Design and characterization of nanostructured electroactive tetraaniline prepared using alternative oxidizing systems

Emeraldine-base tetraaniline (TAni) was synthesized via the oxidative coupling of N-phenyl-p-phenylenediamine using a series of oxidizing agents, namely, ceric ammonium nitrate (CAN), copper(ii) chloride (CC), ammonium persulfate (APS), benzoyl peroxide (BPO), and iron(iii) chloride (FeCl₃). This study establishes a systematic comparison of these chemical routes and their influence on the structural, thermal, morphological, electrical, and electrochemical properties of the resulting oligomers. Structural characterization using FT-IR, ¹H NMR, ESI-MS, CH elemental analysis, and UV-Vis spectroscopy confirmed the successful formation of emeraldine-base TAni with a benzenoid-quinoid framework. TGA, DSC, and FE-SEM analyses revealed a semi-crystalline morphology and good thermal stability under nitrogen. After doping with 1 M HCl, all the tetramers-CAN-TAni, CC-TAni, BPO-TAni, APS-TAni and Fe-TAni_bp-exhibited higher electrical conductivity than Std TAni (3.0 × 10^-3 S cm^-1), which was attributed to their porous nanostructured morphology. Their conductivity followed the order BPO-TAni > CC-TAni > CAN-TAni > Fe-TAni_bp > APS-TAni > Std-TAni. Cyclic voltammetry showed three well-defined redox transitions corresponding to the LEB → EB → pernigraniline transformations, closely resembling the electrochemical behavior of polyaniline. These findings demonstrate that controlled oxidative strategies enable the preparation of structurally robust and electrochemically active tetraaniline with tunable conductivity and morphology, offering promising potential for applications in organic electronics and redox-functional materials.