within the cell
upon treatment with (L1)V(O)(H2O) which is one of the features of
apoptosis.19 Further, the cells were co-stained with PI in addition
to Annexin V to distinguish between apopotic and necrotic cell
death. The results of flow cytometric analysis are shown in
Fig. 9.
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Scheme 2
Fig. 8 Flow cytometric cell cycle analysis (a) before treatment and
(b) after treatment with (L1)V(O)(H2O).
diacetate). Fig. 10(a) and (b) shows the image of the cells
through a confocal microscope before and after treatment with
(L1)V(O)(H2O) respectively.
Fig. 7 Effect of (L1)V(O)(H2O) on survivability of A549 cells. Plot of
dose vs. viable cells to determine the IC50.
Enhanced fluorescent intensity of DCFDA in the
(L1)V(O)(H2O) treated cells (Fig. 10(b))20 indicated the increase
in ROS level within the treated cell after 12 h signifying the
fact that the enhanced accumulation of ROS may be necessary
for apoptotic death of A549 cells. Treatment of the A549 cell
with (L1)V(O)(H2O) in the presence of NAC (a common anti-
oxidant)19e reduced the ROS level, as expected, but surprisingly
the extent of cell death did not alter significantly. Therefore we
inferred that (L1)V(O)(H2O) created such an environment within
the cell that the death program went on either at a very low
concentration of ROS or in a ROS independent pathway.
The bottom-right quadrant of Fig. 9 represents the apoptotic
cells. The results show that the death pattern is apoptotic since
the population is considerable in the bottom right quadrant after
treatment (Fig. 9b) while the untreated cells did not undergo
apoptosis considerably (Fig. 9a).
After observing the apoptotic cell death pattern and an-
tiproliferative ability of (L1)V(O)(H2O) we intended to examine
the oxidative stress within the cell before and after treatment.
Intracellular ROS accumulation was assessed by staining the cells
with ROS sensitive fluorescent dye DCFDA (dichlorofluorescein
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Caspase-3 protein expressions were upregulated considerably in
(L1)V(O)(H2O) treated cells. The expression of Bad as per western
blot analysis is shown in Fig. 11(a).
Fig. 11 Western blot of (a) Bad and (b) procaspase-3 expressions.
Lane 1 represents untreated cells, lane 2 for the cells treated after
12 h and lane 3 is for the treated cells after 24 h. The increase in
intensity and size of the band from lane 1 to lane 3 is consistent with
its gradual upregulation of Bad after treatment. On the other hand,
procaspase-3 protein expression from lane 1 to lane 3 decreased as
shown in Fig. 11(b) but remains unchanged at 12 h after treatment
indicating the upregulation of Caspase-3 after 12 h.
From the results, reported in this paper, we can summarize that
the apoptotic death of A549 cancer cells may occur either at a
very low ROS level or due to activation of pro-apoptotic proteins
upon treatment with (L1)V(O)(H2O). A concerted mechanism, i.e.
activation of ROS at a low concentration vis-a`-vis the upregulation
of proapoptotic proteins could not be ruled out. A detailed study
will allow a more definite conclusion to be reached.
Fig. 9 Flow cytometric measurements on A549 human lung cancer
cell using Annexin V/PI (a) Represents the plot of untreated cells;
(b) Represents the plot for the cells treated with (L1)V(O)(H2O).
Conclusions
To gain further insight into the mechanism of (L1)V(O)(H2O)
induced apoptosis of A549 cells, the expressions of related proteins
were examined. It is well recognized that the expressions of pro-
apoptotic proteins play a crucial role in programmed cell death.21
Herein, the effects on the expressions of Bad and Caspase-3 (pro-
apoptotic proteins), upon treatment with (L1)V(O)(H2O) have
been examined. Western blot analysis showed that the Bad and
Azosalophen oxovanadium complex, (L)V(O)(H2O), could be
prepared after the successful synthesis of free azosalophen ligand,
H2L-which is the latest salen analogue. The scope of studies on the
catalytic oxygenations of organic substrates using (L1)V(O)(H2O)
complexes as catalyst have emanated from the preliminary studies
on oxidations of organic thioethers to sulfoxides and sulfones.
Studies on the cytotoxicity of (L1)V(O)(H2O) toward human
Fig. 10 Images of (a) untreated cells and (b) (L1)V(O)(H2O) treated cells through a confocal microscope.
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lung cancer cells (A549) showed that the pattern of cell death is
apoptotic. Enhancement of ROS accumulation and upregulation
of Bad and Caspase-3 pro apoptotic proteins, within the cell, upon
treatment with (L1)V(O)(H2O) were important observations to
search for a plausible mechanism of cell death pathway.
2-{(2-hydroxy-4-chloro phenyl)azo}aniline, 3c. Yield: 30.23 mg
-1
=
(50%). IR (KBr, cm ): n(NH2); 3446 n(OH); 3300 n(N N); 1460.
