DFT computational studies, biological and antioxidant activities, and kinetic of thermal decomposition of 1,10-phenanthroline lanthanide complexes

[Ln (phen)2(NO3)3] complexes were synthesized by interaction of lanthanide nitrate {Ln (NO3)3.xH2O where Ln = Tb, Eu, Sm, Dy, and La} with 1,10-phenanthroline {phen} in ethylacetate. The complexes were characterized by several analytical and spectroscopic techniques. Density functional theory (DFT) calculations were carried out to optimize the geometries of all prepared complexes at the B3LYP/6-31G(d) level of theory. Vibrational frequencies of the complexes theoretically calculated were in good agreement with experimentally determined values. Most of the complexes exhibited high to moderate antibacterial and antifungal activities in vitro against seven different clinical isolates. The complexes were tested for their antioxidant activity toward 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical. Dy(III) complex showed the highest activity. Thermal degradation of complexes at different heating rates was investigated by thermogravimetric analysis (TGA). The complexes had high thermal stability. The activation energies (Ea) of the degradation were calculated by Kissinger and Flynn-Wall-Ozawa methods.