A new family of decanuclear Ln7Cr3 clusters exhibiting a magnetocaloric effect

Two dimeric Ln-Cr clusters with formula {Ln(H2O)(8)[Ln(6)Cr(3)(L)(6)(CH3COO)(6)(mu(3)-OH)(12)(H2O)(12)]}center dot(ClO4)(6)center dot xH(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 [Gd3Cr2(mu(3)-OH)(6)](9+) worked as building blocks in constructing the metal-oxo cluster core of [Gd6Cr3(mu(3)-OH)(12)](15+) by sharing a common top - a Cr3+ 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(H2O)(8)](3+) and the pi-bond interactions of the pyrazine groups on the two cationic cluster cores. Magnetic calculations indicated a weak ferromagnetic coupling interaction for GdMIDLINE HORIZONTAL ELLIPSISGd and GdMIDLINE HORIZONTAL ELLIPSISCr in compound 1, with its magnetic entropy change (-Delta 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.

Automated summary

Two dimeric Ln-Cr clusters were synthesized using a ligand-controlled hydrolytic method, revealing their core structures through single crystal structure analysis. Compound 1 forms a three-dimensional framework with a one-dimensional nanopore channel, while compound 2 displays frequency-dependency under a direct current magnetic field of 2000 Oe.