1H NMR (500 MHz, CDCl3): d (ppm) = 6.19 (s, NH2,); 6.75
(d, 1H); 6.83 (t, 1H); 7.04–6.99 (m, 2H); 7.20 (t, 1H); 7.29 (t, 1H);
7.67 (d, 1H); 7.76 (d, 1H). UV-Visible spectrum (dichloromethane)
[lmax, nm (e, M-1 cm-1)]: 455 (115892); 323 (17981); 231 (15196).
Elemental analysis: found C 58.20, H 4.02, N 16.99; C12H10N3OCl
(mol wt 247.5) requires C 58.18, H 4.04, N 16.96%.
Experimental
General details
Synthesis of H2L
The solvents used in the reactions were of reagent grade ob-
tained from E. Merck, Kolkata, India and purified and dried
by reported procedures.22 Vanadyl sulfate was purchased from
E. Merck, Kolkata, India. DMEM, FBS, penicillin, strepto-
mycin, 3-(4,5-dimethylthiazol-2,5-yl)-2,5-diphenylterazolium bro-
mide were purchased from Himedia. PI and annexin were pur-
chased from Pharmingen. A549 was purchased from NCCS, Pune.
DCFDA was procured from Sigma. The FACS caliber instrument
is of Becton Dickinson, USA. CO2 incubator is Hillforce, China
made. Fluorescence (FL2-A) detector is of Becton Dickinson. The
Gel kit for western blot was procured from Genei, Bangalore
(India). 2-(Arylazo)aniline and 2-(2-aminophenylazo)phenol, 3
were prepared according to the procedure described earlier.4,23
Electronic spectra were recorded on a Shimadzu UV-2401 PC
spectrophotometer. IR spectra were taken on a Perkin-Elmer
L120–00A FT IR spectrometer (4000–225 cm-1) on KBr pellets. C,
H, N analyses were performed on a Perkin-Elmer 2400 C,H,N,S/O
series II system, NMR spectra were drawn on a Bruker Avance
RPX 500 MHz spectrometer in CDCl3 using TMS as the internal
standard. X-band EPR spectra was recorded on a Varian E-109C
spectrometer (magnetic field up to ~6000 G) using quartz sample
tubes of 3 mm diameter. DPPH was used to calibrate the spectra.
Electrochemical measurements were made under a dinitrogen
atmosphere using a PAR model VERSASTAT-II potentiostat. A
glassy carbon working electrode, platinum wire auxiliary electrode
and standard saturated calomel electrode (SCE) were used in a
three-electrode configuration. 0.1 M Tetraethyl perchlorate was
used as the supporting electrolyte. All electrochemical data were
collected at 298 K and are uncorrected for junction potentials.
ESI mass spectra were recorded on a micro mass Q-TOF mass
spectrometer (serial no YA 263).
Three ligands, H2L1, H2L2 and H2L3 were prepared by a similar
general procedure. The detailed procedure for the preparation of
H2L1 is given below.
H2L1
2-{(o-Hydroxy aryl)azo} aniline, 3a, (100 mg, 0.46 mmol) was
dissolved in diethyl ether (40 mL), and to it salicylaldehyde (63 mg,
0.50 mmol) was added. The mixture was then heated to reflux
for 8 h and then solvent was evaporated in vacuo for 2 h to
obtain the solid product eliminating the excess of salicylaldehyde.
It was further kept in a vacuum desiccator for 24 h before use and
-1
=
characterization. Yield: 141.38 mg (95%). IR (KBr, cm ): n(C N)
1
=
1612; n(N N) 1473; n(OH) 3375. H NMR (500 MHz, CDCl3,):
d (ppm) = 6.95 (t, 1H); 7.06 (t, 2H); 7.11 (d, 1H); 7.25–7.26 (m,
1H); 7.34 (t, 1H); 7.40 (t, 3H); 7.94 (t, 2H); 8.62 (s, 1H); 12.88 (s,
OH); 12.77 (s, OH). UV-Visible spectrum (dichloromethane) [lmax
,
nm (e, M-1 cm-1)]: 323 (23458); 231 (22760). Elemental analysis:
found C 71.95, H 4.75, N 13.20; C19H15N3O2 (mol wt 317) requires
C 71.92, H 4.73, 13.24%.
H2L2
-1
=
=
Yield: 138.52 mg (95%). IR (KBr, cm ): n(C N) 1614; n(N N)
1474; n(OH) 3386. 1H NMR (500 MHz, CDCl3): d (ppm) = 2.37 (s,
3H); 6.82 (d, 2H), 6.95 (t, 1H); 7.11 (d, 1H); 7.24 (s,1H); 7.37–7.43
(m, 3H); 7.51 (t, 1H); 7.81 (d, 1H); 7.91 (d, 1H); 8.66 (s, 1H); 12.79
(s, OH); 12.99 (s, OH). UV-Visible spectrum (dichloromethane)
[lmax, nm (e, M-1 cm-1)]: 334 (17191); 232 (14894). Elemental
analysis: found C 72.47, H 4.15, N 12.70; C20H17N3O2 (mol wt
331) requires C 72.50, H 4.13, N, 12.68%.
