Ferromagnetic coupling between 4f- and delocalized π-radical spins in mixed (phthalocyaninato)(porphyrinato) rare earth double-decker SMMs. Issue 8 (16th July 2019)

• Record Type: Journal Article
• Authors: Yang, Liguo; Wang, Xin; Zhu, Mengliang; Xiao, Tongtong; Ouyang, Zhongwen; Bian, Yongzhong; Wang, Zhenxing; Jiang, Jianzhuang
• Is Part Of: Inorganic chemistry frontiers. Volume 6:Issue 8(2019)
• Page Start: 2142
• Page End: 2147
• Publication Date: 2019-07-16
• Subjects: Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c9qi00595a
• Languages: English
• ISSNs: 2052-1553

Abstract

Abstract : Ferromagnetic π–f exchange couplings were revealed in [RE III (Pc)(Por)] 0 SMMs (RE = Tb and Dy) by HF-EPR measurements. Abstract : Mixed (phthalocyaninato)(porphyrinato) rare earth double-decker complexes M III (Pc)(TNP) (M = Tb (1 ), Dy (2 ), and Y (3 ); Pc = phthalocyaninate; TNP = tetranaphthylporphyrinate) were synthesized and characterized by elemental analysis and a range of spectroscopic methods. They represent the first examples of double-decker rare earth complexes containing a tetranaphthylporphyrin ligand. The neutral radical state of1–3 was revealed by electronic absorption measurements, as indicated by the characteristics involving the semi-occupied molecular orbitals (SOMOs). The IR spectra show a marker band of a phthalocyanine radical anion (Pc˙ − ) at 1312–1314 cm −1, suggesting the high population of a π-radical electron on the Pc ring in the double-decker complexes1–3 . The magnetic behavior of both1 and2 features a slow relaxation of magnetization at low temperature under a zero direct current field, demonstrating the SMM nature of such lanthanide–radical systems. In particular for Dy III (Pc)(TNP) (2 ), the quantum tunneling of magnetization (QTM) was suppressed at an applied direct current (dc) field of 2000 Oe, leading to the extraction of an effective energy barrier of U eff = 15.5 cm −1 (22.3 K) and τ 0 = 7.74 × 10 −7 s. The magnetic exchange couplings were analysed by means of high-frequency electron paramagnetic resonance (HF-EPR) measurements. The results clearly show the ferromagnetic exchange coupling between 4f- and delocalized π-radical spins in Tb III (Pc)(TNP) (1 ) and Dy III (Pc)(TNP) (2 ), with exchange coupling constants ( J Ln-rad ) of 3.43(10) and 2.74(10) cm −1, respectively.