title: Reversible photocapture of a [2]rotaxane harnessing a barbiturate template.
abstract: Photoirradiation of a hydrogen-bonded molecular complex comprising acyclic components, namely, a stoppered thread (1) with a central barbiturate motif and an optimized doubly anthracene-terminated acyclic Hamilton-like receptor (2b), leads to an interlocked architecture, which was isolated and fully characterized. The sole isolated interlocked photoproduct (Φ = 0.06) is a [2]rotaxane, with the dimerized anthracenes assuming a head-to-tail geometry, as evidenced by NMR spectroscopy and consistent with molecular modeling (PM6). A different behavior was observed on irradiating homologous molecular complexes 1⊂2a, 1⊂2b, and 1⊂2c, where the spacers of 2a, 2b, and 2c incorporated 3, 6, and 9 methylene units, respectively. While no evidence of interlocked structure formation was observed following irradiation of 1⊂2a, a kinetically labile rotaxane was obtained on irradiating the complex 1⊂2c, and ring slippage was revealed. A more stable [2]rotaxane was formed on irradiating 1⊂2b, whose capture is found to be fully reversible upon heating, thereby resetting the system, with some fatigue (38%) after four irradiation–thermal reversion cycles.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Tron
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Thornton
authors.forename: Christophe
authors.initials: C
authors.lastname: Lincheneau
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Desvergne
authors.forename: Neil
authors.initials: N
authors.lastname: Spencer
authors.forename: James H R
authors.initials: JH
authors.lastname: Tucker
authors.forename: Nathan D
authors.initials: ND
authors.lastname: McClenaghan
mesh_terms: D000873:Anthracenes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D055668:Photochemical Processes; D043862:Rotaxanes / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D000873:Anthracenes; D043862:Rotaxanes; C034020:anthracene