supplementary materials


im2422 scheme

Acta Cryst. (2013). E69, m232-m233    [ doi:10.1107/S1600536813007733 ]

Poly[diaqua[[mu]6-4,4'-(1,4-phenylene)bis(2,6-dimethylpyridine-3,5-dicarboxylato)]dilead(II)]

Y. Zhu, M.-X. Zhang, S.-S. Yang, F. Xiao, X.-P. Zhang, Y.-Y. Gao, B.-J. Li and K.-L. Huang

Abstract top

The asymmetric unit of the title Pb-based coordination polymer, [Pb2(C24H16N2O8)(H2O)2]n, consists of one PbII cation, half of a 4,4'-(1,4-phenylene)bis(2,6-dimethylpyridine-3,5-dicarboxylate (L4-) ligand and one coordinating water molecule. The centers of the benzene ring of the ligand and the four-membered Pb/O/Pb/O ring are located on centers of inversion. The PbII ion is coordinated in form of a distorted polyhedron by seven O atoms from four separate L4- ligands and by one water O atom. The PbO7 polyhedra share O atoms, forming infinite zigzag [PbO4(H2O)]n chains along [100] that are bridged by L4- ligands, forming a two-dimensional coordination network parallel to (001). O-H...O hydrogen bonds involving the water molecule are observed.

Comment top

In recent years, the chemistry of novel metal-organic hybrid coordination polymers has been the subject of intensive research, due to their interesting molecular structures and their potential as a new class of solid-state materials applied in catalysis, molecular recognition, gas storage, drug delivery, and so on (Liu et al., 2002; O'Keeffe et al., 2008). Generally speaking, the diversity of potential applications in the framework structures of such materials greatly depends on the selection of the metal centers and organic spacers. Recently, carboxylate groups are frequently exploited in the design, syntheses, and crystallization of coordination frameworks, because they exhibit diverse coordination modes, which can enhance the robustness of the architectures. Furthermore, the flexibility of carboxylate groups is always efficient to form fascinating structures. In this paper, we choose a new flexible and multidentate carboxylate ligand, 4,4'-(1,4-phenylene)bis(2,6-dimethylpyridine-3,5-dicarboxylic acid) (H4L).

Up to date, research on coordination polymers has focused on transition metal ions as coordination centers, while less concentration has been given to heavy p-block metal ion, e.g. lead(II). In contrast to transiton metal ions, lead(II), with its large radius, flexible coordination environment, and variable stereochemical activity, provides unique opportunities for the formation of unusual structures with interesting properties (Harrowfield et al.., 2004; Yang et al.., 2007). In addition, the intrinsic features of lead(II), the presence of a 6 s2 outer electron configuration, inspire chemists extensive interest in coordination chemistry, photophysics, and photochemistry. Herein, we report a new photoluminescent complex [Pb(L)(H2O)]n(1) from the flexible 4,4'-(1,4-phenylene)bis(2,6-dimethylpyridine-3,5- dicarboxylic acid) (H4L) and lead salt.

X-ray diffraction analyses reveal that each asymmetric unit of 1 contains half deprotonated L4- ligand, one H2O molecule and one crystallographically independent PbII center(Fig 1). Pb1 center is coordinated with seven O atoms: six (O1#1, O1#2, O2#2,O2#3, O3, O4) from four H4L ligands and one (O5) from the H2O molecule. Of particular interest is the weak coordinative bond that exists between Pb1 and O2#3. Pb1,O1#1, O1#2, O2#2,O2#3, O3, O4, O5 furnish a polyhydral coordination environment (PbO7) with the Pb—O bond lengths are in agreement with those reported in other Pb(II) complexes of O-chelating ligands (Wei et al., 2005; Chen et al., 2012).

As shown in Fig.1, each H4L ligand connects six crystallographically equivalent Pb atoms. The carboxylato group with O1 and O2 coordinates three lead atoms producing two Pb2O2 rings that share one common lead atom. The other carboxylate moiety with donor atoms O3 and O4 coordinates one lead atom in a chelating mode. Notably, the resulting PbO7 polyhedra share the O1#4, O1#5, O2#2, O2#3 atoms to form infinite zigzag chains composed of [PbO4(H2O)]n in which adjacent Pb atoms are coplanar and Pb···Pb distances are 4.077 Å and 4.161 Å respectively (Fig. 2). Another interesting structural feature of complex 1 is that the zigzag [PbO4(H2O)]n chains are bridged by H4L ligands to form a two-dimensional (2-D) coordination network (Fig. 3).

