Poly[diaqua­[μ6-4,4′-(1,4-phenyl­ene)bis­(2,6-dimethyl­pyridine-3,5-dicarboxyl­ato)]dilead(II)]

Yi Zhu; Ming-Xing Zhang; Shan-Shan Yang; Feng Xiao; Xiao-Ping Zhang; Yuan-Yuan Gao; Bing-Jie Li; Kun-Lin Huang

doi:10.1107/S1600536813007733

. 2013 Mar 28;69(Pt 4):m232–m233. doi: 10.1107/S1600536813007733

Poly[diaqua[μ₆-4,4′-(1,4-phenylene)bis(2,6-dimethylpyridine-3,5-dicarboxylato)]dilead(II)]

Yi Zhu ^a, Ming-Xing Zhang ^a, Shan-Shan Yang ^a, Feng Xiao ^a, Xiao-Ping Zhang ^a, Yuan-Yuan Gao ^a, Bing-Jie Li ^a, Kun-Lin Huang ^a,^*

PMCID: PMC3629504 PMID: 23634022

Abstract

The asymmetric unit of the title Pb-based coordination polymer, [Pb₂(C₂₄H₁₆N₂O₈)(H₂O)₂]_n, consists of one Pb^II cation, half of a 4,4′-(1,4-phenylene)bis(2,6-dimethylpyridine-3,5-dicarboxylate (L ⁴⁻) 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 Pb^II ion is coordinated in form of a distorted polyhedron by seven O atoms from four separate L ⁴⁻ 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 L ⁴⁻ ligands, forming a two-dimensional coordination network parallel to (001). O—H⋯O hydrogen bonds involving the water molecule are observed.

Related literature

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 the photoluminescent mechanism of ligand–metal charge transfer, see: Hu et al. (2010 ▶); Zhang et al. (2012 ▶).

Experimental

Crystal data

[Pb₂(C₂₄H₁₆N₂O₈)(H₂O)₂]
M _r = 910.80
Triclinic,
a = 7.2182 (12) Å
b = 9.0635 (14) Å
c = 9.9589 (15) Å
α = 79.202 (2)°
β = 71.683 (2)°
γ = 85.494 (3)°
V = 607.43 (17) Å³
Z = 1
Mo Kα radiation
μ = 13.90 mm⁻¹
T = 298 K
0.25 × 0.23 × 0.23 mm

Data collection

Bruker SMART APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2003 ▶) T _min = 0.129, T _max = 0.142
3168 measured reflections
2119 independent reflections
1932 reflections with I > 2σ(I)
R _int = 0.015

Refinement

R[F ² > 2σ(F ²)] = 0.022
wR(F ²) = 0.055
S = 1.01
2119 reflections
174 parameters
H-atom parameters constrained
Δρ_max = 1.15 e Å⁻³
Δρ_min = −1.16 e Å⁻³

Data collection: APEX2 (Bruker, 2010 ▶); cell refinement: SAINT-Plus (Bruker, 2008) ▶; data reduction: SAINT-Plus; 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 ▶).

Supplementary Material

Click here for additional data file.^{(21.2KB, cif)}

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536813007733/im2422sup1.cif

e-69-0m232-sup1.cif^{(21.2KB, cif)}

Click here for additional data file.^{(104.2KB, hkl)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536813007733/im2422Isup2.hkl

e-69-0m232-Isup2.hkl^{(104.2KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O5—H2⋯O4ⁱ	0.85	2.04	2.834 (6)	155
O5—H1⋯O3ⁱⁱ	0.85	2.05	2.879 (5)	165

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

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).

supplementary crystallographic information

Comment

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 L^4- ligand, one H₂O molecule and one crystallographically independent Pb^II 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 λ_{Ex, 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).

Experimental

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.