Directed Surface Immobilization of Coordination Cages for Host-Guest Studies

Self-assembled coordination cages are bioinspired host-guest systems mimicking natural nanoconfinements and their functions as receptors and reaction compartments. While such systems are conventionally studied in solution or as bulk materials, the examination of surface-immobilized cages has recently emerged as an attractive approach. Here, we investigated the directed immobilization of bowl-shaped coordination cages [Pd2L3(MeCN)2]4+ on carboxy-terminated self-assembled monolayers. Spectroscopic ellipsometry and in situ flow experiments using SPR spectroscopy were used to characterize the immobilization of the coordination cages from the solution. ATR-FTIR confirmed the chemical identities of the surface-bound structures. Encapsulation of C60 in the coordination cages revealed faster surface absorption, consistent with an increase in binding affinity. Immobilized cages containing C60 guests were imaged by atomic force microscopy and revealed surface structures with dimensions consistent with those of the coordination cages, indicating successful capture on self-assembled monolayers.