Synthesis of 2-{(2-hydroxyaryl)azo}aniline, 3. Three com-
pounds, 2-{(2-hydroxyphenyl)azo}aniline, 3a, 2-{(2-hydroxy-
4-methyl phenyl)azo}aniline, 3b and 2-{(2-hydroxy-4-chloro
phenyl)azo}aniline, 3c were prepared by a similar general pro-
cedure as described earlier and the characterization data for 3a
have been reported earlier.4 The characterization data for 3b and
3c are furnished below.
H2L3
-1
=
=
Yield: 134.91 mg (95%).IR (KBr, cm ): n(C N) 1617; n(N N)
1473; n(OH) 3375. 1H NMR (500 MHz, CDCl3): d = 6.96 (t, 1H);
7.06 (t, 2H); 7.11 (d, 1H); 7.25–7.26 (m, 1H); 7.34 (t, 1H); 7.40
(t, 3H); 7.94 (t, 2H); 8.67 (s, 1H); 12.77 (s, OH); 12.88 (s, OH).
UV-Visible spectrum (dichloromethane) [lmax, nm (e, M-1 cm-1)]:
330 (22000); 232 (18750). Elemental analysis: found C 64.89, H
4.00, N 11.92; C19H14N3O2Cl (mol wt 351.5) requires C 64.86, H
3.98, N, 11.94%.
2-{(2-hydroxy-4-methyl
phenyl)azo}aniline,
3b. Yield:
32.17 mg (55%). IR (KBr, cm-1): n(NH2); 3406 n(OH); 3287
1
=
n(N N); 1456. H NMR (500 MHz, CDCl3): d (ppm) = 2.42
(s, 3H); 6.10 (s, NH2); 6.73 (d, 1H); 6.82 (t, 3H); 7.16–7.20 (m,
1H); 7.65–7.62 (m, 2H); 12.89 (s, OH). UV-Visible spectrum
(dichloromethane) [lmax, nm (e, M-1 cm-1)]: 450 (10236); 323
(12150); 230 (10392). Elemental analysis: found C 68.70, H 6.20,
N 18.48; C13H14N3O (mol wt 227) requires C 68.72, H 6.16, N
18.50%.
Synthesis of (L)V(O)(H2O)
Three complexes, (L1)V(O)(H2O), (L2)V(O)(H2O) and (L3)V(O)-
(H2O) were prepared by a similar general procedure. The detailed
procedure for the preparation of (L1)V(O)(H2O) is given below.
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(L1)V(O)(H2O)
products were separated and purified by preparative TLC using
Benzene–acetonitrile (95:5) mixed solvent. The solid PhSOMe and
PhSO2Me were isolated as the third and second fraction respec-
tively. The isolated yields were 40% and 48% respectively. The
products were characterized by IR spectroscopy. For sulfoxides,
nS=O appeared at 1052 cm-1 for sulfones, nS=O appeared at 1313 and
1135 cm-1 ranges. The results of the conversions of other thioethers
to sulfoxides and sulfones are given in Table 2.
H2OL1sal (125 mg, 0.39 mmol) was dissolved in methanol (40 mL),
and to it an aqueous solution of VOSO4·5H2O (100 mg, 0.39 mmol)
was added. The mixture was then heated to reflux for 1 h to
obtain a dark precipitate of (L1)V(O)(H2O). The solid product
was then filtered and washed with water and a little methanol. The
volume of the filtrate was reduced to ~20 mL and kept in a beaker
covered with a watch glass. After 12 h a second crop of product
was collected by filtration. All the products were combined and
recrystallized from dichloromethane–petroleum ether to obtain
pure (L1)V(O)(H2O). Yield: 126.27 mg (80%). IR (KBr, cm-1):
Cell culture
=
=
=
n(C N) 1601; n(N N) 1384; n(V O) 984. UV-Visible spectrum
(dichloromethane) [lmax, nm (e, M-1 cm-1)]: 494 (12900); 418
(17120); 369 (21867); 324 (20720); 244 (42090). Magnetic moment
(m, BM): 1.68. Elemental analysis: found C 57.00, H 3.79, N, 10.45;
C19H15N3VO4 (mol wt 400.28) requires C 56.96, H 3.74, N 10.49%.
MS (EI) m/z, (%): 383.2282 [M - H2O + H]+.
The A549 human lungs cancer cell lines were cultured in DMEM
supplemented with 10% fetal bovine serum along with 100 U/mL
penicillin and ◦100 mg/mL streptomycin. All cell types were
cultured at 37 C in a humidified incubator containing 5% CO2.
