Topological control in heterometallic metal-organic frameworks by anion templating and metalloligand design

Article abstract of DOI:10.1021/ja0645483

Several new heterometallic metal-organic frameworks (MOFs) based on tris(dipyrrinato) metalloligands and Ag⁺ salts are reported. MOFs were prepared systematically to examine the effects of the core metal ion, counteranion, and ligand structure

Full text of DOI:10.1021/ja0645483

Published on Web 11/08/2006
Topological Control in Heterometallic Metal-Organic
Frameworks by Anion Templating and Metalloligand Design
Sara R. Halper, Loi Do, Jay R. Stork, and Seth M. Cohen*
Contribution from the Department of Chemistry and Biochemistry, UniVersity of California,
San Diego, La Jolla, California, 92093-0358
Received July 5, 2006; E-mail: scohen@ucsd.edu
Abstract: Several new heterometallic metal-organic frameworks (MOFs) based on tris(dipyrrinato)
metalloligands and Ag+ salts are reported. MOFs were prepared systematically to examine the effects of
the core metal ion, counteranion, and ligand structure on the topology of the resultant network. The effect
of the metal ion (Fe3+ vs Co3+) on MOF structure was generally found to be negligible, thereby permitting
the facile synthesis of trimetallic Fe/Co/Ag networks. The choice of anion (e.g., silver salt) was found to
have a pronounced effect on the MOF topology. Networks prepared with salts of AgO3SCF3 and AgBF4
reliably formed three-dimensional (10,3) nets, whereas use of AgPF6 and AgSbF6 produced two-dimensional
(6,3) honeycomb nets. The topology generated upon formation of the MOF was found to be robust in
certain cases, as demonstrated by anion-exchange experiments. Anion exchange was confirmed by X-ray
crystallography in a rare set of apparent single-crystal-to-single-crystal transformations. The data presented
here strongly suggest that the coordinative ability of the anion does not play a significant role in the observed
templating effect. Finally, changes in the length of the tris(dipyrrinato) metalloligand were found to override
the anion templating effect, resulting exclusively in two-dimensional (6,3) nets. These studies provide a
basis for the rational design of MOF topologies by choice of ligand structure and anion templating effects.
Furthermore, the results demonstrate the ability of carefully designed metalloligands to generate MOFs of
structure strikingly similar to that of their organic counterparts.
Introduction
tion of complex functionality (e.g., catalysis, luminescence, etc.)
into MOF assemblies.5,11-13 Efforts to introduce more complex
At the forefront of modern materials chemistry and nano-
science is the design and synthesis of solid-state compounds
known as metal-organic frameworks (MOFs).1-4 The com-
pounds are tailorable, low-density solids with tremendous
promise for use in gas storage, molecular sensing, and other
materials applications.5 Many robust, highly porous MOFs have
been prepared that may be particularly useful in gas storage
and separations.6-8 A continuing challenge in the field of MOFs
is the ability to reliably predict the topology of a MOF based
solely on the structure of the individual precursors. Although a
number of MOFs have been prepared and certain structural
motifs are found to be most common,9,10 predicting the structure
of a framework de novo remains elusive. In addition to structure
prediction, another major challenge in the field is the introduc-
functionality include modification of the ligand structure and
forcing sites of unsaturation or labile solvent coordination at
the metal nodes. Among the most attractive strategies for
introducing new functionality is the use of “metalloligands”,
that is coordination complexes as building blocks in lieu of
simple organic ligands.13 Such metalloligands have been shown
to have the ability to introduce rich spectroscopic and magnetic
features to MOFs,14-17 in addition to providing sites for
introducing unsaturated metal centers.18-22
(11) Wu, C. D.; Hu, A.; Zhang, L.; Lin, W. B. J. Am. Chem. Soc. 2005, 127,
8940-8941.
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A. J.; O’Keeffe, M.; Yaghi, O. M. Nature 2004, 427, 523-527.
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J. AM. CHEM. SOC. 2006, 128, 15255-15268
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A R T I C L E S
Halper et al.
an Avatar 360 (Thermo Nicolet) FT-IR instrument (using KBr pellets
or NaCl plates) at the Department of Chemistry and Biochemistry,
University of California, San Diego. 1H/13C/19F NMR spectra were
recorded on Varian FT-NMR spectrometers at the Department of
Chemistry and Biochemistry, University of California, San Diego. UV-
visible spectra were recorded in CH2Cl2 using a Perkin-Elmer Lambda
25 spectrophotometer with the UVWinLab 4.2.0.0230 software package.
[Co(4-pyrdpm)3AgBF4] (MOF-Co/AgBF4-1). In the following
To date, most metalloligands have utilized the same general
donor groups found in many organic ligands used in MOFs (e.g.,
carboxylate, nitrile, and pyridyl ligands), but have not necessarily
reproduced the size and shape of the organic ligands used in
MOF synthesis. The potential advantage of replicating both the
donor atoms and overall structure of an organic ligand in a
metalloligand is the possibility of generating specific, i.e.,
predictable, MOF topologies by prior knowledge of the analo-
gous organic ligand MOF. For example, if a specific MOF is
found to have structural properties (e.g., microporosity, pore
shape, thermal stability, etc.) desirable for a specific application,
then designing a metalloligand that reproduces that structure
with high fidelity would allow for retention of the framework
topology while introducing new functionality that originates
from the metalloligand metal center. The enormous number of
MOF structures derived from organic ligands described to date
provides a general strategy for the preparation of MOFs of a
selected topology and functionality based on analogous met-
alloligand precursors. Realization of this goal is the focus of
the studies detailed herein.
Recently, we have described several dipyrromethene (dipyr-
rinato, dipyrrin) coordination complexes23,24 that generally
reproduce the structures found in a class of organic ligand MOFs
reported by Lee, Moore, and co-workers.25-28 These dipyrrinato,
metalloligand-based MOFs generate materials with strong
optical absorptions and show potential for the synthesis of chiral
MOFs derived from the ∆/Λ configuration at a tris(chelate)
metal center.24 On the basis of these early findings, we report
here a more comprehensive, systematic investigation of these
dipyrrin-based metalloligand systems, describing 14 new, crys-
tallographically characterized MOF structures. A pronounced
anion templating is reported, which permits control over two-
(2D) versus three-dimensional (3D) framework structures. The
consequence of changes in metalloligand composition on MOF
structure have also been studied and are found to closely parallel
those observed in analogous three-fold symmetric organic ligand
systems. All in all, the findings here show that tris(dipyrrinato)
metal complexes appended with peripheral binding groups are
a versatile class of metalloligands for preparing a variety of
functionalized MOF structures.
order,
1 equiv of a benzene solution containing 3.5 mM
[Co(4-pyrdpm)3], neat benzene, and 1 equiv of a benzene solution
containing 3.5 mM AgBF4 were placed into a glass test tube.23 Different
solution volumes were used in order to obtain mixtures containing from
∼0.22 to 1.3 mM of each reactant. At all concentrations, a precipitate
formed immediately upon addition of AgBF4, which was dissolved by
addition of ∼1.0 mL of acetonitrile. The solutions were stored in the
dark and left to slowly evaporate. Orange crystals grew from all
solutions after ∼7-15 days. For a solution containing 1.3 mM [Co-
(4-pyrdpm)3], 1.3 mM AgBF4, and 1.0 mL of acetonitrile (total volume
4.0 mL) the isolated yield of crystalline material was 1.7 mg (36%).
IR (KBr pellet): ν 1540, 1380, 1345, 1247, 1032, 994 cm-1
.
[Fe(4-pyrdpm)3AgOTf] (MOF-Fe/AgOTf-1). The same procedure
was used as in the synthesis of MOF-Co/AgBF4-1. For a solution
containing 2.6 mM [Fe(4-pyrdpm)3], 2.6 mM AgOTf, and 1.0 mL of
acetonitrile (total volume 4.0 mL) the isolated yield of crystalline
material was 4.6 mg (32%). IR (KBr pellet): ν 1561, 1379, 1336, 1242,
1039, 996 cm-1
.
[Co(4-pyrdpm)3AgPF6] (MOF-Co/AgPF6-1). The same procedure
was used as in the synthesis of MOF-Co/AgBF4-1. For a solution
containing 1.7 mM [Co(4-pyrdpm)3], 1.7 mM AgPF6, and 1.0 mL of
acetonitrile (total volume 4.0 mL) the isolated yield of crystalline
material was 4.8 mg (80%). IR (KBr pellet): ν 1561, 1382, 1345, 1247,
1034, 996, 840, 802 cm-1
.
[Fe(4-pyrdpm)3AgPF6] (MOF-Fe/AgPF6-1). The same procedure
was used as in the synthesis of MOF-Co/AgBF4-1. For a solution
containing 1.7 mM [Fe(4-pyrdpm)3], 1.7 mM AgPF6, and 1.0 mL of
acetonitrile (total volume 4.0 mL) the isolated yield of crystalline
material was 3.9 mg (65%). IR (KBr pellet): ν 1550, 1379, 1336, 1242,
1039, 995, 840, 811 cm-1
.
[Co(4-pyrdpm)3AgSbF6] (MOF-Co/AgSbF6-1). The same proce-
dure was used as in the synthesis of MOF-Co/AgBF4-1. For a solution
containing 0.43 mM [Co(4-pyrdpm)3], 0.43 mM AgSbF6, and 1.0 mL
of acetonitrile (total volume 4.0 mL) the isolated yield of crystalline
material was 0.9 mg (49%). IR (KBr pellet): ν 1562, 1380, 1345, 1254,
1032, 995 cm-1
.
