## 2 Materials and Methods  
5-bromo-2,2\({}^{\prime}\)-bitiophene, 2-thienylboronic acid, tetrakis (triphenylphosphine) palladium (0) ([Pd(PPh3)4]), 1,1\({}^{\prime}\)-bis (diphenylphosphino) ferrocene dichloropalladium ([Pd(dppf)Cl2]), trimethylsilylacetylene (TMS), and N-bromo-succinimide (NBS) were from TCI Chemicals. \({}^{1}\)H NMR spectra were recorded with a Varian VXR 300 spectrometer operating at 300.0 MHz. Chemical shifts are given in ppm relative to residual solvent signal [34]. UV-Vis spectra of the monomers were recorded in CH\({}_{2}\)Cl\({}_{2}\) or CH\({}_{3}\)CN solvent using a Hitachi U-2010 spectrophotometer. IR spectra were carried out with a JASCO FT/IR-489 Plus spectrophotometer using KBr disks in the range 4000-400 cm\({}^{-1}\). UV-Vis spectra of polymers were carried out on films electrodeposited on a ITO (indium-tin oxide) slide. Electrochemical tests were performed with a AUTOLAB PGSTAT12 instrument, using the software GPES. The electrochemical synthesis and characterization were performed in a three-electrodes, single compartment cell using a Pt disk (2 mm diameter) as the working electrode, a graphite bar as the counter electrode, and Ag/AgCl equipped with a salt bridge containing the same solvent-supporting electrolyte system as the reference electrode. CH\({}_{3}\)CN or CH\({}_{2}\)Cl\({}_{2}\) (99.8%, packaged under nitrogen), and 0.1 M tetraethylammonium hexafluorophosphate (TEAPF\({}_{6}\), puriss. electrochemical grade) were used as a solvent and supporting electrolyte, respectively. Before each experiment, the working electrode was polished with 1 and 0.3 \(\upmu\)m alumina powder, then rinsed with distilled water in an ultrasonic bath. The monomer concentration in electrosynthesis and monomers characterizations was 2 \(\times\) 10\({}^{-3}\) M. All the electrochemical experiments were performed under Ar atmosphere. The energies of HOMO and LUMO were estimated by the voltammetric response according to Equations (1) and (2) [35]:  
\[\text{HOMO}=-\text{e}(\text{E}_{\text{onset,ox}}+4.71)\text{ (eV)} \tag{1}\]  
\[\text{LUMO}=-\text{e}(\text{E}_{\text{onset,red}}+4.71)\text{ (eV)} \tag{2}\]  
where potential values are in Volts vs. Ag/AgCl and 4.71 is the potential (in Volts) of the redox couple Ag/AgCl versus vacuum, and taking into account that an electronvolt (eV) is defined as the energy gained by an electron moving along a potential of 1 V. The energy gap (Eg) values (difference between LUMO and HOMO) were calculated from the electrochemical data (Eg,ec), or from the UV-Vis spectra (Eg,opt) according to Equation (3):  
\[\text{Eg,opt}=1239.81/\lambda_{\text{onset}} \tag{3}\]  
where \(\lambda_{\text{onset}}\) is the value of wavelength corresponding to 10% of maximum absorbance. DFT calculations.DFT calculations were performed on PC GAMESS software [36], partially based on the GAMESS (US) source code [37] using the PBE0 functional [38] with the basis set split-valence according to reference [39]. Concerning iodide, the corresponding pseudo-potential removing 28 core-electrons was adopted. Harmonic analysis at PBE0/def2-SVP level was carried out on the equilibrium geometries of the substituted 2,2'.5',2''-terthiophenes to confirm the nature of the minimum (i.e., the absence of imaginary frequencies) on the PES (Potential Energy Surface). The first 30 excited states were calculated from the equilibrium geometries at gas phase using the TD-DFT approach [40]. The resulting files were elaborated under Avogadro [41] and Gabedit software [42], released under GNU license. _Synthesis of 2,2'.5',2''-terthiophene_ (**2**), 5-bromo-2,2'-bithiophene (**1**, 0.5827 g, 2.378 mmol) and [Pd(PPh3)4] (0.1644 g, 0.142 mmol) were dissolved in DME (15 mL). After 10 min, 2-thienylylboronic acid (0.4473 g, 4.276 mmol) and 1 M NaHCO3 aqueous solution (5.2 mL) were added. The reaction mixture was stirred at reflux temperature for 30 min and monitored by TLC (petroleum ether/dichloromethane 9/1 as eluent) until **1** disappeared, then cooled at room temperature and filtered.