Co(II)-Based Metallo-Supramolecular Polymers

Abstract

This chapter introduces synthesis, properties, and device application of Co(II)-based metallo-supramolecular polymer (polyCoL1-5) and the derivatives. Section 4.1 shows synthetic procedure of polyCoL1-5 by the 1:1 complexation of Co(II) ions with bis(terpyridine)s (L1-5). The molecular weight (M_w) of polyCoL1 is determined to be 4.31 × 10³ using gel permeation chromatography (GPC) by the addition of a salt to the eluent to prevent decomplexation. The color of the obtained polymers is orange or yellow. Section 4.2 introduces optical and electrochemical properties and yellow electrochromism of the polymers. The electrochromism between yellow and colorless is triggered by the electrochemical redox between Co(II) and Co(III). Section 4.3 describes black electrochromism of polyCoL1, which is caused by the electrochemical reduction from Co(II) to Co(I), upon applying a negative potential in an aqueous solution including an electrolyte. This electrochromic behavior is influenced by pH of the electrolyte solution. Section 4.4 explains Co(III)-based polymer formation via polycondensation of the Co(III) mono complexes. The obtained polymers show nonvolatile memory properties in the device, composed of the polymer film on Si/SiO substrate with Au electrodes (Sect. 4.5). Random access memory (RAM) and read only memory (ROM) properties of the device enable reversible information processing and permanent memory storage capacities.