Poly[(μ4-2,5-dimethoxybenzene-1,4-dicarboxylato)manganese(II) ] and its zinc(II) analogue: Three-dimensional coordination polymers containing unusually coordinated metal centres

Article abstract of DOI:10.1107/S0108270110046950

The title compounds, [Mn(C₁₀H₈O₆)] _n and [Zn(C₁₀H₈O₆)]_n, are isomorphous coordination polymers prepared from 2,5-dimeth-oxy-terephthalic acid (H₂dmt) and the respective metal(II) salts. Both complexes form three-dimensional metal-organic frameworks with each M ^II centre bridged by four 2,5-dimeth-oxy-terephthalate (dmt^2-) anions, resulting in the same type of network topology. The asymmetric unit consists of one M ^II cation on a twofold axis and one half of a dmt^2- anion (located on a centre of inversion). In the crystal structure, the M ^II centres are coordinated in a rather unusual way, as there is a distorted tetra-hedral inner coordination sphere formed by four carboxyl-ate O atoms of four different dmt^2- anions, and an additional outer coordination sphere formed by two meth-oxy and two carboxyl-ate O atoms, with each of the O atoms belonging to one of the four different dmt^2- anions forming the inner coordination sphere. Consideration of both coordination spheres results in a super-dodeca-hedral coordination geometry for the M ^II centres. Besides the numerous M ^II...O inter-actions, both structures are further stabilized by weak C - H...O contacts.

Full text of DOI:10.1107/S0108270110046950

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
such as temperature, solvent and moisture can influence SBU
formation (Hausdorf et al., 2008). Nevertheless, generation of
SBUs subject to linker properties has only rarely been
investigated (Choi et al., 2009).
ISSN 0108-2701
Poly[(l4-2,5-dimethoxybenzene-1,4-
dicarboxylato)manganese(II)] and its
zinc(II) analogue: three-dimensional
coordination polymers containing
unusually coordinated metal centres
Tony Bohle,a Frank Eissmann,b Edwin Weberb and
¨
Florian O. R. L. Mertensa*
While the reaction of 2,5-dihydroxyterephthalic acid and
Zn(NO3)2ꢁ4H2O [carried out under conditions (Tranche-
montagne et al., 2008) comparable with those used here] leads
to MOF-74-type networks (Rosi et al., 2005), the reaction of
2,5-di-n-propoxyterephthalic acid and Zn(NO3)2ꢁ4H2O gives
rise to IRMOF-type structures (Eddaoudi et al., 2002).
However, three-dimensional coordination polymers contain-
ing the dmt2ꢀ anion as a linker with ZnII or MnII as metal ions
for the SBU have not been reported so far. This prompted us
to use the dmt2ꢀ anion as a rigid dicarboxylate with small
weakly coordinating substituents for our investigations of the
formation of appropriate new types of MOCPs.
The title compounds, [Mn(dmt)]n, (I), and [Zn(dmt)]n, (II),
crystallize in the monoclinic space group C2/c, with asym-
metric units containing one MII cation (M = Mn or Zn) and
one half of a dmt2ꢀ anion (Fig. 1). Indeed, the two compounds
are isomorphous, which is shown in the molecular overlay plot
in Fig. 2. Besides a slight difference in the monoclinic angle ꢀ,
the unit-cell dimensions do not differ significantly from each
other.
aInstitut fur Physikalische Chemie, TU Bergakademie Freiberg, Leipziger Strasse 29,
¨
D-09596 Freiberg/Sachsen, Germany, and bInstitut fur Organische Chemie, TU
¨
Bergakademie Freiberg, Leipziger Strasse 29, D-09596 Freiberg/Sachsen, Germany
Correspondence e-mail: florian.mertens@chemie.tu-freiberg.de
Received 3 September 2010
Accepted 12 November 2010
Online 8 December 2010
The title compounds, [Mn(C10H8O6)]n and [Zn(C10H8O6)]n,
are isomorphous coordination polymers prepared from 2,5-
dimethoxyterephthalic acid (H2dmt) and the respective
metal(II) salts. Both complexes form three-dimensional
metal–organic frameworks with each MII centre bridged by
four 2,5-dimethoxyterephthalate (dmt2ꢀ) anions, resulting in
the same type of network topology. The asymmetric unit
consists of one MII cation on a twofold axis and one half of a
dmt2ꢀ anion (located on a centre of inversion). In the crystal
structure, the MII centres are coordinated in a rather unusual
way, as there is a distorted tetrahedral inner coordination
sphere formed by four carboxylate O atoms of four different
dmt2ꢀ anions, and an additional outer coordination sphere
formed by two methoxy and two carboxylate O atoms, with
each of the O atoms belonging to one of the four different
dmt2ꢀ anions forming the inner coordination sphere. Consid-
eration of both coordination spheres results in a super-
dodecahedral coordination geometry for the MII centres.
Besides the numerous MIIꢁ ꢁ ꢁO interactions, both structures
are further stabilized by weak C—Hꢁ ꢁ ꢁO contacts.
As shown in Fig. 1, each of the MII cations adopts a
distorted MIIO4 tetrahedral geometry, coordinated by four O
atoms from four different dmt2ꢀ anions. The Mn1—O1 and
˚
Mn1—O2 bond lengths of 2.1391 (6) and 2.0761 (5) A,
respectively, in (I) are in accordance with those reported for
related manganese(II) terephthalates [Mn—O = 2.100 (4)–
˚
2.188 (3) A; Xu et al., 2010; Luo et al., 2008]. The corre-
sponding O—Mn—O angles range from 93.73 (2) to
141.52 (3)ꢂ, thus deviating considerably from the ideal value of
109.4ꢂ for a tetrahedral coordination sphere. The Zn—O bond
˚
lengths in (II) range from 2.0023 (13) A for Zn1—O1 to
˚
1.9547 (13) A for Zn1—O2 and do not vary significantly from
literature values for related zinc(II) terephthalate-based
Comment
˚
MOCPs [Zn—O = 1.935 (2)–2.104 (5) A; Higuchi et al., 2009;
Metal–organic coordination polymers (MOCPs) are crystal-
line frameworks composed of metal ions or clusters of metal
ions called secondary building units (SBUs) and organic
molecules called linkers, to form one-, two- or three-dimen-
sional structures possessing cavities (Li et al., 1999). In specific
cases, knowledge of the SBU and linker geometries, in
conjunction with their interaction principles, allows the
prediction of network topologies and thus supports rational
framework design. It is known that specific reaction conditions
Wang et al., 2008]. However, the distortion of the O—Zn—O
angles from ideal tetrahedral geometry in (II), ranging from
99.51 (5) to 137.03 (8)ꢂ, is smaller than in (I). These structural
differences between (I) and (II) may be caused by the
different ionic radii of the MnII and ZnII cations (0.91 and
˚
0.83 A, respectively; Riedel, 2004).
The unusual values for the O—MII—O bond angles
mentioned above can be explained by the existence of a
Acta Cryst. (2011). C67, m5–m8
doi:10.1107/S0108270110046950
# 2011 International Union of Crystallography m5