[Fe(4-pyrdpm)3AgSbF6] (MOF-Fe/AgSbF6-1). The same procedure
was used as in the synthesis of MOF-Co/AgBF4-1. For a solution
containing 1.4 mM [Fe(4-pyrdpm)3], 1.4 mM AgSbF6, and 1.0 mL of
acetonitrile (total volume 5.6 mL) the isolated yield of crystalline
material was 3.4 mg (32%). IR (KBr pellet): ν 1561, 1379, 1336, 1242,
Experimental
General. Unless otherwise noted, starting materials were obtained
from commercial suppliers and used without further purification. [Co-
(4-pyrdpm)3] and [Fe(4-pyrdpm)3] (4-pyrdpm ) 5-(4-pyridyl)-4,6-
dipyrrinato) were prepared as previously described.23 Mass spectrometry
was performed at the University of California, San Diego, Mass
Spectrometry Facility in the Department of Chemistry and Biochemistry.
A ThermoFinnigan LCQ-DECA mass spectrometer was used for ESI
or APCI analysis, and the data were analyzed using the Xcalibur
software suite. A ThermoFinnigan MAT 900XL mass spectrometer was
used to acquire the data for the high-resolution mass spectra (HRMS).
Infrared spectra were collected on either a Mattson Research Series or
1040, 996, 769, 657 cm-1
.
[Co(4-pyrdpm)3Fe(4-pyrdpm)3(AgOTf)2] (MOF-CoFe/AgOTf-1).
In the following order, 1 equiv of a benzene solution containing 3.5
mM [Fe(4-pyrdpm)3] and 3.5 mM [Co(4-pyrdpm)3], neat benzene, and
1 equiv of a benzene solution containing 7.0 mM AgOTf were placed
into a glass test tube. Different solution volumes were used in order to
obtain mixtures containing from ∼0.22 to 1.3 mM of each reactant. At
all concentrations, a precipitate formed immediately upon addition of
AgOTf, which was dissolved by addition of ∼1.0 mL of acetonitrile.
The solutions were stored in the dark and left to slowly evaporate. For
a solution containing 0.88 mM [Fe(4-pyrdpm)3], 0.88 mM [Co(4-
pyrdpm)3], 1.75 mM AgOTf, and 1.0 mL of acetonitrile (total volume
4.0 mL) the isolated yield of crystalline material was 2.8 mg (42%).
(23) Halper, S. R.; Cohen, S. M. Inorg. Chem. 2005, 44, 486-488.
(24) Murphy, D. L.; Malachowski, M. R.; Campana, C. F.; Cohen, S. M. Chem.
Commun. 2005, 5506-5508.
(25) Kiang, Y.-H.; Lee, S.; Xu, Z.; Choe, W.; Gardner, G. B. AdV. Mater. 2000,
12, 767-770.
(26) Kiang, Y.-H.; Gardner, G. B.; Lee, S.; Xu, Z.; Lobkovsky, E. B. J. Am.
Chem. Soc. 1999, 121, 8204-8215.
IR (KBr pellet): ν 1563, 1381, 1346, 1252, 1031, 995 cm-1
.
(27) Choe, W.; Kiang, Y.-H.; Xu, Z.; Lee, S. Chem. Mater. 1999, 11, 1776-
[Co(4-pyrdpm)3Fe(4-pyrdpm)3(AgBF4)2] (MOF-CoFe/AgBF4-1).
The same procedure was used as in the synthesis of MOF-CoFe/AgOTf-
1. For a solution containing 0.88 mM [Fe(4-pyrdpm)3], 0.88 mM [Co-
1783.
(28) Xu, Z.; Kiang, Y.-H.; Lee, S.; Lobkovsky, E. B.; Emmott, N. J. Am. Chem.
Soc. 2000, 122, 8376-8391.
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Anion Templating of Metalloligand MOFs
A R T I C L E S
(4-pyrdpm)3], 1.75 mM AgBF4, and 1.0 mL of acetonitrile (total volume
4.0 mL) the isolated yield of crystalline material was 5.5 mg (87%).
[Co(4-papyrdpm)3AgOTf] (MOF-Co/AgOTf-4). The same pro-
cedure was used as in the synthesis of MOF-Co/AgBF4-1. For a solution
containing 1.7 mM [Co(4-papyrdpm)3], 1.7 mM AgOTf, and 1.0 mL
of acetonitrile (total volume 4.0 mL) the isolated yield of crystalline
material was 6.1 mg (69%). IR (KBr pellet): ν 1607, 1563, 1537, 1411,
IR (KBr pellet): ν 1562, 1383, 1346, 1245, 1084, 1040, 996 cm-1
.
[Co(4-quindpm)3]. The same procedure was used as for the
preparation of [Co(4-pyrdpm)3],23 but starting from 5-(4-quinolyl)-
dipyrromethane29 (100 mg, 0.37 mmol). Yield: 48% (51 mg). 1H NMR
(CDCl3 300 MHz, 25 °C): δ 6.35-6.65 (m, 6H), 7.42 (t, 1H), 7.50 (t,
1H), 7.67 (t, 1H), 7.72 (d, 1H), 8.20 (d, 1H), 9.03 (d, 1H). GC-EIMS:
m/z 870.1 [M + H]+. HR-EIMS Calcd for C54H37N9Co: 870.2498.
Found: 870.2492. λmax (CH2Cl2) ) 267, 295, 315, 405, 471, 511 nm.
IR (film from CH2Cl2): ν 1557, 1378, 1360, 1249, 1039, 1023, 1001,
1380, 1346, 1282, 1247, 1221, 1160, 1021, 995 cm-1
.
[Co(4-papyrdpm)3AgBF4] (MOF-Co/AgBF4-4). The same proce-
dure was used as in the synthesis of MOF-Co/AgBF4-1. For a solution
containing 1.7 mM [Co(4-papyrdpm)3], 1.7 mM AgBF4, and 1.0 mL
of acetonitrile (total volume 4.0 mL) the isolated yield of crystalline
material was 7.5 mg (89%). IR (KBr pellet): ν 1559, 1379, 1346, 1249,
1084, 1042, 1030, 999 cm-1
826 cm-1
.
[Co(4-papyrdpm)3AgPF6] (MOF-Co/AgPF6-4). The same proce-
dure was used as in the synthesis of MOF-Co/AgBF4-1. For a solution
containing 1.7 mM [Co(4-papyrdpm)3], 1.7 mM AgPF6, and 1.0 mL
of acetonitrile (total volume 4.0 mL) the isolated yield of crystalline
material was 6.9 mg (77%). IR (KBr pellet): ν 1159, 1380, 1345, 1249,
[Fe(4-quindpm)3]. The same procedure was used as for the
preparation of [Fe(4-pyrdpm)3],23 but starting from 5-(4-quinolyl)-
dipyrromethane29 (250 mg, 0.92 mmol). Yield: 41% (110 mg). GC-
EIMS: m/z 867.0 [M + H]+. HR-EIMS Calcd for C54H37N9Fe:
867.2516. Found: 867.2519. λmax (CH2Cl2) ) 265, 292, 315, 446, 496
(shoulder) nm. IR (film from CH2Cl2): ν 1554, 1380, 1336, 1244, 1039,
1044, 1030, 1000, 843, 816 cm-1
.
996, 825 cm-1
.
Anion-Exchange Studies. Crystals of MOF-Co/AgOTf-1 were
grown according to the procedure described above for MOF-Co/AgBF4-
1.23 Once single crystals had formed, the mother liquor was removed
and quickly replaced with a solution of 30 mM tetrabutylammonium
tetrafluoroborate in a 4:1 benzene/acetonitrile mixture. The solution
was then gently shaken for 24 h. Single crystals were taken from the
solution and analyzed by X-ray diffraction; this net is designated MOF-
Co/Ag×BF4-1, where the “×” designates the exchanged anion. The
remaining crystals were washed with a benzene/acetonitrile solution,
dried, and analyzed by 19F NMR (CDCl3, 300 MHz, 25 °C) giving
signals at -152.1 ppm indicative of the tetrafluoroborate anion. An
identical experiment was performed with a 26 mM solution of
tetrabutylammonium hexafluorophosphate (MOF-Co/Ag×PF6-1). 19F
NMR (CDCl3 300 MHz, 25 °C): δ -69.3, -71.8 ppm.
X-ray Crystallographic Analysis. Single crystals of each compound
suitable for X-ray diffraction structural determination were mounted
on quartz capillaries with Paratone oil and were cooled in a nitrogen
stream on the diffractometer. Data were collected on either a Bruker
AXS or a Bruker P4 diffractometer each equipped with area detectors.
Peak integrations were performed with the Siemens SAINT software
package. Absorption corrections were applied using the program
SADABS. Space group determinations were performed by the program
XPREP. The structures were solved by either Patterson or direct
methods and refined with the SHELXTL software package (Sheldrick,
G. M. SHELXTL Vers. 5.1 Software Reference Manual; Bruker AXS:
Madison, WI, 1997). All hydrogen atoms were fixed at calculated
positions with isotropic thermal parameters, and all non-hydrogen atoms
were refined anisotropically unless otherwise noted. Many of the
structures contained ordered, disordered, or partially occupied solvent
molecules (benzene, acetonitrile); these details are not described in the
text below but have been provided in the Supporting Information. Also,
several structures had some disorder and/or partial occupancy complica-
tions with the anions. Again, the details for each crystallographic
analysis can be found in the Supporting Information. Many of the
structures refined quite well, those that did not (e.g., R1 values >10%)
are presented solely to demonstrate connectivity and net topology.
Thermogravimetric Analysis. All MOF samples were dried in a
vacuum oven at ∼50 °C for 10-12 h prior to analysis. Thermogravi-
metric analysis (TGA) experiments were run on a TA Instruments Q600
using a platinum pan. Samples of each MOF (∼2-10 mg) were
analyzed under a nitrogen flow (100 mL/min) from ∼25 to 1000 °C
with a gradient of 20 °C/min.
