Synthesis, characterization and quantum-chemical investigations of new fluorescent heterocyclic Schiff-base ligands and their cobalt(II) complexes

• Published in: Inorganica Chimica Acta 2019-01, Vol.484, p.450-456
• Main Authors: Ramezani, Shirin, Pordel, Mehdi, Davoodnia, Abolghasem
• Format: Article
• Language: English
• Subjects: Charge transfer; Chemical compounds; Chemical synthesis; Co(II) complex; Cobalt; Cobalt compounds; Coordination compounds; Density functional theory; Fluorescence; Fluorescent Schiff base; Imines; Ligands; Molecular orbitals; NMR; Nuclear magnetic resonance; Organic chemistry; Quantum chemistry; Spectrum analysis; UV–Vis and fluorescence spectroscopy
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2018.09.050

[Display omitted] •New Co(II) complexes were synthesized by reaction of Co(II) with Schiff base ligands.•The structures of the ligands and complexes were characterized by spectral data.•Their optical properties and quantum chemical calculations were studied.•Their energy gap between the HOMO and LUMO frontier orbitals was obtained. Two new fluorescent heterocyclic Schiff base ligands were synthesized and characterized by elemental analyses, IR, mass, and NMR spectra. Results from NOESY experiment confirmed the E configuration of Schiff-bases. Coordination of the bidentate ligands with Co(II) cation led to the formation of deep green complexes. The structures of the complexes have been confirmed by spectral, analytical data and Job’s method. Schiff-base ligands and cobalt complexes were spectrally characterized by UV–Vis and fluorescence spectroscopy. An efficient charge transfer of electron from p-orbital on ligand to Co(II) d-orbital can be proposed as the main reason for the color of the complexes. In addition, the DFT methods were employed to achieve deeper insight into geometry, spectral properties and energy difference between the HOMO and LUMO frontier orbitals of the synthesized compounds. The DFT-calculated spectral properties are in good agreement with the experimental values, confirming suitability of the optimized geometries for Co(II) complexes.