Synthesis and structural flexibility of a series of copper(II) azolate-based metal-organic frameworks

Article abstract of DOI:10.1002/ejic.201000490

The reaction of CuCl2.2H2O with three novel ditopic ligands, 2-methyl-1,4-benzeneditetrazolate (MeBDT^2-), 4,4'- biphenylditetrazolate (BPDT^2-), and 2,3,5,6-tetrafluoro-1,4- benzeneditriazolate (TFBDTri^2-), affords the metal-organic frameworks Cu(MeBDT)(dmf) (1), Cu(BPDT)(dmf) (2), and Cu(TFBDTri)(dmf) (3), respectively. These materials feature a common network topology in which octahedral Cu ²⁺ ions are bridged by azolate ligands and dmf molecules to form one-dimensional chains. The individual chains are connected by the organic bridging units to form diamond-shaped channels, in which the solvent molecules project into the pores. The bridging dmf molecules in 1 are readily displaced by other coordinating solvent molecules, which leads to a change in the pore dimensions according to the steric bulk of the solvent. Interestingly, attempts to exchange the analogous solvent molecules in the expanded framework 2 induced no change in the pore size, revealing the rigidity of the framework. Meanwhile, 3 exhibits modest flexibility and an improved thermal stability consistent with its chemical functionality. The marked difference in flexibility highlights the considerable impact the organic linker can have on the dynamic framework properties.

Full text of DOI:10.1002/ejic.201000490

SHORT COMMUNICATION
DOI: 10.1002/ejic.201000490
Synthesis and Structural Flexibility of a Series of Copper(II) Azolate-Based
Metal–Organic Frameworks
Kenji Sumida,[a] Maw Lin Foo,[a] Satoshi Horike,[a] and Jeffrey R. Long*[a]
Keywords: Metal–organic frameworks / Porous materials / N ligands / Copper
The reaction of CuCl2·2H2O with three novel ditopic ligands,
2-methyl-1,4-benzeneditetrazolate (MeBDT2–), 4,4Ј-biphen-
ylditetrazolate (BPDT2–), and 2,3,5,6-tetrafluoro-1,4-benz-
eneditriazolate (TFBDTri2–), affords the metal–organic frame-
works Cu(MeBDT)(dmf) (1), Cu(BPDT)(dmf) (2), and
Cu(TFBDTri)(dmf) (3), respectively. These materials feature
a common network topology in which octahedral Cu2+ ions
are bridged by azolate ligands and dmf molecules to form
one-dimensional chains. The individual chains are connected
by the organic bridging units to form diamond-shaped chan-
nels, in which the solvent molecules project into the pores.
The bridging dmf molecules in 1 are readily displaced by
other coordinating solvent molecules, which leads to a
change in the pore dimensions according to the steric bulk
of the solvent. Interestingly, attempts to exchange the analo-
gous solvent molecules in the expanded framework 2 in-
duced no change in the pore size, revealing the rigidity of
the framework. Meanwhile, 3 exhibits modest flexibility and
an improved thermal stability consistent with its chemical
functionality. The marked difference in flexibility highlights
the considerable impact the organic linker can have on the
dynamic framework properties.
example, the IRMOF series of frameworks, which feature a
cubic network of tetrahedral [Zn4O]6+ clusters bridged by
dicarboxylate linkers, demonstrates that a common network
type can be adopted despite the use of a diverse range of
ligands.[1a,4] Meanwhile, in the M2(DOBDC) (M = Mg,
Mn, Co, Ni, Zn; DOBDC4– = 2,5-dioxido-1,4-benzene-
dicarboxylate) and the M3[(M4Cl)3(BTT)8]2 (M = Mn, Fe,
Cu; BTT3– = 1,3,5-benzenetristetrazolate) frameworks, the
same network connectivity is facilitated by a variety of met-
als.[5,6] These materials are of significant interest due to the
presence of unsaturated coordination sites on the pore sur-
face, and depending on the metal employed, the frame-
works can exhibit enhanced affinities or selectivities for cer-
tain gas molecules, which is crucial for the development of
high-performance materials for hydrogen storage and car-
bon dioxide capture.
