An unusual (10,3)-d MOF material with nanoscale helical cavities and multifunctionality

Article abstract of DOI:10.1002/ejic.201100566

The Mn^II and Cu^II compounds of 3-(2-pyridyl)-5,6- diphenyl-1,2,4-triazine-4,4'-disulfonic acid (H₂pdtd) were synthesized and systematically characterized. The metal-organic framework (MOF) [Mn₂(pdtd)₂(H₂O)₄] _n·5nH₂O (1) was constructed by a solvothermal method preformed at 140 °C with methanol as the solvent, while [Cu(pdtd)(H₂O)₄]·H₂O (2) was obtained by conventional solution chemistry conducted at 80 °C. Crystallographic analysis revealed that 1 has an acentric structure in which the Mn^II centers are linked via sulfonate groups and chelating nitrogen atoms within the pdtd ligands to give a rare noninterpenetrating (10,3)-d framework with permanent helical cavities. Consequently, 1 exhibits nonlinear optical (NLO) activity, significant CO₂ sorption, and magnetic coupling. In contrast, 2 is a mononuclear complex with coordinated water and lacks functional properties. A (10,3)-d metal-organic framework, [Mn₂(pdtd) ₂(H₂O)₄]_n·5nH₂O (1), containing the asymmetrical 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-P,P'- disulfonate ligand (pdtd) was constructed. XRD analysis revealed that 1 is an acentric structure possessing exposed uncoordinated nitrogen atoms within helical cavities. 1 exhibits multifunctionality: nonlinear optical activity, CO₂ sorption, and magnetic coupling.

Full text of DOI:10.1002/ejic.201100566

FULL PAPER
DOI: 10.1002/ejic.201100566
An Unusual (10,3)-d MOF Material with Nanoscale Helical Cavities and
Multifunctionality
Asiata Omotayo Ibrahim,[a,b] Youfu Zhou,*[a] Feilong Jiang,[a] Lian Chen,[a] Xingjun Li,[a]
Wentao Xu,[a] Oluyemi O. E. Onawumi,[b] Olusegun A. Odunola,[b] and Maochun Hong*[a]
Keywords: Metal-organic frameworks / Helical structures / Nanostructures / Nonlinear optics / Magnetic properties /
Manganese / Copper / Sorption / Carbon dioxide fixation
The MnII and CuII compounds of 3-(2-pyridyl)-5,6-diphenyl-
1,2,4-triazine-4,4Ј-disulfonic acid (H2pdtd) were synthesized
acentric structure in which the MnII centers are linked via
sulfonate groups and chelating nitrogen atoms within the
and systematically characterized. The metal-organic frame- pdtd ligands to give a rare noninterpenetrating (10,3)-d
work (MOF) [Mn2(pdtd)2(H2O)4]n·5nH2O (1) was constructed
by a solvothermal method preformed at 140 °C with meth-
anol as the solvent, while [Cu(pdtd)(H2O)4]·H2O (2) was ob-
tained by conventional solution chemistry conducted at
80 °C. Crystallographic analysis revealed that 1 has an
framework with permanent helical cavities. Consequently, 1
exhibits nonlinear optical (NLO) activity, significant CO2
sorption, and magnetic coupling. In contrast, 2 is a mononu-
clear complex with coordinated water and lacks functional
properties.
