The self-assembly of fullerene-containing [2]pseudorotaxanes: Formation of a supramolecular C<inf>60</inf> dimer

Abstract

With its unique chemical and physical properties. C60 is an attractive molecule to be incorporated into molecular assemblies and supramolecular arrays. This paper reports the syntheses of a C60 derivative with the macrocyclic polyether dibenzo-24-crown-8 (DB24C8) attached to the carbon sphere and of a C60 adduct with a dibenzylammonium salt covalently bonded to the carbon allotrope. The C60 DB24C8 conjugate forms a stable, pseudorotaxane-like 1 : 1 complex (ΔGo = -16.6 kJ mol-1. T = 298 K, CDCl3-CD3CN 1 : 1) with dibenzylammonium hexafluorophosphate. Evidence for this superstructure was provided by 1H NMR spectroscopic studies in solution and by mass spectrometric investigations in the gas phase. Equally, the C60 dibenzylammonium conjugate threads through the cavity of DB24C8 to form a 1 : 1 complex with a pseudorotaxane-like geometry (ΔGo = -23.3 kJ mol-1, CDCl3). Furthermore, the C60 DB24C8 adduct and the C60 dibenzylammonium conjugate interact with each other by means of hydrogen bonding and ion-dipole interactions to form the first supramolecular C60 dimer (ΔGo = -17.0 kJ mol-1, CDCl3-CD3CN 90 : 10). In all three cases, the dibenzylammonium component is threaded through the cavity of the crown ether macrocycle. When DB24C8 is complexed to the C60 dibenzylammonium conjugate, the luminescence associated with the catechol rings of the crown ether is partially quenched upon complex formation. We have profited from this special feature to monitor reversible, acid-base induced dethreading/rethreading processes.