Engineering new metal-organic frameworks built from flexible tetrapyridines coordinated to Cu(II) and Cu(I)

Article abstract of DOI:10.1021/ic8019809

A series of new metal-organic frameworks have been constructed by the coordination of Cu(II) and Cu(I) with pentaerythrityl tetrakis(4-pyridyl) ether (1 = PETPE), a flexible tetradentate ligand. Networks derived from Cu(OOCCH ₃)₂, Cu

Full text of DOI:10.1021/ic8019809

Inorg. Chem. 2009, 48, 2793-2807
Engineering New Metal-Organic Frameworks Built from Flexible
Tetrapyridines Coordinated to Cu(II) and Cu(I)
Patrick E. Ryan, Christophe Lescop, Dominic Laliberte´, Tamara Hamilton, Thierry Maris,
and James D. Wuest*
De´partement de Chimie, UniVersite´ de Montre´al, Montre´al, Que´bec H3C 3J7, Canada
Received October 16, 2008
A series of new metal-organic frameworks have been constructed by the coordination of Cu(II) and Cu(I) with
pentaerythrityl tetrakis(4-pyridyl) ether (1 ) PETPE), a flexible tetradentate ligand. Networks derived from
Cu(OOCCH3)2, Cu(NO3)2, and CuBF4 proved to have different topologies (diamondoid, PtS, and SrAl2, respectively).
This reflects (1) the ability of PETPE (1) to adopt diverse conformations and (2) the varied geometries of complexes
of Cu(II) and Cu(I). Extended PETPE (2), a tetrapyridine with phenyl spacers inserted into the pentaerythrityl core
of PETPE (1), yielded an expanded version of the PtS network derived from simple PETPE (1) and Cu(NO3)2.
However, increases in the ability of the network to accommodate guests were largely offset by interpenetration of
independent networks. Attempts to thwart interpenetration by converting ligand 2 into methyl-substituted derivative
3 led to the construction of networks with alternative topologies. In particular, the reactions of ligand 3 with both
Cu(II) and Cu(I) yielded isostructural Pt3O4 networks, despite the preference of the two oxidation states for coordination
spheres with different geometries. Together, these observations demonstrate that PETPE (1) and related compounds
are useful ligands for constructing metal-organic frameworks, with a distinctive ability to accommodate a single
metal in different oxidation states, as well as to adapt to a metal in a single oxidation state but with different
counterions or secondary ligands.
Introduction
Nevertheless, important progress is being made in the
effort to create new molecular materials by design. In
particular, noteworthy advances have occurred in the field
of engineering crystalline materials built from carefully
selected molecular components. This work has demonstrated
that molecular subunits for the purposeful construction of
crystalline materials are particularly effective when they have
the following features: (1) They incorporate multiple sites
of strong directional intermolecular interactions; and (2) they
hold these sites in particular orientations that favor the
assembly of networks in which each molecule is positioned
predictably with respect to its neighbors.2-4 Interactions that
have proven to be especially suitable for engineering
crystalline materials of this type include hydrogen bonds and
coordinative bonds to metals. Many simple functional groups
that engage in reliable motifs of hydrogen bonding or
coordination to metals can be incorporated in molecules with
A major challenge in science today is to learn how to
prepare new molecular materials with predetermined struc-
tures and properties. Reaching this objective will require
advances in basic science, and it will create opportunities
for breakthroughs in many areas of technology. Unfortu-
nately, developing the necessary understanding remains an
elusive goal, in part because the forces that position
molecules and help determine their collective properties are
complex and hard to control. In general, the structures and
properties of materials are impossible to predict reliably, even
when the most powerful current computational techniques
are used.1
* To whom correspondence should be addressed. E-mail: james.d.wuest@
umontreal.ca.
(1) For examples of recent efforts to use ab initio methods to predict the
structures and properties of molecular crystals, see: Neumann, M. A.;
Leusen, F. J. J.; Kendrick, J. Angew. Chem., Int. Ed. 2008, 47, 2427–
2430. Misquitta, A. J.; Welch, G. W. A.; Stone, A. J.; Price, S. L.
Chem. Phys. Lett. 2008, 456, 105–109. Trolliet, C.; Poulet, G.; Tuel,
A.; Wuest, J. D.; Sautet, P. J. Am. Chem. Soc. 2007, 129, 3621–3626.
(2) For recent references to studies of molecular networks held together
by hydrogen bonds, see: Wuest, J. D. Chem. Commun. 2005, 5830–
5837. Hosseini, M. W. Acc. Chem. Res. 2005, 38, 313–323.
10.1021/ic8019809 CCC: $40.75  2009 American Chemical Society
Inorganic Chemistry, Vol. 48, No. 7, 2009 2793
Published on Web 03/09/2009

Ryan et al.
Scheme 1
diverse geometries, thereby creating countless opportunities
to make new crystalline materials with different composi-
tions, architectures, and properties.
Close conceptual analogies exist between molecular
networks held together by coordinative interactions with
metals, which can have a significant degree of covalent
character, and networks maintained by non-covalent interac-
tions such as hydrogen bonds. Despite underlying similarities,
however, development of the two classes of materials has
tended to occur within the separate confines of inorganic
chemistry and organic chemistry. This approach has empha-
sized how the materials are different, rather than how they
are alike. These circumstances create an attractive op-
portunity to engineer new crystalline materials using an
integrated approach in which understanding of inorganic
chemistry and organic chemistry plays equally important
roles.
Scheme 2
To test the ability of this hybrid approach to yield new
insights, we have begun to explore the coordination chemistry
of pentaerythrityl tetrakis(4-pyridyl) ether (1),5 which will
be referred to as PETPE. PETPE is a flexible tetradentate
other metals in the future. Our work blends inorganic
chemistry and organic chemistry in equal measure, and the
results illustrate how studies in which coordination chemistry
is combined with sophisticated molecular design and syn-
thesis can be productive sources of new insights and hybrid
materials with unusual properties.
Results and Discussion
Synthesis of Tetrapyridines 1-3. PETPE (1) was previ-
ously prepared by converting pentaerythritol into the corre-
sponding tetratosylate,7 which was then heated with 4-hy-
droxypyridine in the presence of base.5 We prepared
tetrapyridine 1 in 86% yield in a single step by treating
4-chloropyridinium chloride with pentaerythritol in the
presence of excess KOH. Extended PETPE (2) was synthe-
sized in 73% yield by Suzuki coupling of the previously
reported tetraboronic acid 48 with 4-bromopyridine (Scheme
1). By the route summarized in Scheme 2, substituted
extended analogue 3 was synthesized in three steps in an
overall yield of 54%. Suzuki coupling of 4-bromopyridine
with (4-methoxy-2-methylphenyl)boronic acid provided 4-(4-
methoxy-2-methylphenyl)pyridine (5) in 85% yield. De-
methylation of intermediate 5 under standard conditions
(HBr/CH3COOH) occurred in 70% yield to give the corre-
sponding phenol 6,9 which was converted into target
compound 3 in 90% yield by treatment with pentaerythrityl
tetratosylate7 in the presence of NaOH.
ligand that has not previously been used to bind metals. In
addition, we have subjected its structure to rational modifica-
tions designed to produce metal-organic frameworks with
new features. In particular, phenyl spacers were inserted into
the pentaerythrityl core of PETPE (1) to create analogue 2,
a precursor of expanded frameworks, and substituted ex-
tended derivative 3 was prepared to thwart intermolecular
aromatic interactions and thereby alter molecular packing.
In this paper, we report the structures and properties of a
series of nine complexes produced when ligands 1-3 bind
Cu(II) and Cu(I),6 and we will describe the coordination of
(3) For recent references to studies of networks linked by coordination to
metals, see: Shimizu, G. K. H. J. Solid State Chem. 2005, 178, 2519–
2526. Hill, R. J.; Long, D.-L.; Champness, N. R.; Hubberstey, P.;
Schro¨der, M. Acc. Chem. Res. 2005, 38, 337–350. Fe´rey, G.; Mellot-
Draznieks, C.; Serre, C.; Millange, F. Acc. Chem. Res. 2005, 38, 217–
225. Ockwig, N. W.; Delgado-Friedrichs, O.; O’Keeffe, M.; Yaghi,
O. M. Acc. Chem. Res. 2005, 38, 176–182. Kitigawa, S.; Uemura, K.
Chem. Soc. ReV. 2005, 34, 109–119. Rosseinsky, M. J. Microporous
Mesoporous Mater. 2004, 73, 15–30. Janiak, C. Dalton Trans 2003,
2781–2804. James, S. L. Chem. Soc. ReV. 2003, 32, 276–288. Robson,
R. J. Chem. Soc., Dalton Trans. 2000, 3735–3744.
Structures of Networks Produced by Treating
PETPE (1) with Cu(OOCCH3)2, Cu(NO3)2, and CuBF4.
Slow mixing of an ethanolic solution of tetrapyridine 1 with
a methanolic solution of Cu(OOCCH3)2 produced deep blue
(4) Brammer, L. Chem. Soc. ReV. 2004, 33, 476–489. Moulton, B.;
Zaworotko, M. J. Chem. ReV. 2001, 101, 1629–1658.
(5) St. Pourcain, C. B.; Griffin, A. C. Macromolecules 1995, 28, 4116–
4121.
(7) Shostakovskii, M. F.; Atavin, A. S.; Mirskova, A. N. Zh. Obshch.
Khim. 1965, 35, 804–807.
(6) For a review of the coordination chemistry of Cu, see: Hathaway,
B. J. In ComprehensiVe Coordination Chemistry; Wilkinson, G.,
Gillard, R. D., McCleverty, J. A., Eds.; Pergamon: Oxford, 1987; Vol.
5, pp 533-594.
(8) Laliberte´, D.; Maris, T.; Wuest, J. D. J. Org. Chem. 2004, 69, 1776–
1787.
(9) Diemer, V.; Chaumeil, H.; Defoin, A.; Fort, A.; Boeglin, A.; Carre´,
C. Eur. J. Org. Chem. 2006, 2727–2738.
2794 Inorganic Chemistry, Vol. 48, No. 7, 2009

