Novel quadruple-stranded heterometallic Ln2Na complexes hosting sodium ions inside the cryptand-like cavity

Abstract

Coordination compounds of lanthanides NEt₄[NaLn₂L₄(H₂O)], Na[NaLn₂L₄(H₂O)]·2H₂O (Ln = La³⁺, Nd³⁺) with the bis-chelating carbacylamidophosphate ligand tetramethyl N,N′-(2,2,3,3,4,4-hexafluoro-1,5-dioxopentane-1,5-diyl)bis(phosphoramidate) (H₂L) were obtained for the first time via reactions of Na₂L with lanthanide nitrates. The complexes were characterized by IR and NMR spectroscopy and laser desorption/ionization mass spectrometry. From X-ray diffraction analysis, it was established that the complex anions in the obtained compounds have a structure of a quadruple-stranded helicate, which encapsulates a sodium cation and a molecule of water into the negatively charged environment of the ligand fluorine and carbonyl oxygen atoms. Upon excitation by the 266 nm harmonic line of the Nd:YAG pulsed laser, the NEt₄[NaNd₂L₄(H₂O)] complex exhibits IR-emission at 300 and 77 K with the ⁴F_3/2 emission lifetime of 2 μs.