[Fe(4-quindpm)3AgOTf] (MOF-Fe/AgOTf-3). The same procedure
was used as in the synthesis of MOF-Co/AgBF4-1. For a solution
containing 0.75 mM [Fe(4-quindpm)3], 0.75 mM AgOTf, and 1.0 mL
of acetonitrile (total volume 4.0 mL) the isolated yield of crystalline
material was 1.3 mg (38%). IR (KBr pellet): ν 1560, 1554, 1400, 1377,
1242, 1038, 995 cm-1
.
[4-(Pyridin-4-ylethynyl)benzaldehyde]. A mixture of 4-(ethynyl)-
benzaldehyde (0.33 g, 2.5 mmol), 4-bromopyridine hydrochloride (0.64
g, 3.3 mmol), Pd(PPh3)2Cl2 (89 mg, 0.13 mmol), CuI (24 mg, 0.13
mmol), and 25 mL of dry diethylamine was stirred under a nitrogen
atmosphere for 24 h. The reaction mixture was subsequently evaporated
to dryness and then redissolved in 75 mL of CH2Cl2. The organic
solution was washed with 75 mL of H2O and 75 mL of brine and was
then dried over MgSO4. The CH2Cl2 was evaporated to dryness, and
the resulting residue was purified by column chromatography (SiO2;
CH2Cl2/1% MeOH) to afford the product as a yellow solid. Yield: 58%
(0.31 g). GC-EIMS: m/z 207.1 [M]+. 1H NMR (CDCl3 400 MHz, 25
°C): δ 7.27 (d, 2H, J ) 6.0 Hz), 7.55 (d, 2H, J ) 8.4 Hz), 7.74 (d,
2H, J ) 8.4 Hz), 8.51 (d, 2H, J ) 4.0 Hz), 9.98 (s, 1H, CHO) ppm.
13C NMR (CDCl3 100 MHz, 25 °C): δ 89.7, 92.2, 125.1, 127.6, 129.1,
130.1, 131.9, 135.6, 149.3, 190.6 ppm.
[5-(4-Pyridin-4-ylethynylphenyl)dipyrromethane]. The same pro-
cedure was used as in the synthesis of 5-(4-pyridyl)dipyrromethane,23,30
but starting from [4-(pyridin-4-ylethynyl)benzaldehyde] (0.31 g, 1.5
mmol). The product was isolated as a pale-yellow solid. Yield: 40%
(0.19 g). ESI-MS: m/z 324.12 [M + H]+, 258.23 [M - pyrrole]+. 1H
NMR (CDCl3 400 MHz, 25 °C): δ 5.50 (s, 1H), 5.90 (m, 2H), 6.17
(m, 2H), 6.72 (m, 2H), 7.23 (d, 2H, J ) 8.0 Hz), 7.37 (d, 2H, J ) 6.0
Hz), 7.49 (d, 2H, J ) 8.4 Hz), 8.07 (bs, 2H, NH), 8.57 (d, 2H, J ) 6.4
Hz). 13C NMR (CDCl3 100 MHz, 25 °C): δ 43.9, 86.6, 93.8, 107.3,
108.4, 117.4, 120.5, 125.4, 128.4, 131.3, 131.6, 132.0, 143.3, 149.5
ppm.
[Co(4-papyrdpm)3]. The same procedure was used as in the
synthesis of [Co(4-pyrdpm)3],23 but starting from 5-(4-pyridin-4-
ylethynylphenyl)dipyrromethane (0.50 g, 1.55 mmol). Yield: 38% (0.20
g). ESI-MS: m/z 1020.08 [M + H]+. HR-FABMS Calcd for C66H42N9-
1
Co: 1020.2968. Found: 1020.2957. H NMR (CDCl3 400 MHz, 25
°C): δ 6.36 (m, 6H), 6.43 (s, 6H), 6.72 (m, 6H), 7.41 (d, 6H, J ) 5.6
Hz), 7.48 (d, 6H, J ) 8.0 Hz), 7.62 (d, 2H, J ) 8.4 Hz), 8.62 ppm (d,
6H, J ) 5.2 Hz). 13C NMR (CDCl3 100 MHz, 25 °C): δ 87.6, 93.3,
118.9, 122.2, 125.4, 130.3, 130.6, 131.0, 132.7, 135.0, 138.6, 144.8,
149.5, 151.7 ppm. λmax (CH2Cl2) ) 228, 279, 293, 335, 398, 469, 506
nm. IR (KBr pellet): ν 1560, 1379, 1344, 1248, 1041, 1029, 998, 812
Results and Discussion
cm-1
.
Preparation of Metalloligands. As shown in Chart 1, three
metalloligand systems have been prepared and utilized in the
MOFs described here. The simplest of these metalloligands,
[M(4-pyrdpm)3], has been previously reported, in addition to
(29) Halper, S. R.; Cohen, S. M. Inorg. Chem. 2005, 44, 4139-4141.
(30) Halper, S. R.; Malachowski, M. R.; Delaney, H. M.; Cohen, S. M. Inorg.
Chem. 2004, 43, 1242-1249.
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A R T I C L E S
Halper et al.
Chart 1. List of Ligands, Metalloligands, and General MOF Connectivity.
two MOFs prepared from this precursor.23 The other metallo-
ligands, [M(4-quindpm)3] and [M(4-papyrdpm)3], have not been
previously reported, although related molecules have been
described in the literature.29,31 For all three metalloligand
systems the synthetic procedure is the same: (1) preparation
of the dipyrromethane from condensation of an aryl aldehyde
(the precursor aldehyde for 4-papyrdpm was synthesized ac-
cording to Scheme S1) and pyrrole; (2) oxidation of the
dipyrromethane to the dipyrromethene (dipyrrin) using DDQ;
and (3) complexation of the dipyrrin to a transition metal salt,
either FeCl3·6H2O or Na3[Co(NO2)6], to generate the desired
coordination complex.23,24,32 The synthesis of these metallo-
ligands proceeds in modest yields; however, the reaction can
be scaled to reasonably obtain 500-750 mg quantities of these
complexes. Each coordination complex possesses three pendant
pyridyl or quinolyl groups, permitting coordination to a second
metal ion, and hence can function as a metalloligand. The rich
electronic absorption spectra of these metalloligands are char-
acteristic of both the metal ion and the dipyrrinato ligand. All
of the dipyrrinato metalloligands display ligand-to-metal charge
transfer (LMCT) bands centered at approximately 470 and 510
nm for the cobalt(III) complexes, and 445 and 496 nm for the
iron(III) complexes. Additional transitions in the ultraviolet
region are attributed to πfπ* transitions of the meso-aryl
substituents, which are observed at approximately 230 and 290
nm for M(4-pyrdpm)3; 270, 295, and 315 for M(4-quindpm)3;
and 228, 279, 293, 335, and 398 nm for Co(4-papyrdpm)3.
Preparation of MOFs: Anion Templating Effects. The
synthesis of all MOFs described herein followed previously
reported methods.23 The metalloligand was dissolved in benzene
and mixed with one equivalent of a silver(I) salt also dissolved
in benzene (combined volume of ∼3 mL); mixing of these two
components results in the formation of an orange-red precipitate,
which redissolves upon addition of a minimal amount of
acetonitrile (e1 mL). The mixtures were then allowed to
evaporate slowly, yielding single crystals in 1-2 weeks.
Incorporation of the metalloligand into the extended structure
was readily apparent from the deep red or orange color of the
crystals (depending on the metal ion), indicative of LMCT bands
from the dipyrrin complex.23,31,32 It is important to note that
the synthetic procedure used with these metalloligands is
essentially identical to that employed in the synthesis of the
analogous organic nitrile MOFs, precluding any need for the
development of new synthetic methods.25-28
In our previous report, the combination of [Co(4-pyrdpm)3]
with AgOTf (OTf- ) triflate, CF3SO3-) or [Fe(4-pyrdpm)3]
with AgBF4 led to the formation of isostructural, doubly
interpenetrated MOF-Co/AgOTf-1 (previously named MOF-Co/
Ag-1) and MOF-Fe/AgBF4-1 (previously named MOF-Fe/Ag-
1), respectively.23 Both of these frameworks crystallized in the
orthorhombic space group Pbcn and possess a (10,3)-d network
(31) Halper, S. R.; Cohen, S. M. Chem. Eur. J. 2003, 9, 4661-4669.
(32) Cohen, S. M.; Halper, S. R. Inorg. Chim. Acta 2002, 341, 12-16.
