Site-specific: Ortho metallation via C-H bond activation and syntheses of ruthenium(III) organometallics: Studies on nitric oxide (NO) reactivity and photorelease of coordinated NO

Article abstract of DOI:10.1039/c6ra17223g

A new family of σ-aryl ruthenium(iii) complexes [Ru(L^1-4)(PPh₃)₂Cl] (1-4) (where L¹H₂ = N-(quinolin-8-yl)benzamide for 1, L²H₂ = 4-chloro-N-(quinolin-8-yl)benzamide for 2, L³H₂ = 4-nitro-N-(quinolin-8-yl)benzamide for 3, L⁴H₂ = 3-nitro-N-(quinolin-8-yl)benzamide for 4 and H = dissociable protons) derived from bidentate ligands having amide bonds was synthesized through C-H bond activation. These organometallic ruthenium(iii) complexes were treated with nitric oxide (NO) to afford the nitrosyl complexes [Ru(NO₂L^1-4)(PPh₃)₂(NO)](ClO₄) (1a-4a) (where NO₂L¹H₂ = N-(5-nitroquinolin-8-yl)benzamide for 1a, NO₂L²H₂ = 4-chloro-N-(5-nitroquinolin-8-yl)benzamide for 2a, NO₂L³H₂ = 4-nitro-N-(5-nitroquinolin-8-yl)benzamide for 3a, NO₂L⁴H₂ = 3-nitro-N-(5-nitroquinolin-8-yl)benzamide for 4a and H = dissociable protons). All ruthenium complexes were characterized by various spectroscopic techniques. An X-ray crystallographic study afforded the molecular structure of complex 4a and the site-specific orthometallation was scrutinized. The coordinated NO molecule was found to be photolabile under visible and UV light.

Full text of DOI:10.1039/c6ra17223g

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Site-specific orthometallation via C–H bond activation and
syntheses of ruthenium (III) organometallics: Studies on nitric
oxide (NO) reactivity and photorelease of coordinated NO
Received 00th January 20xx,
Accepted 00th January 20xx
Rajan Kumar, Sushil Kumar, Manju Bala, Anand Ratnam, U. P. Singh, and Kaushik Ghosh*
DOI: 10.1039/x0xx00000x
A new family of σ-aryl ruthenium(III) complexes [Ru(L1–4)(PPh3)2Cl] (1–4) (where L1H2 = N-(quinolin-8-yl)benzamide for 1,
L2H2 = 4-chloro-N-(quinolin-8-yl)benzamide for 2, L3H2 = 4-nitro-N-(quinolin-8-yl)benzamide for 3, L4H2 = 3-nitro-N-
(quinolin-8-yl)benzamide for 4 and H = dissociable protons) derived from the bidentate ligands having amide bond were
synthesized through C–H bond activation. These organometallic ruthenium(III) complexes were treated with nitric oxide
(NO) to afford the nitrosyl complexes [Ru(NO2L1-4)(PPh3)2(NO)](ClO4) (1a–4a) (where NO2L1H2 = N-(5-nitroquinolin-8-
yl)benzamide for 1a, NO2L2H2 = 4-chloro-N-(5-nitroquinolin-8-yl)benzamide for 2a, NO2L3H2 = 4-nitro-N-(5-nitroquinolin-8-
yl)benzamide for 3a, NO2L4H2 = 3-nitro-N-(5-nitroquinolin-8-yl)benzamide for 4a and H = dissociable protons). All
ruthenium complexes were characterized by various spectroscopic studies. X-ray crystallographic study afforded the
molecular structure of the complex 4a and the site-specific orthometallation was scrutinized. Coordinated NO molecule
was found to be photolabile under visible as well as UV light.
www.rsc.org/
complexes which were taken into account for the design and
synthesis of new ligands achieving the synthesis of Ru(III)
organometallics and corresponding ruthenium nitrosyls. First,
Introduction
A plentiful literatures are available for ruthenium (II) and
ruthenium (III) organometallic complexes because of their
immense importance for organometallic and organic
syntheses.[1–5] There has been considerable current interest in
the design and synthesis of nitric oxide releasing molecules
(NORM) for target specific and on demand delivery of nitric
oxide(NO).[6–17] A marked feature of ruthenium chemistry is
the formation of nitric oxide complex[18] however,
organometallic complexes used for nitric oxide (NO) donation
are scarce in the literature.[19–22] Investigation of chemistry of
ruthenium nitrosyls clearly indicated the stability of complexes
having {RuNO}6 (according to Enemark Feltham notation)6
moiety. Among several routes, synthetically this could be
achieved by a combination of Ru(III) centre and NO. Hence,
recently we have communicated Ru(III) organometallics and
studied their reactivity with NO. Our previous reports clearly
indicated that a bidentate ligand having Nimine and Ophenol
donors (LH2 and L'H2) (shown in Scheme 1 and 2) afforded C–H
bond activation and orthometallation.[20–23] There are two
important aspects of our previous results in terms of the
synthesis of NORM derived from organometallic ruthenium
synthesis of Ru(III) organometallics via C–H bond activation
using a Ru(II) precursor complex and consequently conversion
of bidentate ligands to tridentate ligands, hence donor atoms
present in bidentate ligands are extremely important. Second,
reactivity of nitric oxide with ruthenium(III) organometallics
and the role of the trans directing effect of carbanion for the
coordination and photolability of NO. These results prompted
us to design and synthesize new bidentate ligands which
would enhance the oxidation of ruthenium centre (II to III) and
concomitant Ru–C bond formation via C–H bond activation
and the synthesis of new Ru(III) organometallics.
P
X
Y
Refs.
C
Nazo
Nimine
Ophenol
Ophenol
24–27
Cl
RuIII
21–23, 28, 29
X
Y
Nimine
Namide
Oamide
Npyridine
30–33
This work
P
(P = PPh3)
Scheme 1. Donors (X and Y) in bidentate ligands.
R. Kumar, S. Kumar, M. Bala, Prof. U.P. Singh, Dr. K. Ghosh
Department of Chemistry, Indian Institute of Technology, Roorkee, Roorkee-
247667, Uttarakhand, INDIA
Hence we designed bidentate ligands with Npyridine and
Namide donors (L1–4H2) (shown in Scheme 2) and ligands were
reacted with Ru(II) precursor complex. Deprotonated
carboxamido nitrogen is known to stabilize the higher
oxidation state of metal centre.[34] Moreover, amide nitrogen
Fax: +91-1332-275547, E-mail: ghoshfcy@iitr.ernet.in
† Footnotes relaꢀng to the ꢀtle and/or authors should appear here.
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
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exhibits trans effect and is known for coordination and
photolability of nitric oxide.[7,35]
The reactivity study of NO with ruthenium(III) complexes
) was performed to afford cyclometalated ruthenium
nitrosyl complexes [Ru(NO2L1)(PPh3)2(NO)](ClO4) (1a, where
NO2L1H2
N-(5-nitroquinolin-8-yl)benzamide and
(1–4
R7
R1
=
H
=
R4
dissociable protons), [Ru(NO2L2)(PPh3)2(NO)](ClO4) (2a, where
NO2L2H2 = 4-chloro-N-(5-nitroquinolin-8-yl) benzamide and H =
dissociable protons), [Ru(NO2L3)(PPh3)2(NO)] (ClO4) (3a, where
NO2L3H2 = 4-nitro-N-(5-nitroquinolin-8-yl)benzamide and H =
R8
R2
R5
HC
HN
N
O
NH
N
C
dissociable protons) and [Ru(NO2L4)(PPh3)2(NO)](ClO4) (4a
,
OH
N
OH
where NO2L4H2 = 3-nitro-N-(5-nitroquinolin-8-yl)benzamide
and H = dissociable protons) (Scheme 3). The molecular
structure of 4a was determined by X-ray crystallography. The
redox properties of the metal centre in all the complexes were
investigated. The photolability of coordinated NO was
performed by UV-Vis spectral studies and liberated NO was
trapped by reduced myoglobin. Photoreleased NO was
estimated by a Griess reagent using visible as well as UV light.
