Supramolecular isomerism in cadmium (II) coordination polymers from benzene-1,3,5-tribenzoate (BTB): Syntheses, structures and luminescent properties

Abstract By tuning the solvent mixture, four Cd II -based compounds, [Cd 3 (BTB) 2 (DMA) 4 ]·2DMA ( 1α ), [Cd 3 (BTB) 2 (DMA) 4 ]·2DMA ( 1β ), [Cd 3 (BTB) 2 (DMF) 4 ]·2DMF ( 1γ ), Cd 2 (BTB)(HCOO)(DMF) 3 ( 2 ) have been successfully separated from H 3 BTB ligand and Cd(NO 3 ) 2 salts. Structural analyses revealed that compounds 1α , 1β and 1γ are iso-structural and have essentially identical local and two-dimensional structures constructed from trinuclear Cd 3 (OCO) 6 unit. Their structural differences only arise from the different packing fashions, which are novel modes of supramolecular isomerism in coordination polymers. Compound 2 displays 3D two-fold interpenetrated network based on 1D infinite Cd 3 (μ 1,1,3 -OCO) 2 (HCOO) chains containing mixed BTB 3- and formate ligands. The fluorescence measurements show that compounds 2 exhibit red-shifts (about 25 nm) in the solid state, compared with three iso-structural 1α , 1β and 1γ , and this can be attributed to the cooperative effects of intraligand π-π* transitions and ligand-to-metal charge transfer (LMCT).