In addition to variations in the composition of the mate-
rials, metal–organic frameworks exhibiting reversible struc-
tural flexibility have also received significant attention due
to their structural dynamics and unusual response to the
adsorption of guest molecules.[7] These materials frequently
exhibit stepwise or hysteretic adsorption phenomena owing
to transitions in the framework structure, which can be of
benefit for gas storage and separation applications. For in-
stance, in the separation of gases of very similar kinetic dia-
meters, such as O2 and N2, a potentially viable approach
might be to modulate the gate-opening pressure by tuning
the internal pore surface of the material. Thus, the two stra-
tegies mentioned above, namely modification of the metal
or ligand component of the framework, are potential ave-
nues for the preparation of optimized materials.
Introduction
Metal–organic frameworks have attracted much recent
investigation because of their high permanent porosity, con-
venient modular synthesis, and chemical tunability.[1] The
ability to judiciously select the metal ion and organic linker
suggests that if the appropriate components are combined,
frameworks that are tailor-made for specific applications,
such as gas storage[2] and separation,[3] may be prepared.
However, significant improvements in the understanding of
structure–property relationships within this class of mate-
rial are still needed in order to fulfill their great potential.
Indeed, despite the large number of frameworks studied for
their gas sorption behavior, flexibility, and chemical sta-
bility, it still remains difficult to predict how changes to the
framework constituents or network structure might affect
the observed properties. Thus, improvements in this regard
would greatly aid in materials design, and from a practical
point of view, dramatically reduce the number of com-
pounds that need to be studied for the discovery of high-
performance materials.
The systematic investigation of the adsorptive and dy-
namic properties of materials exhibiting a common network
topology may allow the effect of subtle changes to the
framework, such as the metal node or the functionality or
length of the organic bridging unit, to be elucidated. For
[a] Department of Chemistry, University of California, Berkeley
Berkeley, CA 94720-1460, USA
E-mail: jrlong@berkeley.edu
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201000490 or from
the author.
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K. Sumida, M. L. Foo, S. Horike, J. R. Long
SHORT COMMUNICATION
Recently, we have reported two copper-based frame- crystallizing in the space group Imma (Figure 2), which is
works: Cu(BDT)(dmf) (BDT2– = 1,4-benzeneditetrazolate) isostructural to both Cu(BDT)(dmf)[8] and Cu(BDTri)(L)
and Cu(BDTri)(L) (L = dmf, def; BDTri2– = 1,4-benzenedi- (L = dmf, def).[9] The network consists of octahedral Cu2+
triazolate).[8,9] Despite the use of different azolate func- ions, in which the four equatorial coordination sites are co-
tional groups, the frameworks are isostructural to each ordinated by nitrogen atoms of four different tetrazolate
other, and in the case of the triazolate-based materials, the groups, while the axial sites are occupied by bridging dmf
same network topology is adopted despite a different bridg- molecules resulting in one-dimensional chains in the [010]
ing solvent molecule being present in the structure. Interest- direction. The individual chains are linked by the MeBDT2–
ingly, these materials exhibit reversible changes in the pore ligands, creating diamond-shaped one-dimensional chan-
dimensions depending on the quantity of guest solvent in nels that run parallel to the Cu2+ chains. Note that the
the pores. In the case of the evacuated frameworks, a state methyl substituent on the bridging ligand was crystallo-
in which the pore apertures are closed, a high selectivity of graphically disordered over the four possible sites on the
O2 over N2 is observed due to a kinetic sieving effect based benzene ring. Thermogravimetric analysis of a sample of 1-
on the slightly smaller kinetic diameter of O2 (3.46 Å) rela- AS following immersion in dichloromethane revealed that,
tive to N2 (3.64 Å).[10] Here, we extend this library of metal– following the initial evaporation of dichloromethane up to
organic frameworks based on copper(II) azolate derived approximately 50 °C, the material maintains its structure
from three new organic linkers depicted in Figure 1: 2- until approximately 200 °C, above which the bound dmf
methyl-1,4-benzeneditetrazolate (MeBDT2–), 4,4Ј-biphenyl- molecules are lost, resulting in decomposition of the frame-
ditetrazolate (BPDT2–), and 2,3,5,6-tetrafluoro-1,4-benz- work. The thermal stability is indeed comparable to that of
eneditriazolate (TFBDTri2–). The ligands have been synthe- other tetrazolate-based frameworks reported recently.[6,8]
sized for their different functionalities and lengths, which
are anticipated to allow access to unique dynamic proper-
ties within the resulting frameworks. Indeed, while the re-
sulting frameworks exhibit the same network topology, they
possess significantly different flexibility and chemical sta-
bility profiles with respect to exchange of the bridging li-
gand, demonstrating the exquisite dependence of the frame-
work properties on the organic linker.
