Synthesis, characterization and DFT calculation of 4-fluorophenyl substituted tris(8-hydroxyquinoline)aluminum(III) complexes

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Vol. 118; pp. 66 - 72
• Main Authors: Suliman, FakhrEldin O., Al-Nafai, Isehaq, Al-Busafi, Saleh N.
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 24.01.2014
• Subjects: 8-Hydroxyquinoline; Aluminum(III) complexes; Electrons; Fluorescence; Fluorobenzenes - chemical synthesis; Fluorobenzenes - chemistry; Models, Molecular; OLEDs; Organometallic Compounds - chemical synthesis; Organometallic Compounds - chemistry; Quantum Theory; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet; TD-DFT; Titrimetry; 8-Hydroxyquinoline; Aluminum(III) complexes; Fluorescence; OLEDs; TD-DFT
• ISSN: 1386-1425; 1873-3557
• DOI: 10.1016/j.saa.2013.08.055

[Display omitted] •Synthesis and characterization of new 4-fluorophenyl derivatives of 8-hydroxyquinoline.•Emission spectra of the aluminum complexes of the new ligands show red shift.•Theoretical calculations were performed using TD-DFT methods coupled to B3LYP/6-31G(d) level of theory.•Electronic structure and properties were presented.•HOMO–LUMO energies and contributions from different groups were obtained. 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 525nm and 530nm 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.