Poly[(μ3-benzene-1,3,5-tricarboxyl­ato-κ3 O 1:O 3:O 5)(μ2-2-methyl­imidazolato-κ2 N:N′)tris­(2-methyl­imidazole-κN)dizinc(II)]

Palanikumar Maniam; Norbert Stock

doi:10.1107/S1600536811015844

. 2011 May 7;67(Pt 6):m669–m670. doi: 10.1107/S1600536811015844

Poly[(μ₃-benzene-1,3,5-tricarboxylato-κ³ O ¹:O ³:O ⁵)(μ₂-2-methylimidazolato-κ² N:N′)tris(2-methylimidazole-κN)dizinc(II)]

Palanikumar Maniam ^a, Norbert Stock ^a,^*

PMCID: PMC3120569 PMID: 21754580

Abstract

Hydrothermal reaction involving zinc nitrate hexahydrate, trisodium benzene-1,3,5-tricarboxylate (Na₃BTC) and 2-methylimidazole (2-MeImH) yielded the title compound, [Zn₂(C₉H₃O₆)(C₄H₅N₂)(C₄H₆N₂)₃]. In this mixed-ligand metal-organic compound, Zn²⁺ ions are coordinated by N atoms from 2-MeImH molecules and (2-MeIm)⁻ ions, as well as by O atoms from (BTC)³⁻ ions. This results in two different distorted tetrahedra, viz. ZnN₃O and ZnN₂O₂. These tetrahedra are interconnected via (BTC)³⁻ ions and N:N′-bridging (2-MeIm)⁻ ions, thus forming a layered structure in the bc plane. Hydrogen bonds between the O atoms of carboxylate ions and NH groups of 2-MeImH ligands link the layers into a three-dimensional structure.

Related literature

For metal-organic frameworks, see: Li et al. (1999 ▶); Kitagawa et al. (2004 ▶); Stock (2010 ▶); Maniam et al. (2010 ▶). For related structures, see: Cheng et al. (2001 ▶); Zheng et al. (2010 ▶); Huang et al. (2006 ▶); Martins et al. (2010 ▶); Park et al. (2006 ▶).

Experimental

Crystal data

[Zn₂(C₉H₃O₆)(C₄H₅N₂)(C₄H₆N₂)₃]
M _r = 665.28
Orthorhombic,
a = 18.9722 (6) Å
b = 18.2247 (4) Å
c = 16.5585 (4) Å
V = 5725.3 (3) Å³
Z = 8
Mo Kα radiation
μ = 1.73 mm⁻¹
T = 293 K
0.16 × 0.09 × 0.07 mm

Data collection

Stoe IPDS-1 diffractometer
Absorption correction: numerical (X-RED and X-SHAPE; Stoe & Cie, 2008 ▶) T _min = 0.684, T _max = 0.814
38494 measured reflections
7732 independent reflections
6222 reflections with I > 2σ(I)
R _int = 0.050

Refinement

R[F ² > 2σ(F ²)] = 0.061
wR(F ²) = 0.143
S = 1.13
7732 reflections
370 parameters
H-atom parameters constrained
Δρ_max = 0.47 e Å⁻³
Δρ_min = −0.54 e Å⁻³

Data collection: X-AREA (Stoe & Cie, 2008 ▶); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 2010 ▶); software used to prepare material for publication: XCIF in SHELXTL (Sheldrick, 2008 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811015844/bt5531sup1.cif

e-67-0m669-sup1.cif^{(27KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811015844/bt5531Isup2.hkl

e-67-0m669-Isup2.hkl^{(378.4KB, hkl)}

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

Table 1. Selected geometric parameters (Å, °).

Zn1—O4	1.942 (3)
Zn2—O6	1.968 (3)
Zn2—O1ⁱ	1.976 (2)
Zn1—N2Hⁱⁱ	1.971 (3)
Zn1—N1F	1.998 (3)
Zn1—N1G	2.015 (4)
Zn2—N1H	1.992 (3)
Zn2—N1E	2.027 (3)

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

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2E—H2EN⋯O3ⁱⁱⁱ	0.86	2.06	2.912 (5)	169
N2F—H2FN⋯O2^iv	0.86	1.84	2.693 (5)	172
N2G—H2GN⋯O5^v	0.86	1.94	2.798 (5)	175

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Symmetry codes: (iii) Inline graphic ; (iv) ; (v) .

Acknowledgments

The authors thank Dr Christian Näther and Inke Jess (University of Kiel) for the acquisition of the single-crystal data. This work was supported by the State of Schleswig–Holstein, Germany and the German Research Foundation (DFG; SPP-1362).

supplementary crystallographic information

Comment

Metal-organic frameworks (MOF) are being investigated intensively, mainly for their high specific surface areas (Li et al., 1999; Kitagawa et al., 2004). In our workgroup, we are interested in using organic ligands containing multiple functional groups as the linkers for the MOFs. We employ high-throughput (HT) methods, which allow the rapid and systematic investigation of compound formation fields (Stock, 2010; Maniam et al., 2010). HT-screening of various first row transition metal ions with trisodium benzene-1,3,5-tricarboxylate (Na₃BTC) and 2-methylimidazole (2-MeImH) has yielded the colorless block crystals of (I). The asymmetric unit of compound (I) consists of two crystallographically independent Zn²⁺ ions, one fully deprotonated (BTC)^3-, one 2-methylimidazolate (2-MeIm)^- ion and three 2-MeImH ligands (Fig. 1). The Zn²⁺ ions are tetrahedrally coordinated by oxygen atoms originating from (BTC)^3- and nitrogen atoms from (2-MeIm)^- and 2-MeImH. The Zn···O bond distances lie between 1.942 (3)–1.976 (2) Å which are slightly shorter than Zn···N bonds of 1.971 (3)–2.027 (3) Å. The bond angles in ZnN₃O tetrahedra ranges between 100.42 (14)–116.61 (16)° while in ZnN₂O₂, the bond angles of 96.73 (13)–122.12 (11)° are observed (Tab. 1 & Tab. 2). It was also observed that Zn-(2-MeIm)^-—Zn angle lies at 146.8 (1)° which is close to 145° angles in zeolitic imidazolate frameworks and zeolite structures (Park et al.., 2006). The C=O and C—O bonds in the carboxylate groups can be clearly distinguished from each other by their bond lengths of 1.229 (5)–1.236 (5) Å and 1.266 (4)–1.275 (4) Å, respectively. Weak hydrogen bonds in the 2.6 < d(O···H—N) < 3.0 Å range are observed between the O atoms of the carboxylate ions and N—H groups of the 2-MeImH ligands (Fig. 2).

By considering the ZnN₃O and ZnN₂O₂ tetrahedra bridged by the (2-MeIm)^- as a Zn-(2-MeIm)-Zn dimer, this dimer is connected to three terminal 2-MeImH ligands and three (BTC)^3- ions. Each (BTC)^3- ion is then further connected to two Zn-(2-MeIm)-Zn dimers (Fig. 3) and layers in the bc plane are formed. Through extensive O···H—N hydrogen bonding, the layers are interconnected along the a-axis to form a dense three-dimensional crystal structure (Fig. 4, Tab. 2).

Experimental

All reagents were of analytical grade (Aldrich and Fluka) and were used without further purification. High-throughput (HT) experiments in 300 ml Teflon-lined reactors yielded the crystals of compound (I). The reaction mixture consisted of zinc(II) nitrate hexahydrate (5.9 mg, 0.02 mmol), Na₃(BTC) (2.76 mg, 0.01 mmol), 2-methylimidazole (4.11 mg, 0.05 mmol) and deionized water (200 ml). The mixture was heated in a 300 µl Teflon-lined high-throughput reactor at 423 K for 48 h (Stock, 2010). The mixture was cooled to room temperature over a period of 12 h and colourless plate-like crystals were obtained.