9
15258 J. AM. CHEM. SOC. VOL. 128, NO. 47, 2006

Anion Templating of Metalloligand MOFs
A R T I C L E S
Table 1. X-ray Crystallographic Data for (10,3) Net MOFs Derived from [M(4-pyrdpm)3] (M ) Co3+, Fe3+
)
MOF-Co/AgBF4-1
MOF-Fe/AgOTf-1
MOF-CoFe/AgBF4-1
MOF-CoFe/AgOTf-1
empirical formula
crystal system
space group
C84H60Ag2B2Co2F8N18
monoclinic
P21/c
C160H123Ag3F9Fe3N29O9S3
monoclinic
C2/c
C84H60Ag2B2CoF8FeN18
orthorhombic
Pbcn
C86H60Ag2CoF6FeN18O6S2
orthorhombic
Pbcn
unit cell dimensions
a (Å)
b (Å)
33.41(2)
26.932(16)
12.365(8)
33.186(5)
66.054(10)
14.882(2)
26.939(6)
12.335(3)
33.458(7)
90
90
90
26.813(3)
12.6035(12)
33.472(3)
90
90
c (Å)
R (deg)
90
90
â (deg)
91.533(10)
90
110.699(2)
90
γ (deg)
90
volume (Å3), z
crystal size (mm3)
temperature (K)
reflections collected
independent reflections
data/restraint/parameters
goodness-of-fit on F2
Final R indices I > 2σ(I)a
11123(12), 8
0.30 × 0.22 × 0.16
100(2)
30516(8), 8
0.32 × 0.15 × 0.02
100(2)
11118(4), 4
0.38 × 0.34 × 0.30
100(2)
11311.5(19), 4
0.35 × 0.26 × 0.18
100(2)
94777
133235
99449
96717
24306 [R(int) ) 0.0986]
24306/67/1022
1.090
R1 ) 0.0857
wR2 ) 0.2445
R1 ) 0.1155
wR2 ) 0.2628
27904[R(int) ) 0.1500]
27904/0/1953
1.029
R1 ) 0.0847
wR2 ) 0.2048
R1 ) 0.1620
wR2 ) 0.2314
10174 [R(int) ) 0.0875]
10174/68/559
1.030
R1 ) 0.0738
wR2 ) 0.1880
R1 ) 0.1256
wR2 ) 0.2090
11551 [R(int) ) 0.0431]
11551/0/614
1.106
R1 ) 0.0718
wR2 ) 0.1619
R1 ) 0.0796
wR2 ) 0.1647
R indices (all data)a
2
2
4
a R1 ) ∑||Fo| - |Fc||/∑|Fo| , wR2 ) {∑[w(Fo - Fc )2]/∑[wFo ]}1/2
.
topology (Schla¨fli symbol 103, vertex symbol 102·104·104),9 as
determined by generation of the vertex symbols using the
program OLEX.33 The (10,3) topology was expected on the basis
of comparison to the systems prepared with the organic ligand
1,3,5-tris(4-ethynylbenzonitrile)benzene (TEB) and AgOTf.25-28
pyrdpm)3] was combined with AgPF6 or AgSbF6 to generate
four new networks (Table 3): MOF-Co/AgPF6-1, MOF-Co/
AgSbF6-1, MOF-Fe/AgPF6-1, and MOF-Fe/AgSbF6-1. In all
four MOFs the structure was determined to be a 2D (6,3)
honeycomblike network (Schla¨fli symbol 6,3 vertex symbol 6·
6·6), distinct from the 3D (10,3) nets found with AgOTf and
AgBF4 (Table 2). The structures of MOF-Co/AgPF6-1 and
MOF-Co/AgSbF6-1 are shown in Figure 2; the isostructural iron-
(III) analogues are shown in Figure S1. The MOFs consist of
2D nets, with sheets of [M(4-pyrdpm)3] complexes linked by
silver(I) ions. Each silver(I) ion is coordinated to three different
[M(4-pyrdpm)3] complexes, as found in the (10,3) nets. Each
silver(I) ion is also coordinated by an acetonitrile solvent
-
To demonstrate that the OTf- and BF4 anions result in
identical structure types, the complementary frameworks MOF-
Co/AgBF4-1 and MOF-Fe/AgOTf-1 were synthesized and
characterized. Single crystals of both networks were obtained
by slow evaporation, and the MOF structures were determined
by X-ray crystallography (Table 1). As shown in Figure 1 and
listed in Table 2, MOF-Co/AgBF4-1 and MOF-Fe/AgOTf-1 also
form (10,3) networks. As expected, MOF-Co/AgBF4-1 forms
a doubly interpenetrated (10,3)-d network;9 the only difference
from the earlier structures is that MOF-Co/AgBF4-1 crystallized
in the monoclinic space group P21/c, (albeit with cell parameters
virtually identical to those of earlier reported structures).23 Of
these four structures, MOF-Co/AgOTf-1, MOF-Co/AgBF4-1,
MOF-Fe/AgOTf-1, and MOF-Fe/AgBF4-1, only one is not of
the (10,3)-d topology (Table 2). Although very similar in overall
structure, MOF-Fe/AgOTf-1 was found to form a (10,3)-b
framework. The (10,3)-b framework, or ThSi2-type net,9 has
the same Schla¨fli symbol and vertex symbol descriptors (Schla¨fli
symbol 103, vertex symbol 102·104·104) as the related (10,3)-d
net. Despite the similarities, the (10,3)-b and (10,3)-d nets can
be distinguished by comparison to the idealized nets.9 The
differences in the topology of the nets are best realized by
inspection of the structures along directions of high symmetry
(Figure 1). As found in the other (10,3) nets synthesized here,
the structure of MOF-Fe/AgOTf-1 contains two independent,
interpenetrated nets. The synthesis and crystallization of MOF-
Fe/AgOTf-1 was repeated several times to confirm this surpris-
ing finding, and in every case the same (10,3)-b network was
obtained. This result led us to examine the role of the
counteranions in governing the topology of these MOFs.
To explore the effect of the silver(I) counteranion on the
topology of the resultant network, [Co(4-pyrdpm)3] or [Fe(4-
-
-
molecule (rather than the PF6 or SbF6 anion, Figure 3); the
coordinated solvent was found in all (6,3) nets, but was not
well-ordered in the MOF-M/AgPF6-1 networks (Figure 2). Our
-
-
findings are consistent with reports that the PF6 and SbF6
anions can template identical topologies in coordination solids.34
The overall (6,3) topology of the MOF-M/AgPF6-1 and MOF-
M/AgSbF6-1 frameworks is the same, but the packing of these
honeycomb sheets show different layering patterns (Figure S2).
In MOF-M/AgPF6-1, the nets lie in the crystallographic bc-
plane and an AB stacking pattern is observed. In MOF-M/
AgSbF6-1, the nets lie in the crystallographic ac-plane and
follow an ABCD stacking pattern. Despite the differences
between the MOF-M/AgPF6-1 and MOF-M/AgSbF6-1 frame-
works, the cobalt(III) and iron(III) nets prepared with the same
silver(I) salt are identical (e.g. MOF-Co/AgPF6-1 and MOF-
Fe/AgPF6-1 are isostructural). The preservation of structure with
either cobalt(III) or iron(III) displays the modular nature of this
MOF synthetic approach and indicates that the anions are
playing the dominant structure-determining role. Interestingly,
in both structure types, each individual layer of the (6,3) net is
homochiral, comprising only ∆ or Λ tris(chelate) metal centers.
Each layer neighbors two enantiomerically pure sheets of
opposite chirality (e.g. in MOF-M/AgSbF6-1 if A is ∆, then in
ABCD the chirality of each net alternates as ∆Λ∆Λ). The
(33) Dolomanov, O. V.; Blake, A. J.; Champness, N. R.; Schro¨der, M. J. Appl.
Crystallogr. 2003, 36, 1283-1284.
(34) Dong, Y.-B.; Xu, H.-X.; Ma, J.-P.; Huang, R.-Q. Inorg. Chem. 2006, 45,
3325-3343.
9
J. AM. CHEM. SOC. VOL. 128, NO. 47, 2006 15259

A R T I C L E S
Halper et al.
Figure 1. X-ray structure of the 3D (10,3)-d net MOF-Co/AgBF4-1 (top) and the (10,3)-b net MOF-Fe/AgOTf-1 (bottom). The structures are viewed down
the crystallographic c-axis, showing only one of the two interpenetrated nets for clarity. Cobalt(III), iron(III), and silver(I) centers are represented by blue,
gold, and gray polyhedra, respectively. Hydrogen atoms, anions, and solvent molecules have also been omitted for clarity.
homochirality of these 2D sheets is in contrast to those based
on three-fold symmetric oxalate metalloligands. In the reported
oxalate-based systems both 2- and 3D MOFs are known; the
2D MOFs are racemic, wereas a different set of 3D MOFs were
found to be homochiral.14-16,35 Overall, the anions clearly exhibit
a pronounced templating effect in the synthesis of dipyrrinato,
metalloligand-derived MOFs. Although never described with
the three-fold symmetric 1,3,5-tris(4-ethynylbenzonitrile)ben-
zene ligand, anion templating effects in Ag-nitrile MOFs have
been reported in the literature.36-38
Noting that the iron(III) and cobalt(III) MOFs are generally
isostructural, it was expected that, when using the same silver-
(I) salt, the synthesis of trimetallic (Fe/Co/Ag) MOFs would
be accessible. Under conditions identical to those used for
(36) Hirsch, K. A.; Venkataraman, D.; Wilson, S. R.; Moore, J. S.; Lee, S. J.
Chem. Soc., Chem. Commun. 1995, 2199-2200.
(37) Venkataraman, D.; Lee, S.; Moore, J. S.; Zhang, P.; Hirsch, K. A.; Gardner,
G. B.; Covey, A. C.; Prentice, C. L. Chem. Mater. 1996, 8, 2030-2040.
(38) Hirsch, K. A.; Wilson, S. R.; Moore, J. S. Inorg. Chem. 1997, 36, 2960-
2968.
(35) Pellaux, R.; Schmalle, H. W.; Huber, R.; Fischer, P.; Hauss, T.; Ouladdiaf,
B.; Decurtins, S. Inorg. Chem. 1997, 36, 2301-2308.
9
15260 J. AM. CHEM. SOC. VOL. 128, NO. 47, 2006

Anion Templating of Metalloligand MOFs
A R T I C L E S
Table 2. Network Topologies for the MOFs Prepared from
Dipyrrin Metalloligands and Silver(I) Salts
Fe/AgOTf-1 (which formed the slightly different (10,3)-b net).
