A Mismatch Minimization Strategy for Sorting in [Pd2L2]4+ Macrocycles

Strategies for molecular sorting aim to allow the predictable formation of complex molecules or systems. Here, we report a series of ditopic bis-bidentate ligands, where each bidentate site has one internal hydrogen-bond acceptor or donor. When combined with palladium(II), both homoleptic and heteroleptic combinations show predictable behavior in assembly to maximize favorable hydrogen bonds and, importantly, minimize unfavorable hydrogen:hydrogen or lone-pair:lone-pair clashes. A variety of combinations give narcissistic or statistical sorting, but most interestingly, two low-symmetry [Pd2(L)(L′)]4+ macrocycles form integratively, even though both contain unfavorable interactions. This is because their homoleptic counterparts are even more disfavored. We have developed a scoring system based on these results that can be used in the future to effectively predict the behavior of similar palladium(II)-based assemblies.