A metal-organic framework constructed of 1,2-Di(pyridin-4-yl)ethyne, terephthalic acid, and zinc(II) nitrate

Article abstract of DOI:10.1515/znb-2012-0201

A metal-organic framework (MOF) was prepared from 1,2-di(pyridin-4-yl) ethyne, terephthalic acid and zinc(II) nitrate in dimethylformamide, water and ethanol at 80 °C. The cavities of the MOF are occupied by disordered molecules of dimethylformamide. The crystals are monoclinic, space group P21/c with Z = 4.

Full text of DOI:10.1515/znb-2012-0201

A Metal-Organic Framework Constructed of 1,2-Di(pyridin-4-yl)ethyne,
Terephthalic Acid, and Zinc(II) Nitrate
Marcel Albrechta, Martin Niegerb, and Andreas Schmidta
a Clausthal University of Technology, Institute of Organic Chemistry, Leibnizstraße 6,
38678 Clausthal-Zellerfeld, Germany
b University of Helsinki, Laboratory of Inorganic Chemistry, Department of Chemistry,
00014 University of Helsinki, Finland
Reprint requests to Prof. Dr. Andreas Schmidt. Fax: +49-5323-722858. E-mail: schmidt@ioc.tu-clausthal.de
Z. Naturforsch. 2012, 67b, 103 – 106; received January 12, 2012
A metal-organic framework (MOF) was prepared from 1,2-di(pyridin-4-yl)ethyne, terephthalic
acid and zinc(II) nitrate in dimethylformamide, water and ethanol at 80 ◦C. The cavities of the MOF
are occupied by disordered molecules of dimethylformamide. The crystals are monoclinic, space
group P21/c with Z = 4.
Key words: MOF, Coordination Polymer
Introduction
Metal-organic frameworks (MOF) [1 – 3] combine
properties of both organic and inorganic porous materi-
als as they are stable, ordered, and possess high surface
areas (> 3000 m2 g−1). The combination of metal ions
with polytopic organic linkers allows for a fascinating
diversity of structures which have been the subject of
extensive exploration during the last decade. Potential
Scheme 1. Synthesis of di(pyridin-4-yl)ethyne (2).
by a palladium-catalyzed one-pot reaction of 4-bromo-
pyridine hydrochloride with 2-methyl-but-3-yn-2-ol in
86 % yield in a two-phase system consisting of toluene
and aqueous sodium hydroxide (Scheme 1).
˚
applications of microporous (pores less than 20 A),
˚
mesoporous (pores between 20 – 500 A), and macro-
˚
porous metal-organic frameworks (openings > 500 A)
in hydrogen [4, 5] and methane [6] gas storage, selec-
tive gas absorption [7, 8], sensing [9] and drug stor-
age [10] have been reviewed recently [11 – 13]. A great
deal of attention has also been directed toward cat-
alytic properties of metal-organic frameworks [14, 15],
among those catalytic Mukaiyama aldol reactions [16],
transesterifications [17], and the chiral secondary alco-
hol synthesis by addition of diethyl zinc to aromatic
aldehydes in the presence of a chiral MOF [18]. In
continuation of our studies in preparative organic and
heterocyclic chemistry [19 – 23], catalysis [24 – 27],
materials chemistry [28], and metal-organic frame-
works [29], we report here the preparation and struc-
ture of a MOF constructed of 1,2-di(pyridin-4-yl)eth-
yne, terephthalic acid and zink(II) nitrate.
The metal-organic framework 3 was then prepared
starting from 1,2-di(pyridin-4-yl)ethyne (2), tereph-
thalic acid and a solution of zinc(II) nitrate hexahy-
drate in a solvent mixture of dimethylforma◦mide, wa-
ter, and ethanol in a closed vessel at 80 C over a
period of 3 d in 90 % yield. The results of a single-
crystal X-ray structure determination are given in Ta-
ble 1 and are shown in Figs. 1, 2, and 3. Selected bond
lengths and bond angels are presented in Table 2. The
obtained species crystallized in the monoclinic space
group P21/c with Z = 4.
As shown in Fig. 1 three terephthalic acid molecules
and two 1,2-di(pyridin-4-yl)ethyne molecules form
a pseudooctahedral coordination environment of the
Zn(II) ion. The dicarboxylic acid linkers occupy the
equatorial positions of the octahedron. One carboxy-
late group of each terephthalic acid molecule serves
Results and Discussion
The ligand 1,2-di(pyridin-4-yl)ethyne (2) was pre- as bidentate-chelating ligand to the zinc atom, whereas
pared according to a modified literature procedure [30] the other carboxylate group bridges two zinc atoms.
c
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104
M. Albrecht et al. · A MOF Constructed of 1,2-Di(pyridin-4-yl)ethyne, Terephthalic Acid, and Zinc(II) Nitrate
Table 1. Crystal structure data for MOF 3.
