title: Geometric Complementarity in Assembly and Guest Recognition of a Bent Heteroleptic cis-[Pd2LA2LB2] Coordination Cage.
abstract: Due to the inherent difficulties in achieving a defined and exclusive formation of multicomponent assemblies against entropic predisposition, we present the rational assembly of a heteroleptic [Pd2LA2LB2]4+coordination cage achieved through the geometric complementarity of two carefully designed ligands, LAand LB. With Pd(II) cations as rigid nodes, the pure distinctly angular components readily form homoleptic cages, a [Pd2LA4]4+strained helical assembly and a [Pd4LB8]8+box-like structure, both of which were characterized by X-ray analysis. Combined, however, the two ligands could be used to cleanly assemble a cis-[Pd2LA2LB2]4+cage with a bent architecture. The same self-sorted product was also obtained by a quantitative cage-to-cage transformation upon mixing of the two homoleptic cages revealing the [Pd2LA2LB2]4+assembly as the thermodynamic minimum. The structure of the heteroleptic cage was examined by ESI-MS, COSY, DOSY, and NOESY methods, the latter of which pointed toward a cis-conformation of ligands in the assembly. Indeed, DFT calculations revealed that the angular ligands and strict Pd(II) geometry strongly favor the cis-[Pd2LA2LB2]4+species. The robust nature of the cis-[Pd2LA2LB2]4+cage allowed us to probe the accessibility of its cavity, which could be utilized for shape recognition toward stereoisomeric guests. The ability to directly combine two different backbones in a controlled manner provides a powerful strategy for increasing complexity in the family of [Pd2L4] cages and opens up possibilities of introducing multiple functionalities into a single self-assembled architecture.
authors.affiliation: Faculty of Chemistry and Chemical Biology, TU Dortmund University , Otto-Hahn-Straße 6, 44227 Dortmund, Germany.
authors.forename: Witold M
authors.initials: WM
authors.lastname: Bloch
authors.affiliation: Faculty of Chemistry and Chemical Biology, TU Dortmund University , Otto-Hahn-Straße 6, 44227 Dortmund, Germany.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Abe
authors.affiliation: Faculty of Chemistry and Chemical Biology, TU Dortmund University , Otto-Hahn-Straße 6, 44227 Dortmund, Germany.
authors.forename: Julian J
authors.initials: JJ
authors.lastname: Holstein
authors.affiliation: Institute for Inorganic Chemistry, Georg-August University Göttingen , Tammannstraße 4, 37077 Göttingen, Germany.
authors.forename: Claudia M
authors.initials: CM
authors.lastname: Wandtke
authors.affiliation: Institute for Inorganic Chemistry and Structural Chemistry, Heinrich-Heine University Düsseldorf , Universitätsstraße 1, 40225 Düsseldorf, Germany.
authors.forename: Birger
authors.initials: B
authors.lastname: Dittrich
authors.affiliation: Faculty of Chemistry and Chemical Biology, TU Dortmund University , Otto-Hahn-Straße 6, 44227 Dortmund, Germany.
authors.forename: Guido H
authors.initials: GH
authors.lastname: Clever