Guest-Driven Luminescence: Lanthanide-Based Host-Guest Systems with Bimodal Emissive Properties Based on a Guest-Driven Approach

A series of discrete closed, semi-closed, and polymeric lanthanide-based [{Ln(H2O)(8)}(3+)subset of Ln(2)(III)L(4)] host-guest systems with tetragonal prism-like structure have been designed and synthesized through the ligand-dominated approach. These nanoscopic cages are robust and can be maintained upon guest exchange. Within the restricting space, the luminescence intensity of the encapsulated [Ln(H2O)(8)](3+) species is dramatically enhanced due to the vibrational movements originating from the O-H oscillators in the coordinated water molecules being effectively reduced by the host-guest H-bonding interactions. Based on the guest-driven approach, tunable emission and bimodal emission (UV/Vis/NIR) of these [{Ln(H2O)(8)}(3+)subset of Ln(2)(III)L(4)]supramolecular systems are successfully realized. Moreover, the strong luminescence originating from [{Ln(H2O)(8)}(3+)subset of Ln(2)(III)L(4)] host-guest system can be quenched by encapsulation of d-block metal quenchers, such as Fe3+ and Cu2+ through solid-state f-d metal exchange. Additionally, this study demonstrates that the photoinduced solid-state guest-independent emission spectrum could be one of the most diagnostic techniques for monitoring the solid-state guest-exchange process.