Formula
C20H12N2ZnO4 · C3H7NO
Mr
482.78
Crystal size, mm3
T, K
0.24×0.12×0.06
123(2)
Crystal system
Space group
monoclinic
P21/c (no. 14)
10.400(1)
19.294(2)
10.706(1)
96.94(19
2132.5(4)
4
˚
a, A
˚
b, A
˚
c, A
β, deg
3
˚
V, A
Z
Dcalcd, g cm−3
1.50
1.2
992
µ (MoKα ), cm−1
F(000), e
hkl range
2θmax, deg
13, 25, 13
55
Refl. measured / unique / Rint
Param. refined / restraints / data
R(F) (I ≥ 2σ(I)) / wR (F2) (all refl.)
GoF (F2)
28598 / 4884 / 0.059
284 / 61 / 4884
0.042 / 0.089
1.05
−3
Fig. 2. 1,2-Di(pyridin-4-yl)ethyne, terephthalic acid and the
zinc atom dissected from the crystal structure of 3 (displace-
ment parameters are drawn at the 50 % probability level;
crystallographic numbering).
˚
∆ρfin (max / min), e A
0.56 / −0.37
Fig. 3. Crystal structure of 3. Direct view down the chan-
nels which run parallel to the crystallographic b axis (solvent
molecules omitted).
Fig. 1. Coordination environment of the Zn atom in 3.
(Zn–O4ꢀ), whereas the distances to the bridging carb-
˚
Eight-membered rings of two zinc atoms plus two oxylate group were determined to be 1.988(1) A (Zn–
carboxylate groups are formed. Thus, each terephthalic O1 ) and 2.019(1) A (Zn–O2 ). The Zn–N distances
ꢀ
ꢀ
˚
acid molecule in 3 serves as a ligand of three zinc of the two 1,2-di(pyridin-4-yl)ethyne molecules to the
˚
atoms in such a way that one carboxylate group is a zinc atom were determined to be 2.199(1) A (Zn–N1)
ꢀ
˚
bidentate and the other one a bis-monodentate ligand. and 2.174(1) A (Zn–N12 ). Additional bond lengths,
The distances between the oxygen atoms of the biden- bond angles, and dihedral angles are summarized in
tate terepthalic acid ligand and the zꢀinc atom were de- Table 2. The linkage to additional zinc atoms through
˚
˚
termined to be 2.028(1) A (Zn–O3 ) and 2.483(1) A the axial 1,2-di(pyridin-4-yl)ethynes forms layers at a
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M. Albrecht et al. · A MOF Constructed of 1,2-Di(pyridin-4-yl)ethyne, Terephthalic Acid, and Zinc(II) Nitrate
105
˚
Table 2. Selected bond lengths (A), angles (deg), and dihe-
1,2-Di(pyridin-4-yl)ethyne (2)
dral angles (deg) for MOF 3 with estimated standard devia-
A solution of 37.5 mL 5.5
M
sodium hydroxide
tions in parentheses.
in water, tetrakis(triphenylphosphine)palladium(0) (0.5 g,
0.43 mmol), copper(I) iodide (0.5 g, 2.6 mmol), and ben-
zyltriethylammonium chloride (0.5 g, 2.2 mmol) was treated
with a suspension of 2-methyl-3-butyn-2-ol (3.05 mL,
31.3 mmol) and 4-bromopyridine hydrochloride (12.1 g,
62.5 mmol) in 25 mL of toluene. The mixture was stirred
at 70 ◦C over a period of 5 d, and then treated with 100 mL of
a saturated ammonium chloride solution in water. After stir-
ring for 1 h at r. t., the mixture was extracted four times with
100 mL of toluene. The organic layer was separated, dried
over magnesium sulfate, and evaporated to dryness. Column
chromatography (silica gel; CH2Cl2 · MeOH = 40 : 1) gave
Zn1–O1ꢀ
Zn1–03ꢀ#2
Zn1–N1
N1–C2
1.988(2)
2.028(2)
2.199(2)
1.336(3)
1.396(4)
1.195(4)
1.251(3)
1.236(4)
Zn1–02ꢀ#1
Zn1–N12#3
Zn1–O4ꢀ#2
C2–C3
2.019(2)
2.174(2)
2.483(3)
1.386(4)
1.435(3)
1.261(3)
1.265(4)
C3–C4
C4–C7
C7–C8
O1ꢀ–C1ꢀ
C8ꢀ–O3ꢀ
O2ꢀ–C1ꢀ
C8ꢀ–O4ꢀ
O1ꢀ–Zn1–O2ꢀ#1
O2ꢀ#1–Zn1–O3ꢀ#2
O2ꢀ#1–Zn1–N12#3
O3ꢀ#2–Zn1–N1
120.15(8) O1ꢀ–Zn1–O3ꢀ#2
147.42(9)
89.54(8)
92.36(8)
176.11(8)
92.41(9)
86.20(7)
88.54(8)
149.35(8)
O1ꢀ–Zn1–N12#3
O1ꢀ–Zn1–N1
N12#3–Zn1–N1
O2ꢀ#1–Zn1–O4ꢀ#2
◦
O1ꢀ–Zn1–N1–C2
16.9(2)
O2ꢀ#1–Zn1–N1–C2 137.1(2)
4.85 mg (86 %) of a colorless solid, m. p. 162 C (ref. [30]:
N12#3–Zn1–N1–C2 136.1(11) O4ꢀ#2–Zn1–N1–C2 –73.6(2)
C8ꢀ#2–Zn1–N1–C2 –101.7(2) O2ꢀ#1–Zn1–N1–C6 –40.84(19)
163 – 164 ◦C). – 1H NMR (CDCl3): δ = 8.65 (d, J = 4.5 Hz,
4H, α-H), 7.40 (d, J = 4.5 Hz, 4H, β-H) ppm. – 13C NMR
(CDCl3): δ = 149.9, 130.1, 125.5, 90.5 ppm. – IR (KBr): ν =
3034, 1944, 1597, 1540, 1499, 1412, 1216, 1088, 993, 827,
553, 528 cm1. All spectroscopic data are identical to those
reported in ref. [33].
