ABSTRACT
Threaded molecular wires are shown to feature tunable properties. A new rotaxane based on a quaterthiophene threaded through a single ß-cyclodextrin exhibits delocalization of the aromatic system that is also extended onto the central phenyl rings of the m-terphenylene end-groups. The rotaxane can undergo self-assembly that is better than the analogous bithiophene derivative, due to the increased π-π interactions.
ABSTRACT
A strongly fluorescent bistable rotaxane is described in which the relative position of the macrocyclic ring with respect to a solvatochromic fluorophore gives a strong response in the spectral domain.
ABSTRACT
In rotaxane 1, two co-conformations are populated in CDCl(3) at temperatures between 250 and 330 K. The thermodynamic parameters show strong enthalpy-entropy compensation, and a non-negligible heat capacity difference between the two forms.
Subject(s)
Hydrogen Bonding , Thermodynamics , Magnetic Resonance Spectroscopy , Molecular Conformation , Rotaxanes/chemistryABSTRACT
A dithiophene rotaxane 1 subsetbeta-CD and its shape-persistent corresponding dumbbell 1 were synthesized and fully characterized. 2D NOESY experiments, supported by molecular dynamics calculations, revealed a very mobile macrocycle (beta-CD). Steady-state and time-resolved photoluminescence experiments in solution were employed to elucidate the excited-state dynamics for both systems and to explore the effect of cyclodextrin encapsulation. The photoluminescence (PL) spectrum of 1 subsetbeta-CD was found to be blueshifted with respect to the dumbbell 1 (2.81 and 2.78 eV, respectively). Additionally, in contrast to previous observations, neither PL spectra nor the decay kinetics of both threaded and unthreaded systems showed changes upon increasing the concentration or changing the polarity of the solutions, thereby providing evidence for a lack of tendency toward aggregation of the unthreaded backbone.
