Synthesis and characterization of color-tunable mixed ligand based magnesium complexes for display device applications

In this study, we reported the synthesis and the characterization of mixed-ligand based magnesium chelates with 2-(2-hydroxyphenyl)-1H-benzimidazole (HBI) and 8-hydroxyquinoline (Q) or 5-chloro-8-hydroxyquinoline (ClQ) or 5,7-dichloro-8-hydroxyquinoline (Cl₂Q) or 2-methyl-8-hydroxyquinoline (MeQ) or 5,7-dimethyl-8-hydroxyquinoline (Me₂Q). The photophysical properties of these metal complexes has been investigated by UV–visible absorption and photoluminescence spectroscopy. The electrochemical behaviour of metal complexes was also reported. The metal complexes had good thermal stability (>300 °C). All prepared metal complexes exhibited bright colored light on excitation with a UV light source. The emitted light had color coordinates values at x = 0.17, y = 0.36 for [Mg(HBI)(Q)]; x = 0.21, y = 0.47 for [Mg(HBI)(ClQ)]; x = 0.16, y = 0.26 for [Mg(HBI)(Cl₂Q)]; x = 0.16, y = 0.25 for [Mg(HBI)(MeQ)]; and x = 0.30, y = 0.58 for [Mg(HBI)(Me₂Q)] material. Color tuning by modifying the substituents in 8-hydroxyquinoline ligand was examined in synthesized complexes. In addition, a temperature-dependence photoluminescence spectrum was used to study the emission profile of magnesium complexes. Density functional theoretical calculations had been performed to demonstrate the three-dimensional geometries and the frontier molecular orbitals energy level of metal complexes. Complexes emitting color tuned luminescence could be efficiently used for the fabrication of next generation display devices.