O4ꢀ#2–Zn1–N1–C6 108.54(19) C5–C4–C7–C8
–145(4)
O3ꢀ#2–Zn1–O1ꢀ–C1ꢀ 147.51(19)
O2ꢀ#1–Zn1–O1ꢀ–C1ꢀ –34.7(2)
Symmetry transformation used to generate equivalent atoms: #1 −x,
−y+1, −z+1; #2 −x+0.5, y+0.5, z+0.5; #3 x−1, y, z−1.
˚
distance of 13.995(2) A. Two pyridine rings connected
[C
H
N ZnO ·C H NO] (3)
n
20 12
2
4
3 7
via one zinc atom are slightly twisted to each other
by an angle 5.6◦. The resulting network is shown in
Fig. 3. The inner cavities are occupied by one molecule
of DMF per zinc atom, which is omitted in the draw-
ing for clarity. The porosity (solvent area) of the MOF
is 22.3% and the packing index 56.2. The volume of
one cave (4 per unit cell) is 120 A [31, 32].
A thermogravimetric analysis (TGA) of 3 was per-
formed. A weight loss of approximately 10 % in
the temperature range between approximately 150
1,2-Di(pyridin-4-yl)ethyne (2) (14.0 mg, 0.078 mmol),
terephthalic acid (9.0 mg, 0.054 mmol) and zinc(II) nitrate
hexahydrate (15.0 mg, 0.051 mmol) were dissolved in a sol-
vent mixture of 8 mL of dimethylformamide, 1 mL of wat◦er,
and 1 mL of ethanol, and heated in a closed vessel to 80 C
over a period of 3 d. The resulting colorless crystals were fil-
tered off. The MOF 3 was obtained in 90 % yield (22.0 mg)
with respect to the zinc salt.
3
˚
X-Ray structure determination
◦
and 270 C can be attributed to the partial desorption
Data were collected on a Nonius Kappa-CCD diffrac-
of the DMF from the pores of 3 (calculated weight
tometer using graphite-monochromatized MoKα radiation
(λ = 0.71073 A) at T = −150 C, and the structure was solved
loss: 16 %). Stepwise weight-loss patterns from 330 ◦C
◦
˚
to 420 ◦C (25 %) and 420 ◦C to 540 ◦C (21 %) can be by Direct Methods and refined by full-matrix least-squares
on F2 [34]. A semi-empirical absorption correction was ap-
attributed to the subsequent decomposition of the or-
plied. All non-hydrogen atoms in 3 were refined anisotropi-
cally, and hydrogen atoms were located from ∆F maps and
refined at idealized positions using a riding model. The sol-
vent molecule DMF was found to be disordered. In the re-
finement it was modelled using geometrical restraints for the
1,2- and 1,3-distances (SADI) as well as constraints (EADP)
and restraints (SIMU) for the displacement parameters.
CCDC 861982 contains the supplementary crystallo-
graphic data for this paper. This data can be obtained free
of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data request/cif.
ganic components.
Experimental Section
The 1H and 13C NMR spectra were recorded on a Bruker
Avance DPX 200 (200 MHz) spectrometer. Multiplicities are
described by using the abbreviation “d” for doublet. FT-IR
spectra were obtained on a Bruker Vektor 22 instrument in
the range of 400 to 4000 cm−1 (2.5 % pellets in KBr). The
TGA was performed with a TGA 2950 instrument. Nitrogen
purge gas was used at a flow rate of 24 mL min−1
.
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M. Albrecht et al. · A MOF Constructed of 1,2-Di(pyridin-4-yl)ethyne, Terephthalic Acid, and Zinc(II) Nitrate
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