Tetradecanuclear {Ni ₉ Ln ₅ } Clusters Featuring Encapsulated {Ln ₅ } Trigonal Bipyramids: Modular 3 d ‐4 f Architectures With Broad‐Range Magnetocaloric Response

The solvothermal reaction between Ni(HCOO) 2 . 2H 2 O, 2‐aminoisobutyric acid (aibH), Ln(OAc) 3 ·4H 2 O (Ln = Gd, Y, Dy) and NEt 3 in MeOH/MeCN affords the tetradecanuclear [Ni 9 Ln 5 (OH) 9 (aib) 12 (OAc) x (ΗCOO) y ] . 12MeCN complexes (Ln = Gd, x = 6, y = 6, 1 . 12MeCN; Ln = Y, x = 6, y = 6, 2 . 12MeCN; Ln = Dy, x = 3, y = 9, 3 . 12MeCN) in good yields. All three clusters are isostructural, featuring a trigonal bipyramidal {Ln 5 } core encapsulated within a triply edge‐capped {[Ni II 3 ]Ni II 6 } trigonal prism. Magnetic measurements reveal dominant ferromagnetic intermolecular interactions in the Gd and Dy analogues, whereas the Y derivative exhibits weak antiferromagnetic behavior. Magnetothermal and heat‐capacity measurements for 1 . 12MeCN indicate a significant magnetocaloric effect, reaching −∆ S m = 28.1 J kg −1 K −1 for full demagnetization from B = 7 T at T = 3.9 K, while sustaining large −∆ S m ( T ,∆ B ) and ∆ T ad ( T ,∆ B ) responses across an unusually broad temperature range.