metal-organic compounds
Figure 1
The asymmetric units of (a) (I) and (b) (II), showing the atom-labelling schemes. Displacement ellipsoids are drawn at the 50% probability level.
[Symmetry codes: (ii) ꢀx + 2, y, ꢀz + 32; (iii) ꢀx + 2, ꢀy, ꢀz + 1; (vi) x, ꢀy, z + 12.]
second coordination sphere formed by weak interactions
between the MII cations and the O atoms of the methoxy and
carboxylate groups (Fig. 1). This leads to a distorted
[MIIO4(O)2(OMe)2] super dodecahedron (Fig. 3), where the
methoxy O atoms are located in positions trans to each other,
while the two bidentate and two monodentate carboxylates
coordinate in positions cis to each other (Fig. 4).
iii
˚
The bond lengths for M—OMe [Mn1—O3 = 2.5596 (6) A
and Zn1—O3iii = 2.6224 (17) A; symmetry code: (iii) ꢀx + 2,
˚
iv
ꢀy, ꢀz + 1] and M—O20 [Mn1—O2 = 2.7570 (6) A and
˚
Zn1—O2iv = 2.8772 (16) A; symmetry code: (iv) ꢀx + 2, y,
˚
ꢀz + 12] reveal that these bonds are much weaker than the
M—O bonds of the inner coordination sphere. Similar coor-
Figure 2
dination modes have already been reported for CdII
A molecular overlay of the asymmetric units of (I) and (II), showing only
minor differences in the atom positions. The atoms of (I) are shown as
shaded balls and those of (II) as white balls with shaded borders. H atoms
have been omitted for clarity.
Figure 4
Figure 3
(a) The one-dimensional chains of [Mn–(ꢁ-CO2)2–Mn]n. The MII—O
bonds of the second coordination spheres are shown as dashed lines. (b)
The inorganic MIIO8 SBUs are chains of edge-sharing dodecahedra, in
which the C atoms can be connected to form a zigzag ladder. The atom
coordinates from (I) were exemplarily used to create the diagram.
The super-dodecahedral coordination spheres of MnO4(O)2(OMe)2,
showing the coordination modes of the anions. The MII—O bonds of
the second coordination spheres are shown as dashed lines. The atom
coordinates from (I) were exemplarily used to create the diagram.
ꢃ
m6 Bohle et al.
[Mn(C10H8O6)] and [Zn(C10H8O6)]
Acta Cryst. (2011). C67, m5–m8
¨

