Communication
Dalton Transactions
and Technology (DST), India for financial support (SR/S1/
IC-38/2010); DST-FIST program for X-ray diffraction facility.
Notes and references
‡The crystals were grown by slow diffusion followed by the slow evaporation
technique.
Crystal data for ligand, L2: CCDC no. 930724, C34H56N2O2, M = 524.81, mono-
clinic (P2(1)/c), a = 15.3347(6), b = 10.3571(7), c = 21.7602(10) Å, α = 90°,
β = 99.939(4)°, γ = 90°, V = 3404.2(3) Å3, Z = 4, Dc = 1.024 g cm−3, μ = 0.062 mm−1
,
T = 293(2) K, 5990 reflections, 4127 independent, R(F) = 0.0600 [I > 2δ(I)], wR(F2) =
0.1838 (all data), GOF = 1.059.
Fig. 3 ORTEP diagram of L2’.
Crystal data for complex 1: CCDC no. 930722, C24H42CuN2O3, M = 470.15,
monoclinic (P21/n), a = 10.1575(3), b = 24.1596(8), c = 11.0644(3) Å, α = 90°, β =
103.211(3)°, γ = 90°, V = 2643.36(14) Å3, Z = 4, Dc = 1.181 g cm−3, μ = 0.850 mm−1
,
T = 293(2) K, 4650 reflections, 3374 independent, R(F) = 0.0460 [I > 2δ(I)], wR(F2) =
0.1571 (all data), GOF = 0.955.
In a recent example, it has been demonstrated that both
Cu2+ and Cu2+-peptide complexes can catalyze the tyrosine
nitration in the presence of nitrite and hydrogen peroxide.9 In
this reaction, hydroxyl radicals (•OH) and/or copper(II)-bound
Crystal data for complex 2: CCDC no. 930723, C36H58CuN2O4, M = 646.38, tri-
ˉ
clinic (P1), a = 9.8751(13), b = 13.671(2), c = 14.078(2) Å, α = 98.778(8)°, β =
104.531(8)°, γ = 96.777(8)°, V = 1793.8(4) Å3, Z = 2, Dc = 1.197 g cm−3, μ =
•OH (Cu2+-•OH) are found to be generated from Cu2+ and H2O2 0.647 mm−1, T = 296(2) K, 6545 reflections, 4341 independent, R(F) = 0.0477
[I > 2δ(I)], wR(F2) = 0.1107 (all data), GOF = 0.986.
through a Fenton-like reaction. These radicals may then be
Crystal data for nitration product, L2′: CCDC no. 930725, C26H38N4O6,
M = 502.60, monoclinic (P2(1)/c), a = 15.5224(11), b = 9.7342(9), c = 19.2871(12) Å,
α = 90°, β = 105.076(7)°, γ = 90°, V = 2813.9(4) Å3, Z = 4, Dc = 1.186 g cm−3, μ =
0.085 mm−1, T = 293(2) K, 4824 reflections, 2465 independent, R(F) = 0.0895
[I > 2δ(I)], wR(F2) = 0.1624 (all data), GOF = 1.434.
−
•
scavenged by both NO2 to form NO2 and tyrosine to form
tyrosine radicals (Tyr•), resulting in the tyrosine nitration.
Cu2+/H2O2 was found to catalyze the tyrosine nitration induced
•
•
•
by NO and oxygen. NO was oxidized by O2 to form NO2, and
the role of Cu2+/H2O2 was to generate •OH/Cu2+-•OH to
promote the Tyr• formation.9 It would be worth mentioning
1 H. Wiseman and B. Halliwell, Biochem. J., 1996, 313, 17–29.
2 (a) K. Apel and H. Hirt, Annu. Rev. Plant Biol., 2004, 55,
373–399; (b) R. Radi, Proc. Natl. Acad. Sci. U. S. A., 2004,
101, 4003–4008.
3 (a) M. H. Shishehbor, R. J. Aviles, M. L. Brennan, X. M. Fu,
M. Goormastic, G. L. Pearce, N. Gokce, J. F. Keaney,
M. S. Penn, D. L. Sprecher, J. A. Vita and S. L. Hazen, JAMA,
J. Am. Med. Assoc., 2003, 289, 1675–1680; (b) P. F. Good,
P. Werner, A. Hsu, C. W. Olanow and D. P. Perl,
Am. J. Pathol., 1996, 149, 21–28; (c) S. R. Danielson,
J. M. Held, B. Schilling, M. Oo, B. W. Gibson and
J. K. Andersen, Anal. Chem., 2009, 81, 7823–7828.
4 (a) H. Gunaydin and K. N. Houk, Chem. Res. Toxicol., 2009,
22, 894–898; (b) A. van der Vliet, J. P. Eiserich, B. Halliwell
and C. E. Cross, J. Biol. Chem., 1997, 272, 7617–7625.
5 (a) S. Goldstein, J. Lind and G. Merenyi, Chem. Rev.,
2005, 105, 2457–2470; (b) M. P. Schopfer, J. Wang
and K. D. Karlin, Inorg. Chem., 2010, 49, 6267–6282;
(c) N. B. Surmeli, N. K. Litterman, A. F. Miller and
J. T. Groves, J. Am. Chem. Soc., 2010, 132, 17174–17185.
6 (a) J. Olbregts, Int. J. Chem. Kinet., 1985, 17, 835–848;
(b) J. Su and J. T. Groves, J. Am. Chem. Soc., 2009, 131,
12979–12988; (c) B. Bian, Z. H. Gao, N. Weisbrodt and
F. Murad, Proc. Natl. Acad. Sci. U. S. A., 2003, 100, 5712–
5717.
•
here that in this case, the NO/O2 induced nitration was found
to be catalyzed significantly in the presence of H2O2 and trace
amounts of Cu(II); but a high concentration of Cu(II) was
reported to inhibit the nitration.9 It should be noted that
depending on the biological conditions, the formation of the
+
nitronium ion (NO2 ) as the nitrating agent from peroxynitrite
(−OONO) has been reported earlier.16–18 Superoxide reacts with
•NO to form the strong oxidant peroxynitrite (−OONO). Peroxy-
nitrite, in turn, reacts with superoxide dismutase to result in
an intermediate such as the nitronium ion which nitrates
tyrosine.16
•
However, there is not even a single example where NO2
reduces the Cu(II) centre to Cu(I) resulting in the formation of
+
NO2 which induces phenol ring nitration. It should be noted
•
that for the present study, NO2 does not induce a significant
nitration of the free ligands in the reaction conditions.
Conclusions
Thus, the reduction of the copper(II) center was observed for
both complexes in the presence of NO2 in methanol which
induced phenol ring nitration.
•
7 (a) D. D. Thomas, M. G. Espey, M. P. Vitek, K. M. Miranda
and D. A. Wink, Proc. Natl. Acad. Sci. U. S. A., 2002, 99,
12691–12696; (b) E. Gaggelli, H. Kozlowski, D. Valensin
and G. Valensin, Chem. Rev., 2006, 106, 1995–2044.
8 (a) Y. Lu, M. Prudent, L. A. Qiao, M. A. Mendez and
H. H. Girault, Metallomics, 2010, 2, 474–479; (b) S. P. A. Goss,
Acknowledgements
VK gratefully acknowledges CSIR, India for providing the
fellowship. BM would like to thank the Department of Science
16266 | Dalton Trans., 2013, 42, 16264–16267
This journal is © The Royal Society of Chemistry 2013