Cells in the log phase growth were harvested by trypsinization for
use in viability assays.
(L2)V(O)(H2O)
-1
=
=
Yield: 117.33 mg (75%). IR (KBr, cm ): n(C N) 1606; n(N N)
Cell viability assay
=
1360; n(V O) 979. UV-Visible spectrum (dichloromethane) [lmax
,
nm (e, M-1 cm-1)]: 495 (11250); 420 (14500); 387 (18500); 326
(14400); 245 (31000). Magnetic moment (m, BM): 1.70. Elemental
analysis: found C 57.89, H 4.13, N 10.16; C20H17N3VO4 (mol wt
414.28) requires C 57.93, H 4.10, N 10.13%.
Cell viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-
diphenylterazolium bromide which is commonly known as MTT
assay30 in three replicates. Twenty-four hours later, cells were
treated with (L1)V(O)(H2O) in the concentration range 5 mM
to 25 mM in 10% FBS–supplemented DMEM. The medium
was removed and MTT dye was solubilized in 200 mL/well
DMSO. Absorbance was determined at 570 nm. Concentrations of
compounds that inhibited viability by 50% (IC50) were determined
from the plot of viable cell vs. dose.
(L3)V(O)(H2O)
-1
=
=
Yield: 123.69 mg (80%). IR (KBr, cm ): n(C N) 1610; n(N N)
=
13865; n(V O) 982. UV-Visible spectrum (dichloromethane)
[lmax, nm (e, M-1 cm-1)]: 490 (14750); 420 (16700); 370 (21100); 324
(17000); 244 (36250). Magnetic moment (m, BM): 1.69. Elemental
analysis: found C 52.46, H 3.19, N 9.70; C20H17N3VO4 (mol wt
434.78) requires C 52.44, H 3.22, N 9.66%.
Cell cycle analysis and studies on cell death pattern by flow
cytometry
DFT calculations
For the determination of cell-cycle phase distribution of nuclear
DNA, A549 (1X 106 cells in each case) as harvested from untreated
or treated sets were fixed with 3% p-formaldehyde for 30 min,
trypsinised, and nuclear DNA was labeled with propidium iodide
(PI, 125 mg/mL) after RNase treatment using the Cycle TEST
PLUS DNA reagent kit. Cell-cycle phase distribution of nuclear
DNA was determined on FACS Calibur using CellQuest software,
fluorescence (FL2-A) detector equipped with 488 nm Argon laser
light source and 623 nm band pass filter (liner scale). A total of
10,000 events were acquired for analysis. Treated and untreated
cells (1 ¥ 106 in each case) were harvested, in a double labeling
system. PI and Annexin V fluos were added directly to the
culture medium. The mixture was then incubated for 30 min at
37 ◦C. Excess PI and Annexin V Fluos were then washed off; cells
were fixed and then analyzed on FACS Calibur (equipped with
488 nm Argon laser light source 515 nm band pass filter, FL1-H,
and 623 nm band pass filter, FL2-H) after fixing the cells using
CellQuest software. Electronic compensation of the instrument
was performed to exclude overlapping of the emission spectra.
A total of 10,000 events were acquired, the cells were properly
gated and a dual parameter dot plot of FL1-H (x-axis; Fluos-
fluorescence) versus FL2-H (y-axis; PI-fluorescence) was shown in
logarithmic fluorescence intensity.31
Using the X-ray coordinates of the (L1)V(O)(H2O) complex,
ground state electronic structure calculations have been carried
out using DFT24 methods with the Gaussian 03 program.25 Becke’s
hybrid function26 with the Lee–Yang–Parr (LYP) correlation
function27 was used throughout the study. We employed a triple-
z quality all-electron basis set for vanadium (TZP),28 a double-
z all-electron basis set29 for C, N, and O, and a 6-31G basis set
for H. LANL2DZ valence and effective core potential functions
were used. All energy calculations were performed using the self-
consistent field “tight” option of the Gaussian 03 program to
ensure sufficiently well converged values for the state energies.
Catalytic oxygenation of thioethers
All the catalytic reactions were performed by a similar general
procedure. The detailed procedure for the conversion of PhSMe
to PhSOMe and PhSO2Me is given below.
To a solution of catalyst, (L1)V(O)(H2O) (6.8 mg, 0.0175 mmol)
in methanol–dichloromethane (10:90) mixed solvent, PhSMe
(340 mg, 2.8 mmol) and 1 mL of 50% H2O2 were added at 0 ◦C. The
reaction mixture was stirred for 2.5 h within the temperature
range 0–4 ◦C. The solution was then dried in vacuum. The
6228 | Dalton Trans., 2009, 6220–6230
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Table 3 Crystal data for complex (L1)V(O)(H2O)
University of Kalyani is acknowledged. We are thankful to Dr.