metal-organic compounds
complex network structures to simple SBU-and-linker
networks (Rosi et al., 2005) (Fig. 6). To derive the nets of (I)
and (II), the SBUs were reduced to rods of shaded quad-
rangles linked by sharing opposite edges, which leads to a
ladder-like conformation of the one-dimensional SBU chains.
The linkers are represented by rungs to form a 4-connected
net with parallel rungs, analogous to the Al net in SrAl2. This
is called a network with sra12 topology, also found in metal–
organic frameworks such as MIL-47 (Barthelet et al., 2002),
MIL-53 (Loiseau et al., 2004) and MOF-71 (Rosi et al., 2005).
The main reason for the generation of the more or less
unusual isomorphous structures of (I) and (II) may be the
formation of metal centres with high coordination numbers.
The reaction of Zn(NO3)2ꢁ4H2O with a rigid dicarboxylic acid
in dimethylformamide usually leads to an IRMOF-type
framework (Eddaoudi et al., 2002) containing a four-coordi-
nated Zn metal centre. Performing these reactions with 2,5-
dihydroxyterephthalic acid instead leads to MOF-74-type
frameworks, caused by the linker molecule facilitating the
formation of a much more stable five-coordinated metal
species. The frameworks of (I) and (II) discussed here exhibit
eight-coordinated metal centres, which seems to be the most
stable coordination geometry under these conditions.
Figure 5
A view of the network of (I) and (II) along the c axis with shaded
MIIO4(O)2(OMe)2 super dodecahedra. The large balls show the
accessible pores. The atom coordinates from (I) were used as the
example to create the diagram.
Experimental
All chemicals and solvents were commercially available and used
without further purification. 2,5-Dimethoxyterephthalic acid was
synthesized according to the procedure published by Passaniti et al.
(2002). For the synthesis of [Mn(dmt)]n, (I), MnCl2ꢁ4H2O (105 mg,
0.53 mmol) and 2,5-dimethoxyterephthalic acid (40 mg, 0.18 mmol)
were dissolved in dimethylformamide (40 ml) and heated in a sealed
tube for 24 h at 373 K. Yellow crystals of (I) precipitated after 24 h
(yield 72%). For the synthesis of [Zn(dmt)]n, (II), the same procedure
was used as for (I), using Zn(NO3)2ꢁ4H2O (140 mg, 0.53 mmol)
instead of MnCl2ꢁ4H2O. Colourless crystals of (II) precipitated after
18 h (yield 79%).
Figure 6
The topology of the network, reduced to a simple SBU-and-linker
geometry model. The MIIO4(OMe)2 SBUs are reduced to rods of shaded
quadrangles and the dmt2ꢀ linkers are represented by thin grey rods.
complexes (Li et al., 2008). The MIIO8 super dodecahedra are
edge-sharing, giving a one-dimensional chain along the c axis
(Fig. 4). Two adjacent one-dimensional chains are inter-
connected by dmt2ꢀ anions to obtain a three-dimensional
coordination network, with shortest Mn1ꢁ ꢁ ꢁMn1v and
Zn1ꢁ ꢁ ꢁZn1v distances [symmetry code: (v) ꢀx + 2, ꢀy ꢀ 1,
ꢀz] between the one-dimensional chains of 8.0793 (3) and
Compound (I)
Crystal data
3
˚
II
[Mn(C10H8O6)]
Mr = 279.10
V = 1043.66 (7) A
Z = 4
˚
8.0552 (2) A, respectively. Apart from these M —O inter-
actions, there are weak intermolecular C—Hꢁ ꢁ ꢁO hydrogen-
bonding interactions in both networks, involving C3—
H3ꢁ ꢁ ꢁO1i and C5—H5Bꢁ ꢁ ꢁO2ii for both (I) and (II), contri-
buting to the stabilization of the crystal structures (symmetry
codes are given in Tables 1 and 2).
Monoclinic, C2=c
Mo Kꢂ radiation
ꢁ = 1.28 mmꢀ1
T = 153 K
0.52 ꢄ 0.35 ꢄ 0.33 mm
˚
a = 16.7686 (6) A
˚
b = 8.4646 (3) A
˚
c = 7.4464 (3) A
ꢀ = 99.093 (1)ꢂ
˚
Data collection
One-dimensional rhombic channels of 9.1 ꢄ 13.1 A in cross-
Bruker Kappa APEXII CCD area-
detector diffractometer
Absorption correction: multi-scan
(SADABS; Bruker, 2007)
Tmin = 0.633, Tmax = 0.747
11427 measured reflections
2156 independent reflections
2084 reflections with I > 2ꢃ(I)
Rint = 0.019
section (measured between atoms in opposite corners) are
located along the c axis in the networks of (I) and (II). The
methoxy groups point inside these channels and subdivide
them into two smaller pores, shown as balls in the network
structure (Fig. 5). Taking the van der Waals radii into account,
Refinement
˚
their diameter is reduced to about 1.2 A, which is much too
R[F2 > 2ꢃ(F2)] = 0.019
wR(F2) = 0.052
S = 1.09
79 parameters
H-atom parameteꢀrs3 constrained
small for the uptake of any solvent molecules or nitrogen. A
better understanding of the network structures of (I) and (II)
can be achieved by a topological investigation, reducing
˚
Áꢄmax = 0.42 e A
Áꢄmin = ꢀ0.34 e A
ꢀ3
˚
2156 reflections
ꢃ
Acta Cryst. (2011). C67, m5–m8
Bohle et al.
¨
[Mn(C10H8O6)] and [Zn(C10H8O6)] m7