The photoluminescence spectrum of compound 1 was measured in the solid state at room temperature, as shown in Fig. 4. At room temperature the photoluminescent emission maximum of free H4L was observed at 426 nm (upon λEx, max = 208 nm). For compound 1, excitation at 380 nm leads to strong photoluminescence with an emission maximum at λ = 465 nm. The emission peak of complex 1 is red-shifted by about 40 nm compared to that of the pure H4L ligand, which can be assigned to the ligand-metal charge transfer (LMCT) (Hu et al., 2010; Zhang et al., 2011; Zhang et al., 2012).

Related literature top

For background to metal-organic frameworks, see: Long & Yaghi (2009); Zhao et al. (2003). For related structures, see: Liu et al. (2002); O'Keeffe et al. (2008); Zhang et al. (2011). For lead complexes, see: Harrowfield et al. (2004); Yang et al. (2007). For typical Pb—O distances, see: Chen et al. (2012); Wei et al. (2005). For photoluminescent mechanism of ligand–metal charge transfer, see: Hu et al. (2010); Zhang et al. (2012).

Experimental top

A mixture of Pb(NO3)2 × 6 H2O (66 mg), H4L (40 mg) and DMF (6 ml) was sealed in a 25 ml Teflon-lined stainless steel reactor. The mixture was heated to 373 K for 3 days and then cooled to room temperature. The crystal samples were washed with methanol to yield 18 mg of compound 1.

Refinement top

Methyl H atoms were constrained to an ideal geometry (C—H = 0.96 Å), with Uiso(H) =1.5Ueq(C), but were allowed to rotate freely. Other H atoms attached to C atoms were refined using a riding model [C—H = 0.93 Å (CH) and Uiso(H) = 1.2Ueq (parent atom)].