Figure 2. A portion of the crystal structure of as-synthesized
Cu(MeBDT)(dmf) (1-AS) as viewed down the [010] direction. Tur-
quoise, gray, and blue spheres represent Cu, C, and N atoms,
respectively. Hydrogen atoms and bridging dmf molecules have
been omitted for clarity.
Surprisingly, the single-crystallinity of the as-synthesized
material was lost after evacuation of the pores by immers-
ing the crystals in dichloromethane and evaporating the sol-
vent within the pores under a slow flow of dinitrogen. This
is presumably due to the mechanical stress generated by the
significant changes in the dimensions of the channels within
Figure 1. Protonated forms of the organic bridging units employed
in the present work: 2-methyl-1,4-benzeneditetrazolate (MeBDT2–),
4,4Ј-biphenylditetrazolate (BPDT2–), and 2,3,5,6-tetrafluoro-1,4-
benzeneditriazolate (TFBDTri2–).
the framework. Indeed, comparison of the powder X-ray
diffraction pattern of 1-AS (Figure 3a) with that of the de-
solvated material (1-dmf, Figure 3b) revealed a significant
shift in several of the predominant reflections, most notably
the (101) reflection. Furthermore, full indexing of the pow-
der pattern was possible to a significantly smaller unit cell
within the same space group, Imma, wherein the cell param-
eter c was significantly contracted relative to the solvated
Results and Discussion
The combination of CuCl2·2H2O and H2MeBDT in an structure, indicating partial collapse of the one-dimensional
acidified mixture of dmf and methanol at room temperature channels upon removal of the non-coordinated solvent mo-
yielded blue-green, block-shaped single crystals of the sol- lecules. Infrared spectroscopy confirmed that the bridging
vated form of Cu(MeBDT)(dmf) (1-AS). X-ray diffraction dmf molecules, and hence the original network connectivity,
analysis of the crystals revealed an orthorhombic network had been retained in 1-dmf. Moreover, after solvation of
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Copper(II) Azolate-Based Metal–Organic Frameworks
the pores of 1-dmf by soaking in neat dmf, a powder X-
ray diffraction pattern matching that of 1-AS was obtained,
indicating the opening of the pore aperture.
by the changes in the dimensions of the one-dimensional
channels. However, the powder X-ray diffraction patterns
(Figure 3d–f) could be fully indexed within the space group
Imma in all cases, affording the unit cell parameters tabu-
lated in Table 1. Comparison of the unit cell volumes re-
veals that the pore dimensions follow that of the steric bulk
of the coordinated solvent, suggesting the possibility for
tuning the porosity and the surface chemistry by use of the
appropriate solvent molecule. Notably, the use of solvent
molecules larger than the size of the pores, such as 1-but-
anol and benzyl alcohol, resulted in no displacement of the
bridging solvent, as evidenced by the unchanged powder X-
ray pattern after drying the sample.
The reaction of CuCl2·2H2O and H2BPDT in an acidi-
fied dmf and EtOH mixture at room temperature yielded
blue, block-shaped crystals of the solvated form of
Cu(BPDT)(dmf) (2-AS). Indexing of the powder X-ray dif-
fraction within the space group Imma revealed that the
framework is indeed an expanded version of 1. The unit
cell parameter a [31.559(4) Å] is significantly larger than the
corresponding value observed in 1-AS [22.709(5) Å], which
is consistent with the use of a longer organic linker and the
formation of wider channels. Interestingly, in contrast to 1,
samples of 2 that were washed with dichloromethane and
air-dried retained the same powder X-ray diffraction
pattern (Figure S1), indicating structural rigidity upon
evacuation of the pores of the framework. The flexibility of
2 and its solvent exchange properties were further assessed
by submerging crystals of 2 within the same organic sol-
vents as those successfully incorporated into 1. Surprisingly,
under all conditions, the framework structure remained ri-
gid, and no changes to the powder X-ray diffraction pattern
were detected.
