Triply bridged binuclear lanthanides-Zwitterion complexes: synthesis and characterization of (Gd(III), Nd(III), Sm(III)) complexes

Abstract

2,2'-((1E,1'E)-(Butane-1,4-diylbis (azanylylidene))bis (methanylylidene)) diphenol zwitterion (L) (4′) was prepared by treatment of two equiv. of (3-(2-furyl)acrolein) (1) with one equiv. of 1,4-butanediamine (2) in refluxing ethanol through an intramolecular Diels-Alder reaction. Three new lanthanide compounds based on (4′), [Ln₂(NO₃)₄(H₂O)₂L₃]·2NO₃ (5) (a, Ln = Gd; b, Ln = Nd; c, Ln = Sm), have been obtained and further characterized by elemental analysis, conductivity, magnetic measurements, FT-IR, powder X-ray and thermogravimetric analysis. Compounds 5a–c exhibit a discrete dinuclear structure constructed by three ligands coordinating two Ln³⁺ ions. The oxygen atoms of the diphenol are involved in the coordination of 5, while the nitrogen atoms of the imines are not involved. Hypersensitive transitions could be observed at 877, 807, 753, 588, and 522 nm in the UV–visible absorption spectrum of the neodymium complex 5 b, corresponding to ⁴I_9/2→⁴F_3/2 (877 nm); ⁴I_9/2→⁴F_5/2, ²H_9/2 (807 nm); ⁴I_9/2→⁴S_3/2, ⁴F_7/2 (753 nm); ⁴I_9/2→²G_7/2, ⁴G_5/2 (588 nm); ⁴I_9/2→⁴G_9/2 ⁴G_7/2, and ²K_13/2 (522 nm), respectively. Emission spectra of the ligand and its samarium complex 5c revealed characteristic luminescence within the visible region with the emission of the samarium complex being relatively red shifted.

Graphical Abstract

Keywords:

• Lanthanide complexes
• synthesis
• characterization
• schiff base
• Zwitterion

Acknowledgement

The authors are grateful to Deanship of Scientific Research at Al-Hussein Bin Talal University– Jordan for funding this work through the (Research Project No. 432/2018).

Disclosure statement

The authors claimed to have no possible conflicts of interest.