Solvent-Dependent Self-Assembly Behaviour and Speciation Control of Pd6L8 Metallo-supramolecular Cages

• Published in: Chemistry : a European journal Vol. 20; no. 14; pp. 4117 - 4125
• Main Authors: Henkelis, James J., Fisher, Julie, Warriner, Stuart L., Hardie, Michaele J.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.04.2014; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: Chemistry; Chemistry, Multidisciplinary; coordination cage; ligand exchange; Physical Sciences; Science & Technology; self-assembly; self-sorting; supramolecular chemistry; CATALYSIS; COMPLEX; DESIGN; CAVITAND; CRYPTOPHANES; self-sorting; self-assembly; coordination cage; COORDINATION CAGES; LIGANDS; CHEMISTRY; ligand exchange; CYCLOTRIVERATRYLENE; supramolecular chemistry; BOWL
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201304437

The C3‐symmetric chiral propylated host‐type ligands (±)‐tris(isonicotinoyl)‐tris(propyl)‐cyclotricatechylene (L1) and (±)‐tris(4‐pyridyl‐4‐benzoxy)‐tris(propyl)‐cyclotricatechylene (L2) self‐assemble with PdII into [Pd6L8]12+ metallo‐cages that resemble a stella octangula. The self‐assembly of the [Pd6(L1)8]12+ cage is solvent‐dependent; broad NMR resonances and a disordered crystal structure indicate no chiral self‐sorting of the ligand enantiomers in DMSO solution, but sharp NMR resonances occur in MeCN or MeNO2. The [Pd6(L1)8]12+ cage is observed to be less favourable in the presence of additional ligand, than is its counterpart, where L=(±)‐tris(isonicotinoyl)cyclotriguaiacylene (L1 a). The stoichiometry of reactant mixtures and chemical triggers can be used to control formation of mixtures of homoleptic or heteroleptic [Pd6L8]12+ metallo‐cages where L=L1 and L1 a. All sorted: Stella octangular [Pd6L8]12+ metallo‐cages with chiral propylated cyclotriveratrylene‐type ligands exhibit homochiral self‐sorting in MeCN or MeNO2 but not in DMSO. Furthermore, differences in the favourability of the metallo‐cage with propylated or methylated ligands can be used to control speciation in solution from heteroleptic to predominantly single homoleptic to dual homoleptic metallo‐cages.