Figure 3. Powder X-ray diffraction patterns for (a) as-synthesized
Cu(MeBDT)(dmf) (1-AS), (b) evacuated Cu(MeBDT)(dmf) (1-
dmf), (c) Cu(MeBDT)(def) (1-def), (d) Cu(MeBDT)(MeOH) (1-
MeOH), (e) Cu(MeBDT)(EtOH) (1-EtOH), (f) Cu(MeBDT)-
(dmso) (1-dmso). The filled square symbol indicates the (101) re-
flection, which readily evolves upon solvent exchange.
The ability of the bridging solvent to be modified in the
Cu(BDTri)(L) (L = dmf, def) system prompted our efforts
to probe the extent to which this is possible for 1. In our
hands, while the framework could not be prepared directly
within other solvents, we found that the as-synthesized ma-
terial 1-AS could be immersed in def to generate Cu-
(MeBDT)(def) (1-def), in which the bridging dmf solvent
molecules were fully displaced by def. Furthermore, in-
dexing of the powder X-ray pattern of the dried form of 1-
def (Figure 3c) was possible within the space group Imma
The solvothermal reaction of CuCl2·2H2O and the fluo-
by using a unit cell larger than that observed for 1-dmf, rinated ligand H2TFBDTri at 80 °C in dmf over four days
which is consistent with the slightly greater steric bulk of resulted in the precipitation of Cu(TFBDTri)(dmf) (3-AS)
def relative to dmf.
as a blue-purple powder. Analysis of the powder X-ray dif-
The generality of the substitution of the bridging solvent fraction pattern revealed that the material is indeed iso-
was tested by submerging samples of 1-AS within a number structural to 1. Note that, in the case of perfluorinated li-
of common organic solvents. Indeed, dmf could be dis- gands bearing carboxylate functionalities, materials that are
placed by a broad range of other coordinating solvents, isostructural to their non-fluorinated counterparts have not
such as methanol, ethanol, and dmso, to generate Cu- yet been reported.[11] As expected from the higher coordina-
(MeBDT)(MeOH) (1-MeOH), Cu(MeBDT)(EtOH) (1- tion strength of the ligand, thermogravimetric analysis re-
EtOH), and Cu(MeBDT)(dmso) (1-dmso), respectively. Im- vealed a modest increase in the thermal stability of the
mersion of single crystals of 1-AS within these coordinating framework over 1 and 2 (Figures S4–S6), which may be at-
solvents resulted in rapid cracking of the crystals, which is tributed to the higher thermal stability of the triazole func-
consistent with the significant mechanical stress imparted tionality[12] and/or aryl carbon–fluorine bonds.[13] A similar
Table 1. Unit cell parameters of as-synthesized and solvent-exchanged forms of 1–3 as determined from indexing[a] of the powder X-ray
diffraction patterns.
1-AS
1-dmf
1-def
1-MeOH
1-EtOH
1-dmso
2
3-dmf
3-def
3-dmso
a (Å)
b (Å)
c (Å)
V (Å3)
22.72
7.234
14.95
2349.0
24.66
7.090
9.290
1624.3
24.39
7.124
10.21
1773.0
25.10
7.270
7.561
1379.5
24.88
7.195
8.338
1494.0
25.01
7.137
8.480
1513.6
31.23
6.667
12.98
2702.6
24.54
6.970
9.390
1606.1
24.55
6.980
9.948
1705.0
24.64
6.960
8.618
1478.3
[a] Space group: Imma.
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K. Sumida, M. L. Foo, S. Horike, J. R. Long
SHORT COMMUNICATION
set to a temperature of 150 °C for 24 h prior to use. Toluene was
dried with activated 4 Å molecular sieves, passed through a column
of activated alumina, and degassed with nitrogen. Methanol was
dried with calcium hydride and then distilled. All other syntheses
and manipulations were carried out in air. All reagents were ob-
tained from commercial vendors and used without further purifica-
tion.
soaking of 3-AS within def and dmso generated the corre-
sponding frameworks Cu(TFBDTri)(def) (3-def) and
Cu(TFBDTri)(dmso) (3-dmso), respectively. As was ob-
served for 1, the powder X-ray diffraction patterns (Fig-
ures S2a–c) indicated the flexibility of the framework, and
the resulting unit cell volumes correlate with the steric bulk
of the solvent employed. Surprisingly, when samples of 3-
AS were submerged in water or methanol, significant
broadening of the reflections in the powder pattern was ob-
served, indicating a decrease in the crystallinity of the sam-
ple.
