Three-dimensional 3d–4f hetero-bimetallic coordination polymers through hydrogen bonds: synthesis, structures and mössbauer spectrum analysis

Abstract

Four cyano-bridged 3d–4f hetero-bimetallic Ln(III)–Fe(III) assemblies, {[Ln(DMF)₄(H₂O)₃(µ-CN)Fe(CN)₅]· H₂O} _n (Ln = Ce (1), Nd (2), Sm (3) and Gd (4); DMF = N,N-dimethylformamide), have been synthesized. X-ray crystallographic analysis of both 3 and 4 reveals three-dimensional network structures resulting from hydrogen bonds in the crystals. With respect to the coordination number on Sm(III) atoms, 3 is different from previously reported structures. Structural comparison indicates that the differences in magnetic properties between 3 and 4 do not derive from structural factors. Mössbauer spectra at both 298 and 10 K reveal that the characteristic quadrupole splitting for low-spin Fe(III) ions (S = 1/2) remains unchanged, indicating that the spin state of Fe(III) ions in 1–4 is not affected by temperature. The magnetic anisotropy derived from the ground states of Ln(III) ions with odd 4f ⁿ electrons (n = 1, 3, 5 and 7), ²F_5/2,⁴I_9/2, ⁶H_5/2 and ⁸S_7/2 for Ce(III), Nd(III), Sm(III) and Gd(III), respectively, dominates the exchange interaction in the Ln(III)–NC–Fe(III) systems.

Keywords:

• Synthesis
• Crystal structures
• Mössbauer spectra
• 3d–4f complex
• Cyano-bridged

Acknowledgments

This work was supported by Grant-in-Aid for Scientific Research on Priority Areas (417) and for the 21st century COE program “Keio Life Conjugate Chemistry” from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan.