Different crystal structures and luminescent properties of zinc and cadmium coordination polymers constructed from two flexible thioether ligands with different alkyl chains

doi:10.1016/j.poly.2009.01.009

Polyhedron

Volume 28, Issue 5, 1 April 2009, Pages 1040-1048

https://doi.org/10.1016/j.poly.2009.01.009 Get rights and content

Abstract

Treatments of nitrogen-containing heterocyclic dithioether ligands, 1,2-bis(4-(pyridin-3-yl) pyrimidin-2-ylthio) ethane (L¹) and 1,3-bis (4-(pyridin-3-yl) pyrimidin-2-ylthio) propane (L²), with zinc or cadmium salts have resulted in the interesting frameworks with structural motifs from a mononuclear macrocycle or a dinuclear macrocycle to an one-dimensional structure. A small difference of the alkyl length between L¹ and L² led to conspicuous changes of the fluorescent properties of both ligands and their complexes. Mainly due to the size of metal atoms, structures of [ZnL²I₂] (1) and [CdL²I₂] (2) are varied from a mononuclear macrocycle to a 1D framework, while {[ZnL²(H₂O)₄](ClO₄)₂}₂ (3) and {[CdL²(H₂O)₄](ClO₄)₂}₂ (4) are dinuclear macrocycles in which perchlorate anions may play an important template role. As for complexes 5–8 ([ZnL¹I₂]_n (5), [CdL¹I₂]_n (6), {{[ZnL¹₂(H₂O)₄](ClO₄)₂}_0.5 · L¹_0.5 · CH₃OH} (7), {{[Cd_0.5L¹(H₂O)₂](ClO₄)}₂ · CH₃OH · L¹} (8)), the self-assemble processes were mainly directed by the organic ligand in the reactions of L¹ with metal salts. Complexes 1–4 exhibit blue fluorescence emissions, among which 1 and 2 may be suitable as candidates for blue fluorescent materials.

Graphical abstract

Two series of complexes were prepared from reactions of two dithioether ligands (1,3-bis (4-(pyridin-3-yl) pyrimidin-2-ylthio) propane and 1,2-bis (4-(pyridin-3-yl) pyrimidin-2-ylthio) ethane) with zinc or cadmium salts, respectively. A small difference of the alkyl length between two ligands led to conspicuous changes of the fluorescent properties of both ligands and their complexes with different structural networks.

Introduction

Researchers have shown remarkable interest in the rational design and assembly of new coordination frameworks for their fascinating structural topologies and potential uses as functional materials in recent years [1], [2], [3], [4], [5]. It is well established that the coordination geometry of inorganic metal-ion species and the chemical structure of organic spacers including counter-anions and solvent effects play crucial roles in the generation of coordination architectures with interestingly desired properties.

Although heterocyclic thiolates and flexible thioethers have been extensively studied about their topologies and physical and chemical properties [6], [7], [8], [9], [10], [11], [12], [13], [14], little attention has been paid to pyridyl–pyrimidin dithioethers [15], [16], [17]. In our previous work, a dithioether ligand (L¹, shown in Scheme 1) and its Hg(II) complexes have been investigated for an anion-modulated reversible conversion of molecular assembly between two structural motifs [17]. Considering that a small variation about the ligand can give rise to the big change of structures and properties of the resulting complexes, we have designed and prepared an analogous thioether ligand (L²) which has a longer alkyl chain than that of L¹. Thus, zinc(II) and cadmium(II) complexes of L¹ and L², respectively, were made to study their topologies and photoluminescence properties for comparison.

Section snippets

Materials and methods

All commercially available chemicals were of reagent grade. Analyses for carbon, hydrogen and nitrogen were performed on a Perkin–Elmer 1400C analyzer. Infrared spectra (4000–400 cm⁻¹) were recorded with a Bruker Vector 22 FT-IR spectrophotometer on KBr disks. Electrospray ionization (ESI) mass spectra were measured on a Finnigan MAT SSQ 710 mass spectrometer in a scan range of 100–1200 amu. ¹H NMR spectroscopic measurements were performed on a Bruker AM-500 NMR spectrometer, using TMS (SiMe₄) as

Synthesis and characterization

Similar to solubility of L¹, L² is soluble in common polar organic solvents. Reactions of L² or L¹ with MI₂ (M = Zn²⁺ and Cd²⁺) yielded the neutral species [ZnL²I₂] (1), [CdL²I₂]_n (2), [ZnL¹I₂]_n (5) and [CdL¹I₂]_n (6) by diffusion between solutions of the corresponding ligand and the metal salt. The other compounds were produced by refluxing L² or L¹ with metal salts in methanol. All complexes were prepared in 1:1 metal/ligand molar ratio, and it is found that the relative ratio between the two

Conclusion

In summary, eight novel complexes with different architectures were constructed from 1,3-bis (4-(pyridin-3-yl) pyrimidin-2-ylthio) propane (L²) and 1,2-bis (4-(pyridin-3-yl) pyrimidin-2-ylthio) ethane (L¹). Although the difference of L² from L¹ lies in the length of alkyl chains, complexes derived from L² showed quite distinct coordination architectures and excellent fluorescent properties compared with those derived from L¹. The present study proves that a minor modification about the ligand

Acknowledgements

The authors are grateful to the financial supports from National Natural Science of Foundation of China (Project No. 20801011) and China Postdoctoral Research Fund (Project No. 20070411010).

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Different crystal structures and luminescent properties of zinc and cadmium coordination polymers constructed from two flexible thioether ligands with different alkyl chains

Abstract

Graphical abstract

Introduction

Section snippets

Materials and methods

Synthesis and characterization

Conclusion

Acknowledgements

Inorg. Chim. Acta

Coord. Chem. Rev.

Coord. Chem. Rev.

Inorg. Chem. Commun.

Angew. Chem., Int. Ed. Engl.

Dalton Trans.

Angew. Chem., Int. Ed.

Acc. Chem. Res.

Inorg. Chem.

Inorg. Chem.

Inorg. Chem.

Inorg. Chem.

J. Chem. Soc., Dalton Trans.

J. Chem. Soc., Dalton Trans.

Cryst. Growth Des.

J. Am. Chem. Soc.