Metal-Organic Frameworks Built from Flexible Tetrapyridines
Table 1. Crystallographic Data for Complexes of PETPE (1) with Salts of Cu(II) and Cu(I)
complex with
Cu(OOCCH3)2
Cu(NO3)2
CuBF4
solvent of crystallization
crystal system
space group
a (Å)
b (Å)
c (Å)
CH3CH2OH/CH3OH/H2O
tetragonal
I41/a
22.782(3)
22.782(3)
9.804(12)
90
5089(2)
1.431
4
CH3CH2OH/H2O
orthorhombic
Cccm
9.0229(3)
21.6107(8)
24.0491(9)
90
4689.4(3)
1.406
4
CH2Cl2/CH3CN
monoclinic
C2/c
14.272(2)
24.516(4)
21.640(3)
97.075(4)
7514.0(19)
1.292
ꢀ (deg)
V (Å3)
Dcalc (g cm-3
)
Z
4
temperature (K)
unique
290(2)
2409
223(2)
2404
223(2)
7145
observed (I > 2σ(I))
parameters
2396
154
2061
149
7085
458
restraints
2
7
19
a
R1 (I > 2σ(I))
0.0792
0.1819
0.0932
0.2115
0.947
0.0940
0.2219
0.0945
0.2226
1.138
0.0781
0.1828
0.0849
0.2321
1.106
b
wR2 (I > 2σ(I))
a
R1 (all data)
b
wR2 (all data)
GoFc
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. wR2 ) {∑[w(Fo - Fc2)2]/∑w(Fo )2}1/2
.
GoF ) {∑[w(Fo - Fc2)2]/(n - p)}1/2, where n is the number of reflections and
b
c
2
2
2
p is the total number of parameters refined.
Figure 1. Partial view of the structure of crystals of the complex of Cu(OOCCH3)2 and PETPE (1) grown from CH3CH2OH/CH3OH/H2O. Thermal displacement
ellipsoids are drawn at the 50% probability level, and hydrogen atoms are represented by a sphere of arbitrary size. Atoms of hydrogen appear in white,
carbon in gray, nitrogen in blue, oxygen in red, and Cu(II) in bronze. Molecules of guests not bonded to Cu(II) are omitted. Key bond lengths include
Cu1-N1 ) 2.0168(9) Å, Cu1-O2 ) 1.9732(13) Å, and Cu1-O4 ) 2.589(1) Å.
crystals suitable for analysis by X-ray diffraction. The
crystals proved to have the approximate composition
[Cu2(1)(OOCCH3)4(H2O)4] · 20H2O.10 Crystallographic data
appear in Table 1, and views of the structure are shown in
Figures 1-3. Figure 1 reveals that the coordination sphere
of Cu(II) is approximately octahedral, with bond angles in
the range 86.67(5)-93.33(5)° and trans-oriented pairs of
bound pyridyl groups, water, and monodentate acetate.
Observed lengths for the Cu-N and Cu-O bonds are similar
to those found in related complexes of Cu(II).11 Pronounced
lengthening of the diaxial C-OH2 bonds is a manifestation
of Jahn-Teller distortion, a characteristic structural feature
resulting from the d9 electronic configuration of Cu(II).12
In its complex with Cu(OOCCH3)2, inherently flexible
ligand 1 adopts a conformation that holds four pyridyl groups
in a highly distorted tetrahedral orientation. The distortion
can be assessed by comparing the N · · · Ccore · · ·N angles
defined by the central carbon atom of the pentaerythrityl core
(Ccore) and the nitrogen atoms of the pyridyl groups. These
angles are 4 × 124.58(6)° and 2 × 82.23(6)°, showing that
ligand 1 deviates significantly from tetrahedral geometry.
Similar distortions have been observed in other pentaeryth-
rityl tetraaryl ethers.8,13 The -CH2O- spacers that connect
each pyridyl group to the core adopt conformations that are
nearly fully extended, with Ccore-CH2-O-C dihedral angles
(10) The indicated composition shows only those components of the crystal
that were at least partially ordered and were identified unambiguously
by X-ray diffraction. The crystal also includes an undetermined amount
of disordered guests.
(11) Marin, G.; Andruh, M.; Madalan, A. M.; Blake, A. J.; Wilson, C.;
Champness, N. R.; Schro¨der, M. Cryst. Growth Des. 2008, 8, 964–
975. Du, M.; Jiang, X.-J.; Zhao, X.-J.; Cai, H.; Ribas, J. Eur. J. Inorg.
Chem. 2006, 1245–1254. Chan, C.-W.; Mingos, D. M. P.; White,
A. J. P.; Williams, D. J. Polyhedron 1996, 15, 1753–1767. Cameron,
A. F.; Taylor, D. W.; Nuttal, R. H. J. Chem. Soc., Dalton Trans. 1972,
1603–1608.
(12) Cotton, F. A.; Wilkinson, G.; Murillo, C. A.; Bochmann, M. AdVanced
Inorganic Chemistry; Wiley-Interscience: New York, 1999, pp.
854-876.
Inorganic Chemistry, Vol. 48, No. 7, 2009 2795

Ryan et al.
Figure 3. Representation of the structure of crystals of the complex of
Cu(OOCCH3)2 and PETPE (1) grown from CH3CH2OH/CH3OH/H2O. The
structure is viewed along the c axis and shows a 3 × 3 × 3 array of unit
cells. Acetate and H2O bound to Cu(II) are omitted for clarity, as are
uncoordinated guests. Atoms are represented by spheres of van der Waals
radii to show the cross sections of the channels. Atoms of hydrogen appear
in white, carbon in gray, nitrogen in blue, oxygen in red, and Cu(II) in
bronze.
standard methods.15-17 The guests occupy parallel channels
that run along the c axis and have cross sections that are
approximately 8.5 × 8.5 Å2 (Figure 3).18
To assess the effect of replacing acetate by another anion,
we allowed an ethanolic solution of PETPE (1) to mix slowly
with an aqueous solution of Cu(NO3)2. This yielded violet
crystals suitable for analysis by X-ray diffraction. The
crystals were found to have the approximate composition
[Cu(1)(NO3)2]·20H2O.10 Crystallographic data are provided
in Table 1, and views of the structure appear in Figures 4-6.
Figure 4 reveals that Cu(II) binds four pyridyl groups
contributed by different molecules of ligand 1, yielding a
distorted octahedral metal center with N-Cu-N angles of
2 × 88.73(15)° and 2 × 90.42(15)° and Cu-N bonds of
normal length.11 Two nitrate ions that are 2-fold disordered
Figure 2. (a) Partial view of the distorted diamondoid network found in
crystals of the complex of Cu(OOCCH3)2 and PETPE (1) grown from
CH3CH2OH/CH3OH/H2O. Atoms of hydrogen appear in white, carbon in
gray, nitrogen in blue, oxygen in red, and Cu(II) in bronze. Acetate and
H2O bound to Cu(II) are omitted for clarity, as are uncoordinated guests.
(b) Representation of the 5-fold interpenetration of networks, with nodes
(small spheres) and linkers (large spheres) corresponding to the central
carbon atom of the pentaerythrityl core of ligand 1 and to Cu(II),
respectively.
(14) For discussions of interpenetration in networks, see: Batten, S. R.
CrystEngComm 2001, 3, 76–82. Batten, S. R.; Robson, R. Angew.
Chem., Int. Ed. 1998, 37, 1460–1494.
of 174.65(6)°. However, this extension does not continue
across the central carbon atom (Ccore), and the key
CH2-Ccore-CH2-O dihedral angles are 70.16(4)°.
(15) We estimate the percentage of volume accessible to guests by using
the PLATON program.16 PLATON calculates the accessible volume
by allowing a spherical probe of variable radius to roll over the van
der Waals surface of the network. PLATON uses a default value of
1.20 Å for the radius of the probe, which is an appropriate model for
small guests such as water. The van der Waals radii used to define
surfaces for these calculations are as follows: C, 1.70 Å; H, 1.20 Å;
N, 1.55 Å; O, 1.52 Å; and Cu, 2.32 Å. If V is the volume of the unit
cell and Vg is the guest-accessible volume as calculated by PLATON,
then the porosity P in % is given by 100Vg/V.
Binding of PETPE (1) to Cu(II) thereby defines a three-
dimensional network that has a distorted diamondoid archi-
tecture, as shown in Figure 2a. Within this network, the
central carbon atoms of ligands that share a common atom
of Cu are separated by an intertectonic Ccore · · ·Ccore distance
of 16.731(4) Å. As a result, the network is open enough to
accommodate 5-fold interpenetration (Figure 2b).14 Despite
this interpenetration, approximately 62% of the volume of
the crystals remains accessible to guests, as measured by
(16) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool; Utrecht
University: Utrecht, The Netherlands, 2001. van der Sluis, P.; Spek,
A. L. Acta Crystallogr. 1990, A46, 194–201.
(17) To allow related structures to be compared, the excluded volume was
considered to be that occupied only by Cu and the bound tetrapyridines
1-3. Other ligands, uncoordinated anions, and unbound neutral guests
were all considered to occupy potentially accessible volume.
(18) The dimensions of a channel in a particular direction correspond to
those of an imaginary cylinder that could be passed through the
hypothetical open network in the given direction in contact with the
van der Waals surface. These dimensions give the cross section at the
most narrow constriction, and they no not fully reflect the porosity of
networks with channels that are not uniform and linear.
(13) Laliberte´, D.; Maris, T.; Ryan, P. E.; Wuest, J. D. Cryst. Growth Des.
2006, 6, 1335–1340. Laliberte´, D.; Maris, T.; Demers, E.; Helzy, F.;
Arseneault, M.; Wuest, J. D. Cryst Growth Des. 2005, 5, 1451–1456.
Laliberte´, D.; Maris, T.; Wuest, J. D. CrystEngComm 2005, 7, 158–
160. Laliberte´, D.; Raymond, N.; Maris, T.; Wuest, J. D. Acta
Crystallogr. 2005, E61, o601-o603.
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Metal-Organic Frameworks Built from Flexible Tetrapyridines
Figure 6. Representation of the structure of crystals of the complex of
Cu(NO3)2 and PETPE (1) grown from CH3CH2OH/H2O. The structure is
viewed along the a axis and shows a 2 × 2 × 3 array of unit cells. Nitrate
and neutral guests are omitted for clarity, and atoms are represented by
spheres of van der Waals radii to show the cross sections of the channels.
Atoms of hydrogen appear in white, carbon in gray, nitrogen in blue, oxygen
in red, and Cu(II) in bronze.
Figure 4. Partial view of the structure of crystals of the complex of
Cu(NO3)2 and PETPE (1) grown from CH3CH2OH/H2O. Thermal displace-
ment ellipsoids are drawn at the 50% probability level, and hydrogen atoms
are represented by a sphere of arbitrary size. Only two orientations of the
disordered nitrates are displayed, and molecules of guests are omitted. Atoms
of hydrogen appear in white, carbon in gray, nitrogen in blue, oxygen in
red, and Cu(II) in bronze. Key bond lengths include Cu1-N2 ) 2.036(3)
Å and Cu1-O11 ) 2.628(6) Å.
open PtS network (Figure 5).19,20 In this network, the central
carbon atoms of adjacent ligands bonded to a common atom
of Cu are separated by an intertectonic Ccore · · ·Ccore distance
of 16.784(9) Å, and the Cu · · · Cu distance spanned by a
single ligand is 16.166(9) Å. No interpenetration is observed.
The resulting network defines parallel channels that run along
the a axis and have cross sections of approximate dimensions
6.4 × 7.3 Å2 (Figure 6).18 Approximately 63% of the volume
of the crystals is accessible to disordered nitrate and neutral
guests.15-17
Together, these results show how alterations of the
coordination sphere of Cu(II) can be accommodated by the
intrinsic flexibility of tetrapyridine 1, which is able to produce
highly open networks with distinctly different architectures.
To induce further alterations, we replaced Cu(II) by Cu(I),
which often displays a tetrahedral arrangement of ligands.6
Slow mixing of a solution of PETPE (1) in CH2Cl2 with a
solution of Cu(CH3CN)4BF4 in CH3CN provided yellow
crystals suitable for analysis by X-ray diffraction (Table 1,
Figures 7-9). The crystals proved to have the approximate
composition [Cu(1)(BF4)] ·2CH3CN ·3H2O.10 Figure 7 shows
that Cu(I) binds four pyridyl groups provided by different
molecules of ligand 1, yielding a complex with a distorted
tetrahedral geometry. The N-Cu-N angles range from
101.82(3)° to 122.78(2)°, and the average length of the
Figure 5. Representation of the PtS network found in crystals of the
complex of Cu(NO3)2 and PETPE (1) grown from CH3CH2OH/H2O. Nodes
in the network correspond to the central carbon atom of ligand 1 (gray
spheres) and to Cu(II) (bronze spheres).
complete the sphere of coordination of Cu(II), with C-O
bonds elongated by Jahn-Teller distortion.12
The conformation adopted by PETPE (1) is substantially
different from the one observed in its complex with Cu(OOC-
CH3)2. Again, the -CH2O- spacers that connect each pyridyl
group to the core adopt conformations that are nearly fully
extended,withCcore-CH2-O-Cdihedralanglesof-176.6(3)°.
In the complex with Cu(NO3)2, however, this extension
continues across the central carbon atom (Ccore), giving two
almost fully extended C-O-CH2-Ccore-CH2-O-C chains
that lie in orthogonal planes. As a result, ligand 1 adopts a
flattened conformation in which the N · · · Ccore · · · N angles
are 2 × 88.68(4)°, 2 × 97.85(4)°, and 2 × 152.48(4)°.
In combination, the characteristic flattened geometry of
PETPE (1) and the square-planar arrangement of pyridyl
groups in the coordination sphere of Cu(II) give rise to an
(19) For a description of a network of PtS topology prepared by the reaction
of Cu(NO3)2 with a tetrapyridine related to ligand 1, see: Na¨ttinen,
K. I.; Rissanen, K. Inorg. Chem. 2003, 42, 5126–5134.
(20) For references to other metal-organic frameworks that adopt the PtS
topology, see: Zhao, H.; Qu, Z.-R.; Ye, Q.; Wang, X.-S.; Zhang, J.;
Xiong, R.-G.; You, X.-Z. Inorg. Chem. 2004, 43, 1813–1815.
Inorganic Chemistry, Vol. 48, No. 7, 2009 2797

Ryan et al.
tion chemistry, by allowing them to accommodate (1) various
metals, (2) a single metal in different oxidation states, or
(3) a metal in a single oxidation state but with different
counterions or secondary ligands, which can have profound
effects on the geometry of coordination and on the topology
of the resulting networks.22,23
Structures of Networks Produced by Treating
Extended PETPE (2) with Cu(NO3)2 and CuBF4. To
further probe the usefulness of flexible multidentate ligands
for engineering coordination networks, we synthesized
tetrapyridine 2, which extends the Ccore · · · N distance in
PETPE (1) by the insertion of a phenyl spacer. Our goal
was to crystallize complexes of analogue 2 with the same
three representative salts of Cu(II) and Cu(I) used previously
with ligand 1, so that the resulting structures could be
compared directly. Unfortunately, our attempts to grow
crystals of a complex of extended PEPTE (2) with Cu(OOC-
CH3)2 were unsuccessful, but after significant effort we were
able to crystallize complexes with Cu(NO3)2 and CuBF4.
Slow mixing of a solution of compound 2 in DMF with
an aqueous solution of Cu(NO3)2 produced blue crystals
suitable for analysis by X-ray diffraction (Table 2, Figures
10-12). The crystals proved to have the approximate
composition [Cu(2)(H2O)2](NO3)2 ·2DMF·6H2O.10 Figure 10
shows that the coordination sphere of Cu(II) is approximately
octahedral, with bond angles in the range 87.5(4)-92.5(4)°.
The nitrogen atoms of four bound pyridyl groups derived
from different molecules of ligand 2 lie in a single plane,
and the coordination sphere is completed by two molecules
of water bound in a trans-diaxial orientation. The average
lengths of the Cu-N bonds (2.024(12) Å) and Cu-O bonds
(2.450(20) Å) have normal values.11 The diaxial Cu-O
bonds are lengthened conspicuously by Jahn-Teller distor-
tion.12
Extended analogue 2 adopts a conformation that holds the
four pyridyl groups in an irregular orientation, as shown by
N · · · Ccore · · · N angles of 69.6(4)°, 77.7(4)°, 2 × 129.5(4)°,
and 2 × 129.9(4)°. The -CH2O- spacers that connect each
pyridylphenyl group to the core adopt conformations that
are substantially extended, with Ccore-CH2-O-C dihedral
angles of 2 × 162.2(11)° and 2 × 165.1(14)°. However, this
extension does not continue across the central carbon atom
(Ccore), and the key CH2-Ccore-CH2-O dihedral angles are
2 × 67.2(13)° and 2 × 64.2(13)°. The resulting conformation
is closely analogous to the one adopted by PETPE (1) itself
in its complex with Cu(NO3)2.
Figure 7. Partial view of the structure of crystals of the complex of CuBF4
and PEPTE (1) grown from CH2Cl2/CH3CN. Thermal displacement el-
lipsoids are drawn at the 50% probability level, and hydrogen atoms are
represented by a sphere of arbitrary size. Atoms of hydrogen appear in
white, carbon in gray, nitrogen in blue, oxygen in red, and Cu(I) in bronze.
Anions and neutral guests are omitted. Key bond lengths include Cu1-N15
) 2.0833(7) Å, Cu1-N25 ) 2.0091(6) Å, Cu1-N35 ) 2.0095(6) Å, and
Cu1-N45 ) 2.1090(8) Å.
Cu-N bonds has a normal value (2.052(7) Å).21 In its Cu(I)
complex, PETPE (1) adopts a conformation unlike either of
those observed in its networks with Cu(II). The -CH2O-
spacers that connect each pyridyl group to the core adopt
orientations that are no longer nearly fully extended, and
the Ccore-CH2-O-C dihedral angles have values ranging
from 137.92(5)° to 178.44(5)°. As a result, ligand 1 adopts
a highly irregular conformation in which the N · · · Ccore · · · N
angles vary from 54.67(4)° to 132.39(4)°.
In combination, nominally tetrahedral Cu(I) nodes and
tetradentate ligand 1 yield an SrAl2 network (Figure 8a),
which can be considered to be constructed from two types
of rings, one with a total of four four-connected nodes
(alternating Cu and Ccore) and one with eight four-connected
nodes. The average intertectonic Ccore · · · Ccore distance be-
tween molecules of ligand 1 that are bonded to a common
atom of Cu is 13.367(5) Å, making the network open enough
to accommodate 2-fold interpenetration (Figure 8b). Despite
this interpenetration, 48% of the volume of the crystals
-
remains accessible to the BF4 counterions and to neutral
guests.15-17 The most conspicuous channels run along the
ab diagonal and have a cross section of approximately 4.4
× 4.4 Å2 (Figure 9).18
The PtS architecture of the network derived from PETPE
(1) and Cu(NO3)2 arises from the combination of two key
features: (1) Binding of four pyridyl groups to octahedral
Cu(II) in a planar geometry and (2) an extended flattened
conformation of PETPE (1). These features are unsurprising
but not fully predictable, primarily because the geometry of
coordination to Cu(II) and the conformation of ligand 1 are
In forming networks held together by coordination to
metals, hydrogen bonds, and weaker interactions, PETPE (1)
and other pentaerythrityl tetraaryl ethers all display conspicu-
ous flexibility.13 This compromises their usefulness for
constructing materials with predetermined structures and
properties. In compensation, however, this flexibility gives
ligand 1 and its analogues exceptional versatility in coordina-
(21) Blake, A. J.; Champness, N. R.; Chung, S. S. M.; Li, W.-S.; Schro¨der,
M. Chem Commun. 1997, 1005–1006. MacGillivray, L. R.; Subra-
manian, S.; Zaworotko, M. J. J. Chem. Soc., Chem. Commun. 1994,
1325–1326. Nilsson, K.; Oskarsson, Å. Acta Chem. Scand. 1982, 36A,
605–610.
(22) For a related discussion of the advantages and disadvantages of
flexibility in the design of ligands for use in metallosupramolecular
chemistry, see: Steel, P. J. Acc. Chem. Res. 2005, 38, 243–250.
(23) D´ıaz, P.; Benet-Buchholz, J.; Vilar, R.; White, A. J. P. Inorg. Chem.
2006, 45, 1617–1626.
2798 Inorganic Chemistry, Vol. 48, No. 7, 2009

