Metal-organic frameworks exhibiting strong anion-π interactions

Article abstract of DOI:10.1039/b612660j

Coordination frameworks of pyridazino[4,5-d]pyridazine reveal a pronounced ability for anion-π interactions. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b612660j

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Metal–organic frameworks exhibiting strong anion–p interactions{
a
Il’ya A. Gural’skiy, Pavlo V. Solntsev, Harald Krautscheid and Konstantin V. Domasevitch*
a
b
a
Received (in Cambridge, UK) 1st September 2006, Accepted 19th October 2006
First published as an Advance Article on the web 3rd November 2006
DOI: 10.1039/b612660j
Coordination frameworks of pyridazino[4,5-d]pyridazine reveal
a pronounced ability for anion–p interactions.
In metal complexes the bicyclic N-donor typically acts as a
˚
bitopic connector bridging pairs of metal ions at 9.0–9.2 A, while
…
its p-acidity results in very characteristic direct O(anion)
p
Coordination polymers offer a significant potential for applica-
1
tions in adsorption, guest and anion recognition and sensing.
interactions and hence in elimination of counter anions from the
metal coordination environment. Unlike any of the hitherto
reported structural precedents for anion–p binding, the condensed
pyridazine has a symmetrical bicyclic structure and offers two
equivalent sites for such interactions simultaneously. Thus, in the
Their structure commonly provides binding sites for such specific
…
2
interactions as p–p stacking and XH p hydrogen bonding. The
latter reflects the ability of the p-cloud to interact with positively
polarized atoms. An electrostatic interaction between anionic
species and electron deficient heterocycles, which parallels the
˚
1D chain-like polymer [Zn(H O) (L)](NO ) 1 § (Zn–N 2.085(1) A)
2 4 3 2
each of the p-systems supports equally effective interactions with
3
above binding scheme, is also possible and very recently the
non-coordinated nitrate anions as reflected by short O–C(N)
˚
contacts (mean 3.18 A) and the situation of the oxygen atoms
3
,4
existence of anion–p interactions was proved in the solid state
5
and in solution. This effect may be significant also for
…
exactly above the centroids of the pyridazine rings (O p 2.87 A,
˚
6
biomolecule/solution interfaces, as it occurs in protein structures.
angle of the O…p axis to the plane of the aromatic cycle Q = 86.6u)
Infact, such interactions could be especially relevant for host–guest
chemistry of coordination polymers, particularly for functionali-
zation of hydrophobic crystal cavities and for the design of
(
Fig. 1). The same was observed also for [Cu(H
2: X = NO , n = 2; 3: X = ClO , n = 4) complexes. Their metal–
organic portions adopt a 2D square grid structure and each of the
2 2 2 2 2
O) (L) ]X ?nH O
(
3
4
7,8
geometrically rigid anion receptors. However, typical electron
deficient heterocycles such as 1,3,5-triazines and 1,2,4,5-tetrazines
are very weak donors and they are hardly suitable for bridging
metal ions and the generation of coordination frameworks.
As a system that combines efficient donor properties towards
transition metal ions and a pronounced ability for anion–p
interactions we have developed unsubstituted pyridazino[4,5-
d]pyridazine, which was readily accessible by a novel one-pot
synthesis involving inverse electron demand Diels–Alder cycload-
dition (Scheme 1).{ Unusual anion binding properties of the ligand
…
square meshes houses a pair of the anions forming close O
p
contacts (Fig. 1, b). The shortest ones were supported by the
˚
nitrate anions (2.83 A, Q = 88.5u), while such interactions in 3 were
˚
somewhat weaker (3.05 A, Q = 84.9u), in accordance with very low
nucleophility of the perchlorate anions. To the best of our
…
knowledge, compounds 1 and 2 display the shortest O
p
separations found as yet in crystal structures. Comparable
…
parameters (F p2.80–3.04 A) were registered only for the extreme
˚
2
electron deficient tetrazine and the AsF
6
8,10
anion.
The only
2
known precedent for such interaction of non-coordinated NO
3
may be clearly related to its electron-deficiency (LUMO energy
9
1.591 vs. 20.288 eV for the parent pyridazine), influenced also
…
p
anions (with 1,3,5-triazine cycle) revealed appreciably longer O
2
˚
˚
distances (3.20 A), while the results of an ab initio study (2.75 A; Q =
by N-coordination to such Lewis acids as metal ions.
11
8
6.2u) exactly agree with the geometry of structures 1 and 2.
Although the electron deficiency mitigates against coordination
to many metal ions, the organic module may be readily integrated
into a framework even as a N-tetradentate ligand, which offers
special potential from the design perspective. First, this could be
achieved for typical transition metal ions with the assistance of
suitable inorganic bridges (cf. hydroxo). Second, the tetradentate
function of the ligand may be disposed towards extremely soft
+
+
acids (such as Cu or Ag ) favoring efficient back-bonding and
coordination to unsaturated N atoms.
Both these approaches were suitably applicable to the generation
of 3D frameworks. For copper(II) ions, this was achieved by using
2
N-basic sulfamate anions H NSO facilitating mild hydrolysis in
2 3
Scheme 1 Synthesis of pyridazino[4,5-d]pyridazine. Reagents and con-
ditions: [a] (EtO)
2
2
CHCMCCH(OEt) , dioxane, 90 uC, 20 h; [b] 4% HCl,
6
0 uC, 30 min; [c] N
2
H
4
?H O, r.t., 1 h.
2
aqueous solution and generating the hydroxopolymer [Cu(m-OH)
L)](H NSO )?H O 4. The ligand connects two pairs of adjacent
metal ions from the infinite hydroxocopper(II) chains (Cu–O
(
2
3
2
a
Inorganic Chemistry Department, Kiev University, Volodimirska
Str.64, Kiev, 01033, Ukraine. E-mail: dk@univ.kiev.ua
˚
.95 A); each channel of the resulting 3D framework has inner
1
b
Institut f u¨ r Anorganische Chemie, Universit a¨ t Leipzig, Linn e´ straße 3,
D-04103, Leipzig, Germany
˚
dimensions of 5 6 5 A and hosts a chain of hydrogen bonded
sulfamate ions (Fig. 2). The electron-deficient character of the
{ Electronic supplementary information (ESI) available: Experimental
details. See DOI: 10.1039/b612660j
ligand was reflected by relatively long Cu–N separations (2.10, 2.11
4
808 | Chem. Commun., 2006, 4808–4810
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…
˚
Fig. 1 a) 1D chain in complex 1 showing characteristic O p (2.875(2) A)
2
interactions with nitrate anions. b) Incorporation of ClO
4
anions inside a
Fig. 2 a) Fragment of the structure of 4 showing effective cooperation of
hydroxo and pyridazine bridges and situation of the chain of hydrogen-
bonded sulfamate anions. b) Immobilization of the anions inside the
rectangular cage in structure 3 and their interaction with p-systems.
˚
and 2.39, 2.52 A) and the two most distal nitrogen atoms occupy
… …
channels by O p and N p interactions.
axial positions in a typically distorted Cu(II) coordination octahe-
dron. Actually the same framework structure was adopted by Ag(I)
2 3 3 2
ions in [Ag(m-H O)(L)](CH SO )?H O 5. The ligands connect pairs
of the adjacent metal ions from 1D aquasilver(I) chains (all four
˚
Ag–N distances are in the range 2.46–2.52; Ag–O 2.60 A) that are
exactly similar to the hydroxocopper(II) chains in 4 (Scheme 2).
The uniform framework topology in 4 and 5 is new and it is
2
4 12
related to the rare topological type ‘‘lvt’’ {4 ;8 }, with one extra
bond (m-oxo or m-aqua bridge) for half of the nodes. The overall
connectivity is a binodal four and six connected net, with the metal
atoms representing the 6-c node and the organic tetradentates the
Scheme 2 Chemically different but topologically equivalent motifs
involving infinite hydroxocopper(II) (a) and aquasilver(I) (b) chains.
2
2
2
4 2 4 5
planar 4-c node (total Schl a¨ fli symbol {3 ;6 ;7 }{3 ;4 ;6 ;7 }).
The structure of 4 reveals a very remarkable and unprecedented
mode of anion–p interaction that occurs between the fused
pyridazine functions as a double receptor for oxygen and nitrogen
sites of the anion. The dimensions of the sulfamate and
pyridazino[4,5-d]pyridazine perfectly match each other (N–O
This illustrates the possibility for even multiple O(N)…p
interactions with aromatic polycycles and development of metal–
organic arrays with multicenter aromatic receptors for anions. The
unusual ligand–sulfamate double binding may be directly
compared with the behaviour of methanesulfonate anions in the
closely related structure 5. Such analogy was also suggestive of the
˚
˚
2
.45 A vs. distance between two ring centroids 2.44 A) and this
…
…
…
facilitates effective double binding (O p + N p), in which the
lone pair (N) p attraction since the parameters for the sulfonate–
…
p interactions in both structures (5: O p 3.09 A) are very similar.
˚
corresponding distances to the pyridazine centroids (3.14 and
˚
3
.10 A) are similar to the ones observed for perchlorate (Fig. 3). It
is worth noting that localization of the nitrogen atom lone pair is
evident and it is directed towards the centre of the pyridazine cycle
The NH /CH functionalities were clearly responsible for the
2
3
orientations of the anions towards the aromatic planes (Fig. 3) and
2
…
in the case of CH SO the CH3 p interaction is rather repulsive
3
3
/S–N…p 114u, H–N…p 94 and 114u) (Table 1).
…
˚
(C p 3.97 A). Such effective lone pair p bonding itself has very
…
(
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§ Crystallographic measurements were made at 220 K using a Stoe IPDS
˚
diffractometer (Mo-Ka, l = 0.71073 A).
Crystal data: for [Zn(H O) (L)](NO ) 1: C H N O10Zn, M = 393.59,
3 2 6 12 6
2
4
¯
˚
triclinic, space group P 1, a = 6.3661(7), b = 7.5923(9), c = 8.0357(9) A, a =
3
˚
1
03.58(1), b = 103.12(1), c = 109.69(1)u, V = 334.98(7) A , Z = 1, m(Mo-
21
23
Ka) = 1.904 mm , Dcalc = 1.951 g cm , 1771 unique reflections, R1 =
.025, wR2 = 0.067.
For [Cu(H O) (L)
monoclinic, space group Cc, a = 13.1173(9), b = 13.2215(9), c = 12.0518(8)
0
2
2
2 3 2 2
](NO ) ?2H O 2: C12H16CuN10O10, M = 523.89,
3
21
˚
˚
A, b = 113.404(2)u, V = 1918.2(2) A , Z = 4, m(Mo-Ka) = 1.220 mm
,
23
D
calc = 1.814 g cm , 3769 unique reflections, R1 = 0.041, wR2 = 0.112.
For [Cu(H O) (L) ](ClO ?4H O 3: C12 20Cl CuN 14, M = 634.80,
2
2
2
4
)
2
2
H
2
8
O
¯
˚
triclinic, space group P 1, a = 7.3893(8), b = 9.0008(9), c = 9.0474(9) A, a =
3
˚
9
2.65(1), b = 107.18(1), c = 95.60(1)u, V = 570.4(1) A , Z = 1, m(Mo-Ka) =
21
23
.280 mm , Dcalc = 1.848 g cm , 2691 unique reflections, R1 = 0.028,
1
wR2 = 0.078.
For [Cu(OH)(L)](H NSO
2
3
)?H
2 6 9 5 5
O 4: C H CuN O S, M = 326.78,
monoclinic, space group P2 /c, a = 6.7875(7), b = 10.5615(9), c =
1
3
˚
˚
1
2
4.212(1) A, b = 97.57(1)u, V = 1009.9(2) A , Z = 4, m(Mo-Ka) =
21 23
.395 mm , Dcalc = 2.149 g cm , 2365 unique reflections, R1 = 0.036,
wR2 = 0.096.
For [Ag(H
orthorhombic, space group P2
2
O)(L)](CH
3
SO
3
)?H
2
O 5: C
7 4 5
H11AgN O S, M = 371.13,
1 1 1
2 2 , a = 7.4389(5), b = 10.572(1), c =
3
21
˚ ˚
14.777(1) A, V = 1162.2(2) A , Z = 4, m(Mo-Ka) = 1.934 mm , Dcalc =
23
.121 cm , 2762 unique reflections, R1 = 0.020, wR2 = 0.042.
CCDC 619868–619871 and 622647. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/b612660j
Fig. 3 Modes of the anion–p interactions in the structures of 4 (a,
2
2
2
2
H NSO
3 3 3
) and 5 (b, CH SO ): Accessibility of the lone pair influences
double p,p-binding of sulfamate.
Table 1 Geometry of the anion–p interaction in structures 4 and 5
1
C. Janiak, Dalton Trans., 2003, 2781; B. Moulton and M. J. Zaworotko,
Chem. Rev., 2001, 101, 1629.
…
…
…
X plane
˚
distance/A
Anion
involved
X
C(N)
X
distance/A
centroid
˚
a
Site
range/u
Q /u
2 G. R. Desiraju and T. Steiner, The Weak Hydrogen Bond in Structural
Chemistry and Biology. New York,Oxford University Press Inc., 1999;
P. D. Beer and P. A. Gale, Angew. Chem., Int. Ed., 2001, 40, 487;
E. A. Meyer, R. K. Castellano and F. Diederich, Angew. Chem., Int.
Ed., 2003, 42, 1210.
3 P. de Hoog, P. Gamez, I. Mutikainen, U. Turpinen and J. Reedijk,
Angew. Chem., Int. Ed., 2004, 43, 5815; J. P. Gallivan and
D. A. Dougherty, Org. Lett., 1999, 1, 103; S. Scheiner, T. Kar and
J. Pattanayak, J. Am. Chem. Soc., 2002, 124, 13257; C. Garau,
D. Qui n˜ onero, A. Frontera, P. Ballester, A. Costa and P. M. Dey a` , New
J. Chem., 2003, 27, 211; S.-i. Kawahara, S. Tsuzuki and T. Uchimaru,
Chem.–Eur. J., 2005, 11, 4458.
2
NSO
3
H
H
a
2
O
N
O
C
3.26–3.60
3.09–3.64
3.09–3.65
3.89–4.49
3.140(2)
3.101(2)
3.093(2)
3.971(3)
3.109(3)
3.013(3)
3.011(2)
3.861(3)
81.9
76.3
76.8
76.5
2
3
CSO
3
…
Angle of the X p axis to the plane of the aromatic cycle.
little precedent in the literature; in particular it was involved
as a stabilizing factor for sugar–nucleobase intramolecular
13
interactions.
4
Ya. S. Rosokha, S. V. Lindeman, S. V. Rosokha and J. K. Kochi,
Angew. Chem., Int. Ed., 2004, 43, 4650; S. Demeshko, S. Dechert and
F. Meyer, J. Am. Chem. Soc., 2004, 126, 4508; A. Frontera,
F. Saczewski, M. Gdaniec, E. Dziemidowicz-Borys, A. Kurland,
P. M. Deya, D. Qui n˜ onero andC. Garau, Chem.–Eur. J., 2005, 11, 6560.
O. B. Berryman, F. Hof, M. J. Hynes and D. W. Johnson, Chem.
Commun., 2006, 506.
