Comparative Study of Complexes of Rare Earths and Actinides with 2,6-Bis(1,2,4-triazin-3-yl)pyridine

Abstract

Complexes of group III metals (rare earth and actinides) with 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (BTP) have been investigated by computational (DFT) and, in limited cases, by experimental (FT-IR, X-ray) techniques with the goal of determining the characteristics of metal⁻ligand interactions. The DFT calculations using the M062X exchange-correlation functional revealed that metal⁻ligand distances correlate with the ionic radii of the metals, in agreement with available X-ray diffraction results on the Sc, Y, La, U, and Pu complexes. A related blue-shift trend could be observed in seven characteristic bands in the IR spectra associated with metal⁻ligand vibrations. The computations uncovered considerable charge transfer interactions, particularly in the actinide complexes, as important covalent contributions to the metal⁻ligand bonding. The covalent character of the metal⁻ligand bonds decreases in the actinides, from U to Cm.

Keywords

• rare earth
• actinide
• infrared spectroscopy
• DFT
• donor–acceptor interactions