The role of –NO2 group (electron-withdrawing group) on the
phenyl ring, chelated to the metal centre via σ-aryl bond, will
be discussed in this paper of light-induced delivery of NO.
R6
R3
R7
H
Cl
NO2
H
R8 Ligand
R4 R5
R6
H
Ligand
R1 R2
R3 Ligand
H
CH3 LH2
H
H
H
H
H
H
H
H
H
L1H2
L2H2
L3H2
H
NO2
CH3 L'H2
H
Cl
CH3
NO2
H
H
H
NO2 NO2
NO2 NO2 CH3
NO2 L4H2
Scheme 2. Schematic drawing of ligands LH2, L'H2 and L1–4H2
.
Herein, we designed bidentate ligands having amide bond
and synthesized ligands LnH2 (where n= 1–4). A new family of
σ-aryl ruthenium(III) complexes [Ru(L1)(PPh3)2Cl]
(
1
),
) and [Ru(L4)(PPh3)2Cl]
) (Scheme 3) ( where L1H2 = N-(quinolin-8-yl)benzamide, L2H2
= 4-chloro-N-(quinolin-8- yl)benzamide, L3H2 = 4-nitro-N-
(quinolin-8-yl)benzamide, L4H2
3-nitro-N-(quinolin-8-
[Ru(L2)(PPh3)2Cl] ( ), [Ru(L3)(PPh3)2Cl] (
2 3
Experimental Section
(
4
Materials. All the chemicals used were of reagent grade.
RuCl3.3H2O was puchased from Loba Chemie Pvt. Ltd.,
Mumbai, India. Analytical grade reagents sodium nitrite,
benzoic acid, 4-chlorobenzoic acid, 4-nitrobenzoic acid, 3-
nitrobenzoic acid, naphthylethylenedi- amine dihydrochloride
(NED), sulfanilamide, sodium perchlorate monohydrate,
sodium nitrite (Himedia Laboratories Pvt. Ltd., Mumbai, India),
quinoline-8-amine (Sigma Aldrich, Steinheim, Germany) were
used as obtained. Triphenylphosphine (SRL,Mumbai, India),
disodium hydrogen phosphate anhydrous (RFCL Ltd. New
Delhi, India) and sodium dihydrogen phosphate (Chemport
India Pvt. Ltd. Mumbai, India) were used as obtained. Double
distilled water and distilled solvents were used in during the
experiments. Equine skeletal muscle myoglobin was obtained
from Sigma Aldrich, Steinheim, Germany.
=
yl)benzamide and H = dissociable protons) were synthesized
from these bidentate ligands containing carboxamido group
(Scheme 2). Cyclometalated complexes were characterized by
various spectroscopic techniques and the site-specific
cyclometalation during C–H bond activation will be described
in this report.
R1
+
R1
R2
R2
Ru(PPh3)2(NO)
N
III
Ru (PPh3)2Cl
O
N
O
N
N
Physical measurements. Infrared spectra were obtained as KBr
pellets with Thermo Nicolet Nexus FT–IR spectrometer, using
16 scans and were reported in cm─1. Electronic absorption
spectra of all the complexes were recorded in
dichloromethane solvent with an Evolution 600, Thermo
NO2
P
+
P
C
NO
C
Cl
Ru
P
Ru
P
Namide
1
Scientific (Shimadzu) UV–vis spectrophotometer. H and 31P
Npy
Namide
Npy
NMR spectra were recorded on Bruker AVANCE, 500.13 MHz
spectrometer in the deuterated solvents. Cyclic voltammetric
studies were performed on a CH–600C electroanalyzer in
dichloromethane with 0.1 M tetrabutylammonium perchlorate
(TBAP) as supporting electrolyte. The working electrode,
reference electrode and auxiliary electrode were glassy carbon
electrode, Ag/AgCl electrode and Pt wire respectively. The
concentration of the compounds was in the order of 10–3 M.
The ferrocene/ferrocenium couple occurred at E1/2 = + 0.54
(70) V vs. Ag/AgCl (scan rate 0.1 V/s) in dichloromethane under
the same experimental conditions.
(P = PPh3)
(P=PPh3)
Complex R1
R2
Ligand
Complex R1
R2
Ligand
1a
2a
3a
4a
H
Cl
NO2
H
H
H
H
NO2L1H2
NO2L2H2
NO2L3H2
1
2
3
4
H
Cl
H
H
H
L1H2
L2H2
L3H2
NO2
H
NO2 NO2L4H2
NO2 L4H2
Scheme 3. Schematic drawings of cyclometalated ruthenium
complexes.
2 | J. Name., 2012, 00, 1-3
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Syntheses of ligands:
The precursor complex [Ru(PPh3)3Cl2] was prepared by using
the reported procedure.[20–22,36]
Synthesis of N-(quinolin-8-yl)benzamide (L1H2): The benzoic Caution: perchlorate salts of metal complexes with organic
acid (0.61 g, 5.0 mmol) was taken in 15-20 mL ligands are potentially explosive. Only a small amount of
dimethylformaide solution and then cooled on an ice bath. To material should be prepared and handled with caution.
this solution, 1.48 g (11.0 mmol) of 1-hydroxybenzotriazole
(HOBT)
as
well
as
1.13
g
(5.5 mmol)
of Synthesis of [Ru(L1)(PPh3)2(Cl)] (1): To a 30 mL methanolic
dicyclohexylcarbodiimide (DCC) were added directly and solution of L1H2 (0.034 g, 0.12 mmol) was added directly
mixture was stirred for half an hour at 0°C. Now a batch of ruthenium precursor complex [Ru(PPh3)3Cl2] (0.0958g, 0.10
quinoline-8-amine 0.72 g (5.0 mmol) was added to the mmol) and mixture was refluxed at 85°C for 10–12 h on an oil
reaction mixture with stirring for next 2 hours on the same ice bath to afforded a light brown crystalline solid at room
bath. After, the ice bath was removed and the stirring was temperature and was washed with cold methanol and diethyl
continued overnight at room temperature. By removing the ether. Yield: 48%. Anal. Calcd. for C52H40ClN2OP2Ru (907.13): C,
white precipitate of N,N'-dicyclohexylurea through filtration, 68.83; H, 4.44; N, 3.09. Found: C, 68.48; H, 4.38; N, 3.12. IR
the solvent was concentrated to 10 mL. Within 3-4 days, a light (KBr disk, cm─1): 1558 (νCONH), 746, 692, 520 (νPPh3) cm−1. UV-Vis
yellowish crystalline solid of ligand L1H2 was settled down on (CH2Cl2;
the bottom of beaker which was filtered and washed with (1942).
methanol and diethyl ether. Yield: 52%. Anal. Calcd. For
λmax/nm (ε
, M─1cm─1)): 270 (17280), 335 (4041), 445
C16H12N2O (248.29): C, 77.40; H, 4.87; N, 11.28. Found: C, Synthesis of [Ru(L2)(PPh3)2(Cl)] (2): Complex
2 was synthesized
77.48; H, 4.38; N, 11.41. IR (KBr disk, cm–1): 1674 (νCO, –CONH), through the reaction of [Ru(PPh3)3Cl2] with the ligand L2H2 by
3350 (νN–H). UV–Vis (CH2Cl2; λmax, nm (ε, M–1 cm–1)): 242 following the same procedure as for
1. Yield: 58%. Anal. Calcd.
1
(24166), 270 (6975), 325 (7333). H NMR (CDCl3, 500 MHz): δ for C52H39Cl2N2OP2Ru (941.10): C, 66.32; H, 4.17; N, 2.97.
10.76 (s, 1H), 8.95 (t, 1H), 8.86 (s, 1H), 8.19 (d, 1H), 8.09 (t, Found: C, 66.24; H, 4.09; N, 2.88. IR (KBr disk, cm─1): 1635
2H), 7.61-7.56 (m, 5H), 7.5 (t, 1H) ppm.
(νCONH), 746, 694, 522 (νPPh3) cm−1. UV-Vis (CH2Cl2;
λmax/nm (ε,
M─1cm─1)): 262 (17596), 365 (2804).
