Rotaxane Research Paper

Rotaxane is a mechanically interlocked chemical architecture consisting of a dumbbell shaped molecule which passes through a macrocycle. After it was first introduced in 1980, many researchers in supramolecular chemistry had utilized its unique property to develop diverse chemical sensors for metal ions, anions and even explosives by incorporating different functional groups to the basic rotaxane architecture. However, only few of rotaxane-based sensors have been applied to medical uses. In this project, an anthracene containing dynamic [2] rotaxane is prepared through self-assembly according to Wong, W. et al., and studied for metal ions sensing properties using fluorescence spectrometry. Two metal salts, Fe(ClO4)2 and Fe(ClO4)3 were chosen

Lehn had prepared cryptands and made great contributions to the field and paved the way for much up-to-date advancement. By then, I.T. Harrison and S. Harrison first reported that they had synthesized a “stable complex which consisted of a macrocycle and a threaded chain”,12 which was known as the world’s first rotaxane.
Synthesis Methods
With the advancement of supramolecular chemistry, such as knowing the concept of self-assembly, template effect and so on, Stoddart was able to let the molecules assemble themselves, which forms the basis of common rotaxane synthesis today. Nowadays, there are numerous methods to synthesize rotaxanes. In general, there are 4 common approaches, namely capping, clipping, slipping and active template method. Each of them will be briefly introduced as follow.
Capping method, which is also known as “stoppering”, requires the preparation of a pseudorotaxane precursor, which comprises of a linear moleculae threaded through a macrocyclic one. Then both ends are capped by 2 sufficiently large groups to form a [2] rotaxane.2

Figure 4. Schematic representation of the capping method
For clipping method, a bumbbell-shaped molecule and an acyclic precursor is prepared, then the remaining part of the macrocycle is assembled to the precursor and finally forms a [2]

Synthesis of the Squaraine-RotaxaneAdopted from: Arunkumar, E. et al. Chemistry - A European Journal 2006, 12
The squaraine rotaxane allow the visualization of biological process such as bacterial cell division, which allows the generation of real-time fluorescent movie.3-4 Principles and MethodologiesThe following principles are discussed briefly one by one to aid the more comprehensive understanding of the whole project. They include examples of rotaxane sensors, the property of the anthracence-containing [2] rotaxane, the proposed metal ion sensing mechanism and the principle of fluorescence and fluorescence spectroscopy.
Rotaxane Sensors
The highly flexible rotaxane architecture gives rise to a wide variety of rotaxane sensors. By integrating different functional groups, researchers are able to develop rotaxane sensors for metal ions, anions and even explosives. For example, in 2007, Chen et al. developed a [2] rotaxane which contains a 2,2’-bipyridinium (BP-H2) ion and crown ether like macrocycle which is responsible for the sensing of 5 physiologically metal ions, including Li+, Na+, K+, Mg2+ and