structures and remarkable functionalities.[24,25] The deriva-
tives of 3-pyridyl-1,2,4-triazine have attracted much atten-
tion because of their rich coordination chemistry. For in-
stance, 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine yields col-
ored complexes with some transition metal ions, which may
find potential application in colorimetric analysis.[26] Other
derivatives such as 2,4,6-tris[bis(pyridin-2-yl)amino]-1,3,5-
triazine,[27] 2,6-bis(tetramethylfuryl)-1,2,4-triazin-3-yl)pyr-
idine,[28] and 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine,[29]
have been employed in the construction of MOFs with dif-
ferent degrees of dimensionality. The analog H2pdtd, which
bears phenyl/pyridyl/triazine rings and asymmetrically ar-
ranged N/O donors, not only inherits the advantages of the
3-pyridyl-1,2,4-triazine series, but also meets the require-
ments for the assembly of NLO/gas storage/magnetic
MOFs. It is surprising that crystalline compounds contain-
ing the pdtd ligand (where pdtd is the deprotonated form
of H2pdtd) have not been reported to date. The major diffi-
culty lies in the fact that pdtd is a large asymmetric mole-
cule bearing sulfonate groups that have weaker coordina-
tion abilities compared to common carboxylate groups. The
solvothermal method was chosen for the preparation of
these materials due to high solubility and enhanced reaction
activity of the required reagents under solvothermal condi-
tions, while a general wet chemistry method was also inves-
tigated for the purpose of comparison. MOF materials have
been demonstrated to take up voluminous amounts of CO2
and can act as CO2 reservoirs, and as such have potential
application in gas purification and CO2 sequestration.[30,31]
Taking the above into account, we investigated the self-as-
sembly of pdtd with magnetic transition metal ions for ob-
taining multifunctional NLO/magnet/gas-sorption MOFs.
Introduction
The design and synthesis of MOFs[1–8] by self-assembly
processes has been one of the most fascinating and chal-
lenging areas of research due to their potential application
in NLO devices,[9–12] gas sorption,[13–16] magnetism,[17–20]
and catalysis.[21–23] One of challenges in MOF chemistry is
to construct a compound bearing various functional prop-
erties, such as MOFs with three functionalities: NLO ac-
tivity, magnetism, and gas storage. One of the basic features
required for NLO active materials is an acentric structure,
which can potentially be induced through the introduction
into the structure of an asymmetric ligand. For the con-
struction of porous MOFs ligands with rigid units (such as
phenyl and pyridyl groups) are preferable. Short and conju-
gated bridges within MOFs are efficient for magnetic cou-
pling, and analogs of aromatic rings are typical conjugated
groups. To achieve the goal of preparing multifunctional
MOFs, a ligand containing rigid units and asymmetrically
arranged O/N donors is suitable, and can be self-assembled
with magnetic transition metal ions such as MnII and CuII
to give the desired MOF.
In the past decades, different synthetic methods, such as
hydrothermal, solvothermal, and diffusion, have been em-
ployed to build crystalline MOF materials with intriguing
[a] Fujian Institute of Research on the Structure of Matter,
Chinese Academy of Sciences,
Fuzhou 350002, China
[b] Department of Pure and Applied Chemistry, Ladoke Akintola
University of Technology,
P.M.B. 4001, Ogbomoso, Nigeria
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201100566.
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A MOF Material with Helical Cavities and Multifunctionality
Under tailored reaction conditions, MOF 1 and the mono- sulfonate groups, and the corresponding dihedral angles are
nuclear complex 2 were obtained successfully. To the best slightly different for two the distinct pdtd ligands: 35.9 vs.
of our knowledge, 1 is the first crystalline MOFs based on 37.7° and 41.7 vs. 47.3°. Each pdtd acts as a three-connect-
pdtd, and demonstrates NLO activity, significant CO2 sorp- ing node through two oxygen atoms from separate sulfonate
tion and magnetic coupling. In contrast, 2 is NLO inactive groups and one nitrogen–nitrogen chelating group created
and displays negligible magnetic coupling due to the iso- by the pyridyl and triazine rings (Scheme 1). As shown in
lated nature of the molecular units.
Figure 2, five pdtd ligands are linked by MnII ions to form
a ten-membered nanoscale loop (Mn1–Mn2: 9.1 Å; Mn1–
Mn1C: 25.5 Å). The loops are further connected via edge-
sharing to form a 3D framework with large channels that
Results and Discussion
Compounds 1 and 2 were synthesized under different re-
action conditions. MOF 1 was prepared via the reaction
between MnCl2 and pdtd by a solvothermal method (in
CH3OH at 140 °C for 3 days). Complex 2 was synthesized
by a routine chemical reaction between CuCl2 and pdtd in
a mixture of H2O and C2H5OH, and the resulting crystals
were obtained through slow evaporation of the solution at
room temperature. The crystallographic results revealed
that compounds 1 and 2 have different structural motifs
being a three-dimensional polymeric framework and a mo-
nonuclear unit, respectively. Compared to the more conven-
tional synthesis method the solvothermal method provides
better solubilities and higher reaction activities for the rea-
gents, which overcomes the weak coordination ability of the
ligand and favors the formation of a polymeric structure.
