Coordination-Driven Orthogonal Ligand Pairings through Dual Hydrogen-Bonding/π-π Interaction Complementarity

Multi-layered and orthogonal recognition is an excellent route to controlled molecular complexity. Here we report a series of heteroleptic complexes where two ligands pair together at a palladium(II) metal centre in complementary fashion and with orthogonality to others pairs. This complementarity is driven in part through hydrogen-bonding acceptor or donor sites proximal to the coordination domain (either DD:AA or AD:DA). These interactions alone are insufficient to control ligand pairing identity and/or orientation—secondary π-π interactions between electron-rich and electron-poor aromatic groups in the recognition domain combine with the hydrogen bonding to give high levels of complementarity. Importantly, the different heteroleptic complexes can be combined without significant scrambling or mismatching.