Structural diversity and solvent-induced transformations of a copper-based metal-organic framework with highly aromatic ligands.

A newly designed tetracarboxylic acid ligand precursor 5,5'-([9,9'-bianthracene]-10,10'-diyl)diisophthalic acid (H 4 BADI) has been used to prepare a series of copper-based metal-organic frameworks (MOFs) with the formula [Cu 2 (BADI)( S ) 2 ]· xS (denoted as 1- S , where S = solvent) and exhibiting solvent-induced structural transformations. Single-crystal-to-single-crystal transformation occurs upon exchanging 1-DMF (DMF = N , N -dimethylformamide) with DMSO (DMSO = dimethylsulfoxide). 1-DMF exhibits reversible structural transformation upon treatment with a variety of solvents; of particular interest is the reversible crystalline-to-amorphous phase transformations observed upon exchange with volatile, polar solvents. A thorough structural investigation of the three framework isomers characterized via single-crystal X-ray diffraction experiments is reported and compared to several other tetracarboxylate-based MOFs composed of dimetal secondary building units.