Self-Assembled Palladium and Platinum Coordination Cages: Photophysical Studies and Anticancer Activity

Self-assembled coordination cages are interesting as drug-delivery systems. Therefore, the synthesis of new M2L4 (M = Pd, Pt) molecular cages derived from highly fluorescent, rigid polyaromatic ligands is reported herein, and the first Pt2L4 cage with a ligand consisting of three pyridine moieties is described. The photophysical properties were examined, and they showed high quantum yields phi of up to 48% for the methoxy-functionalized ligands. Coordination of the ligands to palladium and platinum ions did, however, reduce the fluorescence of the metallocages. The host-guest chemistry of the palladium cages with cisplatin was investigated, which confirmed the encapsulation. The cages encapsulating cisplatin show significantly increased cytotoxicity towards A549 (human lung adenocarcinoma) cells relative to that shown by cisplatin and, thus, appear to be promising delivery vectors for the anticancer drug cisplatin.