Since the first discovery of phthalocyanine terbium double-decker complexes (Tb(Pc)₂) as organic single-molecule magnets (SMMs) having high blocking temperature in 2004; double-decker complexes of lanthanide ions and tetrapyrrole ligands have attracted much attention.¹ Recently, Tb(Pc)₂ complexes were applied to spintronic devices due to their excellent properties. We have reported previously that the SMM property of porphyrin terbium double-decker complexes (Tb(Por)₂) can be switched ON/OFF by the absence/presence of a proton or a hydrogen. Asymmetrical protonated forms (Tb(PorH)(Por)) do not exhibit SMM property, while symmetrical deprotonated anionic forms (Tb(Por)₂^-) show prominent SMM character.^2,3 

Herein, we report about fused-porphyrin terbium complexes having two or more terbium ions and several porphyrin cores as ligands. Since these complexes have more than two protons, they have more diversity in electronic structures than single core complexes. We have successfully synthesized fused-porphyrin terbium triple-decker complexes ([Tb₂]) in protonated form (diprotonated-[Tb₂]), anionic form (dianionic-[Tb₂]), and radical form (biradical-[Tb₂]). The structural, spectroscopic and magnetic properties of these complexes were evaluated to show unique character of these complexes. The biradical-[Tb₂] has extraordinarily small energy gap (~2700 nm). Switching of SMM property by the presence and absence of protons was also confirmed in [Tb₂]. The relatively high blocking temperature of dianionic-[Tb₂] could be attributed to its highly symmetrical molecular structure. In addition, SMM property of biradical-[Tb₂] was almost similar to that of radical-Tb(TPP)₂, which will enable highly conductive SMM wire of terbium multiple-decker complex ie. [Tb₄], because of the small energy gap.

References

1) Ishikawa, N.; Sugita, M.; Tanaka, T.; Ishikawa, T.; Koshihara, S.; Kaizu, Y. Inorg. Chem. 2004, 43, 5498.

2) Tanaka, D.; Inose, T.; Tanaka, H.; Lee, S.; Ishikawa, N.; Ogawa, T. Chem. Commun. 2012, 48, 7796.

3) Inose, T.; Tanaka, D.; Tanaka, H.; Ivasenko, O.; Nagata, T.; Ohta, Y.; Feyter, S. D.; Ishikawa, N.; Ogawa, T. Chem. Eur. J. 2014, 20, 11362.