The significant difference in the framework flexibility be-
tween compounds 1, 2, and 3 is quite unexpected, because
of the structural similarities and network connectivity of
the materials. While the exact mechanism giving rise to the
solvent substitution is currently unknown, one origin for
the different behavior may lie in the strength of the binding
of the bridging solvent molecules as a result of electronic
effects and steric demands imposed by the various bridging
ligands. Similar effects have been reported recently by Férey
and co-workers for derivatives of the MIL-53(Fe) structure
type,[14] which exhibited linker-dependent flexibility upon
immersion in a variety of organic solvents. Ongoing studies
will be directed towards gaining a more detailed under-
standing of the mechanism of solvent substitution and ef-
fects on the resulting gas sorption properties.
1,4-Ditetrazol-5-yl-2-methylbenzene (H2MeBDT): Toluene (20 mL)
was added to a 100 mL round-bottom flask containing 2-methyl-
terephthalonitrile (0.34 g, 2.4 mmol), sodium azide (0.95 g,
15 mmol), and triethylamine hydrochloride (2.0 g, 15 mmol). The
reaction mixture was heated at reflux for three days, after which
time a pale-brown solid was observed on the walls of the reaction
vessel. The reaction mixture was dissolved in NaOH (30 mL, 1 )
and vigorously stirred for 30 min, then the aqueous phase was col-
lected by phase separation. This fraction was treated with HCl
(30 mL, 1 ) until the pH of the solution was ca. 1, and the re-
sulting white solid was collected by filtration and dried overnight
at 120 °C. The dried product was finely ground to yield a pale-
yellow powder (0.43 g, 79%). IR (neat): ν = 3137 (m), 3065 (m),
˜
3007 (m br), 2927 (m br), 2827 (m br), 2707 (s br), 2625 (s br),
2495 (s br), 1807 (m br), 1580 (s), 1496 (m), 1454 (m), 1435 (m),
1390 (s), 1350 (w), 1282 (w), 1238 (s), 1153 (m), 1109 (m), 1086
(m), 1030 (m), 986 (s), 920 (s), 887 (s), 835 (s), 741 (s), 705 (w br)
1
cm–1. H NMR ([D6]dmso): δ = 17.10 (br. s, 2 H, -NH), 8.14 (s, 1
H, HPh), 8.07 (d, J = 8 Hz, 1 H, HPh), 7.96 (d, J = 8 Hz, 1 H, HPh),
2.61 (s, 3 H, -CH3) ppm.
4,4Ј-Ditetrazol-5-yl-biphenyl (H2BPDT): Toluene (20 mL) was
added to a 100 mL round-bottom flask containing 4,4-biphenyldi-
carbonitrile (0.50 g, 2.4 mmol), sodium azide (0.95 g, 15 mmol) and
triethylamine hydrochloride (2.0 g, 15 mmol). A workup procedure
analogous to H2MeBDT was followed, yielding the pure product
as an off-white powder (0.61 g, 87%). C14H10N8 (290.28): C 57.93,
Conclusions
The foregoing results demonstrate broad applicability of
the Cu(BDT)(dmf) structure type, allowing for the genera-
tion of three isostructural materials from a variety of or-
ganic linkers. The flexibility within this series of framework
is strongly influenced by the specific organic bridging unit
that is employed, wherein 1 is readily flexible upon the in-
corporation of guest solvent molecules into the pores, while
the 2 remains rigid under all conditions attempted in this
study. Flexibility could also be demonstrated for 3, in which
def and dmso could be exchanged for dmf. Studies directed
towards elucidating the reasons for such a significant differ-
ence in the flexibility between these frameworks are cur-
rently underway. Furthermore, efforts to achieve a more de-
tailed understanding of the chemical properties of the chan-
nels, such as polarity-dependent guest solubility, and the
adsorptive properties of the frameworks, are also ongoing.
We envisage that this structure type can be adopted by an
even broader range of ligand functionalities, which should
lead to an increased understanding of the structure–prop-
erty relationships within this class of metal–organic frame-
work.