Computing details top

Data collection: APEX2 (Bruker, 2010); cell refinement: SAINT-Plus (Bruker, 2008); data reduction: SAINT-Plus (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. Part of crystal structure of the L4- ligand and PbII centres in 1. All H atoms have been omitted for clarity. [symmetry code: (#1) -x, y+1, -z+1; (#2) x, y - 1,z; (#3) -x + 1, -y + 1, -z + 1; (#4) x + 1, y-1, z; (#5) -x + 1, -y + 1, -z + 1.]
[Figure 2] Fig. 2. Sectional crystal structure of zigzag chain [PbO4(H2O)]n. Pb, green; O, red; H, white
[Figure 3] Fig. 3. View along c axis of two-dimensional coordination polymer from Pb ions and L4- ligands. PbO7, polyhedron: green; O: red; N: blue; C: grey.
[Figure 4] Fig. 4. Photoluminescent spectra of 1 (λem at 465 nm, upon λex at 380 nm). I = relative intensity, em = emission, and ex = excitation.
Poly[diaqua[µ6-4,4'-(1,4-phenylene)bis(2,6-dimethylpyridine-3,5-dicarboxylato)]dilead(II)] top
Crystal data top
[Pb2(C24H16N2O8)(H2O)2]Z = 1
Mr = 910.80F(000) = 422
Triclinic, P1Dx = 2.490 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 7.2182 (12) ÅCell parameters from 1580 reflections
b = 9.0635 (14) Åθ = 2.7–23.1°
c = 9.9589 (15) ŵ = 13.90 mm1
α = 79.202 (2)°T = 298 K
β = 71.683 (2)°Block, colorless
γ = 85.494 (3)°0.25 × 0.23 × 0.23 mm
V = 607.43 (17) Å3
Data collection top
Bruker SMART APEXII CCD
diffractometer
2119 independent reflections
Radiation source: fine-focus sealed tube1932 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.015
phi and ω scansθmax = 25.0°, θmin = 2.2°
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
h = 88
Tmin = 0.129, Tmax = 0.142k = 1010
3168 measured reflectionsl = 1011
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.022Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.055H-atom parameters constrained
S = 1.01 w = 1/[σ2(Fo2) + (0.0347P)2]
where P = (Fo2 + 2Fc2)/3
2119 reflections(Δ/σ)max < 0.001
174 parametersΔρmax = 1.15 e Å3
0 restraintsΔρmin = 1.16 e Å3
Crystal data top
[Pb2(C24H16N2O8)(H2O)2]γ = 85.494 (3)°
Mr = 910.80V = 607.43 (17) Å3
Triclinic, P1Z = 1
a = 7.2182 (12) ÅMo Kα radiation
b = 9.0635 (14) ŵ = 13.90 mm1
c = 9.9589 (15) ÅT = 298 K
α = 79.202 (2)°0.25 × 0.23 × 0.23 mm
β = 71.683 (2)°
Data collection top
Bruker SMART APEXII CCD
diffractometer
2119 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
1932 reflections with I > 2σ(I)
Tmin = 0.129, Tmax = 0.142Rint = 0.015
3168 measured reflectionsθmax = 25.0°
Refinement top
R[F2 > 2σ(F2)] = 0.022H-atom parameters constrained
wR(F2) = 0.055Δρmax = 1.15 e Å3
S = 1.01Δρmin = 1.16 e Å3
2119 reflectionsAbsolute structure: ?
174 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Pb10.24557 (3)0.11141 (2)0.47717 (2)0.02892 (9)
O10.0452 (5)0.9117 (4)0.6086 (4)0.0281 (8)
O20.3224 (5)0.8538 (4)0.6568 (5)0.0365 (9)
O30.2253 (5)0.1995 (4)0.7194 (4)0.0343 (9)
O40.0248 (6)0.2448 (5)0.6332 (5)0.0382 (10)
O50.3782 (6)0.0957 (5)0.3132 (5)0.0441 (11)
H10.48810.14120.30190.066*
H20.29240.16290.33790.066*
N10.2153 (6)0.5547 (5)0.9379 (5)0.0275 (10)
C10.1131 (7)0.6798 (6)0.8704 (6)0.0245 (11)
C20.0591 (7)0.6774 (5)0.7553 (5)0.0220 (11)
C30.1282 (7)0.5404 (6)0.7125 (5)0.0213 (10)
C40.0148 (7)0.4140 (6)0.7758 (5)0.0233 (11)
C50.1579 (7)0.4255 (6)0.8888 (6)0.0271 (12)
C60.1922 (8)0.8214 (6)0.9291 (6)0.0341 (13)
H6A0.29070.86620.88720.051*
H6B0.08820.89060.90600.051*
H6C0.24810.79751.03150.051*
C70.1542 (7)0.8222 (6)0.6705 (6)0.0242 (11)
C80.0752 (7)0.2736 (6)0.7103 (6)0.0243 (11)
C90.2867 (8)0.2946 (7)0.9630 (7)0.0379 (14)
H9A0.28690.26921.06110.057*
H9B0.23880.21020.91540.057*
H9C0.41720.32030.96030.057*
C100.3206 (7)0.5253 (5)0.5999 (5)0.0192 (10)
C110.3313 (7)0.5098 (6)0.4608 (5)0.0249 (11)
