Abstract

In the search for a conducting polymers with narrow Energy Band-Gap (Eg), the research focus is centered on increasing the bandwidth of the Highest Occupied Molecular Orbitals (HOMO) or the Lowest Orbital Molecular Orbitals (LUMO) of a conducting polymers through the use of strong electron donor or strong electron acceptor, respectively. In this research, we considered the trend of change in Eg, UV absorption, IR absorption, Density of State (DOS) and Excited state Properties of various forms of Benzobispyrrole-Derived Squaraines using Density Functional Theory (DFT) and Hartree-Fock (HF) methods. The results obtained from various computational methods employed are in good agreement with literature, which observed that the Eg values calculated with ROHF is higher than the expected value, while that calculated with BLYP and SVWN values are about 40 to 50% lower than the expected. The better Eg values in good agreement with expected values are found by hybrid functional B3LYP. However, there is a good correlation in the trend of change in the calculated Eg values of all computational methods with the trend of change in the experimental Eg. Also, DOS, IR Maximum Absorption, Dipole Moment and UV Absorption add meaning to the intrinsic conductivities property of the models.

Key words: Highest occupied molecular orbitals (HOMO), lowest orbital molecular orbitals(LUMO), band gap, UV absorption, density functional theory (DFT), Hartree-Fock (HF)methods, density of state (DOS).