Synthesis, structure, and magnetic properties of lanthanide(III) complexes incorporating a tris-chelate cobalt(III) complex as a metalloligand

Abstract

A series of Co^III–Ln^III–Co^III trinuclear complexes [Ln{Co(Hmtimn)₃}₂](NO₃)₃ were prepared by following a simple one-pot synthesis method, mixing an unsymmetrical bidentate ligand 2-(2-imidazolinyl)-6-methoxypheol (H₂mtimn) with Co(NO₃)₂·6H₂O and LnX₃· 6H₂O (where Ln = La, Ce, Pr, Nd, Gd or Dy and X = NO₃⁻ or Cl⁻) in methanolic solution in the presence of triethylamine in air. In the reaction mixture, this leads to the in situ formation of a tris-chelate Co^III metalloligand unit, which can coordinate Ln^III ions through the interactions of phenolato- and methoxy-O donors. X-ray structural analysis revealed that the Co^III metalloligand functions as a rigid tripodal ligand to coordinate to a Ln^III ion by six oxygen donors. The two metalloligands in the complex exhibit homochiral aggregation (ΔΔ or ΛΛ) upon coordination to the Ln^III ion. The coordination of the central Ln^III ion was found to be a distorted icosahedral geometry. Magnetic susceptibility measurements reveal that both cobalt and central lanthanide ions exist in trivalent states.

Keywords:

• Heteronuclear complex
• Lanthanides
• Co^III Metalloligand
• One-pot synthesis
• Single-crystal X-ray analysis
• Magnetic measurements

Supplementary material

Crystallographic data for all the compounds have been deposited with the Cambridge Crystallographic Data Centre, CCDC No. 2327919–2327925. These data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/, or from the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: [phone]; or E-mail: [email protected]. The supporting material includes tables of crystallographic data, table of continuous shape measurements by using SHAPE 2.1 program, room temperature FT-IR spectra, UV-visible spectra in DMSO, ¹H NMR spectra of mer-[Co(Hmtimn)₃], Co₂La and Co₂Eu complexes in DMSO-d₆, molecular structure of all the complexes, powder XRD pattern of Co₂Ce and Co₂Nd compounds, hydrogen bonding interactions of all the complexes, the field dependence of magnetization curves for all compounds except for Co₂La, and thermogravimetric analysis for all compounds.

Acknowledgement

We thank Prof. Yuji Kikukawa (Kanazawa University) for helping with powder XRD measurements. The crystallographic and magnetic measurements were conducted at the Institute of Molecular Science, supported by ARIM of the MEXT (Project JPMXP1223MS1015).

Disclosure statement

The authors declare that they have no conflicts of interest.

Additional information

Funding

This study was supported by a Grant-in-aid for Scientific Research No. 19K15525 from MEXT, Japan.