Acta Crystallographica Section B

Structural Science, Crystal Engineering and Materials

Volume 70, Part 1 (February 2014)


crystal engineering



Acta Cryst. (2014). B70, 11-18    [ doi:10.1107/S2052520613027224 ]

Distortions of a flexible metal-organic framework from substituted pendant ligands

A. S. Munn, G. J. Clarkson and R. I. Walton

Abstract: Four new variants of the 1,4-benzenedicarboxylate MIL-53 structure have been prepared for CoII under solvothermal conditions and their structures solved and refined from single-crystal X-ray data. All materials contain pendant pyridine-N-oxide ligands that bridge pairs of CoII atoms in the inorganic backbone of the structure via O. By the use of the ligands 3-bromopyridine-N-oxide, 4-methoxypyridine-N-oxide, isoquinoline-N-oxide and 4-phenylpyridine-N-oxide, materials are prepared with the same topology but distinct structures. These illustrate how the MIL-53 structure is able to distort to accommodate the bulk of the various substituents on the pyridine ring. The bulkiest pendant ligand, 4-phenylpyridine-N-oxide, results in a distortion of the diamond-shaped channels in an opposite sense to that seen previously in expanded forms of the parent MIL-53 structure. By comparison with published crystal structures for MIL-53 with various occluded guests, the structural distortions that take place to accommodate the pendant ligands are quantified and it is shown how a twisting of the 1,4-benzenedicarboxylate ligand, instead of a hinging about the [mu]2-carboxylate-metal connection, allows the new structures that are observed.

Keywords: metal-organic framework materials; solvotherm crystallization; flexibility.


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[ doi:10.1107/S2052520613027224/bi5024sup6.pdf ]
Details of compound preparation and characterisation


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