title: Molecular catenation via metal-directed self-assembly and pi-donor/pi-acceptor interactions: efficient one-pot synthesis, characterization, and crystal structures of [3]catenanes based on Pd or Pt dinuclear metallocycles.
abstract: Dinuclear square metallocycles 3a,b assemble spontaneously when M(en)(OTf)2 (M = Pd, Pt) and a 4,4'-bipyridinium ligand are mixed in acetonitrile. Six new [3]catenanes were prepared in good yields by thermodynamically driven self-assembly reaction of molecular squares 3a,b and pi-complementary dioxoaryl cyclophanes. Single-crystal X-ray analyses of the [3]catenanes revealed the insertion of two aromatic units inside the metallocycle cavity. The structures are stabilized by means of a combination of pi-pi stacking, [C-H...pi] interactions, and [C-H...O] hydrogen bonds. [3]Catenane (DB24C8)2-(3a) showed in solid-state two external DB24C8 rings positioned over the Pd(en) corners, which are held in position by [N-H...O] hydrogen bonds. Furthermore, formation of catenane (DB24C8)2-(3a) can be switched off and on in a controllable manner by successive addition of KPF6 and 18-crown-6.
authors.affiliation: Departamento de Química Fundamental, Facultad de Ciencias, Universidade da Coruña, Campus A Zapateira, 15071, A Coruña, Spain.
authors.forename: Víctor
authors.initials: V
authors.lastname: Blanco
authors.forename: Marcos
authors.initials: M
authors.lastname: Chas
authors.forename: Dolores
authors.initials: D
authors.lastname: Abella
authors.forename: Carlos
authors.initials: C
authors.lastname: Peinador
authors.forename: José M
authors.initials: JM
authors.lastname: Quintela
mesh_terms: D043863:Catenanes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D015394:Molecular Structure; D009944:Organoplatinum Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010165:Palladium / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*
chemical_list: D043863:Catenanes; D009944:Organoplatinum Compounds; D010984:Platinum; D010165:Palladium