Metal-Organic Frameworks Built from Flexible Tetrapyridines
Figure 8. (a) Representation of the SrAl2 network found in crystals of the complex of CuBF4 and PETPE (1) grown from CH2Cl2/CH3CN. Nodes in the
network correspond to the central carbon atom of ligand 1 (gray spheres) and to Cu(I) (bronze spheres). (b) 2-fold interpenetration viewed along the a axis,
with one SrAl2 network in blue and the other in red.
Table 2. Crystallographic Data for Complexes of Extended PETPE (2)
with Salts of Cu(II) and Cu(I)
complex with
Cu(NO3)2
CuBF4
solvent of crystallization
crystal system
space group
a (Å)
DMF/H2O
orthorhombic
Pban
39.952(5)
15.031(2)
16.253(2)
9760(2)
0.835a
4
CH2Cl2/CH3CN
tetragonal
P4/n
15.2141(1)
15.2141(1)
13.2235(2)
3060.83(5)
1.271
b (Å)
c (Å)
V (Å3)
Dcalc (g cm-3
)
Z
2
temperature (K)
unique
223(2)
9235
223(2)
3148
observed (I > 2σ(I))
parameters
3458
367
3128
201
restraints
38
9
b
R1 (I > 2σ(I))
0.0645
0.0876
0.1367
0.2243
0.863
0.0422
0.0990
0.0583
0.1234
0.928
c
wR2 (I > 2σ(I))
R1b(all data)
c
Figure 9. Representation of the structure of crystals of the complex of
CuBF4 and PETPE (1) grown from CH2Cl2/CH3CN. The structure is viewed
along the ab diagonal and shows a 1 × 3 × 2 array of unit cells. Anions
and neutral guests are omitted for clarity, and atoms are represented by
spheres of van der Waals radii to show the cross sections of the channels.
Atoms of hydrogen appear in white, carbon in gray, nitrogen in blue, oxygen
in red, and Cu(I) in bronze.
wR2 (all data)
GoFd
a Calculated with no solvent included. b R1 ) ∑||Fo| - |Fc||/∑|Fo|. c wR2
) {∑[w(Fo2 - Fc2)2]/∑w(Fo )2}1/2
.
d GoF ) {∑[w(Fo2 - Fc2)2]/(n - p)}1/2
,
2
where n is the number of reflections and p is the total number of parameters
refined.
pologies have been observed but are rare.25 Increases in
porosity caused by expansion of the network formed by the
reaction of ligand 2 with Cu(NO3)2 are largely counterbal-
anced by the effects of interpenetration, and the percentage
of volume accessible to disordered nitrate ions and neutral
guests rises only from 63% to 66%.15-17 The resulting
network defines interconnected channels that are particularly
conspicuous along the a axis, the b axis, and the ab diagonal
(Figure 12).26
Slow mixing of a solution of extended PETPE (2) in
CH2Cl2/CH3CN with a solution of Cu(CH3CN)4BF4 in
CH3CN produced yellow crystals that could be analyzed by
X-ray diffraction (Table 2, Figure 13). The crystals were
found to have the approximate composition [Cu(2)(BF4)]·
known to vary widely. However, once these features are
revealed in the structure of the complex of PETPE (1) with
Cu(NO3)2, they provide a basis for expecting extended
PETPE (2) to behave in a similar way. Indeed, in the complex
derived from ligand 2 and Cu(NO3)2, four pyridyl groups
are again bound to Cu(II) in a planar array, and the resulting
network has a PtS architecture, now expanded (Figure 11).
In this network, the intertectonic Ccore · · · Ccore distance
between adjacent ligands (25.401(15) Å) is substantially
larger than it is in the PtS network derived from ligand 1
(16.784(9) Å), and the Cu · · ·Cu distance spanned by a single
ligand is increased from 16.166(9) Å to 22.838(15) Å. The
expanded network is open enough to allow 2-fold interpen-
etration (Figure 11).
(24) See the Supporting Information for details.
(25) Baburin, I. A.; Blatov, V. A.; Carlucci, L.; Ciani, G.; Proserpio, D. M.
J. Solid State Chem. 2005, 178, 2452–2474.
(26) Representations of channels were generated by the Cavities option in
the program ATOMS Version 6.2 (Shape Software, 521 Hidden Valley
Road, Kingsport, Tennessee 37663, U.S.A.; www.shapesoftware.
com).
Although the two interpenetrating networks have the same
PtS connectivity, they are not identical. Small structural
differences appear to optimize C-H · · · π aromatic interac-
tions between the networks.24 Structures consisting of
interpenetrating networks with different geometries or to-
Inorganic Chemistry, Vol. 48, No. 7, 2009 2799

Ryan et al.
Figure 10. Partial views of the structure of crystals of the complex of Cu(NO3)2 and extended PETPE (2) grown from DMF/H2O. Thermal displacement
ellipsoids are drawn at the 50% probability level, and hydrogen atoms are represented by a sphere of arbitrary size. Atoms of hydrogen appear in white,
carbon in gray, nitrogen in blue, oxygen in red, and Cu(II) in bronze. Anions and neutral guests are omitted. Key bond lengths include Cu1-N2 ) 2.040(11)
Å, Cu2-O3 ) 2.409(15) Å, Cu2-N1 ) 2.017(14) Å, and Cu2-O4 ) 2.50(2) Å.
tetrahedral orientation, with N · · · Ccore · · · N angles of 4 ×
106.3(4)° and 2 × 116.0(4)°. The -CH2O- spacers that
connect each pyridylphenyl group to the core adopt confor-
mations that are largely extended, with Ccore-CH2-O-C
dihedral angles of 169.90(4)°. However, this extension does
not continue across the central carbon atom (Ccore), and the
key CH2-Ccore-CH2-O dihedral angles are 66.35(4)°.
Combination of the tetrahedral geometry of Cu(I) with the
approximately tetrahedral orientation of the sites of coordina-
Figure 11. Representation of 2-fold interpenetrated PtS networks found
tion in extended PETPE (2) leads to construction of a
diamondoid network.24 In contrast, the pyridyl groups in the
Cu(I) complex of simple PETPE (1) have an irregular
orientation far from the tetrahedral ideal, and a network of
SrAl2 topology is formed. Within the network built from
ligand 2, the intertectonic Ccore · · · Ccore distance between
adjacent ligands is 20.158(1) Å, and the Cu · · · Cu distance
spanned by a single ligand is 21.516(1) Å. The expanded
diamondoid network is open enough to allow 4-fold inter-
penetration, whereas the SrAl2 network formed from simple
PETPE (1) and Cu(I) is only 2-fold interpenetrated. The
diamondoid network defines parallel channels that run along
the c axis and have cross sections that are approximately
6.9 × 6.9 Å2.18,24 About 45% of the volume of the crystals
is accessible to included BF4- ions, H2O, and CH3CN.15-17
We were gratified to observe that replacing flexible
tetrapyridine 1 with extended analogue 2 yielded networks
with identical or related three-dimensional connectivities and
with similar geometries of coordination at Cu. In both cases
studied, extension of the ligand expanded the resulting
network but simultaneously permitted a higher level of
interpenetration, so no dramatic increases in the percentage
of volume accessible to guests were observed. We reasoned
that appropriate substitution of the phenyl spacer in extended
PETPE (2) might prevent independent interpenetrating
networks from approaching closely enough to engage in
stabilizing aromatic interactions, thereby leading to lower
in crystals of the complex of Cu(NO3)2 and extended PETPE (2) grown
from DMF/H2O. The structure is viewed along the c axis, with one network
in blue and the other in red. Nodes in the networks correspond to the central
carbon atom of ligand 2 (small spheres) and to Cu(II) (large spheres).
Figure 12. Stereoscopic representation of interconnected channels in the
structure of crystals of the complex of Cu(NO3)2 and extended PETPE (2)
grown from DMF/H2O. The images show a 1 × 3 × 2 array of unit cells
viewed with the b axis vertical. The outsides of the channels appear in
light gray, and dark gray is used to show where the channels are cut by the
boundaries of the array. The surface of the channels is defined by the
possible loci of the center of a sphere of diameter 5.5 Å as it rolls over the
surface of the ordered network.26
4CH3CN · 6H2O.10 Figure 13 confirms that the coordination
sphere of Cu(I) is approximately tetrahedral, and the
N-Cu-N angles have the values 4 × 103.7(2)° and 2 ×
121.8(5)°. The average length of the Cu-N bonds (2.035(10)
Å) is normal.21 Extended PETPE (2) favors a conformation
that holds the four pyridyl groups in an approximately
2800 Inorganic Chemistry, Vol. 48, No. 7, 2009