Synthesis of 4-chloro-N-(quinolin-8-yl)benzamide (L2H2):
Ligand L2H2 was synthesized from the reaction of p-chloro Synthesis of [Ru(L3)(PPh3)2(Cl)] (3): Complex
3
was prepared
benzoic acid with quinoline-8-amine by following the same with the help of ligand L3H2 through the same procedure as for
procedure as for ligand L1H2. Yield: 61%. Anal. Calcd. For
. Yield: 68%. Anal. Calcd. for C52H39ClN3O3P2Ru (952.12): C,
1
C16H11ClN2O (282.72): C, 67.97; H, 3.92; N, 9.91. Found: C, 65.58; H, 4.13; N, 4.41. Found: C, 65.43; H, 4.08; N, 4.50. IR
66.90; H, 3.64; N, 9.98. IR (KBr disk, cm–1): 1665 (νCO, –CONH), (KBr disk, cm─1): 1632 (νCONH), 744, 694, 515 (νPPh3) cm−1. UV-Vis
3350 (νN–H). UV–Vis (CH2Cl2; λmax, nm (ε, M–1 cm–1)): 242 (CH2Cl2;
λ
max/nm (
ε
, M─1cm─1)): 274 (28626), 460 (5042).
1
(23030), 275 (4970), 324 (6060). H NMR (CDCl3, 500 MHz): δ
10.68 (s, 1H), 8.89-8.82 (m, 2H), 8.15 (q, 1H), 8.01-7.98 (m, Synthesis of [Ru(L4)(PPh3)2(Cl)]
(4
):
Complex
using ligand L4H2 by using the same procedure as for
62%. Anal. Calcd. For C52H39ClN3O3P2Ru (952.12): C, 65.58; H,
4
was obtained by
2H), 7.58-7.44 (m, 5H) ppm.
1
. Yield:
Synthesis of 4-nitro-N-(quinolin-8-yl)benzamide (L3H2): Ligand 4.13; N, 4.41. Found: C, 65.38; H, 4.10; N, 4.52. IR (KBr disk,
L3H2 was prepared from the reaction of p-nitro benzoic acid cm─1): 1625 (νCONH), 742, 692, 514 (νPPh3) cm−1. UV-Vis (CH2Cl2;
with quinoline-8-amine by using the same procedure as for
ligand L1H2. Yield: 68%. Anal. Calcd. For C16H11N3O3 (293.28): C,
λmax/nm (ε
, M─1cm─1)): 274 (25615), 365 (10570), 460 (4966).
65.53; H, 3.78; N, 14.33. Found: C, 65.38; H, 3.46; N, 14.43. IR Synthesis of [Ru(NO2L1)(PPh3)2(NO)](ClO4)
(
1a): A batch of
(KBr disk, cm–1): 1675 (νCO, –CONH), 3350 (νN–H). UV–Vis (0.090 g, 0.1 mmol) of complex
1 was taken in 30 mL of
(CH2Cl2; λmax, nm (ε, M–1 cm–1)): 242 (25017), 335 (6084). H dichloromethane to obtain a yellow colored solution in round
1
NMR (CDCl3, 500 MHz): δ 10.81 (s, 1H), 8.91-8.86 (m, 2H), bottom flask of 100 mL. Now 25 mL acidified distilled water
8.39-8.36 (m, 2H), 8.24-8.21 (m, 3H), 7.63-7.50 (m, 3H) ppm.
was layered over this solution. Sodium nitrite (0.3 g, 4.3 mmol)
was added to the bilayer solution and the mixture was stirred
Synthesis of 3-nitro-N-(quinolin-8-yl)benzamide (L4H2): Ligand at room temperature for 2 hrs to get reddish yellow colored
L4H2 was obtained from the reaction of m-nitro benzoic acid solution of complex 1a. The dichloromethane layer was
and quinoline-8-amine through the same procedure as for separated out and NaClO4 (in excess) with 10 mL of methanol
ligand L1H2. Yield: 71%. Anal. Calcd. For C16H11N3O3 (293.28): C, was added to this solution. Stirring of this solution was
65.53; H, 3.78; N, 14.33. Found: C, 65.38; H, 3.43; N, 14.52. IR continued for another 2 hour. The solvent mixture was
(KBr disk, cm–1): 1670 (νCO, –CONH), 3307 (νN–H). UV–Vis evaporated to get reddish yellow solid. To remove excess of
(CH2Cl2; λmax, nm (ε, M–1 cm–1)): 242 (23734), 262 (9769), 325 NaClO4, this solid was further dissolved in 10 mL of
1
(8146). H NMR (CDCl3, 500 MHz): δ 10.79 (s, 1H), 8.89-8.85 dichloromethane and was filtered out. Now 10 mL of hexane
(m, 3H), 8.42-8.37 (m, 2H), 8.19 (q, 1H), 7.73 (t, 1H), 7.61-7.48 was added to the filtrate to obtain a reddish yellow precipitate
(m, 3H) ppm.
of complex 1a. Yield: 48 %. Anal. Calcd. For C52H39ClN4O8P2Ru
Syntheses of cyclometalated ruthenium complexes
(1046.10): C, 59.69; H, 3.76; N, 5.35. Found: C, 59.39; H, 3.84;
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N, 5.28. IR (KBr disk, cm─1): 1880 (νNO), 1635 (νCONH), 1092, 620 measured by observing the increase in the absorbance at ~
(νClO4), 730, 692, 530 (νPPh3) cm─1. UV-Vis (CH2Cl2; 538 nm due to the formation of azo dye.[22,37]
max/nm (
λ
ε,
M─1cm─1)): 326 (21370). 1H NMR (CDCl3, 500MHz): δ 9.42 (d, Quantum yield measurements: Standard ferrioxalate
1H), 9.09 (d, 1H), 8.20 (s, 1H), 7.71 (s, 2H), 7.69–7.53 (m, 17H), actinometer (0.006 M solution of potassium ferrioxalate in 0.1
7.45–7.39 (m, 9H), 7.33–7.31 (m, 5H), 7.17–6.95 (m, 2H), 6.52 N H2SO4) was used to determine the intensity of the UV light
(s, 1H), 6.13 (d, 1H) ppm. 31P NMR (CDCl3, 500 MHz): δ 29.71 (λirr = 365 nm). Quantum yields (ΦNO) of NO photorelease for
ppm.
nitrosyl complexes 1a
in its electronic absorption band with λmax near 326 nm, 324
Synthesis of [Ru(NO2L2)(PPh3)2(NO)](ClO4) (2a): Complex 2a nm, 434 nmand 424 nm, respectively when irradiated with the
was obtained from complex by following the same procedure light of a UV lamp (λirr = 365 nm) and were calculated by
–4a were determined from the decrease
2
as for 1a. Yield: 51%. Anal. Calcd. For C52H38Cl2N4O8P2Ru following the procedure reported earlier.[22] The cuvette was
(1080.06): C, 57.79; H, 3.54; N, 5.18. Found: C, 57.56; H, 3.62; kept 3 cm away from the UV source to measure the quantum
N, 5.09. IR (KBr disk, cm─1): 1870 (νNO), 1585 (νCONH), 1092, 612 yields.