Thus, the deprotonated oxygen atoms in the sulfonate
groups of 1 link the metal centers in a continuous manner
to form a polymeric structure. The reaction conditions for
2 are milder (80 °C) than for 1 and the resulting product is
a mononuclear complex. The powder XRD patterns of 1
and 2 are consistent with the results predicted from the sin-
gle crystal crystallographic data indicating that the obtained
samples are phase pure (Figure S1, S2 in the Supporting
Information). Furthermore, elemental analyses support the
results of the powder XRD analyses, and show that the
samples are chemically pure.
Figure 1. Coordination environment of the Mn centers in 1 (ellip-
soids are drawn at the 50% probability level and the atom labeling
scheme is also shown). Symmetry codes: A: x, –y, z – 1/2; B: x –
1, y – 1, z; C: x, –y – 1, z + 1/2.
A Single crystal X-ray diffraction study reveals that
MOF 1 crystallizes in the Pc space group. There are two
MnII centers, two pdtd ligands, four coordinated water mo-
lecules and seven free water molecules in the asymmetric
unit. The Mn1 ion is six-coordinate with distorted octa-
hedral geometry, and is bound by four oxygen atoms from
two coordinated water molecules and two sulfonate groups
from two distinct pdtd ligands [Mn1–O: 2.122(8)–
2.197(9) Å] and two nitrogen atoms from another pdtd li-
gand [Mn1–N: 2.269(7)–2.272(9) Å] (Figure 1). The sulfon-
ate oxygen atoms are arranged in a cis fashion around the
MnII center. The coordination sphere of Mn2 is also a dis-
torted octahedron [Mn2–O: 2.14(1)–2.19(1) Å, Mn2–N:
2.274(8)–2.276(7) Å] and is comparable to that of Mn1. The
Mn–O bond lengths are consistent with those reported for
other MnII centers.[32] The deviation from normal octahe-
dral geometry is reflected in the bond angles (°): O1–Mn1–
N8, N5–Mn1–O13A, and O3–Mn1–O2 are 168.3(7), 162.5
(4), and 171.8(3), respectively.[27] It is noteworthy that the
pdtd ligands in 1 are not coplanar. There are obvious twists
Scheme 1. Coordination modes of the pdtd ligand.
Figure 2. View of the pentanuclear loop in 1. Symmetry codes: A:
between the triazine ring and the phenyl rings bearing the x, –y, z + 1/2; B: x, –y – 1, z + 1/2; C: x, y, z + 1.
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Y. Zhou, M. Hong et al.
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run parallel to the a axis (Figure S3 in the Supporting In- viewed in the bc plane the structure projects as a 4ϫ82 net
formation). It is noteworthy that two uncoordinated nitro- with 4- and 8-noded helices of alternating handiness run-
gen atoms of a trizaine group are exposed to the channels, ning parallel to the c axis, resulting in a structure compris-
resulting in the presence of electron-rich lone pairs inside ing 2D layers and parallel helical channels. Each 4-noded
the channels. Lattice water molecules fill the channels, and helix shares common 2-nodes with a neighboring 8-noded
are linked to the framework by hydrogen bonding; the dis- helix to form a 10-noded circuit. The 2D layers are stacked
tance between O17 and O15 (symmetry code: x – 1, –y – in ABAB fashion along the b axis to form the resulting
1, z – 1/2) is 2.91(2) Å, and the hydrogen bond angle is (10,3)-d net. One of the fantastic features in 1 is the nonin-
100(6)°.