Metal-Organic Frameworks Built from Flexible Tetrapyridines
Figure 13. Partial views of the structure of crystals of the complex of CuBF4 and extended PETPE (2) grown from CH2Cl2/CH3CN. Thermal displacement
ellipsoids are drawn at the 50% probability level, and hydrogen atoms are represented by a sphere of arbitrary size. Atoms of hydrogen appear in white,
carbon in gray, nitrogen in blue, oxygen in red, and Cu(I) in bronze. Anions and neutral guests are omitted. Key bond lengths include Cu1-N1 ) 2.035-
(10) Å.
Table 3. Crystallographic Data for Complexes of Substituted Extended PETPE (3) with Salts of Cu(II) and Cu(I)
complex with
Cu(OOCCH3)2
Cu(NO3)2
CuBF4
CuPF6
solvent of crystallization
crystal system
space group
a (Å)
CH3CH2OH/CH3OH
tetragonal
P42/n
30.337(5)
30.337(5)
7.4230(5)
6831.6(17)
0.744a
CH3CH2OH/CH2Cl2
cubic
F43c
31.7641(11)
31.7641(11)
31.7641(11)
32048.6(19)
1.342
CH3CH2OH/CH3CN
cubic
F43c
32.049(9)
32.049(9)
32.049(9)
32919(16)
1.283
8
CH3CH2OH/CH3CN
cubic
F43c
31.9148(8)
31.9148(8)
31.9148(8)
32507.0(14)
1.395
j
j
j
b (Å)
c (Å)
V (Å3)
Dcalc (g cm-3
)
Z
2
8
8
temperature (K)
unique
223(2)
4423
223(2)
2566
293(2)
2572
200(2)
2530
observed (I > 2σ(I))
parameters
2640
241
1974
163
2512
167
1979
160
restraints
121
15
5
9
b
R1 (I > 2σ(I))
0.0616
0.1628
0.0793
0.1688
1.056
0.0628
0.1502
0.0643
0.1506
1.030
0.0749
0.1859
0.0752
0.1859
1.162
2
0.0745
0.1971
0.0842
0.2041
1.059
c
wR2 (I > 2σ(I))
b
R1 (all data)
c
wR2 (all data)
GoFd
a Calculated with no solvent included b R1 ) ∑||Fo| - |Fc||/∑|Fo|. c wR2 ) {∑[w(Fo2 - Fc2)2]/∑w(Fo )2}1/2
.
d GoF ) {∑[w(Fo2 - Fc2)2]/(n - p)}1/2, where
n is the number of reflections and p is the total number of parameters refined.
degrees of interpenetration or to new types of networks,
possibly with larger volumes accessible to guests. To test
this hypothesis, we prepared methyl-substituted derivative
3 and studied its complexation with Cu(II) and Cu(I), using
a representative set of salts that included the same three
initially chosen for the complexation of simple PETPE (1).
the length of the Cu-N bonds, the Cu-Cu distance, and
the average length of the Cu-O bonds (1.985(6) Å) are
closely similar to those found in related binuclear com-
plexes.27 The pyridyl groups of substituted extended PETPE
(3) have a distorted tetrahedral orientation, with N · · ·
Ccore · · · N angles of 4 × 117.3(6)° and 2 × 94.7(6)°. The
-CH2O- spacers that connect each substituted pyridylphenyl
group to the core adopt conformations that are substantially
extended,withCcore-CH2-O-Cdihedralanglesof177.5(12)°.
Structures of Networks Produced by Treating
Substituted Extended PETPE (3) with Cu(OOCCH3)2,
Cu(NO3)2, CuBF4, and CuPF6. Blue-green crystals grew
during slow mixing of an ethanolic solution of compound 3
with a methanolic solution of Cu(OOCCH3)2. The crystals
were delicate and unstable but could nevertheless be analyzed
by X-ray diffraction (Table 3, Figures 14-16). The crystals
were found to have the approximate composition [Cu2(µ2-
OOCCH3)4]2(3).10 Figure 14 reveals that the structure consists
of binuclear paddle-wheel Cu2(OOCCH3)4 clusters bridged
by axially bound pyridyl groups. The values observed for
(27) Yamanaka, M.; Uekusa, H.; Ohba, S.; Saito, Y.; Iwata, S.; Kato, M.;
Tokii, T.; Muto, Y.; Steward, O. W. Acta Crystallogr. 1991, B47,
344–355. Uekusa, H.; Ohba, S.; Saito, Y.; Kato, M.; Tokii, T.; Muto,
Y. Acta Crystallogr. 1989, C45, 377–380. Morosin, B.; Hughes, R. C.;
Soos, Z. G. Acta Crystallogr. 1975, B31, 762–770. Valentine, J. S.;
Silverstein, A. J.; Soos, Z. G. J. Am. Chem. Soc. 1974, 96, 97–103.
Kokoszka, G. F.; Duerst, R. W. Coord. Chem. ReV. 1970, 5, 209–
244. Kokoszka, G. F.; Gordon, G. Transition Metal Chem. 1969, 5,
181–277. Barclay, G. A.; Kennard, C. H. L. J. Chem. Soc. 1961, 5244–
5251.
Inorganic Chemistry, Vol. 48, No. 7, 2009 2801

Ryan et al.
Figure 14. Partial view of the structure of crystals of the complex of Cu(OOCCH3)2 and substituted extended PETPE (3) grown from CH3CH2OH/CH3OH.
Thermal displacement ellipsoids are drawn at the 50% probability level, and hydrogen atoms are represented by a sphere of arbitrary size. Atoms of hydrogen
appear in white, carbon in gray, nitrogen in blue, oxygen in red, and Cu(II) in bronze. Only one part of the disordered arm of ligand 3 is shown, and guests
are omitted. Key bond lengths include Cu1-Cu1A ) 2.6460(17) Å, Cu1-O1 ) 2.002(6) Å, Cu1-O2 ) 1.973(6) Å, Cu1-O3 ) 1.965(6) Å, Cu1-O4 )
2.001(6) Å, and Cu1-N1 ) 2.193(5) Å.
resembles the one adopted by extended PETPE (2) in its
complex with CuBF4.
Combination of linear Cu2 linkers with tetradentate ligand
3 in an approximately tetrahedral conformation yields a
diamondoid network. The intertectonic Ccore · · ·Ccore distance
between adjacent ligands bonded to a common Cu2 cluster
is 28.365(5) Å, and the Cu · · ·Cu distance spanned by a single
ligand is 21.862(5) Å. The resulting network is open enough
to allow 10-fold interpenetration (Figure 15), yet about 52%
of the volume of the crystals remains accessible for the
inclusion of guests.15,16 The guests occupy parallel channels
that run along the c axis and have cross sections that are
approximately 22.7 × 22.7 Å2 (Figure 16).18 The large size
of these channels presumably facilitates the loss of included
guests and accounts for the observed instability of the
crystals.
It is instructive to compare the networks produced by
Figure 15. Representation of the 10-fold interpenetrated diamondoid
complexation of Cu(OOCCH3)2 with PETPE (1) and with
substituted extended analogue 3. Both networks are diamon-
doid, and the extension of ligand 3 helps increase the
intertectonic Ccore · · · Ccore distance from 16.731(4) Å to
28.365(5) Å, thereby enlarging the channels significantly.
However, interpenetration increases from 5-fold to 10-fold,
and the percentage of volume accessible to guests remains
network found in crystals of the complex of Cu(OOCCH3)2 and substituted
extended PETPE (3) grown from CH3CH2OH/CH3OH. Nodes and linkers
in the network correspond to the central carbon atom of ligand 3 (small
spheres) and to the centers of the paddle-wheel Cu2(OOCCH3)4 clusters
(large spheres).
However, this extension does not continue across the central
carbon atom (Ccore), and the key CH2-Ccore-CH2-O dihe-
dral angles are 53.2(10)°. The resulting conformation closely
2802 Inorganic Chemistry, Vol. 48, No. 7, 2009

