Magnetocaloric Properties of Heterometallic 3d-Gd Complexes Based on the [Gd(oda)3]3− Metalloligand

• Published in: Chemistry : a European journal 2016-01, Vol.22 (2), p.802-808
• Main Authors: Qiu, Jiang-Zhen, Wang, Long-Fei, Chen, Yan-Cong, Zhang, Ze-Min, Li, Quan-Wen, Tong, Ming-Liang
• Format: Article
• Language: English
• Subjects: Anisotropy; carboxylate ligands; Chemistry; Chromium; Cobalt; Coordination compounds; Copper; Heat; heterometallic complexes; Iron; lanthanides; Magnetic properties; Manganese; Mathematical analysis; Metal ions; Nickel; Samarium; transition metals; Zinc
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201503796

A series of heterometallic 3d–Gd3+ complexes based on a lanthanide metalloligand, [M(H2O)6][Gd(oda)3]⋅3 H2O [M=Cr3+ (1‐Cr)] (H2oda=2,2′‐oxydiacetic acid), [M(H2O)6][MGd(oda)3]2⋅3 H2O [M=Mn2+ (2‐Mn), Fe2+ (2‐Fe) and Co2+ (2‐Co)], and [M3Gd2(oda)6(H2O)6]⋅12 H2O [M=Ni2+ (3‐Ni), Cu2+ (3‐Cu), and Zn2+ (3‐Zn)], are reported. Magnetic and heat‐capacity studies revealed a significant impact on the magnetocaloric effect depending on the anisotropy of the 3d transition metal ions, as confirmed by comparison of the observed maximum values of −ΔSm between complexes 2‐Co and 1‐Cr. In these two complexes, the 3d metal ions have the same spin (S=3/2 for Co2+ and Cr3+ ions), and the theoretical calculation suggested a larger −ΔSm value for 2‐Co (47.8 J K−1 kg−1) than 1‐Cr (37.5 J K−1 kg−1); however, the significant anisotropy of Co2+ ions in 2‐Co, which can result in smaller effective spins, gives a smaller value of −ΔSm for 2‐Co (32.2 J K−1 kg−1) than for 1‐Cr (35.4 J K−1 kg−1) at ΔH=9 T. Cool magnets: A series of heterometallic 3d–Gd3+ complexes based on the [Gd(oda)3]3− (H2oda=2,2′‐oxydiacetic acid) metalloligand (see figure) are reported. According to the magnetic entropy changes of the complexes, obtained independently from magnetization and heat‐capacity date, besides a high spin value, the use of isotropy 3d metal ions like Cr3+, Fe3+ and Mn2+, also plays an important role for obtaining heterometallic magnetic coolants with large magnetocaloric effect.