terpenetrated nature of the structure. There are only four
The structure of 2 was determined to be a mononuclear reported MOFs with noninterpenetrated (10,3)-d topolog-
complex, and it crystallized in the P21/c space group. As ies.[34–37] Framework 1 differs from the other four (10,3)-d
shown in Figure 3, the central Cu ion is six-coordinate, and MOFs in the following aspects: (i) The three-connected
is bound to two nitrogen atoms [Cu1–N1: 2.007(4) Å, Cu1– pdtd nodes are bigger building units owing to their rigid
N4: 2.042(4) Å] from the triazine ring and pyridyl ring of a pyridyl/triazine/phenyl rings than the nodes in the other
pdtd ligand and four oxygen atoms from four water mole- structures, which leads to potentially larger permanent cavi-
cules. Two oxygen atoms [Cu1–O9: 1.994(4) Å, Cu1–O10: ties; (ii) The space group of 1 is Pc, which is unique com-
1.995(4) Å] and the two nitrogen atoms occupy the basal pared with the groups reported for the other structures
positions of the coordination sphere. The axial oxygen (P21, Pna21); (iii) To the best of our knowledge, 1 demon-
atoms [Cu1–O7: 2.328(5) Å, Cu1–O8: 2.375(4) Å] are in- strates a (10,3)-d net with the largest helical channels (with
volved in longer Cu–O bonds than the oxygen atoms in a cross-section of about 9.1ϫ25.5 Å2, as shown in Figure 2)
the basal positions, which results in a distorted octahedral reported so far.
geometry for the metal ion. The N1–Cu1–N4 angle is
80.3(2)°, which is comparable to the reported N–Cu–N an-
gle in a complex displaying Jahn–Teller distortion.[33] The
dihedral angles between the triazine ring and the phenyl
rings bearing sulfonate groups are 43.3° and 42.1°. The mo-
nonuclear units are consolidated, by hydrogen bonds, to
give a 3D structure (Figure S4 in the Supporting Infor-
mation).
Figure 4. The utp topological net in 1 as viewed along the a axis
(up) and the b axis (bottom). The MnII and pdtd nodes are shown
in purple and blue, respectively.
The IR spectra of 1 and 2 exhibit strong bands at 3421
Figure 3. Asymmetric unit of 2 (ellipsoids are drawn at the 50%
and 3396 cm–1, respectively, which can be assigned to the
probability level and the atom labeling scheme is also shown).
ν(O–H) stretching of the coordinated water molecules.
The structure of 1 was found to be a uninodal net with Weak absorption bands at 2900 and 2924 cm–1 in the spec-
a Schläfli topological term of 103. The net had two three- tra are due to the ν(C–H) vibrations of the aromatic rings
connected topologically equivalent nodes represented by of pdtd, as shown in Figure S9 in the Supporting Infor-
the MnII ions and the averaged pdtd ligand positions. When mation. The absorption band at 2343 cm–1 in the spectrum
the two coordinated water molecules are ignored, the two of 1 is attributed to the ν(N=N) stretch (absorption by the
chelating nitrogen atoms from pdtd are reduced to a single azide group)[38] of the triazine ring of the pdtd ligand. The
topological link, thus the six-coordinate MnII centers be- ν(C=N) absorption bands are observed in the spectra of
come three-connecting nodes. When the structure is viewed compounds 1 and 2 at 1628 and 1638 cm–1, respectively,
in the ac plane it projects as a (6,3) net in which each helix and are of medium intensity. The peaks at 1121 and
is surrounded by six others (Figure 4). It is noteworthy that 1129 cm–1 in the spectra of 1 and 2, respectively, are associ-
the network has both left- and right-handed helices, which ated with the vibrations of the C–N bonds. The peaks at
alternate along the c axis resulting in a racemic network. 1518 and 1526 cm–1 in the spectra of 1 and 2 are attributed