H110.21770.51600.43470.030*
C120.5090 (7)0.4854 (6)0.3615 (5)0.0241 (11)
H120.51460.47610.26890.029*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Pb10.02297 (13)0.02526 (13)0.03649 (14)0.00185 (8)0.00454 (9)0.00765 (9)
O10.0269 (19)0.0225 (19)0.037 (2)0.0014 (15)0.0143 (17)0.0010 (16)
O20.024 (2)0.029 (2)0.054 (3)0.0052 (16)0.0106 (19)0.0020 (18)
O30.034 (2)0.029 (2)0.044 (2)0.0113 (17)0.0165 (19)0.0119 (18)
O40.030 (2)0.036 (2)0.056 (3)0.0017 (17)0.017 (2)0.022 (2)
O50.029 (2)0.048 (3)0.059 (3)0.0011 (19)0.013 (2)0.021 (2)
N10.021 (2)0.031 (3)0.026 (2)0.0005 (19)0.0000 (19)0.008 (2)
C10.020 (3)0.027 (3)0.026 (3)0.002 (2)0.006 (2)0.008 (2)
C20.021 (2)0.018 (3)0.027 (3)0.002 (2)0.009 (2)0.004 (2)
C30.020 (2)0.026 (3)0.018 (2)0.002 (2)0.006 (2)0.005 (2)
C40.023 (3)0.022 (3)0.024 (3)0.001 (2)0.007 (2)0.005 (2)
C50.021 (3)0.033 (3)0.027 (3)0.001 (2)0.009 (2)0.002 (2)
C60.031 (3)0.029 (3)0.037 (3)0.006 (2)0.000 (3)0.014 (2)
C70.024 (3)0.019 (3)0.027 (3)0.001 (2)0.001 (2)0.007 (2)
C80.020 (3)0.021 (3)0.027 (3)0.002 (2)0.002 (2)0.003 (2)
C90.030 (3)0.034 (3)0.041 (4)0.006 (3)0.001 (3)0.003 (3)
C100.018 (2)0.017 (2)0.020 (2)0.0026 (19)0.003 (2)0.0028 (19)
C110.020 (2)0.028 (3)0.029 (3)0.001 (2)0.011 (2)0.005 (2)
C120.023 (3)0.030 (3)0.019 (3)0.001 (2)0.005 (2)0.004 (2)
Geometric parameters (Å, º) top
Pb1—O1i2.327 (4)C2—C31.393 (7)
Pb1—O42.472 (4)C2—C71.507 (7)
Pb1—O1ii2.538 (3)C3—C41.390 (7)
Pb1—O32.638 (4)C3—C101.501 (7)
Pb1—O52.644 (4)C4—C51.405 (7)
O3—C81.248 (6)C5—C91.494 (8)
O4—C81.277 (7)C6—H6A0.9600
C8—C41.510 (7)C6—H6B0.9600
O1—C71.294 (6)C6—H6C0.9600
O1—Pb1iii2.327 (4)C9—H9A0.9600
O1—Pb1ii2.538 (3)C9—H9B0.9600
N1—C51.338 (7)C9—H9C0.9600
N1—C11.348 (7)C10—C12iv1.391 (7)
O2—C71.230 (6)C10—C111.395 (7)
O5—H10.8500C11—C121.383 (7)
O5—H20.8500C11—H110.9300
C1—C21.403 (7)C12—C10iv1.391 (7)
C1—C61.507 (7)C12—H120.9300
O1i—Pb1—O479.28 (13)C3—C4—C5119.1 (5)
O1i—Pb1—O1ii66.21 (14)C3—C4—C8117.7 (4)
O4—Pb1—O1ii75.30 (12)C5—C4—C8122.9 (5)
O1i—Pb1—O389.30 (13)N1—C5—C4121.7 (5)
O4—Pb1—O351.16 (12)N1—C5—C9116.0 (5)
O1ii—Pb1—O3124.84 (11)C4—C5—C9122.3 (5)
O1i—Pb1—O578.92 (13)C1—C6—H6A109.5
O4—Pb1—O5151.48 (13)C1—C6—H6B109.5
O1ii—Pb1—O579.19 (12)H6A—C6—H6B109.5
O3—Pb1—O5146.08 (13)C1—C6—H6C109.5
C8—O3—Pb187.8 (3)H6A—C6—H6C109.5
C8—O4—Pb194.7 (3)H6B—C6—H6C109.5
O3—C8—O4122.3 (5)O2—C7—O1121.6 (5)
O3—C8—C4121.6 (5)O2—C7—C2124.0 (5)
O4—C8—C4115.8 (4)O1—C7—C2114.4 (4)
C7—O1—Pb1iii104.5 (3)C5—C9—H9A109.5
C7—O1—Pb1ii136.9 (3)C5—C9—H9B109.5
Pb1iii—O1—Pb1ii113.79 (14)H9A—C9—H9B109.5
C5—N1—C1119.3 (4)C5—C9—H9C109.5
Pb1—O5—H1125.1H9A—C9—H9C109.5
Pb1—O5—H2107.8H9B—C9—H9C109.5
H1—O5—H2106.8C12iv—C10—C11119.3 (4)
N1—C1—C2122.0 (5)C12iv—C10—C3118.9 (4)
N1—C1—C6115.8 (5)C11—C10—C3121.6 (4)
C2—C1—C6122.2 (5)C12—C11—C10120.7 (5)
C3—C2—C1118.6 (5)C12—C11—H11119.7
C3—C2—C7120.8 (5)C10—C11—H11119.7
C1—C2—C7120.2 (4)C11—C12—C10iv120.0 (5)
C4—C3—C2118.8 (5)C11—C12—H12120.0
C4—C3—C10119.1 (4)C10iv—C12—H12120.0
C2—C3—C10122.1 (5)
Symmetry codes: (i) x, y1, z; (ii) x, y+1, z+1; (iii) x, y+1, z; (iv) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O5—H2···O4v0.852.042.834 (6)155
O5—H1···O3vi0.852.052.879 (5)165
Symmetry codes: (v) x, y, z+1; (vi) x+1, y, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O5—H2···O4i0.852.042.834 (6)155.3
O5—H1···O3ii0.852.052.879 (5)165.4
Symmetry codes: (i) x, y, z+1; (ii) x+1, y, z+1.
Acknowledgements top

This work was supported by the Science and Technology Projects of Chongqing Municipal Education Commission (grant No. KJ120632) and Chongqing Normal University Scientific Research Foundation Project (grant No. 2011XLS30).

references
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