K. K. Rajak of Jadavpur University for DFT calculations.
Formula
M
C19H15N3VO4
400.28
Monoclinic
P21/c
12.149(2)
11.6449(14)
12.0062(14)
90
102.807(2)
90
0.71073
1656.3(4)
4
150
1.605
0.632
0.0415
0.1000
0.082
4269
2840
Crystal system
Space group
References
˚
1 (a) M. Ryang, Y. Sawa, S. N. Somasundaram, S. Murai and S. Tsutsumi,
J. Organomet. Chem., 1972, 46, 375; (b) P. DeShong, D. R. Sidler,
P. J. Rybczynski, G. A. Slough and A. L. Rheinghold, J. Am. Chem.
Soc., 1988, 110, 2575; (c) R. Streubel, H. Wilkens, F. Ruthe and P. G.
Jones, Organometallics, 2006, 25, 4830; (d) J. Ruiz, V. Riera and M.
Vivanco, Organometallics, 1989, 8, 967; (e) K. Ogata, J. Seta, K.
Sugawara, N. Tsutsumi, Y. Yamamoto, K. Kuge and K. Tatsumi,
Inorg. Chim. Acta, 2006, 359, 1549; (f) I. Ojima, Transition metal
compounds in organic synthesis 1, in Comprehensive Organometallic
Chemistry, ed. R. Crabtree, Yale University, New Haven, CT, USA and
M. Mingos, Oxford University, Oxford, UK, Elsevier, 3rd edn, 2006,
vol. 10, Application II; (g) T. Hiyama, Transition metal compounds
in organic synthesis 2, in Comprehensive Organometallic Chemistry,
ed. R. Crabtree, Yale University, New Haven, CT, USA and M.
Mingos, Oxford University, Oxford, UK, Elsevier, 3rd edn, 2006, vol.
12, Application III.
2 (a) E. G. Samsel, K. Srinivasan and J. K. Kochi, J. Am. Chem. Soc.,
1985, 107, 7606; (b) K. Srinivasan, P. Michaud and J. K. Kochi, J. Am.
Chem. Soc., 1986, 108, 2309; (c) R. A. Sheldon, J. K. Kochi, Metal-
Catalyzed Oxidation of Organic Compounds, Academic, New York,
1981; (d) J.-i. Yoshida, K. Kataoka, R. Horcajada and A. Nagaki,
Chem. Rev., 2008, 108, 2265; (e) P. Barbaro and F. Liguori, Chem. Rev.,
in press; (f) K. Srinivasan and J. K. Kochi, Inorg. Chem., 1985, 24, 4671;
(g) J. M. Fraile, J. I. Garc´ıa and J. A. Mayoral, Chem. Rev., 2009, 109,
515; (h) Z. Li, C. Brouwer and C. He, Chem. Rev., 2008, 108, 3239.
3 (a) R. Irie, Y. Ito and T. Katsuki, Synlett, 1991, 265; (b) N. S. Finney,
P. J. Pospisil, S. Chang, M. Palucki, R. G. Konsler, K. B. Hansen and
E. N. Jacobsen, Angew. Chem., Int. Ed. Engl., 1997, 36, 1720; (c) H.
Sasaki, R. Irie, T. Hamada, K. Suzuki and T. Katsuki, Tetrahedron,
1994, 50, 11827; (d) K. Ito and T. Katsuki, Chem. Lett., 1994, 1857;
(e) K. Miura and T. Katsuki, Synlett, 1999, 783; (f) T. Hashihayata,
Y. Ito and T. Katsuki, Tetrahedron, 1997, 53, 9541; (g) W. Zhang, J. L.
Loebach, S. R. Wilson and E. N. Jacobsen, J. Am. Chem. Soc., 1990,
112, 2801; (h) M. S. Sigman, P. Vachal and E. N. Jacobsen, Angew.
Chem., Int. Ed., 2000, 39, 1279; (i) J. M. Keith, J. F. Larrow and E. N.
Jacobsen, Adv. Synth. Catal., 2001, 1, 5; (j) E. N. Jacobsen, M. H. Wu,
Epoxidation of Alkenes Other than Allylic Alcohols, in Comprehensive
Asymmetric Catalysis, E. N. Jacobsen, A. Pfaltz and H. Yamamoto,
Eds.Springer, Berlin, 1999, vol. 2, pp. 649–678; (k) M. Palucki, N. S.
Finney, P. J. Pospisil, M. L. Guler, T. Ishida and E. N. Jacobsen, J. Am.
