ABSTRACT The application of many hetero-aromatic compounds in pharmaceutical and dye industries make the theoretical study of their dipole moment (µ) oscillator strength (f) and other photo-physical properties worthwhile. These properties determine the solubility of many compounds; predict the relationship between their structures, properties and performance. The f, µ, α, transition dipole moment (∆µ), vertical Excitation Energies (EE) and the frontier orbitals energy gap (ΔELUMO-HOMO) of the optimized structures of 3, 4-diphenylthiophene (DPT); 3, 4-dicarboxylic-2, 5-diphenylthiophene (DCDPT); and benzo[b] thiophene (BT) were determined in solvents of different polarity functions (∆P) by Time-Dependent Density Functional Theory, using Becke’s three parameter with Lee-Yang-Parr modification and 6-31G* basis set theory (TD- DFT- B3LYP/6-31G*). The associated quantum chemical descriptors of ΔELUMO-HOMO such as: Ionization Potential (IP) and global hardness (ƞ) for the compounds were also determined with the same level of theory. The µ of the molecules increases with increasing ∆P, but highest for DCDPT. Bathochromic shifts associated with decreasing EE were recorded for the electronic transitions in DCDPT compare with those observed for DPT and BT. The IP and ƞ increased as ∆P increases, suggesting high stability of these compounds in polar solvents. The energy gaps, its associated parameters and positive ∆µ suggested strong activity of the molecules, with DCDPT being the highest. This is in reasonable agreement with the experimental results for the molecules particularly if the experimental uncertainties are considered. Key words: Polarizability; photo-physical; excitation energy; oscillator strength; Time Dependent-Density Functional Theory Manuscript profile

This study investigated the effects of solvents’ polarities on the geometry and electronic properties of 2-(2-nitrovinyl) furan, (NVF). The investigation was carried via theoretical approach, using an ab-initio [Hartree Fock (HF/6-31G*)] and Density Functional Theory (DFT/B3LYP/6-31G*).The properties investigated are optimized structures, energy gaps (ELUMO EHOMO) and associated global properties, chemical potential (ƙ), global hardness (η), ionization energy (IE), Electron affinity (EA), dipole moment (μ), polarizability (α) and electronic charges. NVF was sparingly soluble in water, very soluble and more active in polar organic solvent than non-polar solvents. The solvent polarities do not change the structural parameters of NVF widely, but have significant changes on the electron density re-distribution. The highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) of the molecule showed π-characters, an indication of intermolecular charge transfer characteristics for the excitation of electrons in NVF. The change in the dipole moment associated with low energy gaps for NVF in the polar solvent showed that NVF has strong activity in the solvents. The theoretical data obtained in this study are in good agreement with the earlier reported experimental data. Manuscript profile