Optical and magnetic properties of neodymium(III) six-coordinate complexes of 2,6-lutidine N-oxide derivatives

Highlights: • Complexes NdCl₃(3-Br-4-CH₃OC₇H₇NO)₃ and Nd(C₇H₉NO)₅(C₄H₈O₂)(ClO₄)₃ were synthesized. • The six coordinated polyhedrons contain Nd–Cl and Nd–O bonds or Nd–O bonds. • The ligand singlet and triplet energy levels were performed by DFT calculations. • The lifetime of the ⁴F_3/2 level is of a 2.5–2.7 μs. • EPR measurements confirm the low symmetry of crystal field position of Nd³⁺ ions. -- Abstract: Two neodymium(III) six-coordinate complexes NdCl₃(3-Br-4-CH₃OC₇H₇NO)₃ (Nd1) and Nd(C₇H₉NO)₅(C₄H₈O₂)(ClO₄)₃ (Nd2) have been synthesized and characterized. The FT-IR and FT-Raman data were acquired, and a complete vibrational assignment of the fundamental modes of the compounds was carried out. The frequencies calculated for the both ligands and scaled using the B3LYP approach with the 6-311G(2d,2p) basis set correspond very well to the experimental values. The XRD results, IR and Raman spectra were discussed in terms of a possible structure and composition of the studied compounds. The optical absorption and emission spectra were investigated at room temperature. The emission decay is mono exponential indicating that the energy transfer from the ligand occurs straight to the ⁴F_3/2 level. The lifetime of this level is about 2.5 μs? A possibility of the energy transfer between the ligands under study and neodymium ions was considered. The calculations of the spin Hamiltonian parameters and EPR data simulation were performed using the electron paramagnetic resonance and nuclear magnetic resonance (EPR-NMR) program.