H 3.47, N 38.60; found C 57.75, H 3.49, N 38.30. IR (neat): ν =
˜
3130 (m br), 3064 (m br), 3005 (m br), 2853 (s br), 2731 (s br),
2645 (s br), 1612 (s), 1556 (m), 1486 (s), 1423 (s), 1158 (m), 1055
1
(m), 1034 (m), 987 (m), 847 (w), 823 (s), 741 (s), 698 (w) cm–1. H
NMR ([D6]dmso): δ = 17.01 (br. s, 2 H, -NH), 8.21 (d, J = 8 Hz,
4 H, HPh), 8.04 (d, J = 8 Hz, 4 H, HPh) ppm. MS (FAB): m/z (%)
= 289 (37) [M – H]+.
4,4Ј-(Perfluoro-1,4-phenylene)bis(1H-1,2,3-triazole-4,1-diyl)bis-
(methylene)bis(2,2-dimethylpropanoate) (FBTriMP): Water (3 mL)
and tert-butyl alcohol (6 mL) were added to a 50 mL round-bottom
flask containing 4-diethynyl-2,3,5,6-tetrafluorobenzene (0.17 g,
0.83 mmol) and azidomethyl pivalate (0.29 g, 1.8 mmol). Sodium
-ascorbate (17 mg, 0.042 mmol) and CuSO4 solution (42 µL,
0.083 mmol, 1 ) were added under vigorous stirring. The reaction
mixture was heated to 60 °C for 16 h, after which time an orange
solid was observed. Ice water (10 mL) was added, followed by NH3
solution (3 mL, 10%). The resultant suspension was stirred for 2 h,
and the product was isolated by filtration, washing with water, and
drying under vacuum to yield a pale orange powder (0.35 g, 82%).
C22H24F4N6O4 (512.46): C 51.56, H 4.72, N 16.40; found C 51.29,
H 4.62, N 16.10. IR (neat): ν = 3093 (w), 2983 (w), 1743 (s), 1490
˜
(s), 1435 (m), 1389 (m), 1355 (w), 1275 (m), 1232 (m), 1116 (vs),
1058 (m), 1035 (s), 999 (m), 972 (s), 915 (m), 873 (w), 826 (m), 790
1
(m), 763 (m), 725 (w), 674 (w), 631 (w), 584 (w), 532 (w) cm–1. H
Experimental Section
NMR ([D6]dmso): δ = 8.82 (s, 2 H, -CH), 6.46 (s, 4 H, -CH2), 1.15
[s, 18 H, -C(CH3)3] ppm. 19F NMR ([D6]dmso): δ = –140 ppm.
General: All ligand syntheses were performed under a nitrogen at-
mosphere by using standard Schlenk techniques. Azidomethyl piv-
alate[15] and 1,4-diethynyl-2,3,5,6-tetrafluorobenzene[16] were pre-
pared as previously reported. All glassware was dried in an oven
2,3,5,6-Tetrafluoro-1,4-benzeneditriazolate (H2TFBDTri): Meth-
anol (5 mL) and water (5 mL) were added to FBTriMP (0.55 g,
1.1 mmol) in a 50 mL glass round-bottom flask and vigorously
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Copper(II) Azolate-Based Metal–Organic Frameworks
stirred for 5 h. Water (40 mL) was added, and the mixture was ex-
tracted with ether (4ϫ20 mL). The aqueous layer was then acidi-
fied with an excess of HCl (1 ) to obtain an off-white precipitate.
The product was filtered, copiously washed with water, ether, and
dichloromethane, and dried under vacuum to afford an off-white
powder (0.21 g, 70%). The product can be further purified if neces-
sary from residual copper catalyst by dissolution in aqueous ethyl-
enediamine (15%) followed by precipitation with HCl (1 ) and
2554 data measured, 470 unique data, Rint = 0.0470, R1 = 0.0809,
wR2 = 0.2241 for 470 contributing reflections [IՆ2σ(I)], GOF =
0.902. A description of the refinement procedure can be found in
the Supporting Information. CCDC-778563 contains the supple-
mentary data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Other Physical Measurements: Powder X-ray diffraction data was
collected by using Cu-Kα radiation (λ = 1.5406 Å) with a Siemens
D5000 diffractometer. Indexing of the diffraction patterns for 1–3
was performed within the Bruker EVA software. Single-crystal X-
ray diffraction data were collected with a Siemens SMART 1000
diffractometer, and structures were subsequently solved using the
SHELXTL 5.0[17] software package following absorption correc-
tions applied by SADABS.[18] 1H NMR spectra were recorded at
ambient temperature with Bruker AV-300, AVQ-400, AVB-400, and
AV-600 spectrometers, and all chemical shifts are given in relation
to residual solvent peaks. Thermogravimetric analyses were carried
washing with water, ether, and dichloromethane. IR (neat): ν =
˜
3098 (br. w), 2883 (br. m), 2784 (br. m), 2661 (br. m), 1474 (s), 1445
(m), 1404 (w), 1348 (w), 1245 (m), 1234 (m), 1203 (m), 1157 (m),
1147 (m), 1081 (m), 1018 (w), 976 (vs), 907 (m), 854 (m), 825 (m),
781 (m), 727 (w), 673 (w), 619 (w) cm–1. 1H NMR ([D6]dmso): δ =
15.73 (br. s, 2 H, -NH), 8.41 (br. s, 2 H, -CH) ppm. 13C NMR
1
([D6]dmso): δ = 144 (d, JC,F = 254 Hz, -CF), 134 (s, -CAr), 125
(br. s, -CH), 110 (s, CTri) ppm. 19F NMR ([D6]dmso): –135 ppm.
