Supramolecular Assembly of Molecular Rare-Earth-3,5-Dichlorobenzoic Acid-2,2′:6′,2-Terpyridine Materials: Structural Systematics, Luminescence Properties, and Magnetic Behavior

The syntheses and crystal structures of 16 new rare-earth (RE = La3+-Y3+)-3,5-dichlorobenzoic acid terpyridine molecular materials characterized via single-crystal and powder X-ray diffraction are reported. These 16 complexes consist of four unique structure types ranging from molecular dimers (La3+ and Ce3+) to tetramers (Pr3+-Y3+) as one moves across the RE3+ series. This structural evolution is accompanied by subsequent changes in modes of supramolecular assembly (halogen bonding, halogen-pi, halogen-halogen, and pi-pi interactions). Solid-state visible and near -infrared lifetime measurements were performed on complexes 6 (Sm3+), 7 (Eu3+), 9 (Tb3+), 10 (Dy3+), 11 (Ho3+), 12 (Er3+), and 14 (Yb3+), and characteristic emission was observed for all complexes except 11. Lifetime data for 11, 12, and 14 suggest sensitization by the terpy antenna does occur in near -infrared systems, although not as efficiently as in the visible region. Additionally, direct current magnetic susceptibility measurements were taken for complexes 10 (Dy3+) and 12 (Er3+) and showed dominant ferromagnetic behavior.