title: Planar chiral asymmetric naphthalenediimide cyclophanes: synthesis, characterization and tunable FRET properties.
abstract: A series of planar chiral asymmetric naphthalenediimide (NDI) cyclophanes () consisting of two different NDIs interlinked by rigid meta-dimethylenebenzene spacers was synthesized. A modular synthetic strategy based on the dichloro cyclophane as common precursor gave a straightforward access to racemic mixtures of the NDI cyclophane dyes . In particular the substitution of both chlorine atoms of by tert-butylsulfanyl-, methoxy- and piperidinyl-groups provided racemic mixtures of the fluorescent NDI cyclophane dyes , and respectively. Fluorescence spectroscopy revealed chemically tuneable intramolecular FRET properties, as the spectral overlap between the emission of the unsubstituted NDI and the absorption of the core-substituted NDI subunit of the cyclophane could be adjusted by the core substituents. The racemic nature of the samples of cyclophanes , and in the case of the di-tert-butylsulfanyl functionalized cyclophane the enrichment of both enantiomers, was demonstrated by HPLC using a chiral stationary phase. The solid state structure of was determined by X-ray analysis. A periodic arrangement of both enantiomers of the planar chiral cyclophane in pillars such that NDI- and 2,6-core substituted NDI chromophores alternate periodically was observed.
authors.affiliation: University of Basel, Department of Chemistry, St. Johannsring 19, CH-4056, Basel, Switzerland.
authors.forename: Sandro
authors.initials: S
authors.lastname: Gabutti
authors.forename: Silvia
authors.initials: S
authors.lastname: Schaffner
authors.forename: Markus
authors.initials: M
authors.lastname: Neuburger
authors.forename: Matthias
authors.initials: M
authors.lastname: Fischer
authors.forename: Gabriel
authors.initials: G
authors.lastname: Schäfer
authors.forename: Marcel
authors.initials: M
authors.lastname: Mayor