metal-organic compounds
Table 1
Hydrogen-bond geometry (A, ) for (I).
For both compounds, data collection: APEX2 (Bruker, 2007);
cell refinement: SAINT (Bruker, 2007); data reduction: SAINT;
program(s) used to solve structure: SHELXS97 (Sheldrick, 2008);
program(s) used to refine structure: SHELXL97 (Sheldrick, 2008);
molecular graphics: PLATON (Spek, 2009); software used to prepare
material for publication: SHELXTL (Sheldrick, 2008) and PLATON.
ꢂ
˚
D—Hꢁ ꢁ ꢁA
D—H
Hꢁ ꢁ ꢁA
Dꢁ ꢁ ꢁA
D—Hꢁ ꢁ ꢁA
C3—H3ꢁ ꢁ ꢁO1i
0.95
0.98
2.37
2.47
2.7209 (8)
3.0654 (11)
101
119
C5—H5Bꢁ ꢁ ꢁO2ii
3
2
1
2
3
2
Symmetry codes: (i) ꢀx þ ; ꢀy þ ; ꢀz þ 1; (ii) ꢀx þ 2; y; ꢀz þ .
The authors thank the German Research Foundation within
the priority programme ‘Porous Metal–Organic Frameworks’
(SPP 1362, MOFs).
Table 2
Hydrogen-bond geometry (A, ) for (II).
ꢂ
˚
D—Hꢁ ꢁ ꢁA
D—H
Hꢁ ꢁ ꢁA
Dꢁ ꢁ ꢁA
D—Hꢁ ꢁ ꢁA
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: GG3245). Services for accessing these data are
described at the back of the journal.
C3—H3ꢁ ꢁ ꢁO1i
0.95
0.98
2.36
2.47
2.713 (2)
3.071 (3)
101
120
C5—H5Bꢁ ꢁ ꢁO2ii
3
2
1
2
3
2
Symmetry codes: (i) ꢀx þ ; ꢀy þ ; ꢀz þ 1; (ii) ꢀx þ 2; y; ꢀz þ .
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Crystal data
3
˚
[Zn(C10H8O6)]
Mr = 289.53
Monoclinic, C2=c
˚
a = 16.5936 (6) A
V = 1039.25 (7) A
Z = 4
Mo Kꢂ radiation
ꢁ = 2.38 mmꢀ1
T = 153 K
˚
b = 8.4438 (3) A
˚
c = 7.4838 (3) A
0.21 ꢄ 0.15 ꢄ 0.13 mm
ꢀ = 97.649 (2)ꢂ
Data collection
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Bruker Kappa APEXII CCD area-
detector diffractometer
Absorption correction: multi-scan
(SADABS; Bruker, 2007)
Tmin = 0.695, Tmax = 0.746
6781 measured reflections
1005 independent reflections
898 reflections with I > 2ꢃ(I)
Rint = 0.032
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(2005). J. Am. Chem. Soc. 127, 1504–1518.
Refinement
R[F2 > 2ꢃ(F2)] = 0.022
wR(F2) = 0.049
S = 1.05
79 parameters
H-atom parameteꢀrs3 constrained
˚
Áꢄmax = 0.31 e A
Áꢄmin = ꢀ0.28 e A
ꢀ3
˚
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For both compounds, H atoms were positioned geometrically and
˚
allowed to ride on their respective parent atoms, with C—H = 0.98 A
˚
and Uiso(H) = 1.5Ueq(C) for methyl, and C—H = 0.95 A and Uiso(H) =
1.2Ueq(C) for aryl H atoms.
ꢃ
m8 Bohle et al.
[Mn(C10H8O6)] and [Zn(C10H8O6)]
Acta Cryst. (2011). C67, m5–m8
¨