Novel Hyperbranched Molecules Containing Pyrrole Units from Diacetylene Compounds and their Electronic Properties

Abstract

Novel hyperbranched molecules containing pyrrole units were obtained from ortho-, meta- and para-diaminodiphenyldiacetylenes, as AB₂ type monomers by one-step polymerization. Diacetylenic fragments reacted with terminal amino groups in the presence of copper chloride to give pyrrole units. Diaminodiphenyldiacetylene monomers have been synthesized from ethynilanilines in three steps. The novel monomers and hyperbranched molecules were characterized by NMR, IR and thermal analysis. Some conductivity proofs were also carried out and this behavior was assessed.

The electronic behavior of some of these molecules was studied by means of theoretical methods. DFT optimization processes were carried out for three structures derived from the generation growing. There are at least two conformational isomers of the structure (meta- and para-) which show conductivity properties, the meta-isomer shows semiconductor nature but this species is hard to modeling because the steric hindrances cause optimization problems and indeed the third generation species was not achieved. In other context, the para-isomer allows the calculation of three generations and shows clearly a tendency to narrow the energy gap between the frontier orbitals but besides the behavior of the HOMO-1 seems reinforce the conductivity phenomenon.