Thus, the network has an extended Schläfli symbol of to the ν(C=C) vibrations of the phenyl rings. The character-
102·104·104 and is a (10,3)-d (utp) net. In addition, when istic absorption bands of the sulfonate groups in 1 appear
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A MOF Material with Helical Cavities and Multifunctionality
at 1226, 1181, 1121 cm–1 for νas(SO3 ) and 1043 cm–1 for shows two main weight loss steps (Figure 5). The first
–
–
νs(SO3 ). Similar bands at 1217, 1188, 1119 cm–1 for weight loss of 15.8% occurs from 30–181 °C, and corre-
–
–
νas(SO3 ) and 1047 cm–1 for νs(SO3 ) are found in the spec- sponds to the release of lattice and coordinated water mole-
trum of 2. A weak peak associated with the Mn–O bonds cules from the structure (calcd. 15.7%). The second loss
appears at 532 cm–1 in the spectrum of 1. Weak peaks due starts at 450 °C and reaches 42.5% at 800 °C, and can be
to absorption by the Mn–N and Cu–N bonds appear at 487 hypothesized as corresponding to the combustion of the
and 462 cm–1 in the spectra for 1 and 2, respectively. The pdtd ligands and the collapse of the framework. To confirm
difference between the asymmetric and symmetric sulfonate the TGA results, a crystalline sample of 1 was kept in a
stretching wavenumbers are 183 and 170 cm–1 for 1 and 2, glass container fitted with a glass stopper and heated in a
respectively, which implies that the bonds within the mono- tube oven under vacuum (Ͻ 10 Pa) at 400 °C for 5 h. The
dentate and ionic sulfonate groups are comparable in weight loss was measured by a METTLER XP26 microbal-
strength to those within carboxylates.
ance and was found to be 15.9%, which is consistent with
the TGA result. Powder X-ray diffraction data implied that
1 could readily be activated and maintain a crystalline
framework up to 400 °C (see Figure S1). The TGA curve
Magnetic Study
To investigate the magnetic coupling ability of pdtd the for 2 also exhibits two main weight loss steps (Figure 5).
temperature dependent magnetic susceptibilities of 1 and 2 The release of one lattice and four coordinated water mole-
were measured at 0.1 T. For 1, the observed χmT value of cules from the structure occurs from 30 °C to 221 °C
4.32 cm3 Kmol–1 recorded at room temperature is slightly (calcd.: 14.5%, found: 14.4%), and combustion of the pdtd
smaller than the expected value of 4.37 cm3 Kmol–1 known ligands occurs up to 320 °C (Figure 5).
for isolated MnII ions (S = 5/2) with g = 2.0. The χmT value
undergoes a gradual decrease down to 4.27 cm3 Kmol–1 at
4 K, indicating antiferromagnetic coupling between neigh-
boring MnII ions (see Figure S5 in the Supporting Infor-
mation). It is noteworthy that the χmT value increases to
4.34 cm3 Kmol–1 at 2 K, implying that long-range order is
present due to spin-canting or ferrimagnetic behavior.[39]
The magnetic susceptibility data in the range of 20–300 K
obey the Curie–Weiss law, yielding C = 4.37 cm3 Kmol–1
and θ = –0.16 K. The negative value of θ implies that there
is antiferromagnetic coupling between neighboring MnII
ions. To analyze the experimental data, a model incorporat-
ing isolated ions plus a molecular field was fitted to the
magnetic susceptibility data, χtotal
= χMn/[1 – (2zjЈ
Ng2β2)χMn]. The parameter zjЈ is based on the molecular
field approximation, and is introduced to simulate the mag-
netic interaction between the Mn ions; all the other param-
eters have their usual meanings. The least-squares fitting of
Figure 5. TGA curves for 1 (dashed line) and 2 (solid line) recorded
the model to the observed data led to g = 1.99, zjЈ =
under flowing nitrogen.
2
–0.19 cm–1 and R = ∑(χTobsd. – χTcalcd.)2/∑(χTobsd.