(νClO4), 746, 692, 522 (νPPh3) cm─1. UV-Vis (CH2Cl2;
λ
max/nm (
ε
,
1
M─1cm─1)): 324 (29668). H NMR (CDCl3, 500MHz): δ 9.62 (d, X–ray crystallography: Crystal of complex 4a.CH2Cl2 (reddish
1H), 9.29 (d, 1H), 8.39 (d, 1H), 7.86 (s, 2H), 7.65–7.51 (m, 14H), yellow) was obtained via layering of hexane over a solution of
7.45–7.34 (m, 11H), 7.24–7.08 (m, 8H), 6.29 (d, 1H) ppm. 31P dichloromethane
NMR (CDCl3, 500 MHz): δ 29.73 ppm. diffraction study. The X
complex 4a.CH2Cl2 was performed with Bruker Kappa Apex
Synthesis of [Ru(NO2L3)(PPh3)2(NO)](ClO4) (3a): Complex 3a CCD diffractometer by using graphite monochromated Mo
Kα
was prepared from the complex through the same procedure radiation (λ = 0.71073 Å) at 296 (2). Crystal structur was solved
/
methanol mixture which is suitable for
ray data collection and processing for
II
–
–
–
3
as for 1a. Yield: 56%. Anal. Calcd. For C52H38ClN5O10P2Ru by direct method. Structure solutions, refinement and data
(1091.08): C, 57.23; H, 3.51; N, 6.42. Found: C, 57.14; H, 3.56; output were carried out with the SHELXTL program.[38,39] All
N, 6.36. IR (KBr disk, cm─1): 1830 (νNO), 1645 (νCONH), 1092, 612 non–hydrogen atoms were refined anisotropically. Hydrogen
(νClO4), 746, 694, 520 (νPPh3) cm─1. UV-Vis (CH2Cl2;
λ
max/nm (
ε,
atoms were placed in geometrically calculated positions and
M─1cm─1)): 282 (27107), 434 (20867). 1H NMR (CDCl3, 500MHz; refined using a riding model. Image was created with the
J/Hz): δ 10.21 (d, 4.50, 1H), 8.89 (d, 9.00, 1H), 8.50 (d, 9.00, DIAMOND program.[40]
1H), 8.13 (d, 9.00, 1H), 7.90 (d, 6.50, 5H), 7.65 (d, 8.00, 1H),
7.43–7.31 (m, 15H), and 7.10
(CDCl3, 500 MHz): δ 22.63 ppm.
−
7.06 (m, 13H) ppm. 31P NMR
Results and Discussion
Syntheses
Synthesis of [Ru(NO2L4)(PPh3)2(NO)](ClO4) (4a): Complex 4a
was synthesized from complex by using the same procedure
All the ligands L1–4H2 were obtained in high yield by
condensation reaction of different aromatic acids with
quinoline-8-amine in dimethylformamide in the presence of 1-
hydroxybenzotriazole (HOBT) and dicyclohexylcarbodiimide
(DCC).[41] The solid precursor [Ru(PPh3)3Cl2] was added to a hot
methanol solution (30 mL) of the corresponding ligand L1–4H2
then we obtained the ruthenium(III) complexes [Ru(L1–
4
as for 1a. Yield: 62%. Anal. Calcd. For C52H38ClN5O10P2Ru
(1091.08): C, 57.23; H, 3.51; N, 6.42. Found: C, 57.18; H, 3.60;
N, 6.30. IR (KBr disk, cm─1): 1845 (νNO), 1655 (νCONH), 1090, 614
(νClO4), 742, 692, 514 (νPPh3) cm─1. UV-Vis (CH2Cl2;
λmax/nm (ε,
M─1cm─1)): 288 (30266), 424 (14372). 1H NMR (CDCl3, 500MHz;
J/Hz): δ 10.15 (d, 4.50, 1H), 8.89 (d, 9.00, 1H), 8.54 (d, 9.00,
4)(PPh3)2Cl] (
were yellowish brown in color but complexes
1−
4
) (shown in Scheme 3). The complexes
1
and
2
4
1H), 8.19 (d, 9.00, 1H), 7.97 7.76 (m, 3H), 7.53 (s, 2H), 7.37–
7.07 (m, 12H) ppm. 31P NMR (CDCl3,
−
3
and
7.21 (m, 18H), and 7.11
−
werereddish brown and green in color, respectively.
Complexes were highly soluble in dichloromethane,
dimethylformamide and dimethylsulphoxide but less soluble in
500 MHz): δ 22.35 ppm.
1−4
Transfer of NO to myoglobin: 50 mM phosphate buffer
solution of 6.8 pH was prepared by adding 0.4192 g of
NaH2PO4.2H2O and 0.3283 g of anhydrous Na2HPO4 to 50 mL
of MilliQ water and making the volume to 100 mL in a
volumetric flask. 5 mg equine skeletal muscle myoglobin was
dissolved in 5 mL of the above prepared buffer solution.
water. The complexes [Ru(NO2L1 4)(PPh3)2(NO)](ClO4) (1a
were derived from the complexes , respectively (shown in
Scheme 3). The dichloromethane solutions of all the
complexes were treated with acidified nitrite (NaNO2)
–
4a)
−
1–4
1–4
solution with continuous stirring for 2 h and formation of an
reddish-yellow color was observed. Then a methanolic solution
of NaClO4 was added for the counter anion. All the nitrosyl
complexes were found to be reddish yellow in color and were
highly soluble in organic solvents like dichloromethane,
acetonitrile, dimethylformamide. A dichloromethane/hexane
(50:50) mixture was used for recrystallization of nitrosyl
Griess reagent assay: The photodissociation of nitric oxide
from nitrosyl complexes 1a–4a was also confirmed by
estimating its amount using the Griess reagent (GR). The
reagent was freshly prepared by mixing equal volumes of 1%
sulphanilamide in 5% orthophosphoric acid and 0.1%
naphthylethylenediamine dihydrochloride (NED) in distilled
complexes 1a−4a. The synthetic procedures described above
have been summarized in Scheme 4.
−
water. The estimation of NO or nitrite (NO2 ) ion was
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Spectroscopic studies
All the nitrosyl complexes 1a
−
4a were found redish yellow
in color and their electronic spectra were displayed in Figure
The infrared (IR) spectra of all the ligands and ruthenium
complexes have been recorded by using KBr pellets. In the IR
S18. The electronic spectrum of 1a–4a gave rise to charge-
transfer band near 326 nm, 324 nm, 434 nm, and 424 nm,
respectively which was recognized to a metal to ligand charge
transfer (MLCT) transition dπ(Ru)→π*(NO) type and this
transition has been responsible for the photolability of the
{RuNO}6 moiety.[6,7,46] In the complexes 3a and 4a, we also
found a charge transfer band near 282 nm and 288 nm,
respectively (Table S2).
spectrum of ruthenium complexes
stretching frequency ( CONH) (due to the presence of carbonyl
group of carboxamide moiety) was observed near 1558 cm−1,
1635 cm−1, 1632 cm−1 and 1625 cm−1 for complexes
2, 3 and
respectively,[42–44] which was observed red shifted as
1−4, the (−CONH−)
ν
1,
4
compare to the
= 1674 cm–1; for L2H2,
ν
CONH values of the free ligands (for L1H2, νCONH
ν
CONH = 1665 cm–1; for L3H2,
νCONH = 1675
All the ruthenium nitrosyl complexes 1a−4a were found to
1
be diamagnetic which were confirmed by H and 31P NMR
spectral studies. The 1H and 31P NMR spectra of nitrosyl
complexes 3a and 4a were displayed in Figures S19–S26. In all
the ligands, we observed a peak near 10.75 ppm which was
due to the presence of carboxamido (–CONH–) proton. But in
the nitrosyl complexes, no peak was obtained around 10.75
ppm which indicated the absence of –NH– proton of
carboxamido (–CONH–) group in these nitrosyl complexes and
we obtained other expected multiple signals near 10.20–7.00
ppm range (Table S3).[41] We obtained a single peak near 30.0
MeOH
[RuIIP Cl ]
[RuIII(L1-4)P2Cl]
(1-4)
1-4H2
+
3
2
L
P=PPh3
NaNO2/H+
DCM,
stirring
[Ru(NO2L1-4)P2(NO)](ClO4)
(1a-4a)
ppm (for 1a
which indicated the presence of trans PPh3 groups in all the
nitrosyl complexes 1a
4a (Table S3).[20–22] These 31P NMR data
, 2a) and 22.0 ppm (for 3a,
4a) in 31P NMR spectra
Scheme 4. Synthetic routes for cyclometalaed ruthenium
complexes 1–4 and 1a–4a
−
.
were also consistent with X-ray crystal structure (vide infra).
