title: Mechanical bonds and topological effects in radical dimer stabilization.
abstract: While mechanical bonding stabilizes tetrathiafulvalene (TTF) radical dimers, the question arises: what role does topology play in catenanes containing TTF units? Here, we report how topology, together with mechanical bonding, in isomeric [3]- and doubly interlocked [2]catenanes controls the formation of TTF radical dimers within their structural frameworks, including a ring-in-ring complex (formed between an organoplatinum square and a {2+2} macrocyclic polyether containing two 1,5-dioxynaphthalene (DNP) and two TTF units) that is topologically isomeric with the doubly interlocked [2]catenane. The separate TTF units in the two {1+1} macrocycles (each containing also one DNP unit) of the isomeric [3]catenane exhibit slightly different redox properties compared with those in the {2+2} macrocycle present in the [2]catenane, while comparison with its topological isomer reveals substantially different redox behavior. Although the stabilities of the mixed-valence (TTF2)(•+) dimers are similar in the two catenanes, the radical cationic (TTF(•+))2 dimer in the [2]catenane occurs only fleetingly compared with its prominent existence in the [3]catenane, while both dimers are absent altogether in the ring-in-ring complex. The electrochemical behavior of these three radically configurable isomers demonstrates that a fundamental relationship exists between topology and redox properties.
authors.affiliation: Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Marco
authors.initials: M
authors.lastname: Frasconi
authors.forename: Takashi
authors.initials: T
authors.lastname: Kikuchi
authors.forename: Dennis
authors.initials: D
authors.lastname: Cao
authors.forename: Yilei
authors.initials: Y
authors.lastname: Wu
authors.forename: Wei-Guang
authors.initials: WG
authors.lastname: Liu
authors.forename: Scott M
authors.initials: SM
authors.lastname: Dyar
authors.forename: Gokhan
authors.initials: G
authors.lastname: Barin
authors.forename: Amy A
authors.initials: AA
authors.lastname: Sarjeant
authors.forename: Charlotte L
authors.initials: CL
authors.lastname: Stern
authors.forename: Raanan
authors.initials: R
authors.lastname: Carmieli
authors.forename: Cheng
authors.initials: C
authors.lastname: Wang
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wasielewski
authors.forename: William A
authors.initials: WA
authors.lastname: Goddard
authors.forename: J Fraser
authors.initials: JF
authors.lastname: Stoddart
mesh_terms: D019281:Dimerization; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D006571:Heterocyclic Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D055595:Mechanical Phenomena; D008958:Models, Molecular; D008968:Molecular Conformation; D013237:Stereoisomerism
chemical_list: D005609:Free Radicals; D006571:Heterocyclic Compounds; C063887:tetrathiafulvalene