)
=
1.9ϫ10–4, values that are consistent with those for other
The structure of MOF 1 has large helical channels (with
cross-sections of about 9.1ϫ25.5 Å2) and good thermal sta-
Mn sulfonates.[40]
For 2, the observed χMT vs. T curve is characteristic of bility. PLATON calculations indicate that the crystal struc-
a compound displaying typical paramagnetic behavior (see ture contains 15.0% of void space that is accessible to sol-
Figure S6). The value of χMT at room temperature is vent molecules.[42] In addition, there are uncoordinated tri-
0.440 cm3 Kmol–1, which is close to the expected value of azine nitrogen atoms exposed on the inside surface of the
0.454 cm3 Kmol–1 known for one isolated CuII ion (S = channels, which is advantageous for enhancing the CO2 ad-
1/2) with g = 2.2. The value of χMT remains almost con- sorption enthalpy of 1.[14,43,44] A CO2 adsorption isotherm
stant upon cooling and reaches 0.441 cm3 mol–1K at 2 K. A was measured at 273 K for activated 1 (Figure S7). The po-
linear fit of the 1/χM vs. T data gives C = 0.438 cm3 Kmol–1 rosity of 1 was confirmed by adsorption of CO2, and it has
and θ = 0.07 K. The negligible value of the Weiss constant an apparent Langmuir surface area of 352 m2 g–1. Further-
also demonstrates that there is no obvious magnetic cou- more, the CO2 uptake curve has a large slope, implying that
pling between the well separated magnetic ions.[41]
1 has a high affinity for CO2. The amount of CO2 adsorp-
tion at 1 atm is significant, 39.0 cm3 g–1, indicating that 1 is
a potential CO2 reservoir material. The CO2 sorption capa-
bility of 1 is comparable to that of other MOFs possessing
CO2 Adsorption
Thermogravimetric analyses (TGA) of compounds 1 and exposed uncoordinated nitrogen atoms within their chan-
2 were performed under flowing nitrogen. The curve for 1 nels,[14] which enhance the CO2 binding to the framework
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Y. Zhou, M. Hong et al.
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metric adsorption apparatus (Micromeritics’ ASAP 2020 analyzer).
A 35.4 mg sample was evacuated by heating at 473 K for 5 h and
measurements with this sample were repeated three times.
by the formation of favorable interactions between the
MOF and the electropositive carbons and the quadrupoles
of CO2 molecules.
[Mn2(pdtd)2(H2O)4]n·5nH2O (1):
A mixture of MnCl2·4H2O
(0.119 g, 0.6 mmol), NaHpdtd (0.098 g, 0.2 mmol), and CH3OH
(10 mL) was placed in a Teflon-lined stainless steel vessel. The ves-
sel was sealed and heated at 140 °C for 3 d, then gradually cooled
to room temperature. Orange prismatic crystals of 1 were collected
in 69.4% yield (0.168 g) based on NaHpdtd. C40H42Mn2N8O21S4
(1208.94 gmol–1): calcd. C 39.74, H 3.50, N 9.27; found C 39.70,
NLO Property of MOF 1
1 crystallizes in the acentric space group Pc, Kurtz mea-
surements were conducted to confirm the acentricity as well
as to evaluate the potential application of 1 as a NLO mate-
rial.[38] Preliminary results indicate that 1 displays second
harmonic generation (SHG) efficiency that is approximately
1.2 times greater that that of KDP (potassium dihydrogen
phosphate). The powder SHG response of 1 is modest com-
pared to those of NLO active MOFs.[9,45–47] This may be
H 3.81, N 9.14. Selected IR data (KBr pellet): ν = 3421 (s), 2900
˜
(w), 2343 (w), 1628 (m), 1518 (s), 1121 (m), 1181 (s), 618 (s), 532
(w), 487 (w) cm–1.
[Cu(pdtd)(H2O)4]·H2O (2): A mixture of CuCl2·2H2O (0.034 g,
2.0 mmol), NaHpdtd (0.246 g, 0.5 mmol), H2O (25 mL), and
attributed to the unfavorable arrangement of the donor-ac- C2H5OH (5 mL) was placed in a 50 mL Erlenmeyer flask and
heated at 80 °C for 30 min. The resultant green solution was filtered
and allowed to evaporate at room temperature. After one week,
green prismatic crystals of 2 were collected in 45.2% yield (0.142 g)
based on NaHpdtd. C20H22CuN4O11S2 (622.08 gmol–1): calcd. C
38.62, H 3.56, N 9.01; found C 38.43, H 3.57, N 8.94. Selected IR
ceptor components within the pdtd ligand, which is some-
what circular in configuration, which results in weakened
polarization. We have demonstrated the influence of the do-
nor-acceptor component arrangement (parallel or antipar-
allel) on the NLO response of MOFs.[45] The circular con-
figuration of 1 confirmed the effect the arrangement of an
unsymmetrical ligand has upon NLO efficiency.
data (KBr pellet): ν = 3396 (s), 2924 (w), 1638 (m), 1526 (s), 1129
˜
(m), 1188 (s), 616 (s), 462 (w) cm–1.
