Sb- and Bi-Based Salphen Capsules: Pnictogen Bonding, Macrocycle Formation, and ON/OFF Catalysis

The incorporation of these heavier pnictogen centers has a pronounced influence on both self-assembly and reactivity. Depending on the substitution pattern of the salphen and the nature of the metal center (M = Zn, Mg), 1D coordination polymers, discrete 1:3 supramolecular capsule-like assemblies or hierarchically assembled multicapsule macrocycles can be formed.

Combining Bi(3-py)₃ with unsubstituted Zn-salphen gives an unprecedented polymeric architecture supported by synergistic pyridyl coordination and intermolecular Bi···O pnictogen bonding (PnB). In contrast, Zn salphens with bulky substituents suppress PnB-mediated aggregation and favor capsule formation. Replacing Zn(II) with Mg(II) in the salphen unit redirects the assembly toward heterobimetallic macrocycles {[E(3-py)₃]₆·(MgSal-^<i>t</i>Bu)₁₀} derived from capsule-like subunits.