In this case, where the iron(III) and cobalt(III) monomers form
slightly different MOF topologies, the more commonly observed
(10,3)-d net predominates. Overall, these results show that
multimetallic MOFs can be prepared and that the MOF structure
can be predicted on the basis of individual metalloligand
systems.
M
)
framework
Co
Fe
CoFe
interpenetration/stacking
MOF-M/AgOTf-1
MOF-M/AgBF4-1
MOF-M/AgPF6-1
MOF-M/AgSbF6-1
(10,3)-d (10,3)-b (10,3)-d two-fold
(10,3)-d (10,3)-d (10,3)-d two-fold
(6,3)
(6,3)
(6,3)
(6,3)
n.d.
(6,3)
n.d.
n.d.
AB stacked layers
ABCD stacked layers
two-fold
MOF-M/Ag×BF4-1 (10,3)-d n.d.
Silver(I) Coordination Environments. For the (10,3)-d
networks (MOF-Co/AgOTf-1, MOF-Co/AgBF4-1, MOF-Fe/
AgBF4-1, MOF-CoFe/AgOTf-1, MOF-CoFe/AgBF4-1), the sil-
ver(I) ions generally adopt a distorted trigonal pyramidal
arrangement (Figure 3), in which the metal center is occupied
by three pyridyl nitrogen atoms (from three different metallo-
ligands) and by either an oxygen or fluorine atom from the
weakly coordinated anion in the apical position (Table S2). The
Ag-N distances lie in the range of 2.21-2.28 Å (sum of van
der Waals radii 3.27 Å)39 and the three Ag-N bonds form a
nonideal trigonal plane, with N-Ag-N angles of ∼110-125°.
The interaction between the silver(I) ion and the fourth ligating
atom (from the anion) exhibit slightly different Ag-X (X )
O, F) distances and N-Ag-X angles in each structure. Binding
of the OTf- anion to silver(I) was found to have a Ag-O
distance of ∼2.57 Å (sum of van der Waals radii 3.24 Å)39 for
both MOF-Co/AgOTf-1 and MOF-CoFe/AgOTf-1. Similar bond
lengths and angles were observed in the MOF-M/AgBF4-1
structures (Table S2). The Ag-F contacts in MOF-Fe/AgBF4-1
and MOF-CoFe/AgBF4-1 were found to be 2.69 and 2.60 Å,
respectively (sum of van der Waals radii 3.19 Å).39 MOF-Co/
AgBF4-1 actually has two independent silver(I) centers, with
similar Ag-F contacts of 2.52 and 2.58 Å. While the anions
(OTf- and BF4-) are located within the cavity of two inter-
penetrated (10,3)-d nets, they are coordinated to only one silver-
(I) center, even though the position of the anions is suggestive
of a bridging interaction between the two adjacent networks.
MOF-M/Ag×PF6-1 (10,3)-d n.d.
two-fold
MOF-M/AgOTf-3
MOF-M/AgOTf-4
MOF-M/AgBF4-4
MOF-M/AgPF6-4
n.d.
(10,3)-b n.d.
two-fold
(6,3)
(6,3)
(6,3)
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
AB stacked layers
AB stacked layers
AB stacked layers
preparing the aforementioned frameworks, [Fe(4-pyrdpm)3],
[Co(4-pyrdpm)3], and AgBF4 were combined to obtain dark-
green crystals of MOF-CoFe/AgBF4-1 (Table 1), which was
anticipated to be a (10,3)-d net on the basis of the structures of
MOF-M/AgBF4-1. X-ray diffraction revealed that MOF-CoFe/
AgBF4-1 crystallized in the orthorhombic space group Pbcn and
is a (10,3)-d net (Table 2) that is isostructural with the parent
MOF-M/AgBF4-1 networks (Figure 1).23 The presence of both
iron(III) and cobalt(III) in MOF-CoFe/AgBF4-1 was confirmed
by the electronic absorption spectrum of MOF crystals after
dissolution in acetonitrile; the resultant solution showed transi-
tions characteristic of both dipyrrin complexes (Figure S7). A
second trimetallic MOF was prepared by a combination of [Fe-
(4-pyrdpm)3], [Co(4-pyrdpm)3], and AgSbF6 in a benzene/
acetonitrile solvent mixture. Determination of the cell parameters
for MOF-CoFe/AgSbF6-1 was consistent with the (6,3) net cell
parameters observed for MOF-Co/AgSbF6-1 and MOF-Fe/
AgSbF6-1 (Table 3). Finally, trimetallic MOFs were prepared
with [Fe(4-pyrdpm)3], [Co(4-pyrdpm)3], and AgOTf. Single
crystals proved more challenging to grow, but were obtained;
X-ray diffraction revealed a doubly interpenetrated (10,3)-d net
crystallized in the orthorhombic space group Pbcn (Table 1).
The space group, cell parameters, and topology are identical to
those of one of the parent networks, MOF-Co/AgOTf-1.23 The
(10,3)-d net is the same topology found for MOF-Co/AgOTf-
1, MOF-M/AgBF4-1, MOF-CoFe/AgBF4-1, but not for MOF-
While structurally similar to the (10,3)-d nets, the (10,3)-b
net MOF-Fe/AgOTf-1 possesses four distinct silver(I) coordina-
tion environments. At two of the silver(I) centers there are no
close contacts to the anions (<3.0 Å), generating a trigonal
planar center (although there are OTf- anions in proximity to
Table 3. X-ray Crystallographic Data for (6,3) Net MOFs Derived from [M(4-pyrdpm)3] (M = Co3+, Fe3+
)
MOF-Co/AgPF6-1
MOF-Fe/AgPF6-1
MOF-Co/AgSbF6-1
MOF-Fe/AgSbF6-1
empirical formula
crystal system
space group
unit cell dimensions
a (Å)
C45H33AgCoF6N9P
triclinic
P1h
C58H43.5AgF6FeN12.5
triclinic
P1h
P
C54.2H43.2AgCoF6N10Sb
monoclinic
P21/c
C53H42AgF6FeN10Sb
monoclinic
P21/c
13.120(3)
16.111(3)
16.134(3)
110.178(3)
112.416(3)
97.335(3)
2824.0(10), 2
0.50 × 0.30 × 0.23
100(2)
13.089(3)
16.265(3)
16.105(3)
110.124(3)
112.084(3)
98.571(3)
2826.3(9), 2
0.47 × 0.41 × 0.18
100(2)
15.7911(14)
25.454(2)
16.3779(14)
90
109.8240(10)
90
6193.0(9), 4
0.53 × 0.50 × 0.45
100(2)
15.874(2)
24.606(3)
16.377(2)
90
110.009(2)
90
6010.7(13), 4
0.22 × 0.20 × 0.04
100(2)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
volume (Å3), z
crystal size (mm3)
temperature (K)
reflections collected
independent reflections
data/restraint/parameters
goodness-of-fit on F2
final R indices I > 2σ(I)a
23611
23676
49135
44457
10212 [R(int) ) 0.0353]
10212/0/616
1.072
R1 ) 0.0652
wR2 ) 0.1765
R1 ) 0.0739
wR2 ) 0.1815
10208 [R(int) ) 0.0295]
10208/63/899
1.053
R1 ) 0.0508
wR2 ) 0.1347
R1 ) 0.0683
wR2 ) 0.1449
12651 [R(int) ) 0.0386]
12651/17/757
1.042
R1 ) 0.0695
wR2 ) 0.1902
R1 ) 0.0802
wR2 ) 0.1968
10996 [R(int) ) 0.0622]
10996/17/683
1.078
R1 ) 0.1070
wR2 ) 0.2651
R1 ) 0.1297
wR2 ) 0.2759
R indices (all data)a
2
2
4
a R1 ) ∑||Fo| - |Fc||/∑|Fo| , wR2 ) {∑[w(Fo - Fc )2]/∑[wFo ]}1/2
.
9
J. AM. CHEM. SOC. VOL. 128, NO. 47, 2006 15261

A R T I C L E S
Halper et al.
Figure 2. X-ray structure of (6,3) nets MOF-Co/AgPF6-1 (left) and MOF-Co/AgSbF6-1 (right). Cobalt(III) and silver(I) centers are represented by blue and
gray polyhedra, respectively. The top view of these MOFs is along the plane of the (6,3) net; for MOF-Co/AgPF6-1 this is the crystallographic bc-plane and
for MOF-Co/AgSbF6-1 this is the crystallographic ac-plane. The bottom views are roughly 90° normal to these planes (90° rotation relative to the top
perspectives). Hydrogen atoms and anions have been omitted for clarity. All solvent molecules, except for the apical, silver(I)-coordinated acetonitrile
molecules in MOF-Co/AgSbF6-1, have been omitted for clarity. The corresponding MOF-Fe/AgX-1 compounds are isostructural (see Supporting Information).