Metal-Organic Frameworks Built from Flexible Tetrapyridines
analogues 1 and 2 were both found to react with Cu(NO3)2
to form PtS networks. The new network can be considered
to be constructed from rings in which four Cu nodes are
linked by four molecules of ligand 3 (Figure 18a). The
network is open enough to permit 4-fold interpenetration
(Figure 18b), and approximately 20% of the volume of the
crystal is accessible for inclusion of disordered counterions
and neutral guests.15,16 No significant channels are defined,
and the disordered species instead occupy isolated cavities.24
Our finding that the complex of Cu(NO3)2 with ligand 3 does
not follow the pattern set by analogues 1 and 2 is consistent
with the hypothesis that substitution thwarts interpenetration
and thereby directs assembly toward a new topology that
can offer a higher density of packing.
To test this notion, we examined networks produced by
the reaction of substituted extended PETPE (3) with salts of
Cu(I). Slow mixing of an ethanolic solution of ligand 3 with
solutions of either Cu(CH3CN)4BF4 or Cu(CH3CN)4PF6 in
CH3CN yielded yellow-green crystals with the approximate
composition [Cu4(3)3(CH3CN)4](X)4 (X ) BF4 or PF6).10 To
our great surprise, the crystals of both salts proved to belong
Figure 16. Representation of the structure of crystals of the complex of
Cu(OOCCH3)2 and substituted extended PETPE (3) grown from CH3CH2OH/
CH3OH. The structure is viewed along the c axis and shows a 3 × 3 × 3
array of unit cells. Guests are omitted for clarity, and atoms are represented
by spheres of van der Waals radii to show the cross sections of the channels.
Atoms of hydrogen appear in white, carbon in gray, nitrogen in blue, oxygen
in red, and Cu(II) in bronze.
j
to the cubic space group F43c and to be isostructural with
those of the corresponding complex of Cu(NO3)2, even
though Cu(II) and Cu(I) normally have distinctly different
geometries of coordination and therefore give rise to
networks with completely different topologies. Crystal-
lographic data appear in Table 3, and views of the coordina-
tion sphere of Cu(I) in both salts are shown in Figure 19.
Figure 19 establishes that the coordination sphere of Cu(I)
is approximately tetrahedral and consists of three bound
pyridyl groups and one partially disordered molecule of
essentially unchanged. Because ligands 1 and 3 differ both
in length and substitution, we cannot determine whether
substitution has reduced the degree of interpenetration, as
intended, or whether it has helped lead to the incorporation
of Cu2 clusters instead of the simple Cu1 nodes favored by
ligand 1.
-
CH3CN. In the BF4 salt, the N-Cu-N angles have the
values 3 × 106.94(8)° and 3 × 111.90(16)°, and the average
length of the Cu-N bonds is normal (2.013(8) Å for bound
CH3CN and 2.053(2) Å for the pyridyl groups). Closely
By allowing a solution of compound 3 in CH2Cl2 to mix
slowly with an ethanolic solution of Cu(NO3)2, we obtained
green crystals that could be analyzed by X-ray diffraction
(Table 3, Figures 17-18). The crystals proved to have the
-
similar values are observed for the PF6 salt. In both
networks, ligand 3 adopts the same flattened and extended
conformation found in the complex with Cu(NO3)2, and again
two C-O-CH2-Ccore-CH2-O-C chains are almost fully
extended and lie in orthogonal planes.
10
approximate composition [Cu4(3)3(H2O)12](NO3)8 and to
28,29
j
belong to the unusual cubic space group F43c.
Figure
17 reveals that the coordination sphere of Cu(II) is ap-
proximately octahedral and consists of three facially bound
pyridyl groups and three molecules of H2O. The O-Cu-O
angles are 63.2(4)°, and the other angles at Cu lie in the
range 95.9(3)-98.4(2)°. The average lengths of the Cu-N
bonds (2.099(3) Å) and Cu-O bonds (1.923(7) Å) are
normal.11 Ligand 3 adopts a flattened and extended confor-
mation closely similar to the one favored by simple analogue
1 in its complex with Cu(NO3)2, with N · · · Ccore · · · N angles
of 4 × 94.5(4)° and 2 × 147.6(4)°. In both cases, two
C-O-CH2-Ccore-CH2-O-C chains are almost fully ex-
tended and lie in orthogonal planes.
In the isostructural crystals derived from substituted
extended PETPE (3), different coordination spheres are
observed for Cu(II) and Cu(I), as expected, yet facial binding
of three pyridyl groups by octahedral Cu(II) and coordination
of three pyridyl groups by tetrahedral Cu(I) generate nodes
with similar geometry. A 4-fold interpenetrated network with
identical topology (Figure 18) is thereby generated by the
reaction of tetrapyridine 3 with Cu(I), and approximately
10% of the volume of the crystals is accessible for inclu-
sion.15,16 In crystals derived from CuBF4 or CuPF6, the
tetrahedral geometry of coordination, the reduced number
of ligands bound to Cu, and the lower percentage of volume
needed to accommodate counterions all provide strong
circumstantial evidence that copper remains in the Cu(I)
oxidation state. Additional evidence was obtained by record-
ing diffuse-reflectance spectra of crystalline samples in the
UV-visible region. These spectra showed broad reflectance
bands at λ ) 500-550 nm, which are characteristic of Cu(I).
Joining non-planar 3-connected Cu nodes with 4-connected
nodes derived from substituted extended PETPE (3) yields
a network with a distorted Pt3O4 topology. In contrast,
(28) Of the 415,256 entries in Version 5.28 of the Cambridge Structural
Database (including updates),29 only 2002 structures belong to one
j
of the 35 cubic space groups, and the particular group F43c has merely
37 representatives.
(29) Allen, F. H. Acta Crystallogr. 2002, B58, 380–388.
Inorganic Chemistry, Vol. 48, No. 7, 2009 2803

Ryan et al.
Figure 17. Partial views of the structure of crystals of the complex of Cu(NO3)2 and substituted extended PETPE (3) grown from CH3CH2OH/CH2Cl2.
Thermal displacement ellipsoids are drawn at the 50% probability level, and hydrogen atoms are represented by a sphere of arbitrary size. Atoms of hydrogen
appear in white, carbon in gray, nitrogen in blue, oxygen in red, and Cu(II) in bronze. Anions are omitted. Key bond lengths include Cu1-N10 ) 2.099(3)
Å and Cu1-O61 ) 1.923(7) Å.
In contrast, spectra of crystalline samples of the complex of
substituted extended PETPE (3) with Cu(NO3)2 showed
broad bands at λ < 500 nm, which are typical of Cu(II).
The cubic networks derived from tetrapyridine 3 have only
modest porosity (10-20%) and no obvious channels to
permit the exchange of anions or neutral guests.24 Neverthe-
less, addition of a solution containing excess CuPF6 in
CH3CH2OH/CH3CN to crystals produced by the reaction of
ligand 3 with CuBF4 led to quantitative anion exchange, as
revealed in IR spectra by disappearance of the BF4- peak at
O2, Br2, and I2, but no change in the oxidation state of copper
was observed in the solid state.
Conclusions
Our work has demonstrated that tetrapyridines 1-3 are
effective ligands for the construction of new metal-organic
frameworks. Studies of their complexation with Cu(II) and
Cu(I) have revealed a distinctive ability to accommodate a
single metal in different oxidation states, as well as to adapt
to a metal in a single oxidation state but with different
counterions or secondary ligands. The adaptability of ligands
1-3 arises primarily from their flexibility and ability to
assume a set of conformations in which the four pyridyl
groups are held in geometries that are approximately
tetrahedral, flattened, or irregular. As expected, conversion
of simple tetrapyridine 1 into extended analogue 2 by the
insertion of phenyl spacers leads to expanded networks.
Expansion is accompanied by increased degrees of inter-
penetration by independent networks, so dramatic increases
in porosity are not observed. Attempts to thwart normal
interpenetration by converting extended tetrapyridine 2 into
substituted derivative 3 were successful, and they yielded
complexes that crystallized in the unusual cubic space group
-
817 cm-1 and appearance of a PF6 peak at 840 cm-1.
Moreover, this exchange occurs without overall loss of
crystallinity, as demonstrated by powder X-ray diffraction.
These exchanges may occur by sequential dissolution and
recrystallization,30 but the demonstrated ability of ligand 3
to assume different conformations may allow the crystalline
networks to flex, thereby facilitating exchange. A similar
-
-
replacement of PF6 by BF4 in crystals initially produced
by the reaction of ligand 3 with CuPF6 could not be achieved
under the same conditions. Greater affinity of the network
for PF6- may result from its better fit within the cavities of
the cubic network.24
The feasibility of exchanges, combined with the shared
topology of the Cu(II) and Cu(I) networks, suggested that it
might be possible to change the oxidation state of copper
without loss of crystallinity, thereby producing mixed-valence
crystals containing variable ratios of Cu(II) and Cu(I). We
attempted to oxidize Cu(I) to Cu(II) in crystals of the
complexes of substituted extended PETPE (3) with CuBF4
and CuPF6. In these experiments, crystals were exposed
under diverse conditions to various oxidants, including H2O2,
j
F43c. Surprisingly, the complexes of ligand 3 with both
Cu(II) and Cu(I) gave rise to networks with the same
architecture, despite the well-established preference of the
two oxidation states of Cu for coordination spheres with
different geometries. Together, these results underscore the
ability of flexible multidentate ligands to generate metal-
organic frameworks with unusual structures and properties.
In addition, our observations confirm that interdisciplinary
approaches, in which equal attention is devoted to the
(30) Thompson, C.; Champness, N. R.; Khlobystov, A. N.; Roberts, C. J.;
Schro¨der, M.; Tendler, S. J. B.; Wilkinson, M. J. J. Microscopy 2004,
214, 261–271.
2804 Inorganic Chemistry, Vol. 48, No. 7, 2009

