ABSTRACT
In recent years, expanded porphyrins have emerged as a new class of functional molecules in light of their large conformational flexibility, rich metal
coordination behavior, unprecedented chemical reactivities and exceptional nonlinear optical properties [1-3]. Expanded porphyrins are macrocycles consisting of more than four pyrrole rings linked together either directly or through one or more spacer atoms in such a manner that the internal pathway contains a minimum of 17 atoms [4]. Owing to their tunable photophysical and chemical properties with external stimuli, expanded porphyrins represent a very promising platform to develop molecular switches for molecular electronic devices [5-7]. Molecular switches are regarded as the most basic component in molecular electronic devices that can reverse from an active/on state to a passive/off state. The switch between two or more states with distinct properties is triggered by external stimuli such as light, pH or voltage [8]. As opposed to normal switches, molecular switches are extremely tiny and their application in nanotechnology, biomedicine and computer chip design opens up brand new horizons. However, despite their potential, the design of molecular switches based on expanded porphyrins has only been scarcely investigated [7, 9, 10].