12
MS (HR-ESI): m/z = 284.0438 (100.00%; C10H4N6F4), 285.0462
(12.16%; 12C913CH4N6F4).
Cu(MeBDT)(dmf) (1, Cu-MeBDT): H2 MeBDT (9.0 mg, out with a TA Instruments TGA 2950 instrument at a temperature
0.04 mmol) and CuCl2·2H2O (6.8 mg, 0.04 mmol) were added to a
4 mL scintillation vial. A 1:1 (v/v) mixture of dmf and ethanol
(2 mL), and concentrated HCl (20 µL) were added to the solids,
and the vial was placed on a hotplate set at 120 °C following tight
sealing with a Teflon-lined cap. A blue-purple microcrystalline
powder was collected after two days to afford 5.0 mg of product
ramping rate of 4 °C/min under a flow of nitrogen gas. Infrared
spectra were collected by using a Nicolet Avatar 360 FTIR spec-
trometer equipped with an attenuated total reflectance accessory
(ATR). Carbon, hydrogen, and nitrogen analyses were performed
by the Microanalytical Laboratory at the University of California,
Berkeley.
(37%). IR (neat): ν = 3305 (m, br), 3154 (w), 2977 (w), 1652 (s),
˜
Supporting Information (see footnote on the first page of this arti-
cle): Powder X-ray diffraction patterns, TGA profiles, and details
of the structure refinement procedure.
1568 (w), 1475 (w), 1438 (m), 1395 (m), 1364 (w), 1265 (w), 1213
(m), 1156 (m), 1119 (m), 1090 (m), 986 (s), 849 (m), 823 (s) cm–1.
Crystals appropriate for single-crystal X-ray diffraction analysis
were prepared as follows: A solution of H2MeBDT (9.0 mg,
0.042 mmol) in dmf (1 mL) was added to a solution of CuCl2·2H2O
(6.8 mg, 0.040 mmol) in methanol (1 mL) in a 4 mL scintillation
vial. Concentrated HCl (20 µL, 12 ) was added to the reaction
mixture to yield a green solution, which was kept at room tempera-
ture for five days. The resulting pale blue rod-shaped crystals were
stored in the mother liquor.
Acknowledgments
This work was supported by the Center for Gas Separations Rel-
evant to Clean Energy Technologies, an Energy Frontier Research
Center funded by the U.S. Department of Energy, Office of Science,
Office of Basic Energy Sciences under award number DE-
SC0001015, and the Korea Research Foundation Grant funded by
the Korean Government (MEST) (KRF-2009-220-C00021). We
thank Fulbright New Zealand for partial support of K. S., and Dr.
A. G. DiPasquale for helpful discussions.
Cu(BPDT)(dmf) (2, Cu-BPDT): H2BPDT (12 mg, 0.041 mmol) and
CuCl2·2H2O (6.8 mg, 0.040 mmol) were added to a 4 mL glass scin-
tillation vial. A 1:1 (v/v) mixture of dmf and methanol (2 mL), and
concentrated HCl (20 µL) were added to the solids, and the vial
was placed on a hotplate set at 90 °C following tight sealing with
a Teflon-lined cap. A blue-purple microcrystalline powder was col-
lected after two days to afford 6.0 mg (37%) of product. IR (neat):
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Received: May 1, 2010
Published Online: July 5, 2010
3744
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Eur. J. Inorg. Chem. 2010, 3739–3744