Lanthanide complexes of the tridentate Schiff base ligand salicylaldehyde-2- picolinoylhydrazone: Synthesis, characterization, photophysical properties, biological activities and catalytic oxidation of aniline

Designing of Novel Sm(III) Metal-Based Macrocyclic Complex Bearing N3O3 Donor Moiety with Prominent Photoluminescence, Antimicrobial, and Antioxidant Activities

Novel luminescent N3O3-donor Sm(III) macrocyclic complex i.e., [Sm(C17H25N3O5)].3NO3; [(2Z,17Z)-7,10,13-trioxa-3,17-diaza-1(2,6)-pyridinacycloocta-decaphane-2,17-diene-2,18-diol] has been synthesized through the template synthetic route by using 1,13-diamino-4,7,10-trioxatridacane and pyridine-2,6-dicarboxylic acid ligand precursors in the presence of Sm(NO3)3.6H2O in (1:1:1) molar ratios. Elemental analysis, 1H NMR, 13C NMR, UV-Vis, FTIR, XRD, and mass spectrometry techniques have been utilized for the characterization of the synthesized complex. The crystalline nature of the complex is confirmed by the existence of sharp narrow peaks in the X-ray diffractogram. Optical property (Photoluminescence) is analyzed by PL-spectroscopy and results manifested that under 272 nm excitation wavelength, the complex exhibited three characteristic emission peaks at 563 nm, 602 nm, and 644 nm corresponded to the 4G5/2→6H5/2, 4G5/2→6H7/2, and 4G5/2→6H9/2 transitions respectively. This property leads the use of this reported complex as an optical active material which could be used as sensor for analysis and detection purpose such as cell or tissue imaging, solar cell, luminescent probe etc. Antimicrobial screening of the complex against E. coli, & S. aureus bacterial strains and Alternaria alternate & Fusarium solani fungal strains has also been performed to investigate their antimicrobial potential and revealed satisfactory results. Antioxidant potential of the complex has been checked by applying a DPPH free radical scavenging assay and the complex appeared with notable result. Cyclic voltammetry results indicated the electrochemical nature of the complex as prominent redox material for redox reactions.

Structural Study of a La(III) Complex of a 1,2,3-Triazole Ligand with Antioxidant Activity

The 1,2,3-triazole derivative 2-(4-chlorophenyl)-5-(pyrrolidin-1-yl)-2H-1,2,3-triazole-4-carboxylic acid with potential anticancer activity was used as a ligand in complex formation with the lanthanum(III) ion. The molecular structure and vibrational spectra of the complex were optimized at three DFT levels, and the scaled IR and Raman spectra were compared to the experimental ones. Several scaling procedures were used. Through a detailed analysis, the structure predicted for the newly synthetized La(III) complex was confirmed by the good accordance of the calculated/experimental IR and Raman spectra. The best DFT method appeared to be M06-2X with the Lanl2mb basis set, followed closely by Lanl2dz. The effect of the lanthanide atom on the molecular structure and atomic charge distribution of the triazole ring was evaluated. The potential free radical scavenging activity of both the ligand and the complex was investigated in several radical-generating model systems. The potential mechanisms of antioxidant action (hydrogen atom transfer (HAT) and single-electron transfer (SET)) were elucidated.

Mono- and Mixed Metal Complexes of Eu3+, Gd3+, and Tb3+ with a Diketone, Bearing Pyrazole Moiety and CHF2-Group: Structure, Color Tuning, and Kinetics of Energy Transfer between Lanthanide Ions

Three novel lanthanide complexes with the ligand 4,4-difluoro-1-(1,5-dimethyl-1H-pyrazol-4-yl)butane-1,3-dione (HL), namely [LnL₃(H₂O)₂], Ln = Eu, Gd and Tb, were synthesized, and, according to single-crystal X-ray diffraction, are isostructural. The photoluminescent properties of these compounds, as well as of three series of mixed metal complexes [Eu_xTb_1-xL₃(H₂O)₂] (Eu_xTb_1-xL₃), [EuxGd_1-xL₃(H₂O)₂] (Eu_xGd_1-xL₃), and [Gd_xTb_1-xL₃(H₂O)₂] (Gd_xTb_1-xL₃), were studied. The Eu_xTb_1-xL₃ complexes exhibit the simultaneous emission of both Eu³⁺ and Tb³⁺ ions, and the luminescence color rapidly changes from green to red upon introducing even a small fraction of Eu³⁺. A detailed analysis of the luminescence decay made it possible to determine the observed radiative lifetimes of Tb³⁺ and Eu³⁺ and estimate the rate of excitation energy transfer between these ions. For this task, a simple approximation function was proposed. The values of the energy transfer rates determined independently from the luminescence decays of terbium(III) and europium(III) ions show a good correlation.