A new family of decanuclear Ln 7 Cr 3 clusters exhibiting a magnetocaloric effect.

Two dimeric Ln-Cr clusters with formula {Ln(H 2 O) 8 [Ln 6 Cr 3 (L) 6 (CH 3 COO) 6 (μ 3 -OH) 12 (H 2 O) 12 ]}·(ClO 4 ) 6 · x H 2 O (Ln = Gd, x = 35 for 1 and Ln = Dy, x = 45 for 2, HL = 2-pyrazinecarboxylic acid) were obtained by a ligand-controlled hydrolytic method with a mixed ligand system (2-pyrazinecarboxylic acid and acetate). Single crystal structure analysis showed that two trigonal bipyramids of [Gd 3 Cr 2 (μ 3 -OH) 6 ] 9+ worked as building blocks in constructing the metal-oxo cluster core of [Gd 6 Cr 3 (μ 3 -OH) 12 ] 15+ by sharing a common top - a Cr 3+ ion. Additionally, compound 1 forms a three-dimensional framework with a one-dimensional nanopore channel along the a -axis through a hydrogen-bond interaction between the cationic cluster core and the free mononuclear cation [Gd(H 2 O) 8 ] 3+ and the π-bond interactions of the pyrazine groups on the two cationic cluster cores. Magnetic calculations indicated a weak ferromagnetic coupling interaction for Gd⋯Gd and Gd⋯Cr in compound 1, with its magnetic entropy change (-Δ S m ) reaching 21.1 J kg -1 K -1 at 5 K, 7 T, while compound 2 displayed an obvious frequency-dependency at H dc = 2000 Oe.