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Published online: 3 October 2007 | doi:10.1038/nchina.2007.202

Coordination chemistry: Tubes by design

Felix Cheung

Introduction

© (2007) RSC

Materials scientists are interested in synthetic tubes, such as carbon nanotubes, because of their wide range of applications in chemistry and biology. Metal–organic microtubes are rare though. Until now, only one type of metal–organic microtube based on a hexanuclear repeating unit has ever been made. Miaoli Zhu and Liping Lu at Shanxi University in Taiyuan and co-workers have now fabricated another type using highly symmetrical nanoclusters¹.

Inspired by principles of supramolecular assembly, the researchers came up with a design of a cluster formed by the coordination of six planar ligands with five metal atoms in a pentanuclear metal-oxide core (see image). To fabricate this cluster, they heated a mixture of copper oxide, nickel chloride, ethylene glycol and water at a temperature of 448 K for 92 hours. When the mixture had cooled down, 30% yield of brown tubular crystals (see image) were collected.  

The tubular crystals are hollow tetragonal prisms or cones with one end open and the other closed, ranging from 250–750 m long and 30–70 m wide, with a wide variation in wall thickness (around 15 m on average). The researchers' calculations indicate that the neighbouring clusters in the crystal are joined by hydrogen bonds between non-coordinated nitrogen atoms, chloride ions and water molecules.

The symmetry of the cluster might also play a role in the formation of the tubular crystals, though the exact mechanism is unclear. The findings open possibilities for using symmetrical nanoclusters to make a wide range of metal–organic microtubes.

The authors of this work are from:
Institute of Molecular Science, Key Laboratory of Chemical Biology and Molecular Engineering, Ministry of Education, Shanxi University, Taiyuan, China; State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing, China; Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, Massachusetts, USA.

Reference

1. Feng, S., Zhu, M., Lu, L. & Guo, M. Single-crystal metal–organic microtubes self-assembled from designed D₃ symmetrical nanoclusters with a capped triple-helix pentanuclear M₅O₆ core. Chem. Comm. doi: 10.1039/b711695k (2007). | Article |