New class of 2,5-di(2-thienyl)pyrrole compounds and novel optical properties of its conducting polymer

(1)

New class of 2,5-di(2-thienyl)pyrrole compounds and novel optical

properties of its conducting polymer

Hakan Can Söyleyici

a

, Metin Ak

b,*

_{, Yüksel S¸ahin}

a

_{, Dilek Odac}

_{ı Demikol}

c

_{, Suna Timur}

c

a_{Adnan Menderes University, Faculty of Art and Science, Chemistry Department, Aydın, Turkey} b_{Pamukkale University, Faculty of Art and Science, Chemistry Department, Denizli, Turkey} c_{Ege University, Faculty of Art and Science, Biochemistry Department, Izmir, Turkey}

h i g h l i g h t s

New type SNS derivative was synthesized using hydrazide instead of amine. P(HKCN) has superior properties compared with other SNS derivatives.

Electrochemical copolymerization was performed for different feed ratios of monomers.

a r t i c l e i n f o

Article history:

Received 19 April 2013 Received in revised form 25 June 2013 Accepted 10 July 2013 Keywords: Polymers Electrochemical properties Semiconductors Optical properties

a b s t r a c t

New type 2,5-di(2-thienyl)pyrrole derivative namely 4-amino-N-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl) benzamide (HKCN) have been synthesized via reaction of 1,4-di(2-thienyl)-1,4-butanedione and p-aminobenzoyl hydrazide. Using hydrazide instead of amine not only increases product yield but also improves properties of the corresponding polymer. Spectroelectrochemical investigations revealed that P(HKCN) is more stable and it has lowest band gap and better long-term stability compared with other SNS derivatives. Chronoamperometry experiment showed that P(HKCN) polymer ﬁlm has excellent redox stability, moderate switching time and high optical contrast. Electrochemical copolymerization of HKCN with EDOT was performed in DCM/TBP6solution for different feed ratios of monomers. We describe a proposal to determination copolymer composition by means of the optical properties of conducting copolymers.

1. Introduction

Conjugated polymers have attracted strong interest because they are utilized for advanced technologies such as sensory, elec-trochromic, nonlinear optical, photo- and electroluminescent de-vices, and photovoltaic dede-vices, etc.[1e4]. Interest in chemically functionalized conducting polymer materials continues to expand. Therefore, there is a great interest in the methodology of chemical synthesis for the precursor monomer and oligomer units particu-larly in respect of thiophene and pyrrole. Well-developed methods for synthesis of substituted pyrrole and especially thiophene monomers have been reported. However, introduction of substit-uent groups onto the pyrrole and thiophene monomers has a

detrimental inﬂuence and often results in materials with poor

electronic conductivity. This is attributed to the effect of

neighboring group steric interactions that reduce the conjugation length of the polymer strands and is most noticeably the case for

N-substituted pyrroles [5]. In reply to this trouble many research

groups are focusing on functionalized oligomeric species such as

sexithiophene [6], terthiophene [7], and dithienylpyrrole [8,9]

derivatives.

2,5-Di(2-thienyl)pyrroles (SNS) consist of thiophene and pyrrole

rings interconnected by their

a

-positions and are undoubtedly of

interest in the preparation from them of electroconductive mate-rials, in particular as components of smart devices. The extremely high reactivity of a pyrrole system creates the possibility of intro-ducing a substituent into the

b

-position of the pyrrole ring even with

the free

a

-positions of thiophene rings which makes possible

further modiﬁcation of the properties[10]. Also this strategy yields centrosymmetric polymer precursors and seeks to minimize the steric inﬂuence of the central substituent through the addition of the thiophene spacers[11]. In a large number of the papers aimed at investigation of N-substituted 2,5-di(2-thienyl)pyrroles the Paale Knorr synthesis, where the main starting compound was

1,4-di(2-* Corresponding author.

E-mail addresses:metinak@pau.edu.tr,metin-ak@hotmail.com(M. Ak).

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Materials Chemistry and Physics

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / m a t c h e m p h y s

http://dx.doi.org/10.1016/j.matchemphys.2013.07.019