We would like to mention here that we were unable to
1
generate a good H NMR spectra for 1a and 2a although the
cm–1; for L4H2, CONH = 1670 cm–1) (shown in Figures S1–S8 and
ν
same for complexes 3a and 4a were reasonable. 31P NMR data
are ~22ppm for 1a and 2a whereas ~30ppm for 3a and 4a. This
prompted us to have a closer look to νNO and 31P NMR data
along with 1H NMR spectra (Table S4 in supporting
information). These data clearly express that complexes 1a
and 2a are having one type of electronic structure and
complexes 3a and 4a possess a different type of electronic
structure. All the complexes contain {Ru–NO}6 moiety6 and
{RuII–NO+}6 description was suggested.6 However {RuII–NO+}6
description predicts complete transfer of electron density from
NO to ruthenium. This may vary for different complexes
depending upon the other ligands present in the complex.
Presence of –NO2 group in the ligand frame probably facilitates
complete transfer and formation of diamagnetic {RuII–NO+}6
(for complexes 3a and 4a). The substituents are different (-H
and -Cl) for complexes 1a and 2a and hence they have
different electronic structure. These are the probable reasons
for the bad 1H NMR signals and shift in 31P NMR spectra for 1a
Table S1). This red shift indicated the coordination of
deprotonated ligands in these cyclometalated complexes and
three peaks near 746-742, 694-692 and 520-515 cm–1 were
examined due to the presence of PPh3 groups (Table S1).[20–22]
On the other hand, the presence of the {Ru–NO}6 moiety in all
the nitrosyl complexes was confirmed by the characteristic
peaks in the infrared spectra. In the IR spectra, the N−O
stretching frequencies (νNO) of nitrosyl complexes 1a, 2a, 3a
and 4a were observed around 1880 cm–1, 1870 cm–1, 1830 cm–
1
and 1845 cm−1 respectively, which were expected for
{Ru−NO}6 species in the nitrosyl complexes (shown in Figures
S9–S16 and Table S1).[20–22,42–44] In the literature, the range of
N−O stretching frequencies (νNO) was reported 1820−1960
cm−1 for {Ru−NO}6 species.[38] These data were also supported
by representative X-ray crystal structure of complex 4a (vide
infra). The values of
cm–1, 1585 cm–1, 1645 cm–1 and 1655 cm−1 for complexes
1a
4a), respectively.[42–44] The values of stretching
−CONH− group were found around 1635
(
−
frequencies due to PPh3 groups (νPPh3) were observed in the
range near 746-730 cm−1, 694-692 cm−1 and 530-522 cm−1 for
and 2a
.
the ruthenium nitrosyl complexes 1a
The UV–Vis spectra of ruthenium (III) complexes
displayed in Figure S17. In complexes , we observed charge
transfer band with λmax near 445 nm as well as 335 nm for
complex , 365 nm for complex , 460 nm for and 460 as
well as 365 nm for (shown in Figure S17). These bands were
probably due to the result of ligand–to–metal charge transfer
(LMCT) transition.[32,33,45] In all the complexes
4, a charge
−
4a (Table S1).[20–22]
Description of molecular structure
The molecular structure
[Ru(NO2L4)(PPh3)2(NO)](ClO4).CH2Cl2 (4a. CH2Cl2) is depicted in
Figure 1. The selected bond lengths and bond angles of
complex 4a.CH2Cl2 are given in Table 1. Crystal data collection
and refinement detail of the structure of complex 4a.CH2Cl2 is
summarized in Table 2.
1−4 were
of
the
complex
1−4
1
2
3
4
1−
In the crystal structure of 4a·CH2Cl2, the equatorial plane
was involved of carbanion (C2), Cl(1), pyridine nitrogen (N2)
transfer band was also found around 270 nm which considered
as ligand based transition (Table S2).[30,31]
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Journal Name
and NO. We observed that both the phosphine groups were ring.[48] It is well known in the literature[49] that nuclear
trans to each other which was supported by 31P NMR spectral nitration for simple aromatic compounds proceeds via
data. The ruthenium center adopted a distorted-octahedral
electrophilic pathway. So ligand nitration (–NO2) was found on
the phenyl ring of quinoline containing the amine function and
the site of nitration was trans to the amine group.
In the nitrosyl complex, Ru–NNO (1.759(2) Å)[20–22] and N–O
(1.139(2) Å)[20,22] bond distances were obtained similar to the
reported values in the literature. The N–O stretching
frequency and N–O distance along with Ru–N–O angle (∼175°)
clearly expressed {RuII–NO+}6 description of {Ru–NO}6 moiety
in the nitrosyl complex.[20–22] These data were supported
through IR spectroscopic studies and the presence of trans-
phosphine groups were also indicated by 31P NMR data. Ru–
N(1) (pyridine nitrogen) and Ru–P distances were also close to
the values already reported.[20,22]
Table 2. Summary of crystal data and structural refinement
parameters for complex 4a·CH2Cl2.
Empirical formula
C53H40Cl3N5O10P2Ru
Formula weight
Temperature /K
1176.26
296(2)
0.71073
Triclinic
P –1
12.0096(5)
12.6429(5)
19.2406(8)
81.340(2)
64.743(2)
86.300(2)
2612.02(19)
2
Figure 1. ORTEP diagram (30% probability level) of the cation
of the [Ru(NO2L4)(PPh3)2(NO)](ClO4).CH2Cl2
λ
(Å) (Mo
-
Kα)
(4a.CH2Cl2). All
Crystal system
Space group
A (Å)
hydrogen atoms, solvent molecule and all the phenyl rings of
PPh3 groups are omitted for clarity.
B (Å)
C (Å)
geometry. The nitrogen atom of carboxamido (–CONH) ligand
was coordinated to the metal center and the ruthenium-
carboxamido nitrogen (Ru(1)–N(2)) bond distance (2.042(2) Å)
was found to be closer to the reported values.[42,44,47] The Ru–
C(53) (2.068(3) Å) distance was also consistent with the values
reported in the literature[22,30] and found to be very close to
the bond length reported by Pal and coworkers.[31] In this
structure, the carboxamido nitrogen atom (–CONH–) was
bound to the metal center so there was no peak of amide
hydrogen atom in the 1H NMR spectrum.
α
(˚)
(˚)
(˚)
γ
β
V (Å3)
Z
ρcalc (gcm-3)
F(000)
1.496
1196
Theta range
Index ranges
1.07−28.34
−11< h< 16,
−16< k< 16,
−25< l< 25
13031/0/668
1.211
Data/restraints/par.
GOFa on F2
R1b [I > 2σ(I)]
R1[all data]
0.0456
0.0567
0.1458
0.1631
wR2c [I > 2σ(I)]
wR2 [all data]
Table 1. Selected bond lengths (Å) and bond angles (deg.) of
complex 4a·CH2Cl2.
aGOF = [Σ[w(Fo2 − Fc )2] /M − N]1/2 ( M = number of reflections,
2
Bond lengths (Å)
Bond angles (°)
N(2)−Ru(1)−N(3)
N = number of parameters refined). bR1 = Σ
║Fo│− │Fc
║/Σ│Fo│.
Ru(1)−C(53) 2.068(3)
174.69(9)
79.63(10)
76.66(8)
92.51(7)
91.53(7)
175.52(2)
175.3(2)
2
c wR2 = [Σ[w(Fo2 −Fc )2]/Σ [(Fo2)2]]1/2
.
