Inorganic Chemistry
Article
organic part was extracted by dichloromethane. Purification using
alumina column chromatography yielded pure ligand LH. Yield: 1.19 g
d), 7.19 (1H, s), 3.88 (2H, s), 3.81 (2H, s), 3.13−3.10 (1H, m), 1.42
13
(9H, s), 1.18−1.16 (6H, d).). C NMR: (400 MHz, CDCl ): δ
:
3
ppm
(
65%). Elemental analysis for C H N O, calcd(%): C, 78.21; H,
164.0, 157.5, 149.4, 139.2, 137.5, 136.9, 123.5, 123.2, 122.6, 122.5,
54.8, 53.3, 49.9, 35.1, 29.1, 17.2. Mass: Calcd: (357.205), Found:
358.173 (M+1).
24
36
2
9
.85; N, 7.60; found(%): C, 78.28; H, 9.87; N, 7.73. FT-IR (KBr
−1
1
pellet) 2961, 1593, 1482, 1390, 1360, 1238, 1166, 1080 cm : H
NMR: (400 MHz, CDCl ): δ : 8.50−8.49 (1H, d), 7.64−7.61 (1H,
Spin-Trapping Experiment to Establish the Formation of
3
ppm
t), 7.41−7.39 (1H, d), 7.19 (1H, s), 7.14−7.11 (1H, t), 6.86 (1H, s),
NO. Complex 2 (300 mg) was dissolved in dry and degassed methanol
3
.80 (2H, s), 3.77 (2H, s), 3.12−3.09 (1H, m), 1.42 (9H, s), 1.27 (9H,
in a Schlenk flask attached through a rubber tubing to another flask
13
II
s), 1.16−1.14 (6H, d). C NMR: (400 MHz, CDCl ): δ : 159.0,
containing a solution of [Fe (dtc)
2
] (100 mg in 20 mL of acetonitrile).
:Ar, 1:25 v/
3
ppm
1
5
54.4, 149.1, 140.6, 136.8, 135.6, 124.0, 123.6, 122.9, 122.3, 121.5,
5.7, 53.7, 49.6, 35.0, 34.3, 31.8, 29.8, 17.3. Mass: Calcd: (368.283),
Equivalent amount of NO
2
gas (diluted using Ar gas; NO
2
v) was purged in the solution of complex 2 using a gastight syringe.
The mixture was stirred for 10 min. Ar gas was bubbled for 5 min
Found: 369.295 (M+1).
Complex 1. To a stirred solution of copper(II) acetate
through the reaction mixture to push the gas mixture into the flask
II
containing [Fe (dtc) ]. X-Band EPR spectrum of this solution was
monohydrate Cu(OAc) ·H O (0.398 g, 2 mmol) in acetonitrile (ca.
2
2
2
then recorded to establish the presence of NO.
20 mL) was added a solution of LH (0.740 g, 2 mmol) in chloroform
(
ca. 20 mL). The reaction mixture was stirred for 2 h, and then the
volume was reduced under vacuum to ∼5 mL. A layer of benzene (10
mL) was made, and the mixture was kept in freezer over night to
obtain the metal complex 1 as green crystalline solid. Yield: 0.94 g
CONCLUSION
■
(
II
Thus, the reaction of Cu(II) complex [Cu (LH)(O CCH ) ]
1) with equivalent amount of NO resulted in reduction of
2
3 2
(
6
(
85%). Elemental analysis for C H CuN O .CH CN, calcd(%): C,
2
28
42
2
5
3
Cu(II) to Cu(I) with concomitant nitration at the phenol ring.
The in situ generated intermediate Cu(I) complex of the
0.94; H, 7.67; N, 7.11; found(%): C, 60.99; H, 7.66; N, 7.19. UV−vis
−1 −1
methanol): λ (ε, M cm ): 676 nm (400) and 470 nm (600). X-
max
band EPR (in methanol at 77 K): g , 2.369; g , 2.049. FT-IR (KBr
nitrated ligand reacts with additional equivalent of NO to
∥
⊥
2
II
1
pellet): 2948, 1707, 1687, 1610, 1587, 1474, 1385, 1288, 1174, 766
afford corresponding O-nitrito Cu(II) complex, [Cu (L′)(η -
−1
cm . The complex 1 behaves as non-electrolyte in methanol solution
ONO)] (2). It was not observed earlier. Subsequent addition of
−1
[
1
Λ
(S cm ), 54]. The calculated magnetic moment is found to be
.65 μB.
