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The nitrogen base 1,2-Me2Im has a stronger electron-donating Notes and references
ability than other nitrogen bases that yielded Co(III)-lpp-type
1 (a) D. M. Kurtz, in Comprehensive Coordination Chemistry II, ed. L. Que
and W. B. Tolman, Elsevier, Tokyo, 2004, vol. 2, pp. 229–260;
(b) M. F. Perutz, M. G. Rossmann, A. F. Cullis, H. Muirhead, G. Will
and A. C. T. North, Nature, 1960, 185, 416–422; (c) B. Shaanan, Nature,
1982, 296, 683–684; (d) J. R. H. Tame and B. Vallone, Acta Crystallogr.,
Sect. D, 2000, 56, 805–811; (e) J. C. Kendrew, G. Bodo, H. M. Dintzis,
R. G. Parrish, H. W. Wyckoff and D. C. Phillips, Nature, 1958, 181,
662–666; ( f ) J. C. Kendrew, R. E. Dickerson, B. E. Strandberg,
R. G. Hart, D. R. Davies, D. C. Phillips and V. C. Shore, Nature, 1960,
185, 422–427; (g) U. Flogel, M. W. Merx, A. Godecke, U. K. M. Decking
and J. Schrader, Proc. Natl. Acad. Sci. U. S. A., 2001, 98, 735–740;
(h) A. Ostermann, I. Tanaka, N. Engler, N. Niimura and F. G. Parak,
Biophys. Chem., 2002, 95, 183–193.
2 (a) T. L. Poulos, in The Porphyrin Handbook, ed. K. M. Kadish,
K. M. Smith and R. Guilard, Academic Press, San Diego, 2000, vol. 4,
pp. 189–218; (b) B. Meunier, in Comprehensive Coordination Chemistry II,
ed. L. Que and W. B. Tolman, Elsevier, Oxford, 2004, vol. 8,
pp. 261–280; (c) T. L. Poulos, S. T. Freer, R. A. Alden, S. L. Edwards,
U. Skogland, K. Takio, B. Eriksson, N.-H. Xuong, T. Yonetani and
J. Kraut, J. Biol. Chem., 1980, 255, 575–580; (d) M. A. Miller, A. Shaw
and J. Kraut, Nat. Struct. Biol., 1994, 1, 524–531; (e) P. R. Ortiz de
Montellano and K. Auclair, in The Porphyrin Handbook, ed.
K. M. Kadish, K. M. Smith and R. Guilard, Academic Press, San
Diego, 2000, vol. 12, pp. 183–210; ( f ) T. Matsui, M. Furukawa,
M. Unno, T. Tomita and M. Ikeda-Saito, J. Biol. Chem., 2005, 280,
2981–2989; (g) M. Unno, T. Matsui and M. Ikeda-Saito, Nat. Prod.
Rep., 2007, 24, 553–570.
complexes by treatment with 1 (Fig. S28 in the ESI†). To
examine whether or not the conversion of 1 to 2 is due to the
strong electron-donating ability of the axial ligand, we studied
the reaction of 1 with 1,5-dicyclohexylimidazole (1,5-Cy2Im),
which has a similar strong electron-donating ability to that of
1,2-Me2Im. Single-crystal X-ray analysis and elemental analysis
clearly showed that the reaction product is not a Co(III)-ampord-
type complex, but [CoIII(lpp)(1,5-Cy2Im)] (3) (page 5 and Fig. S3–S5
in the ESI†). This result means that the formation of 2 in this
system is not due to stronger electron donation from the axial
ligand, but most likely is due to the steric effect of the methyl
groups of 1,2-Me2Im.
To obtain insight into the steric effects of the 1,2-Me2Im on
the reactivity of 1 toward O2, structures of [CoII(amtpp)B] (1ÁB)
(B = 1-MeIm and 1,2-Me2Im) were estimated by density func-
tional theory (DFT) calculations at the B3LYP/6-31G* level.9
Their optimized structures are shown in Fig. S29 (ESI†). For
1Á1-MeIm, although the phenyl group in the position trans to
the benzamide bends down slightly, the conjugating porphyrin
framework including four meso-carbon atoms remains planar.
In contrast, for 1Á1,2-Me2Im, the porphyrin framework signifi-
cantly deviates from planarity because of the steric repulsion
from the methyl group of 1,2-Me2Im in the 2-position. The two
cis-meso-carbon atoms bend down from the porphyrin plane,
while the trans-meso-carbon site bends up from the plane.
Selective hydroxylation at the trans-meso-carbon atom induced
by 1,2-Me2Im in this system would be due to the approach of
the trans-meso-carbon atom to the activated O2 species, and the
separation of the cis-meso-carbon atom from the activated O2
species. It is likely that terminal oxygen of the activated O2
molecule is a source of a hydroxyl group which was introduced
to the meso-carbon, and the residual oxygen would be the
source of OHÀ bound at the Co(III) site.