Chem. Soc., 1998, 120, 948; (l) N. S. Finney, P. J. Pospisil, S. Chang,
M. Palucki, R. G. Konsler, K. B. Hansen and E. N. Jacobsen, Angew.
Chem., Int. Ed. Engl., 1997, 36, 1720; (m) E. N. Jacobsen, W. Zhang,
A. R. Muci, J. R. Ecker and L. Deng, J. Am. Chem. Soc., 1991, 113,
7063; (n) E. N. Jacobsen and W. Zhang, J. Org. Chem., 1991, 56, 2296;
(o) T. Katsuki and K. B. Sharpless, J. Am. Chem. Soc., 1980, 102, 5974;
(p) W. Zhang, J. L. Loebach, S. R. Wilson and E. N. Jacobsen, J. Am.
Chem. Soc., 1990, 112, 2801; (q) E. J. Allain, L. P. Hager, L. Deng and
E. N. Jacobsen, J. Am. Chem. Soc., 1993, 115, 4415.
a/(A)
˚
b/(A)
˚
c/(A)
a/◦
b/◦
g /◦
˚
l (A)
3
˚
Unit cell vol./A
Z
T/K
r (Mg/m-3)
m/mm-1
R1 [I>2s(I)]
wR2 [all data]
R (int)
Uniq. Data
Uniq Data with
[I>2s(I)]
GoF
1.01
Measurement of reactive oxygen species production with
DCFH-DA
To measure the production of reactive oxygen species, cells (5 ¥
105 cells/mL of culture medium) were incubated for 1 h at
37 ◦C in the dark with 10 mM/L of DCFH-DA molecular
probes (Sigma). The 2,7-Dichlorofluorescein (DCF) fluorescence
resulting from the oxidation of DCFH-DA was measured in cells
on a fluorescence microscope.
Western blotting
For western blot analysis of Bad32 and Caspase-3,33 cell lysate was
loaded into a 10% SDS-polycrylamide gel.34 After electrophoresis
the gel was transferred to a nitrocellulose membrane and blocked
with nonfat milk and was monitored by measuring the chemilu-
minescence at different intervals (12 h and 24 h).
Crystallography
Crystals of (L1)V(O)(H2O) were grown by slow diffusion of
dichloromethane–petroleum ether at 298 K respectively. Data
were collected on a Bruker SMART CCD diffractometer using
a Mo-Ka monochromator (l = 0.71043). Structure solutions
were performed using the SHELXL 97 PC version program.35
The refinement was performed using the full matrix least squares
method; with the non-hydrogen atoms modeled using anisotropic
displacement parameters. Hydrogen atoms were included at
calculated positions. The data collection parameters and relevant
crystal data are collected in Table 3.
4 P. Pattanayak, J. L. Pratihar, D. Patra, A. Burrows, M. Mohan and S.
Chattopadhyay, Eur. J. Inorg. Chem., 2007, 4263.
5 (a) M. R. Maurya, U. Kumar, I. Correia, P. Ada˜o and J. C. Pessoa,
Eur. J. Inorg. Chem., 2008, 577; (b) N. H. Khan, S. Agrawal, R. I.
Kureshy, S. H. R. Abdi, V. J. Mayani and R. V. Jasra, Eur. J. Org.
Chem., 2006, 3175.
6 C. J. Chang, J. A. Labinger and H. B. Gray, Inorg. Chem., 1997, 36,
5927.
7 (a) J. L. Pratihar, N. Maiti and S. Chattopadhyay, Inorg. Chem., 2005,
44, 6111; (b) J. Pratihar, D. Patra and S. Chattopadhyay, J. Organomet.
Chem., 2005, 690, 4816; (c) D. Patra, J. L. Pratihar, B. Shee, P.
Pattanayak and S. Chattopadhyay, Polyhedron, 2006, 25, 2637.
8 (a) G. Barone, N. Gambino, A. Ruggirello, A. Silvestri, A. Terenzi and
V. T. L iv e r i , J. Inorg. Biochem., 2009, (In Press); (b) M. A. Neelakantan,
F. Rusalraj, J. Dharmaraja, S. Johnsonraja, T. Jeyakumar and M. S.
Pillai, Spectrochimica Acta, Part A: Mol Biomol. Spectrosc., 2008, 71,
1599; (c) G. A. Woldemariam and S. S. Mandal, J. Inorg. Biochem.,
2008, 102, 740; (d) J. E. Reed, A. A. Arnal, S. Neidle and R. Vilar,
J. Am. Chem. Soc., 2006, 128, 5992; (e) X. Zhou, J. Shearer and S. E.
Rokita, J. Am. Chem. Soc., 2000, 122, 9046.
Acknowledgements
We are thankful to the DST (New Delhi) for funding and a
fellowship to PP under SERC scheme (no. SR/S1/IC-0026/2007).
We are also thankful to CSIR for fellowship to JP. The necessary
laboratory and infrastructural facility are provided by the Dept.
of Chemistry, University of Kalyani. The support of DST under
FIST program and DRS-SAP to the Department of Chemistry,
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 6220–6230 | 6229
©

View Article Online
9 K Oyaizu, K. Yamamoto, K. Yoneda and E. Tsuchida, Inorg. Chem.,
1996, 35, 6634.