Figure 3. Representative coordination environments at the silver(I) ions in (from left to right): MOF-Co/AgBF4-1, MOF-Co/Ag×BF4-1, MOF-Fe/AgOTf-
1, and MOF-Co/AgSbF6-1. Only the coordinating anions or solvent and pyridyl nitrogen atoms are shown for clarity. Bond length shown is between the
silver(I) ion and coordinating anion/solvent molecule. Colors: boron (pale pink), carbon (gray), nitrogen (blue), oxygen (red), fluorine (yellow), sulfur
(orange), and silver (magenta).
the silver(I) ions in the lattice). At the third silver(I) center there
is a close contact to one OTf- anion at 2.62 Å for a trigonal
pyramidal geometry (Figure 3). Finally, the fourth silver(I) ion
in MOF-Fe/AgOTf-1 has two close contacts with OTf- anions,
with Ag-O bond lengths of 2.66 and 2.71 Å. The two oxygen
atoms in this third silver(I) center are bound axially to the
resultant trigonal bipyramidal silver(I) center.
position of silver(I) ion is bound by the nitrogen atom of an
acetonitrile solvent molecule, to give an overall trigonal
pyramidal coordination sphere (Figure 3). In the MOF-M/
AgSbF6-1 networks the solvent was reasonably well ordered
with Ag-N (CH3CN) distances of 2.50-2.53 Å, within the sum
of the van der Waals radii (3.27 Å).39
Anion-Exchange Reactions. Having observed a pronounced
anion templating effect in the series of MOF-M/AgX-1 struc-
tures, we sought to elucidate the origin of this anion effect and
to determine whether any of these MOFs were stable to anion-
exchange conditions. To probe this effect, single crystals of
MOF-Co/AgOTf-1 were grown as described,23 followed by
removal of the mother liquor and rapid replacement with a 4:1
benzene/acetonitrile solution containing 30 mM tetrabutylam-
monium tetrafluoroborate. The solution was then gently shaken
for ∼24 h. No significant dissolution or change in morphology
of the original MOF-Co/AgOTf-1 crystals was observed in this
time period; single crystals were removed from the tetrabutyl-
ammonium tetrafluoroborate solution and analyzed by X-ray
diffraction (Table 4). The resultant framework (MOF-Co/
Ag×BF4-1, the × designates an exchanged anion) is identical
to the parent structure (Figure 4); complete anion exchange is
Similar to the (10,3) nets, the metalloligands in the (6,3)
MOFs are assembled by a three-fold linkage of the peripheral
nitrogen atoms of the metalloligand to the silver(I) center with
Ag-N bonds lengths of 2.20-2.38 Å. In contrast to the (10,3)
nets, the trigonal plane of the silver(I) centers in the (6,3) nets
undergo a significant distortion toward T-shape (Figure 3), with
one N-Ag-N angle substantially more obtuse (145-150°) than
the other two (Table S3). Unlike the 3D MOFs described, the
apical position of the silver(I) centers are not bound by anions.
The anions in these structures are intercalated between the
graphitelike sheets of the MOF, exhibiting no close interactions
between the anions and the silver(I) ions. Rather, in all four
MOF-M/AgPF6-1 and MOF-M/AgSbF6-1 networks the apical
(39) Bondi, A. J. Phys. Chem. 1964, 68, 441-451.
9
15262 J. AM. CHEM. SOC. VOL. 128, NO. 47, 2006

Anion Templating of Metalloligand MOFs
A R T I C L E S
Table 4. X-ray Crystallographic Data for Anion-Exchange Experiments on (10,3) Net MOF-Co/AgOTf-1
MOF-Co/AgOTf-1b
MOF-Co/Ag
×BF4-1
MOF-Co/Ag×PF6-1
empirical formula
crystal system
space group
C55H48AgCoF3N15O3S
orthorhombic
Pbcn
C42H30AgBCoF4N9
orthorhombic
Pbcn
C42H30AgCoF6N9P
orthorhombic
Pbcn
unit cell dimensions
a (Å)
b (Å)
26.713(3)
12.5800(13)
33.455(3)
90
90
90
26.914(7)
12.327(3)
33.375(8)
90
90
90
26.847(2)
12.6272(10)
33.438(3)
90
90
c (Å)
R (deg)
â (deg)
γ (deg)
90
volume (Å3), z
crystal size (mm3)
temperature (K)
reflections collected
independent reflections
data/restraint/parameters
goodness-of-fit on F2
final R indices I > 2σ(I)a
11243(2), 8
0.40 × 0.33 × 0.15
100(2)
11073(5), 8
0.30 × 0.20 × 0.10
100(2)
11335.5(15), 8
0.55 × 0.34 × 0.22
100(2)
93010
97394
96034
12681 [R(int) ) 0.0828]
12681/0/574
1.041
R1 ) 0.0704
wR2 ) 0.1842
R1 ) 0.0921
wR2 ) 0.1946
10133 [R(int) ) 0.1194]
10133/16/551
1.045
R1 ) 0.0975
wR2 ) 0.2579
R1 ) 0.1575
wR2 ) 0.2856
12951 [R(int) ) 0.0558]
12951/0/578
1.062
R1 ) 0.0514
wR2 ) 0.1316
R1 ) 0.0756
wR2 ) 0.1396
R indices (all data) a
2
2
4
a R1 ) ∑||Fo| - |Fc||/∑|Fo| , wR2 ) {∑[w(Fo - Fc )2]/∑[wFo ]}1/2
.
b Taken from ref 23.
observed with preservation of the (10,3)-d network topology
that is common to both MOF-Co/AgOTf-1 and MOF-Co/
AgBF4-1. The tetrafluoroborate anions occupy the same posi-
tions in the crystal lattice as the displaced triflate anions (Figure
4) at a similar distance and geometry as found in MOF-Co/
AgBF4-1 (Figure 3). Taking crystals of MOF-Co/Ag×BF4-1,
rinsing them with a 4:1 benzene/acetonitrile solution, and
dissolving the dried crystals in either CDCl3 or d6-DMSO and
examining the 19F NMR confirmed the complete exchange of
anions; a single resonance at -152.1 ppm was the only spectral
feature observed, consistent with the tetrafluoroborate anion.
An identical experiment was performed using MOF-Co/
AgOTf-1 and tetrabutylammonium hexafluorophosphate. In this
case, MOF-Co/AgOTf-1 is a (10,3)-d net while MOF-Co/
AgPF6-1 is a (6,3) net; therefore, it was unclear whether anion
exchange would occur, if the framework would be stable, and
what the structure of the resulting MOF would be. As in the
earlier experiment, no change in crystal morphology or stability
was observed during the anion-exchange process. After ∼24 h
exposure to tetrabutylammonium hexafluorophosphate, single
crystals were analyzed to reveal the structure of MOF-Co/
Ag×PF6-1. MOF-Co/Ag×PF6-1 retains the (10,3)-d net topol-
ogy while achieving complete anion exchange of the triflate
counterions. As in the previous example, the PF6- anions occupy
the same positions in the crystal lattice as the displaced triflate
anions (Figure 4). 19F NMR again confirmed the complete
exchange of the triflate anions for PF6-, with resonances at
-69.3 and -71.8 ppm (a doublet is observed due to coupling
anion is not required for maintaining the structural stability of
the resulting framework.
The aforementioned anion-exchange experiments are notable
for several reasons. One important observation is that both
experiments described represent an apparent single-crystal-to-
single-crystal transformation, where the MOF was sufficiently
robust to characterize by high-resolution X-ray diffraction. We
are unaware of anion-exchange reactions confirmed by single-
crystal X-ray diffraction in MOFs; the use of powder diffraction
is common40-44 and solid-state NMR has also been used,45 but
to our knowledge, single crystal analysis after anion exchange
is unprecedented (although examples of single-crystal-to-single-
crystal solvent exchange are known).46-48 Although the pres-
ervation of the MOF topology as confirmed by X-ray diffraction
is compelling evidence for the proposed single-crystal-to-single-
crystal transformation, it should be noted that we cannot entirely
rule out the role of a dissolution process in the anion exchange.49
To absolutely confirm a single-crystal-to-single-crystal trans-
formation, rigorous microscopy studies must be performed.
Nevertheless, the ability to perform these experiments and
characterize the MOFs in this manner suggests that MOF-Co/
AgOTf-1 is quite robust.
Another important observation is that both experiments
demonstrate anion exchange against the generally reported trends
for anion coordinative ability. Several studies, most recently
by Jung et al.,41,50 have reported on numerous anion-exchange
(40) Hamilton, B. H.; Kelly, K. A.; Wagler, T. A.; Espe, M. P.; Ziegler, C. J.
Inorg. Chem. 2002, 41, 4984-4986.
-
to the 31P nucleus). The ability of the large PF6 anion to
(41) Jung, O.-S.; Kim, Y. J.; Lee, Y.-A.; Park, K.-M.; Lee, S. S. Inorg. Chem.
2003, 42, 844-850.
completely displace the triflate anion in MOF-Co/AgOTf-1
strongly suggests that the templating effect observed in these
(42) Min, K. S.; Suh, M. P. J. Am. Chem. Soc. 2000, 122, 6834-6840.
(43) Zhao, W.; Fan, J.; Okamura, T.-a.; Sun, W.-Y.; Ueyama, N. New J. Chem.
2004, 28, 1142-11550.
-
MOFs is not due exclusively to anion size. Clearly, the PF6
(44) Zhao, W.; Fan, J.; Okamura, T.-a.; Sun, W.-Y.; Ueyama, N. Microporous
Mesoporous Mater. 2005, 78, 265-279.
can fit within the (10,3)-d net with minimal structural perturba-
tions, and therefore it must be some other property of the anion
that leads to the formation of a (6,3) net during MOF synthesis
(45) Hamilton, B. H.; Wagler, T. A.; Espe, M. P.; Ziegler, C. J. Inorg. Chem.
2005, 44, 4891-4893.
(46) Wu, C.-D.; Lin, W. B. Angew. Chem., Int. Ed. 2005, 44, 1958-1961.
(47) Choi, H. J.; Suh, M. P. J. Am. Chem. Soc. 2004, 126, 15844-15851.
(48) Deiters, E.; Bulach, V.; Hosseini, M. W. Chem. Commun. 2005, 3906-
3908.
-
in the presence of either PF6 or SbF6-. Anion-exchange
experiments with some of the (6,3) nets described here resulted
in loss of crystallinity, and were not pursued further. These
findings suggest that in MOF-Co/AgOTf-1 the anion may be
important in templating the formation of the MOF, but a specific
(49) Thompson, C.; Champness, N. R.; Khlobystov, A. N.; Roberts, C. J.;
Schroder, M.; Tendler, S. J. B.; Wilkinson, M. J. J. Microsc. (Oxford) 2004,
214, 261-271.
