TOPICAL REVIEW: Electrochromic materials using mechanically interlocked molecules

Abstract

Recent investigations on the design and synthesis of electrochromic materials based on switchable three-station [2]catenanes are summarized. The reasoning and preliminary experiments behind the design of electrochemically controllable red–green–blue (RGB), donor–acceptor [2]catenanes are presented. A basis for color generation is discussed in which the tetracationic cyclophane, cyclobis(paraquat-p-phenylene), serves as the π-electron deficient ring which circumrotates between three π-electron rich recognition sites within a macrocyclic polyether, generating the three different colors (RGB) based on the different charge transfer interactions between the tetracationic cyclophane and recognition sites based on 1,5-dioxynaphthalene (R), tetrathiafulvalene (G) and benzidine (B). Issues relating to the realization of an RGB [2]catenane are raised and discussed: they include (i) color tuning, (ii) thermodynamic considerations, (iii) electrochemistry on model compounds, (iv) molecular design, (v) the electrochemical behavior of three-station [2]catenanes and (vi) electrochromism in polymer gel matrices. Finally, the challenges that need to be met in the future if the ideal RGB catenane is to be prepared, are outlined.

Keywords

• interlocked molecules
• catenanes
• electrochromism
• carge-transfer complex
• electronic paper display