D-π-A Organic Compounds And Crown Ether Derivatives: Synthesis And Electrogenerated Chemiluminescence

Electrogenerated chemiluminescence(ECL) has become an important and valuable detection method because of high sensitivity, a wide range of analytical applications, inexpensive instrumentation, detection in situ, and so on. Many applications have been found in environmental assays, food and water testing, immunoassays and DNA analyses, even the military and defense application, and so on. Compared with the noble metal ruthenium complexes, which were widely utilized, organic compounds, which have many advantages such as inexpensive, wide resources of materials and easily molecular design for desired photophysical photochemical properties, are emerging as new luminescent materials.Three series of donor-acceptorÏ€-conjugated (D-Ï€-A) molecules 1, 2, and 3 have been designed and synthesized with a N, N-dimethylamino, Julolidine group (2,3,6,7-tetrahydro-1H, 5H-pyrido[3, 2, 1-ij]quinolinyl), or N, N-diphenylamino group as the donor moiety, a phenylvinyl or thienylvinyl unit as the bridge, and a bromide or aldehyde group as the acceptor moiety. The photophysical, electrochemical and ECL characters of these compounds have been studied in a 1: 1(v/v) PhH/MeCN mixed solvent. Three different categories of ECL mechanisms for each of the three families of compounds are discussed respectively. Series 1 compounds produce typical and simple monomer ECL emission resulting from the annihilation of their radical cations and radical anions. The ECL emission of series 2 compounds can be ascribed as an excimer emission. Series 3 compounds exhibit an aggregate ECL emission. X-ray crystal structures of compounds 1b, 2a, and 3a provide further proof for the above mentioned reaction mechanisms. All these compounds show stable ECL emission via the singlet excited state(S-route) without the addition of any co-reactant or additional compound.Novel organic compounds C1-C3 without reported so far, with high fluorescence quantum yields(Φ_em) and appropriate water solubility, bearing 15-crown-5 moiety have been designed and synthesized. The photophysical, electrochemical and ECL characters of these compounds have been studied in a 1: 1(v/v) PhH/MeCN mixed solvent. The ECL mechanism of the series of compounds is discussed detailed. It is found that there is a good correlation between the observed ECL intensity andΦ_em. The ECL intensities of C1-C3 are enhanced greatly with the increases of theirΦ_em. We reported their ECL behaviors using annihilation method and co-reactant method(tri-n-propylamine was used as a co-reactant) respectively. In annihilation reactions, the ECL of compounds C1-C3 can be ascribed to the typical and simple monomer ECL emission produced by the annihilation of radical anions and radical cations during repeated pulsing. X-ray crystal structure of compound C3 provide further evidence for ECL mechanism. Under the same experimental conditions, the ECL maxima produced by co-reactant method are the same as that produced by annihilation method. However, the ECL intensities formed in co-reactant reactions are distinctly higher than that formed in annihilation reactions. The stable ECL emissions of all compounds can be observed via S-route using both methods. The ECL behaviors of compounds C1-C3 have also been studied in a 4:1(v/v) MeCN/H₂O mixed solvent. ECL emission was not found.