X-Ray Crystallography: Diffraction data for compounds 1 and 2
were collected on a Rigaku Saturn 70 CCD diffractometer with
Mo-Kα radiation (λ = 0.7107 Å) at 173 K and 298 K, respectively.
Lorentz polarization (Lp) corrections were applied to the data. The
structures were solved by direct methods and all calculations were
performed with the SHELXL-97 program.[48] The metal atoms
were found in the electron density map, and subsequent difference
Fourier syntheses gave all the coordinates for the non-hydrogen
atoms, which were then refined anisotropically. The lattice water
atoms were refined isotropically. All hydrogen atoms were added
to the structure with riding models and refined isotropically. Crys-
tallographic data for 1 and 2 are summarized in Table S1 (Support-
ing Information), and selected bond lengths and bond angles are
listed in Tables S2 and S3.
Conclusions
Under solvothermal conditions, the self-assembly of
MnII and pdtd afforded an acentric (10,3)-d framework 1,
which is NLO-active and displays magnetic coupling.
Furthermore, 1 contains nanoscale helical cavities and exhi-
bits significant CO2 sorption capability. In contrast, as-
sembly conducted under milder reaction conditions yielded
the mononuclear CuII complex 2, which is centric and lacks
functionality. Compound 1 is the first structurally charac-
terized MOF containing pdtd, and exhibits potential appli-
cation as a CO2 sponge, and as a NLO and magnetic mate-
rial.
CCDC-796037 (for 1) and -796036 (for 2) contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Experimental Section
Supporting Information (see footnote on the first page of this arti-
cle): Crystallographic data (1 and 2), PXRD spectra, packing struc-
tures and magnetic properties for 1 and 2, CO2 sorption isotherm
for 1.
Materials and Methods: All chemicals were analytical grade and
were used as received without further purification. Powder X-ray
diffraction (PXRD) data were collected on a Rigaku MiniFlex II
diffractometer. Elemental analyses were carried out on an Elemen-
tal Vario EL III microanalyzer. Infrared spectra were measured on
a Perkin–Elmer Spectrum One FTIR spectrometer with KBr pel-
lets. Thermogravimetric analyses within the 30–800 °C range were
carried out with a Netzsch STA 449C Jupiter at a heating rate of
10 °C/min and with a nitrogen flow rate of 20 cm3/min. Variable
temperature magnetic measurements were conducted in an external
field of 1.0 kG with a Quantum Design PPMS model 6000 magne-
tometer and with the samples sealed in capsules. Diamagnetic cor-
rections were estimated with Pascal constants, and data for back-
ground corrections were obtained from experimental measurements
of the sample holders. The NLO properties of the samples were
measured by the Kurtz powder SHG method. The illuminating
Acknowledgments
The authors thank the financial support by the National Natural
Science Foundation of China (NSFC) (grant numbers 21071143,
91022035), the 973 Program of China, the Third World Organiza-
tion for Women in Science (TWOWS) postgraduate fellowship, and
the Authority of Ladoke Akintola University of Technology, Og-
bomoso, Nigeria. We also thank Prof. Ding Li for the help of the
Kurtz measurement.
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source was
a Q-switched mode-locked Nd-YAG laser (λ =
1064 nm), and potassium dihydrogen phosphate (KDP) was the ref-
erence material. Adsorption isotherms were measured by a volu-
5004
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A MOF Material with Helical Cavities and Multifunctionality
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Received: June 4, 2011
Published Online: October 11, 2011
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Eur. J. Inorg. Chem. 2011, 5000–5005
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