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−π, halogen–halogen,
and π–π 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.