Electroluminescence-producing chemical reaction

Electrogenerated chemiluminescence (ECL) is the process whereby a chemiluminescence emission is produced directly, or indirectly, as a result of electrochemical reactions. It is also commonly known as electrochemiluminescence and electroluminescence. In general, electrically generated reactants diffuse from one or more electrodes, and undergo high-energy electron transfer reactions either with one another or with chemicals in the bulk solution. This process yields excited-state molecules, which produce a chemiluminescent emission in the vicinity of the electrode surface. 

Polymerization of thiophenes can be carried out in many different ways and the most commonly used methods can be generalized into three categories (i) electropolymerization, (ii) metal-catalyzed coupling reactions and (iii) chemical oxidative polymerization. Electropolymerization is a widely used method to prepare insoluble films of PTs and represents a simple and efficient way to study the optical and electronic properties of PTs [4], although it is rarely used in the preparation of electroluminescent materials. In 1980, Yamamoto et al. reported the Ni-catalyzed polycondensation of 2,5-dibromothiophene 1. The latter was allowed to react with Mg in THF, affording 2-magnesiobromo-5-bromothiophene 2, which in the presence of Ni(bipy)Cl2 (bipy = 2,2 -bipyridyl) produced PT 3 (Scheme 19.2) [15], In the same year, Lin and Dudek described another example of a metal-catalyzed route to unsubstituted PT 3, exploiting acetylacetonates of Ni, Pd, Co and Fe as catalysts [16]. 

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