21 (a) H. Engelberg-Kulka, S. Amitai, I. Kolodkin-Gal and R. Hazan,
´
PLoS Genetics, 2006, 2, 1518; (b) M. C. Carrillo, M. de L. Alvarez and
A. D. Quiroga, Ann. Hepatol., 2006, 5, 244.
10 (a) J. Ku¨hnert, T. Ru¨ffer, P. Ecorchard, B. Bra¨uer, Y. Lan, A. K. Powell
and H. Lang, Dalton Trans., 2009, 4499.
22 (a) P. Chattopadhyay, M. K. Nayak, S. P. Bhattacharya and C. Sinha,
Polyhedron, 1997, 16, 1291; (b) F. Basuli, P. Chattopadhyay and C.
Sinha, Polyhedron, 1996, 15, 2439.
23 (a) N. Maiti, S. Pal and S. Chattopadhyay, Inorg. Chem., 2001, 40, 2204;
(b) N. Maiti, B. K. Dirghangi and S. Chattopadhyay, Polyhedron, 2003,
22, 3109; (c) N. Maiti and S. Chattopadhyay, Indian. J. Chem., 2003,
42A, 2327.
11 K. I. Smith, L. L. Borer and M. M. Olmstead, Inorg. Chem., 2003, 42,
7410.
12 (a) K. Oyaizu, E. L. Dewi and E. Tsuchida, Inorg. Chem., 2003, 42,
1070; (b) J. A Bonadies, W. M. Butler, V. L. Pecoraro and C. J. Carrano,
Inorg. Chem., 1987, 26, 1218.
13 (a) P. Chaudhuri, C. N. Verani, E. Bill, E. Bothe, T. Weyhermu¨ller
and K. Wieghardt, J. Am. Chem. Soc., 2001, 123, 2213; (b) X. Sun, H.
Chun, K. Hildenbrand, E. Bothe, T. Weyhermu¨ller, F. Neese and K.
Wieghardt, Inorg. Chem., 2002, 41, 4295; (c) P. Ghosh, K. Stobie, E.
Bill, E. Bothe, T. Weyhermu¨ller, M. D. Ward, J. A. McCleverty and
K. Wieghardt, Inorg. Chem., 2007, 46, 522; (d) R. Kapre, K. Ray, I.
Sylvestre, T. Weyhermu¨ller, S. D. George, F. Neese and K. Wieghardt,
Inorg. Chem., 2006, 45, 3499.
14 (a) D. J. Robinson, L. Davies, N. McGuire, D. F. Lee, P. McMorn, D. J.
Willock, G. W. Watson, P. C. B. Page, D. Bethell and G. J. Hutchings,
Phys. Chem. Chem. Phys., 2000, 2, 1523; (b) J. Brinksma, R. L. Crois,
B. L. Feringa, M. I. Donnolib and C. Rosinib, Tetrahedron Lett.,
2001, 42, 4049; (c) S. Patai and Z. Rappoport, Synthesis of Sulfones,
Sulfoxides, and Cyclic Sulfides, John Wiley, Chichester, 1994.; (d) M.
Madesclaire, Tetrahedron, 1986, 42, 5459; (e) A. Padwa, W. H. Bullock
and A. D. Dyszlewski, J. Org. Chem., 1990, 55, 955.
24 R. G. Parr and W. Yang, Density Functional Theory of Atoms and
Molecules, Oxford University Press, Oxford, 1989.
25 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb,
J. R. Cheeseman Jr. J. A. Montgomery, T. Vreven, K. N. Kudin, J. C.
Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci,
M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox,
H. P. Hratchian, J. B. Cross, R. ammi, C. Pomelli, J. W. Ochterski, P. Y.
Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G.
Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K.
Malick A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q.
Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A.
Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith,
A. Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W.
Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez and J. A. Pople,
Gaussian 03W, revision C.02 Gaussian, Inc., Wallingford, CT, 2004.
26 A. D. Becke, J. Chem. Phys., 1993, 98, 5648.
27 C. Lee, W. Yang and R. G. Parr, Phys. Rev. B., 1998, 37, 785.
28 A. Schaefer, C. Huber and R. Ahlrichs, J. Chem. Phys., 1994, 100, 5829.
29 A. Schaefer, H. Horn and R. Ahlrichs, J. Chem. Phys., 1992, 97, 2571.
30 (a) G. Jie, Z. Lin, L. Zhang, H. Lv, P. He and B. Zhao, J. Agric. Food
Chem., 2006, 54, 8058; (b) L. O. Cinteza, T. Y. Ohulchanskyy, Y. Sahoo,
E. J. Bergey, R. K. Pandey and P. N. Prasad, Mol. Pharm., 2006, 3, 415;
(c) J. Gao, G. Liang, B. Zhang, Y. Kuang, X. Zhang and B. Xu, J. Am.
