**3. Results and discussion**

120 Electropolymerization

of 1-(2-pyrrolyl)-2-(2-thienyl) ethylene (PTE). It was found that the conductivity, electroactivity and redoxability of polythiophene and poly(3-methyl thiophene) are

In this work, the effects of conjugated molecule (SNS) on the electropolymerization and electrochemical behaviour of pyrrole was investigated. Firstly, the electropolymerization of pyrrole and SNS were carried out separately by CV method. Secondly, the electropolymerization of pyrrole in the presence of small amount of SNS was carried out and then the influence of SNS on the electropolymerization and electrochemical behaviour of pyrrole was investigated. In addition, the effect of SNS addition on the electron transfer reaction of ferro/ferricyanide redox system on the polypyrrole film was studied and finally the conductivity of poly(Py-SNS) was determined by electrochemical impedance

Solvents were purified and dried according to the common procedures in the literature [Perin & Armarego, 1998]. Acetic anhydride, ammonium acetate, ferro/ferricyanide were purchased from Merck and lithium perchlorate were bought from Fluka and all of them

2,5-di-(2-thienyl)-pyrrole (SNS) was prepared by the method described by Wynberg and Metselaar [Wynberg & Metselaar, 1984]. The yield was improved by refluxing the solution of the intermediate 1,4-di-(-2-thienyl)-1,4-butanedione (3 *g*) with ammonium acetate (40.3 *g*), glacial acetic acid (120 *ml*) and acetic anhydride (24 *ml*) overnight under a nitrogen atmosphere. The reaction mixture was then poured into 250 *ml* of distilled water and the resulting dark-green solid was chromatographed over a silica gel column with dichloromethane: hexane (3:2) elution to give SNS with 75% yield, as pale yellow crystals of

The electropolymerization was carried out using digital potentiostate/galvanostate (Autolab PGSTAT 30). A glassy carbon (GC) disk (2 *mm* diameter) as working electrode, a platinum wire as a counter electrode and Ag/AgCl as a reference electrode were used. Acetonitrile was distilled over P2O5 and lithium perchlorate was used as an electrolyte in 0.1 *M* concentration. The electropolymerization of pyrrole (0.5 *ml*, 7.4 *mmole*) and SNS (16 *mg*, 0.074 *mmole*) in 0.1 *M* LiClO4/acetonitrile electrolyte were performed separately in two different potential ranges vs. Ag/AgCl at the scan rate of 50 *mV.s-1*. Similar conditions were adopted for the electropolymerization of pyrrole in the presence of SNS (7.4 *mmole*: 0.074 *mmole*). In the study of the cyclic voltammetry experiment of electron transfer, 1 mM

For the EIS measurements, the AC frequency range extended from 100 *kHz* to 10 *mHz*, a 10 *mV* peak-to-peak sine wave was as the excitation signal. Both real and imaginary

IR(KBr): 3490 cm-1 (N-H); 1H NMR(CDCl3): δ: 6.2(2H,d), 6.8(6H,m), 8.0(1H,s).

**2.3 Electropolymerization method and conductivity measurements** 

ferro/ferricyanide in the 1 *M* H2SO4 media at 50 *mV.s-1* scan rate was used.

improved in the presence of PTE [Kiani et al., 2008a, 2008b].

**2.2 Preparation of 2,5-di-(2-thienyl)-pyrrole (SNS)** 

spectroscopy (EIS) method.

**2. Experimental** 

were used directly.

melting point 82-83 ºC.

**2.1 Materials** 
