title: Synthesis, characterization and DFT calculation of 4-fluorophenyl substituted tris(8-hydroxyquinoline)aluminum(III) complexes.
abstract: New 4-fluorophenyl substituted 8-hydroxyquinoline derivatives, 5-(4-fluorophenyl)quinolin-8-ol and 5,7-bis(4-fluorophenyl)quinolin-8-ol, were synthesized and characterized by spectroscopic methods. The aluminum complexes of 5-(4-fluorophenyl)quinolin-8-ol (AlQF) and of 5,7-bis(4-fluorophenyl)quinolin-8-ol (AlQF2) exhibit strong fluorescence emission centered at 525 nm and 530 nm respectively. The quantum yield of both complexes were enhanced compared to the parent tris(8-hydroxyquinolinato)aluminum(III) complex. Electronic structures and photophysical properties of the new complexes were investigated theoretically by ab initio and density functional theory (DFT) and time dependent DFT (TD-DFT). Geometries of the ground state (S0) and the first excited state (S1) of the new complexes were optimized at the B3LYP/6-31G(d) functional and configuration interaction singles (CIS) method respectively. The aryl substituents were found to contribute significantly to the frontier molecular orbitals (FMOs). We have observed that in both cases the lowest occupied molecular orbital (LUMO) energy decreases while the energy of the highest occupied molecular orbital is slightly increased. The most significant increase was observed for AlQF2.
authors.affiliation: Department of Chemistry, College of Science, Sultan Qaboos University, Box 36, Al-Khod 123, Sultanate of Oman, Oman. Electronic address: fsuliman@squ.edu.om.
authors.forename: Fakhreldin O
authors.initials: FO
authors.lastname: Suliman
authors.forename: Isehaq
authors.initials: I
authors.lastname: Al-Nafai
authors.forename: Saleh N
authors.initials: SN
authors.lastname: Al-Busafi
mesh_terms: D004583:Electrons; D005464:Fluorobenzenes / Q000138:chemical synthesis* / Q000737:chemistry*; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D017186:Titrimetry
chemical_list: D005464:Fluorobenzenes; D009942:Organometallic Compounds; C547306:tris-(8-hydroxyquinoline)aluminum
keywords: 8-Hydroxyquinoline; Aluminum(III) complexes; Fluorescence; OLEDs; TD-DFT