Ru(1)−N(1)
Ru(1)−N(2)
Ru(1)−P(1)
Ru(1)−P(2)
Ru(1)−N(3)
N(3)−O(1)
2.176(2)
2.040(2)
2.4710(7)
2.4647(7)
1.759(2)
1.139(3)
N(2)−Ru(1)−C(53)
N(1)−Ru(1)−N(2)
N(3)−Ru(1)−P(1)
N(3)−Ru(1)−P(2)
P(1)−Ru(1)−P(2)
O(1)−N(3)−Ru(1)
Site Specific Orthometallation: A Reaction Model
The reaction of Ru(PPh3)3Cl2 with ligands having amide bond
afforded cyclometalated ruthenium complexes via C–H bond
activation and orthometallation. During this reaction, we
observed that the orthometallation happened in the phenyl
ring of benzoic acids. However it is important to note here that
in case of m-nitrobenzoic acid, there are two probable sites
accessible for C–H bond activation and orthometallation. This
is a situation similar to our previous results.[22] After the
completion of reaction, we observed only
orthometallated product. In resultant
a
single
Quinoline shows the chemistry of benzene as well as pyridine
and electrophilic substitution occurs at the benzene ring
whereas nucleophilic substitution takes place at the pyridine
ruthenium
organometallics, the nitro group was found to be at a para
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position with respect to orthometallated carbon. According to centre could act as a nucleophile or an electrophile.[22,50–52]
the literature, at the time of orthometallation, the metal
O
R
R
C
P
N
C
Ru(PPh3)3Cl2
+
Cl
Cl
NH
A
O
Ru
P
N
N
B
(P = PPh3)
CMD Mechanism
O
+
R
C
N
P
H
R
Cl-
Cl
O
Ru
P
C
N
H
P
Ru
P
N
Cl
Cl
Wheland intermediate
D
N
C
O
R
C
P
Ru
P
-HCl
N
-HCl
N
Cl
E
Scheme 5. Proposed reaction model for cyclometalation.
In the present study the precursor ruthenium complex better stability of Ru(III) center in case of complexes
3 and 4.
contains Ru(II) centre and coordination of deprotonated amide This happened probably due to the presence electron
nitrogen will stabilize Ru(III). In higher oxidation state metal withdrawing group (–NO2) in the ligand frame. In case of
centre behaves as an electrophile and Ru-C bond is formed via complex
4
, slightly less E1/2 value of Ru(III)/Ru(II) response was
found as compare to the E1/2 value of complex indicated that
revealed that different the presence of –NO2 with respect to carbanion (para or meta)
H bond activation and could not be ignored (Figure 2). In case of ruthenium nitrosyl
metal-carbon bond formation. Electrophilic aromatic complexes 1a and 2a, we did not observed any redox couple
substitution (SEAr) and concerted metalation deprotonation but found only cathodic peak near –1.09 V and –0.96 V,
C–H bond activation.
3
[50,57]
Investigation of literature
reaction pathways were proposed for C
-
-
(CMD) are the two important reaction pathways that have respectively (Figure 3). Lahiri and coworkers explained ligand
received most attention in this regard.[57] In the SEAr (nitric oxide) centered reduction of (RuII–NO+)6/(RuII–NO·)7 and
mechanism, reaction proceeds via formation of Wheland then second reduction for the appearance of such type two
intermediate. In Wheland intermediate a metal ion is bound to peaks at negative potentials.[53] In the cyclic voltammogram of
the carbon atom of the arene via a covalent bond and metal– complex 3a, we obtained two redox couple near –0.68 V and –
carbon bond is formed before the C
CMD transition state, metal bound chloride ion abstracts a were also exhibited near –0.67 V and –1.02 V vs. Ag/AgCl.
proton from C H bond while, at the same time, a metal carbon (Figure 3). In the negative potential quasi-reversible
-
H bond is cleaved. In a 1.00 V vs. Ag/AgCl. In case of complex 4a, two redox couples
-
bond is being formed. Hence we propose a possible reaction couples(RuIII/RuII) for nitrosyl complexes were reported by
model in Scheme 5.
Mascharak and coworkers.[44,54]
Electrochemistry
We have investigated the redox properties of ruthenium
Photolysis experiments for ruthenium nitrosyl complexes
center in complexes 1–4 and 1a–4a with the help of cyclic
voltammetric studies. In the voltammograms of precursor the ll the nitrosyl complexes 1a
complexes ( ), we found quasi-reversible redox couples with under light and the photolability of coordinated NO of nitrosyl
E1/2 values near +0.56 V (for
and +0.92 V (for ) vs. Ag/AgCl which were attributed to
Ru(III)/Ru(IV) couples (Figure 2).[22,30,31] In case of complexes
−4a were found to be photolabile
1–4
1), +0.60 V (for
2
), +0.92 V (for
3)
complexes was performed under visible as well as UV light.
4
3
and
4, we also obtained quasi-reversible redox couples
near−0.37V and –0.32 V vs. Ag/AgCl respectively which were
assigned as Ru(III)/Ru(II) couple (Figure 2).[22,31,32] The results
obtained for precursor complexes (1−4) clearly indicated
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(a)
Journal Name
(a)
-1.0
-0.5
Potential (V)
0.0
0.5
1.0
-1.5 -1.0 -0.5 0.0
0.5
1.0
Potential (V)
(b)
(b)
-1.0
-0.5
Potential (V)
0.0
0.5
1.0
-1.5 -1.0 -0.5 0.0
0.5
1.0
Potential (V)
(c)
(c)
-1.0
-0.5
Potential (V)
0.0
0.5
1.0
-1.5 -1.0 -0.5 0.0
0.5
1.0
Potential (V)
(d)
(d)
-1.0
-0.5
Potential (V)
0.0
0.5
1.0
-1.5 -1.0 -0.5 0.0 0.5 1.0
Potential (V)
Figure 2. Cyclic voltammograms of 10–3 M solutions of (a)
complex , (b) complex , (c) complex , (d) complex in
1
2
3
4
Figure 3. Cyclic voltammograms of 10–3 M solutions of (a)
complex 1a, (b) complex 2a, (c) complex 3a, (d) complex 4a in
dichloromethane in presence of 0.1 M tetrabutylammonium
perchlorate (TBAP) using working electrode, glassy-carbon;
reference electrode, Ag/AgCl; auxiliary electrode, platinum
wire and scan rate, 0.1 V/s
dichloromethane in presence of 0.1 M tetrabutylammonium
perchlorate (TBAP) using working electrode, glassy-carbon;
reference electrode, Ag/AgCl; auxiliary electrode, platinum
wire and scan rate, 0.1 V/s.
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(a)
0.4
case of complex 2a, we also observed the same disappearance
of a peak near 324 nm (shown in Figure S 27). When a solution
of complex 3a was illuminated under UV light, we obtained a
decrease in peak intensities near 435 as well as 282 nm and we
found two isobestic points near 482 nm and 350 nm (shown in
Figure S 28). The spectral changes were also observed with
complex 4a in the dichloromethane solution. In this case, we
also found a decrement in peak intensities near 424 nm as well
as 288 nm under UV light (Figure 4(b)).
0.28
0.24
0.20
0.16
0.3
0.2
0.1
0
10
20
30
40
50
Time(Sec)
Trapping of photoreleased NO by reduced myoglobin
0.0
The photocleavage of coordinated NO from ruthenium nitrosyl
complexes was also confirmed by trapping the liberated NO by
250
300
350
400
450
500
Wavelength (nm)
(a)
(b)
0.3
0.12
0.10
0.08
0.06
0.3
420 nm
0.2
0.2
0.1
0.0
0
8
16 24 32 40 48 56
Time (mnt)
0.1
0.0
400
450
500
550
600
650
700
300
400
500
600
Wavelength (nm)
Wavelength (nm)
(b)
Figure 4. Photodissociation of NO from complexes (a) 1a (~ 1.5
x 10–5 M) and (b) 4a (~ 1.2 x 10−5 M) in dichloromethane
solutions under illumination with a UV light (λirr = 365 nm).
Repetitive scans were taken in 5 seconds intervals for 1a and
in 4 minutes intervals for 4a.Inset: Changes in absorbance with
time at λ = 326 nm and λ = 424 nm for 1a and 4a respectively
at room temperature.
0.3
0.2
0.1
0.0
424 nm
In dark condition, there was no color change observed. On the
other hand in the presence of light we observed a color change
from reddish-yellow to reddish brown. In the presence of
visible light (100 Watt tungsten lamp), we did not observed
much change in the UV-Vis spectra of nitrosyl complexes.
