Crystal structures and fluorescence properties of lanthanide complexes prepared with 2,2′-biphenyldicarboxylic acid and 2,2′:6′,2″-terpyridine

Five lanthanide complexes of Ln 2 (dpdc) 2 (tpy) 2 (NO 3 ) 2 (H 2 O) 2 [Ln=La ( 1 ), Ce ( 2 ), Pr ( 3 ), Sm ( 4 ), Gd ( 5 ), H 2 dpdc=2,2’-biphenyldicarboxylic acid and tpy=2,2′:6′,2″-terpyridine] were prepared at room temperature and characterized by X-ray diffraction, FT-IR and thermo-gravimetric analysis. The results showed that complexes 1–5 were isostructural and consisted of dinuclear units [Ln 2 (dpdc) 2 (tpy) 2 (NO 3 )(H 2 O) 2 ] bridged by two dpdc 2− ligands. The dinuclear units with strong intramolecular hydrogen bonds were assembled into 2D supramolecular layers by the weak π … π staking interactions between pyridine rings of tpy. The TG analysis showed that the complexes 1 – 5 behaved higher thermal stability with no mass loss at < 320 °C. The lanthanide contraction effect and the solid state luminescence properties of complexes 1 – 5 were also investigated. The luminescence emission spectra of complexes 1 – 5 exhibited ligands emission bands and complex 3 and 4 had no typical emission in the visible region.