Metal-Organic Frameworks Built from Flexible Tetrapyridines
Figure 19. (a) Partial view of the structure of crystals of the complex of
CuBF4 and substituted extended PETPE (3) grown from CH3CH2OH/
CH3CN. Key bond lengths include Cu1-N13 ) 2.053(2) Å and Cu1-N100
) 2.013(8) Å. (b) Partial view of the structure of crystals of the complex
of CuPF6 and tetrapyridine 3 grown from CH3CH2OH/CH3CN. Key bond
lengths include Cu1-N13 ) 2.074(4) Å and Cu1-N100 ) 2.070(6) Å.
Both views show three orientations of disordered CH3CN coordinated to
Cu(I), and anions are omitted. Atoms of hydrogen appear in white, carbon
in gray, nitrogen in blue, oxygen in red, and Cu(I) in bronze.
Figure 18. (a) Representation of the Pt3O4 network found in crystals of
the complex of Cu(NO3)2 and substituted extended PETPE (3) grown from
CH3CH2OH/CH3OH. Alternating nodes in the network correspond to the
central carbon atom of ligand 3 (gray spheres) and to Cu(II) (bronze spheres).
(b) Representation of the 4-fold interpenetrated Pt3O4 networks.
sealed X-ray tube or (2) a Bruker AXS SMART 4K/Platform
diffractometer equipped with an FR591 rotating anode generator.
Tetrakis[(pyridin-4-yloxy)methyl]methane (1) (PETPE).5 A
mixture of pentaerythritol (0.454 g, 3.33 mmol), 4-chloropyridinium
chloride (2.00 g, 13.3 mmol), and NaOH (0.980 g, 24.5 mmol) in
DMSO (30 mL) was heated at 60 °C for 72 h. The mixture was
then cooled to 25 °C, and water (500 mL) was added. The resulting
precipitate was separated by filtration, washed with water, and dried
under vacuum to give tetrakis[(pyridin-4-yloxy)methyl]methane (1;
1.28 g, 2.88 mmol, 86%) as a colorless solid. An analytically pure
sample was obtained by crystallization from toluene: mp 188-190
°C (lit.5 198 °C); 1H NMR (400 MHz, CDCl3) δ 8.46 (d, 8H, 3J )
coordination chemistry of metals and to the design and
synthesis of complex ligands, are a productive source of new
materials.
Experimental Section
All reagents and solvents were purchased from commercial
sources and used without further purification unless otherwise
indicated. NMR spectra were recorded using a Bruker AV400
spectrometer, and high-resolution mass spectra were obtained using
an Agilent LC-MSD TOF spectrometer. Elemental analyses were
performed at the Universite´ de Montre´al. Diffuse-reflectance spectra
were acquired using a Cary 5E UV-vis-NIR spectrophotometer
with a Praying Mantis accessory. IR spectra were recorded using
a Bruker Vector 22 spectrometer. X-ray diffraction studies were
performed with Cu KR radiation using either (1) a Bruker AXS
SMART 2K/Platform diffractometer equipped with a standard
3
6.2 Hz), 6.85 (d, 8H, J ) 6.2 Hz), 4.41 (s, 8H); 13C NMR (100
MHz, CDCl3) δ 164.2, 151.4, 110.3, 65.7, 44.4; HRMS (FAB,
3-nitrobenzyl alcohol) calcd for C25H25N4O4 m/e 445.18759, found
445.18670. Anal. Calcd for C25H24N4O4: C, 67.55; H, 5.44; N,
12.60. Found: C, 67.55; H, 5.36; N, 12.49.
Inorganic Chemistry, Vol. 48, No. 7, 2009 2805

Ryan et al.
Tetrakis[4-(pyridin-4-yl)phenoxymethyl]methane (2) (Exten-
ded PETPE). Tetraboronic acid 4 (1.23 g, 2.00 mmol),8 4-bro-
mopyridine hydrochloride (1.94 g, 9.98 mmol), Pd(PPh3)4 (0.464
g, 0.402 mmol), and Na2CO3 (2.12 g, 20.0 mmol) were combined
under N2 in a deoxygenated mixture of water and THF (80 mL,
1:3 v/v). The resulting mixture was stirred at 50 °C for 48 h and
was then cooled to 25 °C. Water (200 mL) was added, and the
mixture was extracted with CH2Cl2. The organic phase was dried
over anhydrous Na2SO4 and filtered, and volatiles were removed
by evaporation under reduced pressure. The residual solid was
purified by flash chromatography (silica, CH2Cl2 (90%)/CH3CH2OH
(9%)/N(CH2CH3)3 (1%), Rf 0.42) to yield tetrakis[4-(pyridin-4-
yl)phenoxymethyl]methane (2; 1.09 g, 1.46 mmol, 73%) as a beige
solid: mp 216-217 °C; IR (KBr) 3032, 2933, 2884, 1596, 1518,
1487, 1283, 1244, 1179, 1038, 1016, 815, 756, 628 cm-1;1H NMR
(400 MHz, CDCl3) δ 8.63 (d, 8H, 3J ) 6.1 Hz), 7.60 (d, 8H, 3J )
8.8 Hz), 7.45 (d, 8H, 3J ) 6.1 Hz), 7.08 (d, 8H, 3J ) 8.8 Hz), 4.49
(s, 8H); 13C NMR (100 MHz, CDCl3) δ 159.76, 150.43, 147.77,
131.22, 128.39, 121.26, 115.45, 66.75, 45.11; MS (FAB, 3-ni-
trobenzyl alcohol) calcd for C49H41N4O4 m/e 749.9, found 749.3.
Anal. Calcd for C49H40N4O4 ·1.5H2O: C, 75.85; H, 5.59; N, 7.22.
Found: C, 75.71; H, 5.28; N, 7.07.
in DMF (15 mL), and the mixture was heated at reflux for 16 h.
The resulting mixture was then cooled to 25 °C, and water (200
mL) was added. The resulting precipitate was separated by filtration,
washed with water (30 mL) and CH3CN (30 mL), and dried under
vacuum to give tetrakis{[3-methyl-4-(4-pyridinyl)phenoxy]-
methyl}methane (3; 1.03 g, 1.28 mmol, 90%) as an off-white solid.
An analytically pure sample was obtained by crystallization from
1
anhydrous CH3CH2OH: mp 260-261 °C; H NMR (400 MHz,
3
3
CDCl3) δ 8.62 (d, 8H, J ) 6.1 Hz), 7.22 (d, 8H, J ) 6.1 Hz),
7.16 (d, 4H, 3J ) 8.2 Hz), 6.91 (s, 4H), 6.89 (d, 4H, 3J ) 8.2 Hz),
4.45 (s, 8H), 2.28 (s, 12H); 13C NMR (100 MHz, CDCl3) δ 158.9,
149.7, 149.6, 136.9, 132.3, 130.7, 124.6, 117.0, 112.4, 66.5, 45.0,
20.7; MS (FAB+, DMSO) calcd for C53H49N4O4 m/e 805.371,
found 805.374. Anal. Calcd for C53H48N4O4: C, 79.08; H, 6.01; N,
6.96. Found: C, 78.68; H, 6.03; N, 6.93.
Preparation and Crystallization of Complexes. PETPE (1)/
Cu(OOCCH3)2. A solution of Cu(OOCCH3)2 (33 mg, 0.18 mmol)
in CH3OH (6 mL) was placed in a test tube, and a mixture of
CH3CH2OH and CH3OH (12 mL, 1:1 v/v) was carefully layered
on top. A solution of PETPE (1; 40 mg, 0.090 mmol) in CH3CH2OH
(2 mL) was then added on top of the other two layers. The tube
was sealed, and the contents were allowed to mix slowly. After 2
weeks, blue crystals suitable for X-ray diffraction were obtained.
PETPE (1)/Cu(NO3)2. A solution of Cu(NO3)2 hemipentahydrate
(42 mg, 0.18 mmol) in water (2 mL) was placed in a test tube, and
a mixture of CH3CH2OH and water (15 mL, 1:1 v/v) was carefully
layered on top. A solution of PETPE (1; 40 mg, 0.090 mmol) in
CH3CH2OH (2 mL) was then added on top of the other two layers.
The tube was sealed, and the contents were allowed to mix slowly.
After 1 month, violet crystals suitable for X-ray diffraction were
obtained. After being dried under vacuum, they had the composition
[Cu(1)(NO3)2]·3H2O. Anal. Calcd for C25H30CuN6O13: C, 43.8; H,
4.4; N, 12.2. Found: C, 43.5; H, 4.1; N, 12.2.
PETPE (1)/CuBF4. A solution of PETPE (1; 40 mg, 0.090
mmol) in a mixture of CH3CN and CH2Cl2 (7 mL, 6:1 v/v) was
placed in a test tube, and CH3CN (15 mL) was carefully layered
on top. A solution of Cu(CH3CN)4BF4 (28 mg, 0.090 mmol) in
CH3CN (2 mL) was then added on top of the other two layers. The
tube was sealed, and the contents were allowed to mix slowly. After
1 week, yellow crystals suitable for X-ray diffraction were obtained.
After being dried under vacuum, they had the composition
[Cu(1)(BF4)]·CH3CN ·2H2O. Anal. Calcd for C27H31BCuF4N5O6:
C, 48.26; H, 4.65; N, 10.42. Found: C, 48.28; H, 4.42; N, 10.92.
Extended PETPE (2)/Cu(NO3)2. A solution of Cu(NO3)2
hemipentahydrate (25 mg, 0.11 mmol) in water (2 mL) was placed
in a test tube, and a mixture of DMF and water (10 mL, 1:1 v/v)
was carefully layered on top. A solution of extended PETPE (2;
40 mg, 0.053 mmol) in DMF (24 mL) was then added on top of
the other two layers. The tube was sealed, and the contents were
allowed to mix slowly. After 6 weeks, blue crystals suitable for
X-ray diffraction were obtained.
4-(4-Methoxy-2-methylphenyl)pyridine (5). (4-Methoxy-2-me-
thylphenyl)boronic acid (3.00 g, 18.1 mmol), 4-bromopyridinium
chloride (3.86 g, 19.8 mmol), Pd(PPh3)4 (0.800 g, 0.692 mmol),
and Na2CO3 (3.83 g, 36.1 mmol) were combined under N2 in a
deoxygenated mixture of water and CH3CN (60 mL, 1:3 v/v). The
mixture was heated at 80 °C for 72 h and was then cooled to 25
°C. Water (90 mL) was added, and the mixture was extracted with
CH2Cl2. The organic phase was dried over anhydrous Na2SO4 and
filtered, and volatiles were removed by evaporation under reduced
pressure. The residual oil was purified by gradient column chro-
matography (silica, CH3COOCH2CH3/hexanes (1:9 to 1:1)) to yield
4-(4-methoxy-2-methylphenyl)pyridine (5; 3.06 g, 15.4 mmol, 85%)
1
as a colorless solid: mp 70-72 °C; H NMR (400 MHz, DMSO-
d6) δ 8.60 (d, 2H, 3J ) 6.0 Hz), 7.35 (d, 2H, 3J ) 6.0 Hz), 7.19 (d,
3
4
3
1H, J ) 8.4 Hz), 6.91 (d, 1H, J ) 2.5 Hz), 6.88 (dd, 1H, J )
8.4 Hz, J ) 2.5 Hz), 3.79 (s, 3H), 2.26 (s, 3H); 13C NMR (100
4
MHz, DMSO-d6) δ 160.1, 150.3, 149.4, 137.2, 131.9, 131.4, 125.1,
116.9, 112.6, 55.9, 21.1; MS (ESI, DMSO) calcd for C13H14NO
m/e 200.1, found 200.1. Anal. Calcd for C13H13NO: C, 78.36; H,
6.58; N, 7.03. Found: C, 78.01; H, 6.90; N, 6.99.
3-Methyl-(4-pyridin-4-yl)phenol (6).9 Aqueous HBr (10.0 mL,
48%) was added to a solution of 4-(4-methoxy-2-methylphenyl)py-
ridine (5; 2.07 g, 10.4 mmol) in acetic acid (10 mL), and the mixture
was stirred and heated at reflux for 4 h. The resulting mixture was
then cooled to 25 °C, and the pH was raised to ∼ 6.0 by adding
aqueous NaOH (6 N). The resulting precipitate was separated by
filtration, washed with water, and dried under vacuum. Crystal-
lization from CH3OH gave 3-methyl-(4-pyridin-4-yl)phenol (6;
1.34 g, 7.23 mmol, 70%) as an analytically pure colorless solid:
mp 204-206 °C (lit.9 206 °C); 1H NMR (400 MHz, DMSO-d6) δ
9.59 (s, 1H), 8.57 (d, 2H, 3J ) 6.1 Hz), 7.33 (d, 2H, 3J ) 6.1 Hz),
7.08 (d, 1H, 3J ) 8.2 Hz), 6.72 (d, 1H, 4J ) 2.4 Hz), 6.70 (dd, 1H,
Extended PETPE (2)/CuBF4. A solution of extended PETPE
(2; 20 mg, 0.027 mmol) in a mixture of CH3CN and CH2Cl2 (7
mL, 6:1 v/v) was placed in a test tube, and CH3CN (15 mL) was
carefully layered on top. A solution of Cu(CH3CN)4BF4 (56 mg,
0.18 mmol) in CH3CN (2 mL) was then added on top of the other
two layers. The tube was sealed, and the contents were allowed to
mix slowly. After 2 weeks, yellow crystals suitable for X-ray
diffraction were obtained. After being dried under vacuum, they
had the composition [Cu(2)(BF4)]. Anal. Calcd for C49H40BCuF4N4-
O4: C, 65.45; H, 4.48; N, 6.23. Found: C, 65.95; H, 4.64; N, 6.50.
Substituted Extended PETPE (3)/Cu(OOCCH3)2. A solution
of Cu(OOCCH3)2 (30 mg, 0.17 mmol) in CH3OH (10 mL) was placed
4
3J ) 8.2 Hz, J ) 2.4 Hz), 2.21 (s, 3H); 13C NMR (100 MHz,
DMSO-d6) δ 158.4, 150.2, 149.7, 136.9, 131.5, 130.2, 125.1, 118.1,
114.1, 21.1; HRMS (ESI, DMSO) calcd for C12H12NO m/e
186.0874, found 186.0934. Anal. Calcd for C12H11NO: C, 77.81;
H, 5.99; N, 7.56. Found: C, 78.11; H, 5.99; N, 7.60.
Tetrakis{[3-methyl-4-(4-pyridinyl)phenoxy]methyl}methane
(3) (Substituted Extended PETPE). Pentaerythrityl tetratosylate
(1.08 g, 1.43 mmol)7 was combined with 3-methyl-(4-pyridin-4-
yl)phenol (6; 1.33 g, 7.18 mmol) and NaOH (0.288 g, 7.20 mmol)
2806 Inorganic Chemistry, Vol. 48, No. 7, 2009

