%0 Journal Article
%T Synthesis and Optoelectronic Characterization of Some Star-Shaped Oligomers with Benzene and Triphenylamine Cores
%A Teofilia Ivan
%A Loredana Vacareanu
%A Mircea Grigoras
%J ISRN Organic Chemistry
%D 2012
%R 10.5402/2012/976178
%X Six star-shaped oligomers containing triphenylamine (D1¨CD3) and benzene unit (D4¨CD6) as cores have been synthesized by Wittig condensation or Heck coupling reaction using aromatic aldehydes and triphenylphosphonium salts or aromatic halogenated compounds with vinyl triphenylamine. All oligomers have well-defined molecular structure and high purity. Characterization of the oligomers was made by FT-IR, 1H-NMR spectroscopy, UV-Vis, and fluorescence spectroscopy. The electrochemical behavior was studied by cyclic voltammetry (CV). The cyclic voltammograms have revealed that oligomers undergo quasireversible or irreversible redox processes. The irreversible process is associated with electrochemical polymerization of oligomers by dimerization of unsubstituted triphenylamine groups. Thermal characterization was accomplished by TGA and DSC methods and evidenced that all oligomers were stable materials until 250¡ãC and have formed stable molecular glasses after first heating scan. 1. Introduction Conjugated oligomers with linear, highly branched and dendrimer structures form an important class of electro- and photoactive materials, investigated both in academic and industrial laboratories [1¨C9]. These architectures have advantages to offer molecules with a well-defined form and structure, a high chemical purity, and degree of order, being characterized by a polydispersity degree of one. It is important to note that the purity of materials is vital for the long-term stability of optoelectronic devices. Dendrimers can be obtained using laborious step-by-step synthesis in a convergent or divergent methodology [10]. The advantage of using small conjugated compounds is based on the possibility of tuning their photophysical properties by changing the chemical structure, for example, by introduction of side substituents, end-capping groups, insertion of certain specific functional groups, and by changing the oligomer length. Moreover, conjugated oligomers are used as model compounds for conducting polymers since their monodispersity, defectless structure, and better supramolecular organization in the solid state facilitate their experimental and theoretical investigations. The real interests for conjugated oligomers emerge also from interesting application such as active components in organic electronic or electrochemical devices, such as organic light emitting diodes (OLEDs) [11¨C15], photovoltaic cells [16, 17], optical power limiting [18], and field-effect transistors [19]. One of the important challenging goals of the conjugated oligomer chemistry is to develop new
%U http://www.hindawi.com/journals/isrn.organic.chemistry/2012/976178/