Lanthanide complexes based on a new bis-chelating carbacylamidophosphate (CAPh) scorpionate-like ligand

The novel bis-chelating carbacylamidophosphate type ligand, tetramethyl[pyridine-2,6-diyldi(iminocarbonyl)]diamidophosphate (H₂L), and its sodium salt, NaHL, have been synthesized and their structural properties have been investigated. Coordination compounds of lanthanides [Ln(HL)₂NO₃]·i-PrOH (Ln = Eu³⁺, Tb³⁺) were obtained for the first time, isolated in the individual state and characterized by means of IR and NMR spectroscopies, electrospray ionization mass spectrometry (ESI-MS), potentiometric titration, and elemental, thermal gravimetric and X-ray diffraction analyses. It was shown that H₂L behaves like a scorpionate type ligand and in a mono-deprotonated form coordinates in a tridentate manner via the oxygen atoms of phosphoryl and carbonyl groups with formation of a mononuclear metal complex. The protonation constants of H₂L and stability constants of Eu³⁺ and Tb³⁺ complexes have been determined. According to the results of X-ray diffraction analysis the H₂L and [Ln(HL)₂NO₃]·i-PrOH molecules have monomeric structure but NaHL is a dimer. The Hirshfeld surface and fingerprint plots of the compounds have been used to analyze various hydrogen bonds and intermolecular interactions displayed in the crystal structure.