However, rapid spectral changes were observed when the
solutions were exposed to low intensity light of the UV lamp
400
450
500
550
600
650
700
(λirr = 365 nm). A dichloromethane solution of complex 1a was
Wavelength (nm)
exposed to low intensity UV light and we observed the
disappearance of a peak near 326 nm. These results are
indicative of photolability of coordinated NO (Figure 4(a)).In
Figure 5. Electronic spectra for conversion of reduced Mb to
Mb−NO adducts upon reacꢀon with 3a and 4a in buffer
solutions (50 mM phosphate buffer, pH 6.8) under exposure of
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(a)
UV light (λirr = 365 nm). Red line, oxidized Mb (intense band at
~ 409 nm); blue line, reduced Mb (at ~ 433 nm, with excess of
sodium dithionite). (a) Black line, Mb–NO adduct (at ~ 420
nm), obtained by Mb and solution of 3a (~ 10−5 M) exposed to
UV light for 2-3 minutes. (b) Black line, Mb–NO adduct (at ~
424 nm) obtained by Mb and solution of complex 4a (~4.3 x
10−5 M) exposed to UV light for 10-11 minutes.
0.25
0.20
0.15
0.10
0.05
0.00
0.3
0.2
0.1
0.0
reduced myoglobin (Mb) using low intensity UV lamp in
phosphate buffer (pH ~ 6.8).[22] In electronic absorption
spectra, we obtained an intense band at 409 nm (Soret band)
for oxidized myoglobin (Mb). In the same solution, the sodium
dithionite was added in excess and then we obtained an
intense band near ~ 433 nm in the UV-Vis spectra due to the
reduced myoglobin. Acetonitrile solution of nitrosyl complexes
were added to a solution containing reduced myoglobin and
no reaction was obtained under dark conditions. However,
0
2
4
6
8
10 12 14 16
Time(mnt)
500
550
600
650
700
Wavelength (nm)
when the same solution was illuminated with UV light (λirr
=
365 nm) for 2-3 minutes then absorption spectra at near 420
nm (for 1a near 421, for 2a near 424 (Figure S29) and for 3a
420 (Figure 5(a))) clearly indicated the formation of Mb–NO
adducts.[20–22] However in case of 4a, the same solution
mixture was kept under exposure to the light of UV lamp for
10-11 minutes then we observed a band near 424 nm in UV-
Vis spectra indicating the formation of Mb–NO adduct (Figure
5(b))[20–22] with a longer exposure to light.
(b)
0.4
0.20
0.15
0.10
0.05
0.00
0.3
0.2
0.1
0.0
0
2
4
6
8
10 12 14 16
Time (mnt)
Estimation of photoreleased NO by Griess reaction
We estimated the amount of photoliberated NO from
ruthenium nitrosyl complexes in the presence of UV light (λirr
365 nm) by using Griess reagent assay.[22,34,37] The photolability
of NO in complexes 1a 4a was further observed through
=
–
500
550
600
650
700
increasing in optical density of the produced azo dye at ~ 538
nm in the presence of ultraviolet light. In dark conditions, a
little amount of NO was found to be released. When the
Wavelength (nm)
solutions of complexes 1a–4a (50
exposed with UV light for 15 minutes then the amount of NO
was liberated 5.2 M (for 1a), 4.6 M (for 2a, Figure S30),
6.3 M (for 3a, Figure 6(a)) and 5.0 M (for 4a, Figure
ꢀM) with Griess reagent was
Figure 6. Electronic spectra of dye formation when Griess
reagent (100 L) was treated with complexes (a) 3a (50 M)
(b) 4a (50 M) in the presence of UV light (λirr = 365 nm).
∼
ꢀ
∼
ꢀ
ꢀ
ꢀ
∼
ꢀ
∼
ꢀ
ꢀ
6(b)). The change in absorbance spectra of produced azo dye
was found to be small under visible light (100 Watt tungsten
lamp) (Figure S31 and Table 3). The results of estimated NO
from our nitrosyl complexes were compared with the data
Repetitive scans were taken in 1 minute intervals. Inset: Time
dependent changes in absorbance at λirr = 538 nm at room
temperature.
obtained from sodium nitroprusside (SNP), a standard nitric Table 3 Estimation of NO production from 1a, 2a, 3a, 4a and
oxide (NO) donor[6,55,56] in same experimental conditions. In
sodium nitroprusside (SNP) in Griess reagent assay.
ultraviolet light (low intensity), 50
nitroprusside released 3.4 M of nitric oxide (Table 3). These
data gave rise to the formation of NO and the amount of
photoreleased NO form complexes 1a 4a was found to be
ꢀM solution of sodium
Complex Complex
conc.
NO produced (µM)a
Griess reaction
Visible light UV light
∼
ꢀ
Dark
0.42
0.50
0.30
0.48
0.04
−
1a
2a
3a
4a
50
50
50
50
50
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
M
M
M
M
M
2.4
3.6
3.1
5.8
0.2
5.2
4.6
6.3
5.0
3.4
close to the amount of NO released by SNP under UV light.
Interestingly 4a gave rise to roughly similar amount of NO
under visible as well as UV light (Figure S32). This is probably
due to extended delocalization of charge from NO
→Ru→phenyl ring→NO2 (para with respect to carbanion).
SNP
a Average of three experiments.
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Conclusions
Notes and references
1
P. B. Arockiam, C. Bruneau, P. H. Dixneuf, Chem. Rev. 2012,
112, 5879.
V. Ritleng, C. Sirlin, M. Pfeffer, Chem. Rev. 2002, 102, 1731.
P. G. Bomben, K. C. D. Robson, B. D. Koivisto, C. P.
Berlinguette, Coord. Chem. Rev. 2012, 256, 1438.
The following are the major findings of the present study. First,
a different combination of donor atoms (pyridyl nitrogen and
2
3
amide nitrogen) were utilized to investigate the C−H bond
activation and the bidentate ligand was converted to a
tridentate one with the formation of Ru–C bond. These data
and our previous results clearly indicate that the presence of
at least one Ru(III) stabilizing donor in the ligand frame was
necessary to afford orthometallation and synthesis of Ru(III)
organometallic complexes. Second, new family of
4
5
6
Y. Aihara, N. Chatani, Chem. Sci. 2013, 4, 664.
Y. Zhao, C. Snieckus, Adv. Synth. Catal. 2014, 356, 1527.
M. J. Rose, P. K. Mascharak, Coord. Chem. Rev. 2008, 252
2093 and references therein.
,
7
N. L. Fry, P. K. Mascharak, Acc. Chem. Res. 2011, 44, 289 and
references therein.
U. Schatzschneider, Eur. J. Inorg. Chem. 2010, 1451.
P. C. Ford, Nitric Oxide 2013, 34, 56.
ruthenium(III) cyclometalate complexes [Ru(L1–4)(PPh3)2Cl] (
) were obtained via C–H bond activation and were
1–
8
9
4
10 N. L. Fry, P. K. Mascharak, Dalton Trans. 2012, 41, 4726.
11 S. Sarkar, B. Sarkar, N. Chanda, S. Kar, S. M. Mobin, J. Fiedler,
W. Kaim, G. K. Lahiri, Inorg. Chem. 2005, 44, 6092.
12 P. De, B. Sarkar, S. Maji, A. K. Das, E. Bulak, S. M. Mobin, W.
Kaim, G. K. Lahiri, Eur. J. Inorg. Chem. 2009, 2702.
13 A. D. Chowdhury, P. De, S. M. Mobin, G. K. Lahiri, RSC Adv.
2012, 2, 3437.
14 M. G. Sauaia, R. G. de Lima, A. C. Tedesco, R. S. da Silva, J.
Am. Chem. Soc. 2003, 125, 14718.
15 M. G. Sauaia, R. G. de Lima, A. C. Tedesco, R. S. da Silva,
Inorg. Chem. 2005, 44, 9946.
16 F. Roncaroli, M. Videla, L. D. Slep, J. A. Olabe, Coord. Chem.
Rev. 2007, 251, 1903.
17 M. Sieger, B. Sarkar, S. Zalis, J. Fiedler, N. Escola, F.
Doctorovich, J. A. Olabe, W. Kaim, Dalton Trans. 2004, 1797.
18 F. A. Cotton, G. Wilkinson, “Advanced inorganic chemistry”
5th ed.; Wiley, New York, 1930.