T. Steiner, Biophys. Chem., 2002, 95, 195; M. Egli, in Neutron
macromolecular crystallography at the spallation neutron source,
Workshop report, Argonne National Laboratory, Agronne, IL, USA,
In conclusion, the ability of the pyridazine compounds for
anion–p interactions provides an attractive structural prototype
and a unique p-bifunctional building block for novel polymeric
and molecular anion receptors. The system reported herein is
important for solid-state modelling of 4 + 1 cycloaddition
reactions, similar to those that occur between tetrazines and
5
6
1
4
isocyanides. Our results demonstrate also a useful methodology
for annelation of pyridazine cycles and provide the easiest chemical
2003, p. 24.
15
access to the pyridazino[4,5-d]pyridazine frame.
7 M. Mascal, Angew. Chem., Int. Ed., 2006, 45, 2890; M. Mascal,
A. Armstrong and M. D. Bartberger, J. Am. Chem. Soc., 2002, 124,
The authors acknowledge support from Deutsche Forschungs-
gemeinschaft, grant UKR 17/1/06 (HK and KVD).
6274; C. Garau, D. Qui n˜ onero, A. Frontera, A. Costa, P. Ballester and
P. M. Dey a` , Chem. Phys. Lett., 2003, 370, 7.
8
9
B. L. Schottel, H. T. Chifotides, M. Shatruk, A. Chouai, L. M. Perez,
J. Bacsa and K. R. Dunbar, J. Am. Chem. Soc., 2006, 128, 5895.
N. Haider, Tetrahedron, 1991, 47, 3959; N. Haider, Acta Chim. Slov.,
1994, 41, 205.
Notes and references
{
Pyridazino[4,5-d]pyridazine. A solution of 5.83 g (71 mmol) 1,2,4,5-
tetrazine and 15.30 g (66 mmol) acetylenedialdehyde tetraethyl acetal in
0 mL of dry dioxane was stirred at 90 uC for 20 h and then evaporated
in vacuo. The dark residue was dissolved in 100 mL of 4% HCl and stirred
at 60 uC for 30 min, after which 10 mL of N ?H O was added and
10 B. L. Schottel, J. Basca and K. R. Dunbar, Chem. Commun., 2005, 46.
11 P. U. Maheswari, B. Modec, A. Pevec, B. Kozlev cˇ ar, C. Massera,
P. Gamez and J. Reedijk, Inorg. Chem., 2006, 45, 6637.
12 B. Rather, B. Moulton, R. D. B. Walsh and M. J. Zaworotko, Chem.
Commun., 2002, 694; L. Carlucci, N. Cozzi, G. Ciani, M. Moret,
D. M. Proserpio and S. Rizzato, Chem. Commun., 2002, 1354; I. Boldog,
E. B. Rusanov, A. N. Chernega, J. Sieler and K. V. Domasevitch,
J. Chem. Soc., Dalton Trans., 2001, 893.
13 S. Sarkhel, A. Rich and M. Egli, J. Am. Chem. Soc., 2003, 125, 8998;
I. Berger and M. Egli, Chem.–Eur. J., 1997, 3, 1400.
14 P. Imming, R. Mohr, E. M u¨ ller, W. Overheu and G. Seitz, Angew.
Chem., 1982, 94, 291.
8
2
H
4
2
stirring was continued for an additional hour. The black solution was
extracted with 30 6 200 mL chloroform and the extracts were evaporated
to dryness. The solid was sublimed (180 uC, 0.2 Torr) and then crystallized
from methanol yielding pure product (4.54 g, 52%) as faintly yellow
needles.
Coordination compounds were prepared from aqueous solutions of the
components. In a typical synthesis, a solution of 0.031 g (0.1 mmol) of
Cu(H
was slowly evaporated over a period of 7–8 d yielding green prisms of
Cu(OH)(L)](H NSO )?H O 4 (0.023 g, 70%).
2 3 2 2
NSO ) ?3H O and 0.016 g (0.12 mmol) of the ligand in 3 mL water
15 G. Adembri, F. De Sio, R. Nesi and M. Scotton, Chem. Commun., 1967,
1006.
[
2
3
2
4
810 | Chem. Commun., 2006, 4808–4810
This journal is ß The Royal Society of Chemistry 2006