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

Abstract

A newly designed tetracarboxylic acid ligand precursor 5,5′-([9,9′-bianthracene]-10,10′-diyl)diisophthalic acid (H₄BADI) has been used to prepare a series of copper-based metal–organic frameworks (MOFs) with the formula [Cu₂(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.