title: Electronic spectra and DFT calculations of some pyrimido[1,2-a]benzimidazole derivatives.
abstract: Ground state properties of 2,4-diphenyl-1,4-dihydrobenzo[4,5]imidazo[1,2-a]pyrimidine, compound 1, and its derivatives are investigated experimentally and theoretically in Dioxane and DMF. The calculations show that all the studied compounds (1-7) are non-planar, resulting in a significant impact on the electronic and structural properties. The ground state properties of compounds 1-7 at B3LYP/6-311G (d, p) show that compound 5 has the lowest EHOMO, ELUMO, and ΔE indicating highest reactivity. Compound 7 is found to have the highest polarity. The observed UV spectra in Dioxane and DMF of compounds 1-4 show 2 bands, while compounds 5-7 show 4 bands in both solvents. Band maxima (λmax) and intensities of the spectra are found to have solvent dependence reflected as blue and red shifts. The theoretical spectra computed at TD-B3LYP/6-311G (d, p) in gas phase, Dioxane and DMF indicate a good agreement with the observed spectra.
authors.affiliation: Chemistry Department, College of Science, Cairo University, University Ave., Dokki, 12613 Cairo, Egypt.
authors.forename: Mohamed E
authors.initials: ME
authors.lastname: Elshakre
authors.affiliation: Chemistry Department, College of Science, Cairo University, University Ave., Dokki, 12613 Cairo, Egypt. Electronic address: husseinmam@hotmail.com.
authors.forename: H
authors.initials: H
authors.lastname: Moustafa
authors.affiliation: Chemistry Department, College of Science, Cairo University, University Ave., Dokki, 12613 Cairo, Egypt.
authors.forename: Huwaida M E
authors.initials: HME
authors.lastname: Hassaneen
authors.affiliation: Chemistry Department, College of Science, Cairo University, University Ave., Dokki, 12613 Cairo, Egypt.
authors.forename: Abdelrahim Z
authors.initials: AZ
authors.lastname: Moussa
mesh_terms: D001562:Benzimidazoles / Q000737:chemistry*; D004583:Electrons; D008958:Models, Molecular; D008968:Molecular Conformation; D011743:Pyrimidines / Q000737:chemistry*; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D055672:Static Electricity; D013816:Thermodynamics
chemical_list: D001562:Benzimidazoles; D011743:Pyrimidines
keywords: DFT/B3LYP; Pyrimido[1,2-a]benzimidazoles; Solvent effect; TD-DFT; UV