(50) Lee, J. W.; Kim, E. A.; Kim, Y. J.; Lee, Y.-A.; Pak, Y.; Jung, O.-S. Inorg.
Chem. 2005, 44, 3151-3155.
9
J. AM. CHEM. SOC. VOL. 128, NO. 47, 2006 15263

A R T I C L E S
Halper et al.
Figure 4. Stereoview of MOF-Co/AgOTf-1 highlighting the location of the anions before (top) and after anion exchange with either tetrabutylammonium
tetrafluoroborate (MOF-Co/Ag×BF4-1, middle) or tetrabutylammonium hexafluorophosphate (MOF-Co/Ag×PF6-1, bottom). The structure is depicted using
30% thermal ellipsoids. Solvent molecules have been omitted for clarity.
experiments in coordination solids and used their observations
to establish a trend from strongly to weakly coordinating
the related [M(4-pyrdpm)3] complexes (Figure S4, Figure 5).23
MOFs were prepared under the same conditions used with [M(4-
pyrdpm)3], and crystalline materials were readily obtained. In
general, the quality and stability of these MOF crystals,
designated MOF-M/AgX-3, were poorer than those obtained
for MOF-M/AgX-1. Although structural characterization proved
more challenging, the structure of MOF-Fe/AgOTf-3 was
determined. As shown in Figure 5, the structure of MOF-Fe/
AgOTf-3 reveals a (10,3)-b net in the orthorhombic space group
Fddd. Although the space group and cell parameters differ,
MOF-Fe/AgOTf-3 forms the same doubly interpenetrated
(10,3)-b network topology (ThSi2-type net, Schla¨fli symbol 103,
vertex symbol 102·104·104) as MOF-Fe/AgOTf-1. The frame-
work structure is well ordered, with the exception of one of the
quinoline rings, which is disordered with respect to a glide plan
(see Supporting Information). Also, the location of the OTf-
anions in this structure could not be reliably determined (see
Supporting Information); thus, no comments can be provided
on their location in the structure in comparison to the other
MOFs described here. Although the structure of MOF-Fe/
AgOTf-3 is not of high quality, it is sufficient to show the
-
-
-
-
-
anions: NO2 > NO3 > CF3CO2 > CF3SO3 > PF6
>
-
- 41
ClO4 > BF4
.
The X-ray structure determinations and 19F
NMR experiments performed here show the ability of PF6- and
BF4 to displace the CF3SO3 (OTf-) anion from MOF-Co/
AgOTf-1. Furthermore, on the basis of the aforementioned
series, the strongest coordinating anion (OTf-) and weakest
coordinating anion (BF4-) examined both generate (10,3) nets.
Therefore, we conclude that the coordinative ability of the anion
does not play a significant role in the templating effect observed
in these MOFs.
-
-
MOFs with Modified Dipyrrin Metalloligands. Two ad-
ditional metalloligand systems were explored in order to
determine how changes in metalloligand structure would affect
the anion templating effect and hence the topology of the
resultant MOFs. The first of these systems were quinoline
derivatives of the previously prepared systems, namely [M(4-
quindpm)3]. The structure of both metalloligands, [Co(4-
quindpm)3] and [Fe(4-quindpm)3], were determined (Table 5);
the structures are unremarkable and generally consistent with
9
15264 J. AM. CHEM. SOC. VOL. 128, NO. 47, 2006

Anion Templating of Metalloligand MOFs
A R T I C L E S
Table 5. X-ray Crystallographic Data for Metalloligands [M(4-quindpm)3] (M ) Co3+, Fe3+) and the Resultant Framework MOF-Fe/AgOTf-3
[Co(4-quindpm)3]
[Fe(4-quindpm)3]
MOF-Fe/AgOTf-3
empirical formula
crystal system
space group
unit cell dimensions
a (Å)
C54H36CoN3
rhombohedral
R3h
C54H36FeN9
rhombohedral
R3h
C54H36AgFeN9
orthorhombic
Fddd
25.322(5)
25.322(5)
14.746(6)
90
90
120
25.335(8)
25.335(8)
14.613(9)
90
90
120
24.601(5)
16.546(4)
65.775(14)
90
90
90
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
volume (Å3), z
crystal size (mm3)
temperature (K)
reflections collected
independent reflections
data/restraint/parameters
goodness-of-fit on F2
final R indices I > 2σ(I)a
8188(4), 6
0.32 × 0.22 × 0.12
100(2)
8123(6), 6
0.55 × 0.54 × 0.08
100(2)
26773(10), 16
0.28 × 0.21 × 0.13
150(2)
22921
23026
57467
3728 [R(int) ) 0.0601]
3728/ 0/193
1.116
R1 ) 0.0732
wR2 ) 0.2469
R1 ) 0.0941
wR2 ) 0.2615
3697 [R(int) ) 0.0371]
3697/0/193
1.136
R1 ) 0.0759
wR2 ) 0.2468
R1 ) 0.0872
wR2 ) 0.2563
6142 [R(int) ) 0.1179]
6142/3/260
0.756
R1 ) 0.0608
wR2 ) 0.1638
R1 ) 0.1132
wR2 ) 0.1809
R indices (all data)a
2
2
4
a R1 ) ∑||Fo| - |Fc||/∑|Fo| , wR2 ) {∑[w(Fo - Fc )2]/∑[wFo ]}1/2
.
network connectivity. Overall, this finding suggests that modi-
fication of the metalloligand from a pyridyl to a quinolyl-
derivatized dipyrrin does not substantially change the overall
MOF topology and that the templating effect of the anion is
preserved.
pattern, with the anions located in an interdigitated fashion near,
but not coordinated to, the silver(I) centers. The planes of these
honeycomblike sheets are not oriented coincident with any of
the crystallographic axes. As in the other (6,3) nets described,
each individual layer is homochiral, comprising only ∆ or Λ
tris(chelate) metal centers (alternating ∆Λ with the AB stacking
pattern). Also similar to the other (6,3) nets, the silver(I)
coordination sphere shows a distortion toward T-shape in the
trigonal plane, with one larger N-Ag-N angle of ∼140° (Table
S3). Among these three MOFs, only MOF-Co/AgOTf-4 shows
a significant bonding interaction between the silver(I) ion and
the anion, with a Ag-O distance of 2.60 Å, similar to the Ag-O
distances found in MOF-Co/AgOTf-1 and MOF-CoFe/AgOTf-
1. For MOF-Co/AgBF4-4 and MOF-Co/AgPF6-4 the anions are
not coordinated with distant Ag-F contacts of 2.86 and 2.81
Å, respectively.
The second modification made to the basic metalloligand
system utilized here was an extension of the metalloligand
framework by insertion of a rigid phenylethynyl spacer between
the dipyrrin and pyridyl binding groups in [M(4-papyrdpm)3].
The structure of [Co(4-papyrdpm)3] was determined (Table 6)
and shows the expected geometry (Figure 6). Like other
dipyrrinato complexes with elongated meso substitutents,31 the
pendant arms surrounding [Co(4-papyrdpm)3] are slightly bent.
Combination of [Co(4-papyrdpm)3] with AgOTf, AgBF4, or
AgPF6 under standard crystallization conditions generated single
crystals suitable for X-ray analysis. Interestingly, the structures
of MOF-Co/AgOTf-4, MOF-Co/AgBF4-4, and MOF-Co/
AgPF6-4 (Figure 6) revealed the formation of extended (6,3)
nets (Schla¨fli symbol 63, vertex symbol 6·6·6). The three MOFs
are essentially isostructural (Table 6). All three of the 2D nets
MOF-Co/AgX-4 show a tightly packed, head-to-tail AB stacking
The structures of MOF-Co/AgOTf-4 and MOF-Co/AgBF4-4
are a striking contrast to the structures of MOF-Co/AgOTf-1
and MOF-Co/AgBF4-1 which both form (10,3)-d network
topologies.23 This finding shows that some modifications of the
ligand system can override the anion templating effect. Changes
Figure 5. Structural diagram of [Fe(4-quindpm)3] (left) with partial atom numbering scheme (ORTEP, 50% probability ellipsoids). X-ray structure of the
(10,3) net MOF-Fe/AgOTf-3 (right) viewed down the crystallographic a-axis (only one of two interpenetrated nets are shown, disorder in the quinoline
fragment of one dipyrrinato ligand shown). Iron(III) and silver(I) centers are represented by gold and gray polyhedra, respectively. Hydrogen atoms, anions,
and solvent molecules have been omitted for clarity.
9
J. AM. CHEM. SOC. VOL. 128, NO. 47, 2006 15265

A R T I C L E S
Halper et al.
