state. The metal centre is coordinated to both terpy motifs in the
expected octahedral environment (selected Fe–N bond dis-
tances are shown in the Fig. 2 caption). Additionally, one half of
the macrocyclic cavity is occupied by an acetone molecule,
whose position is stabilised through weak electrostatic inter-
actions between the hydrogen atoms of C65 and C67 and the
oxygen atoms of the spacer linkage (all distances between C65
and C67 and oxygen atoms O1–O4 in the range 3.45–3.75
Å).
Formation of this metallomacrocycle in high yield is very
unexpected, as polymeric structures could be formed through
either coordination to the bipy motif, or through coordination of
each metal centre to binding domains of different ligand
molecules. The formation of a single thermodynamic product is
in this case remarkable due to the far greater length and
flexibility of the spacers in L compared to previously published
examples of multitopic ligands containing two terpy do-
mains.2,3
In conclusion, we have shown that the tritopic ligand L,
which contains mixed metal-binding domains connected
through large flexible spacers, self-assembles to form a
thermodynamically stable [1 + 1] metallomacrocycle in the
presence of iron(II). Current investigations involve varying the
length and flexibility of the spacer regions with a view to
regulating the assembly process.
We would like to thank the University of Birmingham for
support.
Notes and references
†
Selected data for compound 2: ESMS: m/z 627 ([M + Na]+). 1H NMR
(CDCl3, 300 MHz) d 8.92 (d, 2H, H6A), 8.49 (d, 2H, H3A), 8.02 (dd, 2H,
H4A), 7.41 (t, 2H, H5B), 7.25 (m, 2H, H6B), 7.23 (m, 2H, H2B), 6.97 (dd, 2H,
H
4B), 4.23 (t, 4H), 3.91 (t, 4H), 3.75 (m, 12H), 3.63 (t, 4H).
L. ESMS: m/z 1089 ([M + Na]+). 1H NMR (CDCl3, 500 MHz) d 8.88 (d,
2H, H6A), 8.66 (m, 4H, H6D), 8.60 (t, 4H, H3D), 8.45 (d, 2H, H3A), 8.04 (s,
4H, H3C), 7.97 (dd, 2H, H4A), 7.82 (m, 4H, H4D), 7.36 (t, 2H, H5B), 7.31 (m,
4H, H5D), 7.20 (m, 4H, H3B/H6B), 6.95 (dd, 2H, H4B), 4.40 (t, 4H), 4.21 (t,
4H), 3.93 (m, 8H), 3.80 (m, 8H).
‡ X-Ray quality crystals were obtained through diffusion of diethyl ether
into an acetone solution of the complex. Crystal data: C64H58F12Fe-
N8O8P2·C3H6O (purple prisms), M = 1471.05, monoclinic, space group
P21/n, a = 9.4845(5), b = 20.2873(12), c = 33.9574(18), b = 93.440(3),
U = 6522.1(6) Å3, T = 223(2), Z = 4, m(Cu-Ka) = 3.184 mm21. 12903
reflections measured, 7257 unique, 2216 observed with I > 2sI, R(obs.) =
cc/b2/b205233d/ for crystallographic data in CIF or other electronic
format.
Fig. 1 The aromatic region of the 500 MHz 1H NMR spectrum of a CD3CN
solution of [FeL][PF6]2 showing the assignments.
1 Comprehensive Coordination Chemistry, ed. J.-M. Lehn, volume eds. J.-
P. Sauvage and M. W. Hosseini, Pergamon, Oxford, 1996, vol 9; A. M.
W. Cargill Thompson, Coordination Chemistry Reviews, 1997, 160, 1; G.
F. Swiegers and T. J. Malefetse, Chem. Rev., 2000, 100, 3483.
2 G. U. Priimov, P. Moore, P. K. Maritim, P. K. Butalanyi and N. W.
Alcock, J. Chem. Soc., Dalton Trans., 2000, 445.
3 F. M. Romero, R. Ziessel, A. Dupont-Gervais and A. Van Dorsselaer,
Chem. Commun., 1996, 551.
4 For self-assembly of a trinuclear iron(II) complex from a ligand
containing three tpy binding domains connected through long flexible
spacers, see: E. C. Constable and D. Phillips, Chem. Commun., 1997,
827.
5 The synthesis of this compound will be presented in detail elsewhere. It
involves Suzuki coupling of 3-methoxyphenylboronic acid and 5,5A-
dibromo-2,2A-bipyridine. For the preparation of 5,5A-dibromo-2,2A-
bipyridine, see: F. M. Romero and R. Ziessel, Tetrahedron Lett., 1995,
6471.
6 E. C. Constable and M. D. Ward, J. Chem. Soc., Dalton Trans., 1990,
1405.
7 For examples of this methodology, see: E. C. Constable, C. E.
Housecroft, M. Cattalini and D. Phillips, New J. Chem., 1998, 193; U. S.
Schubert, C. Eschbaumer, O. Hien and P. R. Andres, Tetrahedron Lett.,
2001, 4705.
8 R. Chotalia, E. C. Constable, M. J. Hannon and D. A. Tocher, J. Chem.
Soc., Dalton Trans., 1995, 3571; E. C. Constable, M. J. Hannon, A. M.
W. Cargill Thompson, D. A. Tocher and J. V. Walker, Supramol. Chem.,
1993, 2, 243.
Fig. 2 X-Ray structure of the [1 + 1] metallomacrocycle showing the
encapsulated acetone molecule. Hydrogen atoms and counter ions have
been omitted. Ellipsoids are drawn at the 50% probability level. Selected
Fe–N bond distances (Å): Fe1–N1, 2.014; Fe1–N2, 1.853; Fe1–N3, 1.998;
Fe1–N4, 1.998; Fe1–N5, 1.936; Fe1–N6, 2.012.
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