Metal-Organic Frameworks Built from Flexible Tetrapyridines
in a test tube, and a mixture of CH3CH2OH and CH3OH (10 mL, 1:1
v/v) was carefully layered on top. A solution of substituted extended
PETPE (3; 30 mg, 0.037 mmol) in CH3CH2OH (15 mL) was then
added on top of the other two layers. The tube was sealed, and the
contents were allowed to mix slowly. After 1 week, blue-green crystals
suitable for X-ray diffraction were obtained.
eters, and structure refinement details are given in Tables 1-3.
Structures were solved by direct methods and refined by full-matrix
least-squares techniques.33 Except in the case of one structure with
severe disorder, all non-hydrogen atoms were refined with aniso-
tropic displacement parameters. Hydrogen atoms were placed at
calculated positions and refined as riding atoms in the subsequent
least-squares model refinements, except for certain hydrogen atoms
of water molecules that were located by the Fourier difference map
or placed at positions to favor hydrogen bonding, then refined using
restraints on distances and angles. The isotropic thermal parameters
were estimated to be 1.2 (1.5 for methyl hydrogens) times the values
of the equivalent isotropic thermal parameters of the non-hydrogen
atoms to which hydrogen atoms are bonded. Counterions and neutral
guests were usually located and refined using multisite models for
disorder, except for two structures that were found to have large
voids filled with disordered anions and neutral guests, which could
not be modeled in a satisfactory way. In these cases, the SQUEEZE
option implemented in PLATON was used to account for the
contribution of the disordered guest.16 More information about
structural refinement is provided in the CIF files available as
Supporting Information.
Substituted Extended PETPE (3)/Cu(NO3)2. A solution of
substituted extended PETPE (3; 30 mg, 0.037 mmol) in CH2Cl2 (4
mL) was placed in a test tube, and a mixture of CH3CH2OH and
CH2Cl2 (8 mL, 1:1 v/v) was carefully layered on top. A solution
of Cu(NO3)2 hemipentahydrate (35 mg, 0.15 mmol) in CH3CH2OH
(4 mL) was then added on top of the other two layers. The tube
was sealed, and the contents were allowed to mix slowly. After 3
weeks, green crystals suitable for X-ray diffraction were obtained.
Substituted Extended PETPE (3)/CuBF4. A solution of
substituted extended PETPE (3; 30 mg, 0.037 mmol) in CH3CH2OH
(4 mL) was placed in a test tube, and a mixture of CH3CN and
CH3CH2OH (6 mL, 1:1 v/v) was carefully layered on top. A solution
of Cu(CH3CN)4BF4 (47 mg, 0.15 mmol) in CH3CN (5 mL) was
then added on top of the other two layers. The tube was sealed,
and the contents were allowed to mix slowly. After 1 week, yellow-
green crystals suitable for X-ray diffraction were obtained. After
being dried, they had the composition [Cu4(3)3](BF4)4. Anal. Calcd
for C159H144B4Cu4F16N12O12: C, 63.31; H, 4.81; N, 5.57. Found: C,
63.53; H, 4.68; N, 6.04.
Substituted Extended PETPE (3)/CuPF6. A solution of sub-
stituted extended PETPE (3; 30 mg, 0.037 mmol) in CH3CH2OH
(4 mL) was placed in a test tube, and a mixture of CH3CN and
CH3CH2OH (6 mL, 1:1 v/v) was carefully layered on top. A solution
of Cu(CH3CN)4PF6 (56 mg, 0.15 mmol) in CH3CN (7 mL) was
then added on top of the other two layers. The tube was sealed,
and the contents were allowed to mix slowly. After 1 week, yellow-
green crystals suitable for X-ray diffraction were obtained.
X-ray Crystallographic Studies. Intensity data were collected
with 0.3° width ω scans to get a full sphere of reciprocal space.
Data were processed using SAINT software.31 Data reduction
included absorption corrections by the multiscan method with
SADABS software.32 Crystallographic data, data collection param-
Acknowledgment. We are grateful to the Natural Sciences
and Engineering Research Council of Canada, the Ministe`re
´
de l′Education du Que´bec, the Canada Foundation for
Innovation, the Canada Research Chairs Program, and
Universite´ de Montre´al for financial support. We thank Dr.
Alexandra Furtos and Karinne Venne for obtaining mass
spectra, Dr. Christian Reber and Vale´rie Baslon for helping
us record UV-visible diffuse-reflectance spectra, and Prof.
Jurgen Sygusch for providing access to a diffractometer
equipped with a rotating anode.
Supporting Information Available: Additional structural views
and crystallographic details (CIF files) for the complexes of Cu(II)
and Cu(I) with ligands 1-3. This material is available free of charge
via the Internet at http://pubs.acs.org.
(31) SAINT-Plus, Versions 6.35A and 7.34a; Bruker AXS Inc.: Madison,
WI, 2002, 2006.
IC8019809
(32) Sheldrick, G. M. SADABS, Versions 2.05 and 2007/2; University of
Go¨ttingen: Go¨ttingen, Germany, 2002, 2007.
(33) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.
Inorganic Chemistry, Vol. 48, No. 7, 2009 2807