3 (a) Y. Watanabe, in The Porphyrin Handbook, ed. K. M. Kadish,
K. M. Smith and R. Guilard, Academic Press, San Diego, 2000, vol.
4, pp. 97–117; (b) M. Sono, M. P. Roach, E. D. Coulter and
J. H. Dawson, Chem. Rev., 1996, 96, 2841–2887.
´
4 C. K. Chang, G. Aviles and N. Bag, J. Am. Chem. Soc., 1994, 116,
12127–12128.
5 (a) J. P. Collman, R. Boulatov, C. J. Sunderland and L. Fu, Chem. Rev.,
2004, 104, 561–588; (b) A. L. Balch, Coord. Chem. Rev., 2000, 200–202,
349–377; (c) J. P. Collman, R. R. Gagne, R. R. T. R. Halbert, J. C.
Marchon and C. A. Reed, J. Am. Chem. Soc., 1973, 95, 7868–7870;
(d) J. P. Collman, R. R. Gagne, C. A. Reed, W. T. Robinson and
G. A. Rodley, Proc. Natl. Acad. Sci. U. S. A., 1974, 71, 1326–1329;
(e) G. E. Wuenschell, C. Tetreau, D. Lavalette and C. A. Reed, J. Am.
Chem. Soc., 1992, 114, 3346–3355; ( f ) J. D. Soper, S. V. Kryatov,
E. V. Rybak-Akimova and D. G. Nocera, J. Am. Chem. Soc., 2007, 129,
5069–5075; (g) J.-G. Liu, Y. Naruta and F. Tani, Chem.–Eur. J., 2007, 13,
6365–6378; (h) J.-G. Liu, T. Ohta, S. Yamaguchi, T. Ogura, S. Sakamoto,
Y. Maeda and Y. Naruta, Angew. Chem., Int. Ed., 2009, 48, 9262–9267;
In summary, reaction of air-stable Co(II) complex 1 with O2
in the presence of 1,2-Me2Im was studied. The reaction site,
which is created by the amide group and 1,2-Me2Im at the fifth
position, activated the O2 molecule under mild conditions, and
then yielded a new Co(III)-porphodimethene-type complex 2.
Isotope-labeling experiments showed that OHÀ at the Co(III)
center and a hydroxyl group at the meso-carbon of 2 originate
from the O2 molecule. This reaction mimics the ‘‘push–pull’’ O2
activation observed in heme-containing metalloenzymes. Pre-
liminary studies on the effects of 1,2-Me2Im on selective
hydroxylation at the trans-meso-carbon were carried out using
DFT calculations. Further studies of the reaction mechanism
are currently in progress.
´
(i) I. Hijazi, T. Roisnel, M. Fourmigue, J. Weiss and B. Boitrel, Inorg.
Chem., 2010, 49, 3098–3100; ( j) M. T. Kieber-Emmons, M. F. Qayyum,
Y. Li, Z. Halime, K. O. Hodgson, B. Hedman, K. D. Karlin and
E. I. Solomon, Angew. Chem., Int. Ed., 2012, 51, 168–172.
6 K. Yamanishi, M. Miyazawa, T. Yairi, S. Sakai, N. Nishina, Y. Kobori,
M. Kondo and F. Uchida, Angew. Chem., Int. Ed., 2011, 50, 6583–6586.
7 (a) M. Harmjanz, H. S. Gill and M. J. Scott, J. Am. Chem. Soc., 2000, 122,
10476–10477; (b) M. Harmjanz and M. J. Scott, Chem. Commun., 2000,
397–398; (c) M. Harmjanz, H. S. Gill and M. J. Scott, J. Org. Chem., 2001,
´
66, 5374–5383; (d) H. S. Gill, M. Harmjanz, J. Santamarıa, I. Finger and
M. J. Scott, Angew. Chem., Int. Ed., 2004, 43, 485–490.
8 CCDC 908586 (3) and 908587 (2). Single crystal data; 2Á2CHCl3:
C52H40Cl6CoN7O3, M = 1082.58, monoclinic, P21/n, a = 10.7642(5) Å, b =
20.7043(12) Å, c = 22.5542(12) Å, b = 96.087(3)1, V = 4998.2(5) Å3, T = 293 K,
reflections collected/unique reflections/parameters refined: 31 876/8708/
757, Rint = 0.0556, final R1 = 0.0777 (I > 2s(I)), wR2 = 0.1395 (all data); 3Á3.
%
25CHCl3: C63.25H55.25Cl9.75CoN7O3, M = 1366.03, triclinic, P1, a
=
This work was supported by JSPS Fellowship for Young
Scientists. We thank K. Terasaki and A. Yamamoto of the
Center for Instrumental Analysis in Shizuoka University for
support in obtaining the elemental analysis data.
12.8053(7) Å, b = 12.8800(6) Å, c = 21.7874(17) Å, a = 87.958(6)1, b =
80.671(6)1, g = 62.793(4)1, V = 3150.6(4) Å3, T = 173 K, reflections collected/
unique reflections/parameters refined: 20 445/10 799/1018, Rint = 0.0364,
final R1 = 0.0538 (I > 2s(I)), wR2 = 0.1138 (all data).
9 SPARTAN ’04 for Windows, Wavefunction Inc, Irvine, CA, USA, 2004.
c
This journal is The Royal Society of Chemistry 2013
Chem. Commun.