II
1
M
NO led to the corresponding O-nitrato complex [Cu (L′)(η -
2
ONO )] (3) with concomitant formation of NO. Complexes 2
2
Complex 2. Complex 1 (550 mg, 1.0 mmol) was dissolved in dry
and 3 were isolated and structurally characterized. Isotopic
methanol (ca. 20 mL) in a Schlenk flask fitted with a rubber septum
and degassed using argon gas. To this, 2 equiv of nitrogen dioxide/
argon (1:25 v/v) were added through a gastight syringe, and the
mixture was stirred for 1/2 h. This volume of the solution was reduced
under vacuum to ∼5 mL, and a layer of diethyl ether (∼10 mL) was
made. The mixture was kept in freezer over night to afford complex 2
as greenish solid. Yield: 0.350 g (∼75%). Elemental analysis for
C H CuN O , calcd(%): C, 51.55; H, 5.62; N, 12.02; found(%): C,
labeling experiment revealed that the oxo transfer takes place
1
from NO to the coordinated η -ONO group. The oxo transfer,
2
though reported in cases of iron and manganese porphyrine
complexes, was not found in literature in copper complexes.
ASSOCIATED CONTENT
■
2
0
26
4
5
−1
−1
*
S
Supporting Information
5
1.61; H, 5.61; N, 12.10.UV−vis (methanol): λ (ε, M cm ): 660
nm (240), 386 nm (17890). X-band EPR (in methanol at 77 K): g ,
max
FT-IR, H and 13C NMR, ESI-MS, UV-vis, X-band EPR, and
GC-MS spectral data and crystallographic data in CIF files. This
1
∥
2
.367; g , 2.058. FT-IR (KBr pellet): 2953, 1611, 1588, 1428, 1275,
⊥
−1
1199, 1110, 770 cm . The complex 2 behaves as non-electrolyte in
−1
methanol solution [Λ (S cm ), 40]. The calculated magnetic
moment is found to be 1.68 μ .
M
B
Complex 3. To a degassed solution of complex 1 (275 mg, 0.5
mmol) in dry methanol (ca. 10 mL), excess nitrogen dioxide gas was
purged for 1 min. The resulting green colored solution was dried
under vacuum to reduce its volume to ∼5 mL. Diethyl ether (ca. 20
mL) was then added to give green precipitate of complex 3. Product
was further crystallized from acetonitrile solvent. Yield: 168 mg (70%).
Elemental analysis for C H CuN O .CH CN, calcd(%): C, 51.10; H,
AUTHOR INFORMATION
Notes
■
The authors declare no competing financial interest.
22
29
5
6
3
5
.72; N, 14.89; found(%): C, 51.16; H, 5.74; N, 14.98. UV−vis
−1 −1
ACKNOWLEDGMENTS
(
methanol): λ (ε, M cm ): 685 nm (245), 370 nm (18 840). X-
■
max
band EPR (in methanol at 77 K): g , 2.362; g , 2.060. FT-IR (KBr
∥
⊥
The authors thank the Department of Science and Technology
DST), India, for financial support.
−
1
pellet): 2946, 1611, 1585, 1492, 1384, 1295, 1107, 776 cm . The
complex 3 behaves as non-electrolyte in methanol solution [Λ (S
cm ), 47]. The calculated magnetic moment is found to be 1.60 μ .
Alternatively, complex 3 can be prepared by purging nitrogen dioxide
into the methanol solution of complex 2, also.
Isolation of Nitrated Ligand, L′H. To 30 mL of methanol
solution of complex 1 (550 mg), equivalent amount of freshly
prepared nitrogen dioxide/argon (1:25 v/v) was added through a
gastight syringe. This resulting solution was allowed to stir for 10 min
at room temperature. Then it was opened to air and continued stirring
for 1 h. The solvent was removed under vacuum using rotavapor, and
(
M
−1
B
REFERENCES
■
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then excess aqueous Na S was added to give black precipitate. Solution
2
was filtered, and modified ligand L′H was extracted with dichloro-
methane. Yield: 215 mg (60%). Elemental analyses for C H N O ,
(2) (a) Averill, B. A. Chem. Rev. 1996, 96, 2951. (b) Gladwin, M. T.;
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20
27
3
3
calc(%): C, 67.20; H, 7.61; N, 11.76; found(%): C, 67.29; H, 7.62; N,
1
1
1.87. FT-IR (in KBr): 2967, 1590, 1515, 1476, 1438, 1335, 1285,
−1 1
166, 1099, 902, 749 cm . H NMR: (400 MHz, CDCl ): δppm: 8.56
(3) van der Vliet, A.; Eiserich, J. P.; Halliwell, B.; Cross, C. E. J. Biol.
3
(
1H, s), 8.09 (1H, s), 7.83 (1H, s), 7.68−7.64 (1H, t), 7.32−7.30 (1H,
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F
Inorg. Chem. XXXX, XXX, XXX−XXX