The synthesis and characterization of 2,7-bis(hydroxymethyl)naphtho[1,2-b:5,6-b′]dithiophene 1 is described. Electrochemical investigations revealed that 1 and its precursor naphtho[1,2-b:5,6-b′]dithiophene (NDT) are moderate π-electron donors. It was found that both compounds can form 1:1 complexes with the π-electron accepting cyclophane cyclobis(paraquat-p-phenylene) (CBPQT4+). UV/Vis spectroscopy was used to determine the binding constants (Ka) associated with the complexation process leading to the formation of the pseudorotaxanes and the superstructures were characterized using 1H NMR spectroscopy and molecular modelling. The results show that the Ka value for 1⊂CBPQT4+ is approximately seven times larger as compared to NDT⊂CBPQT4+, which can be ascribed to the fact that 1 is a better π-electron donor compared to the parent NDT and therefore is capable of forming stronger charge transfer (CT) interactions with CBPQT4+. The strong π-electron donor tetrathiafulvalene (TTF) was used to carry out switching studies between the pseudorotaxanes NDT⊂CBPQT4+ and TTF⊂CBPQT4+ and the results suggest that NDT derivatives in combination with TTF appear as promising building blocks for the development of new electroactive molecular machines based on CBPQT4+.
- Charge transfer complex
- Molecular machines