Chem. Soc., 2007, 129, 1428.
31 A. Bratasz, N. M. Wei, N. L. Parinandi, J. L. Zweier, R. Sridhar, L. J.
Ignarro and P. Kuppusamy, Pharmacology, 2006, 103, 3914.
32 (a) B. Diesel, S. Kulhanek-Heinze, M. Ho¨ltje, B. Brandt, H.-D. Ho¨ltje,
A. M. Vollmar and A. K. Kiemer, Biochemistry, 2007, 46, 2146;
(b) D. T. Chao and S. J. Korsmeyer, BCL-2 family: regulator of cell
death, Annu. Rev. Immunol., 1998, 16, 395; (c) A. M. Petros, E. T.
Olijinczak and S. W. Fesik, Structural biology of the bcl-2 family
of proteins, Biochim. Biophys. Acta, 2004, 644, 83 and references
therein.
33 (a) A. Aulabaugh, B. Kapoor, X. Huang, P. Dollings, W.-T. Hum, A.
Banker, A. Wood and G. Ellestad, Biochemistry, 2007, 46, 9462; (b) B.
Feeney, C. Pop, P. Swartz, C. Mattos and A. C. Clark, Biochemistry,
2006, 45, 13249 and references therein.
15 (a) M. Matteucci, G. Bhalay and Mark Bradley, Org. Lett., 2003, 5,
235; (b) M. Madesclaire, Tetrahedron, 1986, 42, 5459; (c) D. J. Procter,
J. Chem. Soc., Perkin Trans., 2000, 1, 835.
16 J. Sun, C. Zhu, Z. Dai, M. Yang, Y. Pan and H. Hu, J. Org. Chem.,
2004, 69, 8500.
17 (a) J. Ye, M. Ding, S. S. Leonard, V. A. Robinson, L. Millecchia, X.
Zhang, V. Castranova, V. Vallyathan and X. Shi, Mol. Cell. Biochem.,
1999, 202, 9; (b) X. Yin, A. J. Davidson and S. S. Tsang, Mol. Cell.
Biochem., 1992, 115, 85; (c) Z. Zhang, H. Chuanshu, J. Li, S. S. Leonard,
R. Lanciotti, L. Butterworth and X. Shi, Arch. Biochem. Biophys., 2001,
392, 311; (d) C. Huang, M. Ding, J. Li, S. S. Leonard, Y. Rojanasakul, V.
Castranova, V. Vallyathan, G. Ju and X. Shi, J. Biol. Chem., 2001, 276,
22397; (e) J. Rivadeneira, D. A. Barrio, G. Arrambide, D. Gambino, L.
Bruzzoned and S. B. Etcheverry, J. Inorg. Biochem., 2009, 103, 633.
18 J. H. Boo, H. Song, J. E. Kim, D. E. Kang and I. Mook-Jung, PLoS
One, 2009, 4, 1.
19 (a) L. Ding, J. Stilwell, T. Zhang, O. Elboudwarej, H. Jiang, J. P. Selegue,
P. A. Cooke, J. W. Gray and F. F. Chen, Nano Lett., 2005, 5, 2448;
(b) S. L. Hockley, V. M. Arlt, D. Brewer, R. t. Poele, P. Workman, I.
Giddings and D. H. Phillips, Chem. Res. Toxicol., 2007, 20, 1797; (c) T.
Mandimika, H. Baykus, Y. Vissers, P. Jeurink, J. Poortman, C. Garza,
H. Kuiper and A. Peijnenburg, J. Agric. Food Chem., 2007, 55, 10055;
(d) B. Pei, S. Wang, X. Guo, J. Wang, G. Yang, H. Hang and L. Wu,
Chem. Res. Toxicol., 2008, 21, 1530; (e) B. -C. Jang, J.-G. Park, D. -K.
Song, W. -K. Baek, S. K. Yoo, K. -H. Jung, G.-Y. Park, T. -Y. Lee and
S. -I. Suh, Toxicol. in Vitro, 2009, 23, 281.
34 P. Andersen and I. Heron, J. Immunol. Methods, 1993, 161, 29.
35 (a) G. M. Sheldrick, SHELXS-97, University of Go¨ttingen, Go¨ttingen,
Germany, 1990; (b) G. M. Sheldrick, SHELXL-97, Program for the
Refinement of Crystals Structures from Diffraction Data, University of
Go¨ttingen, Go¨ttingen, Germany, 1997.
20 M. Y. Kim, S. Lee, K. Y. Yi, S. E. Yoo, D. H. Lee, H. Lim, H. S. Kim,
S. H. Lee, E. J. Baik, C. H. Moon and Y. S. Jung, Arch. Pharm. Res,
2005, 28, 1358.
6230 | Dalton Trans., 2009, 6220–6230
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