19 H. Hadadzadeh, M. C. DeRosa, G. P. A. Yap, A. R. Rezvani, R.
J. Crutchley, Inorg. Chem. 2002, 41, 6521.
20 K. Ghosh, S. Kumar, R. Kumar, U. P. Singh, N. Goel, Inorg.
Chem. 2010, 49, 7235.
characterized by different spectroscopic studies. The ligand
frame utilized in this report is related to the works by Chatani
and coworkers.[4] and in the propose mechanism they have
mentioned the formation of Ru–C bond via C–H activation
(intermediate 32, in Scheme 1 in reference 4) during C–C bond
formation. To the best of our knowledge there is no structural
characterization of intermediate 32. Hence this is the first
example of structurally characterized intermediate which
clearly show the site specific C–H activation. Third, nitric oxide
(NO) reactivity studies previously gave rise to the coordination
of NO in trans position to carbanion. Here, two groups present
in the ligand are carboxamido (–CONH–) and carbanion
groups, which exhibit trans effect. We found the dissociation
of chloride ion from the metal centre which was situated in
trans position to deprotonated nitrogen of carboxamido group
and then NO was coordinated to the metal centre to afford
ruthenium nitrosyl complexes [Ru(NO2L1–4)(PPh3)2(NO)](ClO4)
(1a–4a) and these nitrosyl complexes were characterized by
21 K. Ghosh, S. Kumar, R. Kumar, U. P. Singh, N. Goel,
Organometallics 2011, 30, 2498.
22 K. Ghosh, S. Kumar, R. Kumar, U. P. Singh, Eur. J. Inorg.
Chem. 2012, 929.
23 K. Ghosh, R. Kumar, S. Kumar, M. Bala, U. P. Singh, Transition
Met. Chem. 2015, 40, 831.
24 G. K. Lahiri, S. Bhattacharya, M. Mukherjee, A. K. Mukherjee,
A. Chakravorty, Inorg. Chem. 1987, 26, 3359.
spectroscopic studies. The molecular structure of
representative complex 4a was examined by X–ray
crystallography. Fourth, ligand nitration was also observed in
the activated phenyl group containing –NH2 function in the
qunoline moiety. Fifth, resultant nitrosyl complexes were
found to be photosensitive under visible as well as UV light
and we have also investigated the liberation of NO by trapping
experiment with the help of reduced myoglobin. We have
quantified the amount of photoreleased nitric oxide (NO) by
using Griess reaction. Sixth, we have observed that in the
25 G. Venkatachalam, R. Ramesh, Tetrahedron Lett. 2005, 46
5215.
,
26 G. Venkatachalam, R. Ramesh, S. M. Mobin, J. Organomet.
Chem. 2005, 690, 3937.
27 S. Kannan, R. Ramesh, Y. Liu, J. Organomet. Chem. 2007, 692
3380.
,
complexes 1a, 2a and 3a released nitric oxide easily under
28 P. Ghosh, A. Pramanik, N. Bag, G. K. Lahiri, A. Chakravorty, J.
Organomet. Chem. 1993, 454, 237.
29 P. Munshi, R. Samanta, G. K. Lahiri, J. Organomet. Chem.
1999, 586, 176.
30 R. Raveendran, S. Pal, J. Organomet. Chem. 2007, 692, 824.
visible as well as UV light and the amount of NO released
under UV light was more as compare to NO released under
visible light. Complex 4a provided roughly same amount of NO
under UV and visible light. We are trying to modify the ligand
to observe photorelease of NO in the desired range 700-1000
nm and work is under progress.
31 R. Raveendran, S. Pal, S. J. Organomet. Chem. 2009, 694
1482.
32 K. Nagaraju, S. Pal, J. Organomet. Chem. 2013, 737, 7.
,
33 K. Nagaraju, S. Pal, J. Organomet. Chem. 2013, 745–746, 404.
34 K. Ghosh, R. Kumar, S. Kumar, J. S. Meena, Dalton Trans.
2013, 42, 13444.
Acknowledgements
35 K. Ghosh, A. A. Eroy-Reveles, B. Avila, T. R. Holman, M. M.
Olmstead, P. K. Mascharak, Inorg. Chem. 2004, 43, 2988.
36 T. A. Stephenson, G. J. Wilkinson, J. Inorg. Nucl. Chem. 1966,
28, 945.
37 K. Ghosh, R. Kumar, K. Kumar, A. Ratnam, U. P. Singh, RSC
Adv. 2014, 4, 43599.
KG is thankful to CSIR, New Delhi, India for financial assistance
no. (01(2720)/13/EMR–II dated 17–04–2013). RK, SK and MB
are thankful to CSIR, New Delhi and AR is thankful to MHRD for
their fellowships. U. P. S. is thankful for support by single-
crystal X-ray facility of the IIT Roorkee.
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Journal Name
38 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr.,
1990, 46, 467.
39 G. M. Sheldrick, SHELXTL-NT 2000 version 6.12, Reference
Manual, University of Gottingen, Pergamon, New York, 1980.
40 B. Klaus, DIAMOND, Version 1.2 c, University of Bonn,
Germany, 1999
.
41 K. Ghosh, S. Kumar, R. Kumar, U. P. Singh, J. Organomet.
Chem. 2014, 750, 169.
42 A. K. Patra, M. J. Rose, K. A. Murphy, M. M. Olmstead, P. K.
Mascharak, Inorg. Chem. 2004, 43, 4487.
43 N. L. Fry, B. J. Heilman, P. K. Mascharak, Inorg. Chem. 2011,
50, 317.
44 M. J. Rose, A. K. Patra, E. A. Alcid, M. M. Olmstead, P. K.
Mascharak, Inorg. Chem. 2007, 46, 2328.
45 K. Ghosh, S. Kumar, R. Kumar, Eur. J. Inorg. Chem. 2014,
1454.
46 K. Ghosh, S. Kumar, R. Kumar, Inorg. Chim. Acta 2013, 405
24.
,
47 N. L. Fry, M. J. Rose, D. L. Rogow, C. Nyitray, M. Kaur, P. K.
Mascharak, Inorg. Chem. 2010, 49, 1487.
48 J. Clayden, N. Greeves, S. Warren, P. Wothers, Organic
Chemistry, Oxford University Press, 2001.
49 S. Chattopadhyay, K. Ghosh, S. Pattanayak, A. Chakravorty,
Dalton Trans 2001, 1259 and references therein.
50 N. Chitrapriya, V. Mahalingam, M. Zeller, K. Natarajan,
Polyhedron 2008, 27, 1573.
51 R. L. Brainard, W. R. Nutt, T. R. Lee, G. M. Whitesides,
Organometallics 1988, 7, 2379.
52 R. Cordone, W. D. Harman, H. Taube, J. Am. Chem. Soc. 1989,
111, 2896.
53 S. Maji, B. Sarkar, M. Patra, A. K. Das, S. M. Mobin, W. Kaim,
G. K. Lahiri, Inorg. Chem. 2008, 47, 3218.
54 A. K. Patra, P. K. Mascharak, Inorg. Chem. 2003, 42, 7363.
55 A. A. Eroy-Reveles, Y. Leung, C. M. Beavers, M. M. Olmstead,
P. K. Mascharak, J. Am. Chem. Soc. 2008, 130, 4447.
56 C. Xin Zhang, S. J. Lippard, Curr. Opin. Chem. Biol. 2003,
481.
57 S. I. Gorelsky, Coord. Chem. Rev. 2013, 257, 153.
7,
12 | J. Name., 2012, 00, 1-3
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Graphical Abstract Pictogram
Graphical Abstract Synopsis
A new family of σꢀaryl ruthenium(III) complexes derived from the bidentate ligands having
amide bond through C–H bond activation were synthesized. These organometallic complexes
were treated with nitric oxide (NO) to afford organometallic nitrosyl complexes. All the
ruthenium complexes were characterized by various spectroscopic techniques and
electrochemical studies. The molecular structure of representative complex was established by
Xꢀray crystallography. Nitric oxide molecule was found to be photolabile in these nitrosyl
complexes under light.