On the role of torsional dynamics in the solid-state fluorescent properties of a new bifluorene-tetracarboxylic acid and its supramolecular assemblies: a structural and TD-DFT investigation

A novel butterfly-shaped tetracarboxylic acid [9,9′-methylene-bis(9-methylfluorene-2,7-dicarboxylic acid), H 4 L ] featuring a co-facial bifluorene core was designed and synthesised. Reactions of H 4 L with Cd II produced the luminescent supramolecular frameworks 2 and 3 , with different dimensionalities and wingspans of L 4− . Their solid-state emission properties were rationalised based on the torsional dynamics of the facing bifluorene units by means of X-ray diffraction analysis and TD-DFT calculations. The solid-state emission properties of bifluorene-tetracarboxylic acid were reported and rationalised on the basis of fluorene torsional dynamics by SC-XRD and DFT calculations.