Steric Hindrance and Secondary Interactions Govern Reconfiguration Between Two Complex Cu I Coordination Cages

ABSTRACT A tetramine subcomponent featuring 1,5‐naphthylene arms was designed to exhibit extensive secondary interactions when assembled around stereochemically flexible tetracoordinate Cu I ions. Using 6‐methyl‐2‐formylpyridine, a [Cu I 12 L 6 ] 12+ pseudo‐hexagonal prismatic cage formed, stabilized by 29–32 C─H···π interactions and 12 arene stacking interactions. Replacing the aldehyde component with 3‐methyl‐2‐formylpyridine introduced steric clashes that partially prevented these interactions, leading instead to the formation of a [Cu I 8 L 4 ] 8+ rectangular open prism. The system exhibited structural interconversion: adding 6‐methyl‐2‐formylpyridine to the [Cu I 8 L 4 ] 8+ cage transformed it into the [Cu I 12 L 6 ] 12+ structure through selective displacement of 8 out of 24 aldehyde residues per cage, matching the number of sterically‐hindered positions predicted from structural analysis. This work demonstrates rational control over cage architecture through fine‐tuning of steric factors and intermolecular interactions, providing design principles for generating diverse structures from identical building blocks.