-
Table 6. X-ray Crystallographic Data for Metalloligands [Co(4-papyrdpm)3] and the Resultant Frameworks MOF-Co/AgX-4 (X ) OTf-, BF4
,
-
PF6
)
[Co(4-papyrdpm)3]
MOF-Co/AgOTf-4
MOF-Co/AgBF4-4
MOF-Co/AgPF6-4
empirical formula
crystal system
space group
unit cell dimensions
a (Å)
C145H113Cl3Co2N18
triclinic
P1h
C93H69AgCoF3N10O3S
triclinic
P1h
C74H51AgBCoF4N10
triclinic
P1h
C90H66AgCoF6N9P
triclinic
P1h
15.2681(12)
20.2619(16)
21.5668(17)
69.4900(10)
84.2850(10)
87.069(2)
9.3693(9)
19.3886(19)
22.869(2)
94.659(2)
94.855(2)
9.4031(17)
18.794(4)
22.803(4)
91.311(3)
94.990(3)
9.4026(13)
19.385(3)
22.645(3)
93.820(2)
95.353(2)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
91.655(2)
94.994(3)
92.800(2)
volume (Å3), z
crystal size (mm3)
temperature (K)
reflections collected
independent reflections
data/restraint/parameters
goodness-of-fit on F2
final R indices I > 2σ(I)a
6217.0(8), 2
0.27 × 0.26 × 0.10
100(2)
4123.0(7), 2
0.90 × 0.24 × 0.20
100(2)
3997.5(13), 2
0.50 × 0.15 × 0.09
100(2)
4094.0(10), 2
0.44 × 0.17 × 0.07
100(2)
53738
35002
33394
33968
22587 [R(int) ) 0.0440]
22587/0/1479
1.063
R1 ) 0.0661
wR2 ) 0.1666
R1 ) 0.0989
wR2 ) 0.1810
14945 [R(int) ) 0.0261]
14945/0/982
1.045
R1 ) 0.0468
wR2 ) 0.1188
R1 ) 0.0569
wR2 ) 0.1230
14466 [R(int) ) 0.0415]
14466/0/876
0.944
R1 ) 0.0663
wR2 ) 0.1713
R1 ) 0.0843
wR2 ) 0.1790
14809 [R(int) ) 0.0548]
14809/0/973
1.043
R1 ) 0.0845
wR2 ) 0.2210
R1 ) 0.1213
wR2 ) 0.235
R indices (all data)a
a R1 ) ∑||Fo| - |Fc||/∑|Fo| , wR2 ) {∑[w(Fo - Fc )2]/∑[wFo ]}1/2
.
2
2
4
in MOF topology due to lengthening of the metalloligand in
[Co(4-papyrdpm)3] directly parallels findings from the organic
MOF literature. Networks synthesized by Lee and co-workers
with 1,3,5-tris(4-ethylbenzonitrile)benzene (TEB) and AgOTf
form a (10,3)-b network structure, but extension of this ligand
motif using 1,3,5-tris(4-(4-ethynylbenzonitrile)phenyl)benzene
and AgOTf generates a (6,3) net.26 A comparison of the lengths
from the center of 1,3,5-tris(4-(4-ethynylbenzonitrile)phenyl)-
benzene and [Co(4-papyrdpm)3] to the peripherial donor atoms
in these systems shows that they are very similar (Figure 7) at
∼15.0 Å26 and ∼14.4 Å, respectively. The results presented
here show that a rationally designed metalloligand, with donor
atoms and structural parameters similar to those of known
organic MOF building blocks, can be used to reliably form
heterometallic MOFs of predictable structure. These findings
demonstrate that extension of the ligand structure overrides the
anion templating effect and can be used as a second means to
effect dependable structural control. Because of the large number
of organic ligand-derived MOFs, our findings suggest that a
large number of heterometallic, and potentially functional MOFs,
can be prepared with foreseeable topologies.
Thermal Analysis. Thermogravimetric analysis (TGA) of
several of the evacuated frameworks showed the compounds
were quite thermally stable. None of the frameworks tested
displayed any significant weight loss below 200 °C (Table S1).
Indeed, the average temperature at which a 5% weight loss was
observed across all nine frameworks tested was 262 °C. Above
400 °C more significant losses were observed, from 25 to 80%,
depending on the MOF under examination. As further evidence
that the topology and hence the physical behavior of the
frameworks are independent of the metalloligand metal ion, it
was observed that MOF-M/AgX-1 frameworks had similar TGA
profiles. For example, the TGA traces of MOF-Co/AgOTf-1
and MOF-CoFe/AgOTf-1 are very similar, whereas those of
MOF-Co/AgPF6-1 and MOF-Fe/AgPF6-1 are comparable (Fig-
ure S5). This supports our proposition that the metalloligand
metal ion can add new chemical and electronic properties to
the MOF without altering the physical robustness of the network.
Conclusions
The findings reported here demonstrate that judicious met-
alloligand design can result in the construction of predictable
Figure 6. Structural diagram of [Co(4-papyrdpm)3] (left) with partial atom numbering scheme (ORTEP, 50% probability ellipsoids). X-ray structure of the
(6,3) net MOF-Co/AgPF6-4 (right) viewed to highlight the (6,3) net topology. Cobalt(III) and silver(I) centers are represented by blue and gray polyhedra,
respectively. Hydrogen atoms, anions, and solvent molecules have been omitted for clarity.
9
15266 J. AM. CHEM. SOC. VOL. 128, NO. 47, 2006

Anion Templating of Metalloligand MOFs
A R T I C L E S
Figure 7. Comparison of the metalloligand/ligand length in [Co(4-papyrdpm)3] and 1,3,5-tris(4-(4-ethynylbenzonitrile)phenyl)benzene. The red, wavy lines
indicate the lengths measured.
framework structures that possess augmented physical proper-
ties. The approach is modular as demonstrated by the preparation
of both iron(III) and cobalt(III) MOFs and of MOFs that contain
three metal ions (Co/Fe/Ag). The experiments described provide
a conceptual and synthetic strategy for the construction of a
wide range of new MOFs. Both ligand design and anion
templating are shown to be useful tools in controlling network
topology. Experiments indicate that some of the MOFs presented
are stable and can perform guest exchange with preservation
of the originally templated MOF topology. Prediction of the
MOF architecture based on these metalloligands can be obtained
by comparison to MOFs based on analogous organic ligands
already reported in the literature.
Whether the observed templating is kinetic or thermodynamic
in origin, it is of interest to identify what features of the anion
are generating this templating phenomenon. The observation
that AgOTf (strongly coordinating) and AgBF4 (weakly coor-
dinating) precursors yielded similar nets indicates that coordi-
native ability of the anion does not play a significant role in
the anion templating effect. This is further supported by a
computational study of fluorinated anions, which evaluated
partial charges on several species, and ranked the coordinative
-
-
- 51
ability of BF4 lower than PF6 or SbF6
.
Another possible
source of the templating effect might be the larger size of the
-
-
PF6 and SbF6 anions. While many reports demonstrate that
the shape and size of the anion can direct the assembly of
supramolecular structures,52 this does not appear to be the
exclusive driving force in the systems presented here. The
observation that the larger metalloligand [Co(4-papyrdpm)3]
overrides the anion templating effect (consistent with the
analogous organic system) to generate exclusive (6,3) nets is
suggestive of an effect due to size (volume) of the anion.
It is clear from the series of MOFs constructed in this study
that the selection of silver(I) salts is crucial to the topological
arrangement of some metalloligands in the final MOF. Anion
templating is found to play a significant role in the assembly
of these MOFs, and the templated structure is robust to anion
exchange in some cases. Understanding the templating effect
of these anionic species can be considered by a careful
assessment of the X-ray crystallographic data of the MOFs, as
well as by anion-exchange studies. Networks prepared from
[M(4-pyrdpm)3] and AgOTf or AgBF4 yielded 3D (10,3) nets,
whereas those formed from AgPF6 or AgSbF6 gave 2D (6,3)
nets. The difference in net topology could be a kinetic effect,
e.g., the PF6- or SbF6- anions “trap” an intermediate (6,3) net
by a change in MOF solubility. Alternatively, the observed
topologies may be due to thermodynamic differences, that is,
However, substitution of OTf- (MOF-Co/AgOTf-1) by PF6
-
in MOF-Co/Ag×PF6-1 shows that the (10,3) nets can accom-
modate the larger anion, indicating that differences in anion size
alone are not sufficient to explain the templating effect. An
additional possibility is that the hydrogen-bonding propensity
of the anion causes the observed templating effect.52-56 There
(51) Krossing, I.; Raabe, I. Chem. Eur. J. 2004, 10, 5017-5030.
(52) Vilar, R. Angew. Chem. Int. Ed. 2003, 42, 1460-1477.
(53) Grepioni, F.; Cojazzi, G.; Draper, S. M.; Scully, N.; Braga, D. Organo-
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-
the presence of the PF6 or SbF6 anions results in the (6,3)
net being more stable relative to the (10,3) net.42
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A R T I C L E S
Halper et al.
are some C-H···F contacts in the structures of MOF-M/AgPF6-1
and MOF-M/AgSbF6-1 that are consistent with this hypothesis
(Figure S6), although we do not have sufficient data at this stage
to evaluate the importance of a hydrogen-bonding contribution.
It is likely that a combination of parameters (such as hydrogen
bonding and, to a lesser extent, size) leads to the observed
structural variations. Ongoing studies in our laboratory will help
to further elucidate the role of the anions in the formation of
these and related MOFs.
Acknowledgment. We thank Prof. Arnold L. Rheingold
(U.C.S.D.) for help with the X-ray structure determinations, Dr.
Yongshan Su for performing the mass spectrometry experiments,
Prof. Clifford P. Kubiak and Prof. David N. Hendrickson for
use of their FT-IR instruments. This work was supported by
the University of California, San Diego, a Chris and Warren
Hellman Faculty Scholar award, and the donors of the American
Chemical Society Petroleum Research Fund, and the National
Science Foundation (CHE-0546531 and a Graduate Research
Fellowship to S.R.H.). S.M.C. is a Cottrell Scholar of the
Research Corporation. Crystallographic details are available at
http://www.ccdc.cam.ac.uk. Refer to CCDC reference numbers
611122, 611123, 611124, 611125, 611126, 611127, 611128,
611129, 611130, 611131, 611132, 611133, 611134, 611135,
611136, 611137, and 611138.
Supporting Information Available: Details of X-ray crystal-
lographic analyses, Scheme S1, Figures S1-S6, and Tables S1-
S3; X-ray crystallographic files in CIF format. This material is
available free of charge via the Internet at http://pubs.acs.org.
JA0645483
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