Two Octa-Nuclear {Ln₈} (Ln = Tb, Dy) Complexes with “4 + 4” Covalent Organic Macrocycles: Structure, Solution Behavior, Luminescence, and Magnetic Properties

In this study, two octa-nuclear lanthanide complexes consisting of a templated Ln8 (Ln = Tb, Dy) cluster and a ″4 + 4″ type Schiff-base covalent organic macrocycle, named Ln8L4+4, were constructed successfully. The stepwise solution assembly process of Tb8L4+4 from the initial organic subcomponents and metal templates was tracked as Tb1L1+2 → Tb2L1+2 → Tb3L1+2 → Tb3L2+2 → Tb4L2+2 → Tb4L3+2 → Tb5L3+2 → Tb6L3+2→ Tb8L4+4, through ESI-MS technology. Interestingly, Tb8L4+4 can be used as a sensitive and selective fluorescence-sensing material to determine the level of dipicolinic acid (DPA), and Dy8L4+4 has the characteristics of a single molecule magnet behavior.