Synthetic Metals 166 (2013) 22–32 Contents lists available at SciVerse ScienceDirect Synthetic Metals journa l h o me pag e: www.elsevier.com/locate/synmet On the photo-physical properties of soluble oligomer from anodic oxidation of chlorine-substituted anisole (OPClAn) S. Ayachi a , S. Bergaoui b , I. Ben Khalifa a , A. Haj Said b , M. Chemek a , F. Massuyeau c , J. Wéry c , E. Faulques c , K. Alimi a,∗ a Unité de Recherche (UR 11ES55), Matériaux Nouveaux et Dispositifs Electroniques Organiques, Faculté des Sciences, Université de Monastir-Tunisie, Tunisia b Laboratoire Interfaces et Matériaux Avancés, Faculté des Sciences, Université de Monastir-Tunisie, Tunisia c Institut des Matériaux Jean Rouxel, Université de Nantes, CNRS, UMR 6502, 2 rue de la Houssinière, 44322 Nantes, France a r t i c l e i n f o Article history: Received 23 May 2012 Received in revised form 13 December 2012 Accepted 26 December 2012 Available online 14 February 2013 Keywords: Substituted-anisole Radical polymerization Optical properties DFT TR-PL a b s t r a c t This work aims at completing theoretically the oligomerization mechanism, vibrational and optical prop- erties of soluble oligomer obtained from anodic oxidation of p-chloro-anisole (OPClAn) with a view to get some insight into structure–property relationships. The obtained results were compared with those of oligomers from p-fluoro-anisole (OPFAn) and p-phenylene (OPP). Spectroscopic characterization based on infrared absorption, Raman scattering, optical absorption, photoluminescence (PL) and decays of time- resolved photoluminescence (TR-PL) in chloroform solution and in film states of OPClAn was performed. Further investigations on conformational, geometrical parameters, and electronic structures of these compounds were carried out by applying Density Functional Theory (DFT) calculation based on B3LYP with 6-31G(d,p) and 3-21G* as basis sets. The optimized structures, HOMO–LUMO gaps ( H–L ), in addition to the ionization potentials (IPs) and electron affinities (EAs) were calculated. The  H–L s, Egs, IPs and EAs of the oligomers were obtained by extrapolating those of the oligomers to the inverse chain length for n = 13. From the combined results, we have evoked an oligomerization mechanism consistent with the OPClAn prepared material. Furthermore, we have shown that introducing electron-donating/withdrawing sub- stituents on oligo-phenylene backbone can tune the HOMO and LUMO levels and thereby control the opto-electronic properties of the designed oligomers. © 2013 Elsevier B.V. All rights reserved. 1. Introduction In the last few years, researchers have focused their attention on the synthesis of oligomers with controlled and modulated proper- ties that could be exploited in organic electronic devices [1–4]. To attempt this objective, the correlation structure–properties could be well understood as well as the synthesis route. In the case of poly(para-phenylene) (PPP), the synthesis seems to be limited, so obtaining PPP with a well-defined structure is not easy [5,6]. Thus, many synthetic routes have been developed in order to obtain mod- ified PPPs with a regular structure and an easy processability [7–9]. In this frame, substituted anisole is widely used as starting mate- rial for electro-synthesis of PPP derivatives [10–12]. Furthermore, many previous works have described polymers elaboration from alkoxy anisoles [13,14] and methyl anisoles [15,16]. Experimen- tally, the introduction of halogen into the polymer backbone has been an effective way to improve some properties such as stability ∗ Corresponding author at: Faculté des Sciences de Monastir, 5000 Monastir, Tunisia. Tel.: +216 73 500 274; fax: +216 73 500 278. E-mail address: kamel.alimi@fsm.rnu.tn (K. Alimi). and optical properties due to the high strengths of the C X bonds [17–19] and gives the opportunity for a post-polymerization func- tionalization. In our previous work [19], short oligomer from the p-fluoro- anisole, denoted OPFA, has been synthesized and characterized. In the present work and as continuation in this approach, we herein report photo-physical properties of oligo-p-chloro-anisole (OPClAn), with the same degree of polymerization. The obtained results will be discussed in comparison with those of OPFAn, taking into account the electron withdrawing effect of the substituent’s on the oligo-anisole rings. That’s why some previous results well be recall in order to make easy the comparison. The ionization potential (IP) and electron affinity (EA) are well- defined properties that can be calculated by Density Functional Theory (DFT) on the geometries in the neutral, cationic and anionic states to estimate the energy barrier for the injection of both holes and electrons into the polymer [20]. In order to complete the experimental studies and to predict the correlation structure–properties of organic compound, theoretical calculations based on DFT were performed. These theoretical stud- ies are focused on the mechanism of the electro-oligomerization and on the intrinsic oligomer properties, such as HOMO 0379-6779/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.synthmet.2012.12.026