Supramolecular Frameworks Assembled by [EuL2]3+ Units with Different Coordination Configurations

Self-assembly is an important strategy to construct supramolecular frameworks. Small change in the assembling units often leads to significant variations in the self-assembly structures. In the work, we obtain two supramolecular frameworks assembled by different [EuL2]3+ units (L = tris((5,6-dimethyl-1H-benzo[d]imidazol-2-yl)methyl) amine). One meso compound {[EuⅢL2]·(H2O)6·Cl3} (Meso-EuL2) is assembled by an achiral meso-[EuL2]3+ unit, forming a supramolecular three-dimensional framework through six-fold intermolecular π‒π interactions. The other is a racemic compound {[EuⅢL2]·(CH3OH)5·Cl3} (Rac-EuL2), assembled by two chiral rac-[EuL2]3+ units predominantly via hydrogen bonding, leading to a layered supramolecular framework. The luminescent properties are different between Meso-EuL2 and Rac-EuL2, with Meso-EuL2 exhibiting more excimer-like emissions, which is likely caused by its stronger π‒π interactions in the structure.