Available online at www.derpharmachemica.com Scholars Research Library Der Pharma Chemica, 2012, 4(6):2214-2221 (http://derpharmachemica.com/archive.html) ISSN 0975-413X CODEN (USA): PCHHAX 2214 www.scholarsresearchlibrary.com Theoretical study on the structural and electronic properties of new materials based on benzothiodiazole and pyrrole derivative A. Adejoro 1 , B. T. Ogunyemi 1* and B. Semire 2 1 Department of Chemistry, University of Ibadan, Ibadan, Nigeria. 2 Department of Pure and Applied Chemistry, Ladoke Akintola University of Technology, Ogbomosho, Nigeria. _____________________________________________________________________________________________ ABSTRACT The theoretical study on the ground state geometries and electronic properties of new conjugated compounds using benzothiadiazole and pyrole as substrates was carried out using density functional theory (DFT) method at B3LYP level with 6-31G* basis set. The dihedral angle, bond length, electronic and UV-Visible absorption properties were determined. The coupling (of the donor and acceptor) and substituent effects on the geometry and electronic properties of these substrates were discussed.The results show that the geometries of the materials were significantly affected by the substituents. The substitution of the pyrrole ring with pyrrolium oxide destabilizes the HOMO, LUMO levels with a decrease in a band gap and results in a red shifting in the absorption spectrum. The theoretical results suggest that both the donor strength and the stable geometry contribute significantly to the electronic properties of alternating donor–acceptor conjugated copolymers. These electronic properties compared favourably with conjugated copolymers that had been used in optoelectroniv devices. Hence, these copolymers could have potential applications in transparent conductors, or photovoltaic devices. Key words: conjugated polymers; benzothiazole-pyrrole; electronic property; DFT _____________________________________________________________________________________________ INTODUCTION Conjugated polymers, a class of organic or novel molecular based conductors not only possess the optoelectronic properties of Si, Ge, group iii-iv and group ii-vi inorganic semi-conductors but also possess the processing advantages and mechanical properties of polymers (1), have attracted great interest for their use in transparent conductors, photovoltaic cells, light emitting diodes, and semi-conductor layers in field effect transistors (FET) [2]. A key feature of these novel semiconductors materials is that manipulation of the chemical structures allows control of the optical band gap [3]. Low band gap which is the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of conjugated polymers can afford intrinsic conductivity with enhanced nonlinear optical properties,and harvest more photon with long wavelength [4]. Many ways to design low band gap energy polymers have been reported in the literatures but this work will concentrate on donor–acceptor type of polymer, based on benzothiadiazole and pyrrole. 2,1,3-benzothiadiazole and its derivatives have been widely studied and has been incorporated in a growing number of low- band-gap materials in large part, due to the ease of preparation of 4,6-dibromo-2,1,3-benzothiadiazole(5]. It is a well-