Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.elsevier.com/locate/synmet Dianiline conjugated Schif base molecule: Electrical and electrochemical properties Apparao Thota a,b , Karteek Boga a,b , Ravi Arukula a , Ramanuj Narayan a,b , Chepuri R.K. Rao a,b, ⁎ a Polymers and Functional Materials Division, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad, 500007, Telangana State, India b Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, India ARTICLE INFO Keywords: Schif bases molecule Oxi-Schif bases molecule Electrical conductivity UV–vis Fluorescence Electrochemical property ABSTRACT Schif bases are small molecules possessing eC]Ne functional groups which are exploited for coordinating inorganic cations to form stable complexes which play the critical role in catalysis. Here we synthesized a new Schif base molecule (SBM) by condensation of terephthalaldehyde and conjugated dianiline to study its elec- trical and electrochemical properties. This Schif base molecule (SBM) can be oxidized with ammonium per- oxodisulfate in presence of 1 M HCl solution into emeraldine base form (O-SBM). Interestingly, the O-SBM molecule exhibits electrical conductivity after doping. The structure of the synthesized products (SBM and O- SBM) were characterized by Fourier-transform infrared (FT-IR) spectra, 1 H NMR, ESI-MASS, elemental analysis, UV–vis, and fuorescence spectral techniques. The oxidized state (O-SBM) is dopable with 1 M HCl, to give better electrically conducting material than few oligoanilines such as trianiline, tetraaniline and pentaaniline. The electrical conductivity of O-SBM is 4.5 ⨯ 10 −2 S/cm at room temperature. The redox behavior of SBM and O-SBM is investigated by cyclic voltammetry. 1. Introduction Conducting conjugated aromatic polymers are interesting materials for the fact that they are useful in organic semiconductors, electronic, electrochemical and non-linear optical devices [1]. Among the con- ducting polymers, polyaniline is an interesting material, because of its ease of synthesis, inexpensive monomer, excellent environmental sta- bility, high electrical conductivity [2], and for easy negotiable oxida- tion-reduction chemistry [3]. Polyaniline has been extensively studied for their electrochemical applications [4]such as supercapacitor [5,6], anti-corrosion coatings [7], sensors [8,9], batteries [10] and electro- chromic devices [11]. The main problem for practical application of polyaniline is in its inadequate processability due to insolubility in common organic solvents, and its low solubility even in high-polar coordinating solvents such as DMF, DMSO, NMP [12,13]. Therefore it is necessary to solve this problem and a new method is required to im- prove the solubility and processability of polyaniline. Many researchers have focused on the monodisperse π-conjugated oligoanilines, because of their well-defned structure, end-group fctionalization andgood so- lubility [14,15]. These oligoanilines are considered as model com- pounds for polyaniline [16,17] and synthesis of some aniline oligomers has been reported [18] to this efect. Among conjugated oligomers, those with extended π systems involving alternating C]C, CeC, C–N, and C]N bonds play a key role in conjugation. This is the case for many conducting conjugated oligomers, such as tetraaniline, pentaaniline, octaaniline, poly(p-phenylene-vinylene) (PPV) [19]and poly(p-pheny- lene). Since the CH]N group is isoelectronic with the CH]CH group, the incorporation of nitrogen atoms into the conjugated system leads to another class of conjugated polymers and these polymers are known as polyazomethines or poly(Schif bases) or polyketanils(polyketimines) [20,21]. Schif bases with a system of conjugated double bonds mainly eC]Ce, eC]Ne in the main chain have attracted much attention of researchers owing to their nonlinear optical properties, electronic, and electrochemical properties [22–24]. Azomethines (−CH]Ne) func- tional groups found in Schif base polymers are isoelectronic with vinyl groups (−CH]CHe) (eg. polyacetylene). M.L. Petrus and E. Schab- Balcerzak [25–28] showed that the Schif base polymers exhibit good thermal resistance, due to the presence of hetero atoms such as nitrogen with their lone pair of electrons in the conjugated chain. Therefore the Schif bases treated with Lewis acids form complexes/doped states, using their unpaired electrons of imine nitrogen. For example, poly- azines when doped with iodine gave air stable, electrically conducting, material with room temperature conductivity as high as 1.3 S/cm [29]. https://doi.org/10.1016/j.synthmet.2018.12.013 Received 2 September 2018; Received in revised form 12 December 2018; Accepted 13 December 2018 ⁎ Corresponding author at: Polymers and Functional Materials Division, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad, 500007, Telangana State, India. E-mail address: ramchepuri@csiriict.in (C.R.K. Rao). Synthetic Metals 247 (2019) 240–247 0379-6779/ © 2018 Published by Elsevier B.V. T