title: Synthesis of benzimidazoles containing pyrazole group and quantum chemistry calculation of their spectroscopic properties and electronic structure.
abstract: Five benzimidazole compounds containing pyrazole group were synthesized via one-step reaction of o-phenylenediamine and 1-arylpyrazole-4-carbaldehyde in ethanol under mild conditions. The composition and structure of resultant benzimidazole compounds were analyzed by means of elemental analysis, mass spectrometry, (1)H-nuclear magnetic resonance spectroscopy and X-ray single crystal diffraction. The ultraviolet-visible light spectra and fluorescent spectra of the products were measured. Their ground-state (S(0)) equilibrium geometries and vibrational frequencies were determined based on B3LYP method, and their first excited-state (S(1)) geometries were fully optimized based on 6-31G (d, p) basis set of TD-B3LYP method. Besides, the spectroscopic properties of the products were computed based on cc-pVTZ basis set of TD-B3LYP method and compared with corresponding experimental data. It has been found that benzimidazole compounds containing pyrazole group can be readily synthesized in a high yield via one-step reaction of o-phenylenediamine and 1-arylpyrazole-4-carbaldehyde in ethanol solvent. The fluorescence properties of the five synthesized compounds are closely related to their molecular structure; and their computed fluorescence spectra well correspond to their experimental values. Moreover, they have stable structure and strong fluorescence, showing potential application in time-resolved fluoroimmunoassay and DNA probe.
authors.affiliation: Fine Chemistry and Engineering Research Institute, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, 475004, People's Republic of China. rtg@henu.edu.cn
authors.forename: Tie-gang
authors.initials: TG
authors.lastname: Ren
authors.forename: Hong-bin
authors.initials: HB
authors.lastname: Cheng
authors.forename: Jing-lai
authors.initials: JL
authors.lastname: Zhang
authors.forename: Wei-jie
authors.initials: WJ
authors.lastname: Li
authors.forename: Jia
authors.initials: J
authors.lastname: Guo
authors.forename: Li-rong
authors.initials: LR
authors.lastname: Yang
mesh_terms: D000042:Absorption; D001562:Benzimidazoles / Q000737:chemistry*; D004583:Electrons; D008958:Models, Molecular; D008968:Molecular Conformation; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry*; D011789:Quantum Theory; D013057:Spectrum Analysis
chemical_list: D001562:Benzimidazoles; D011720:Pyrazoles; C031280:pyrazole; C031000:benzimidazole