| Abstract |
Three heterometallic Fe(6)Ln(4) clusters were self-assembled by using N-methyldiethanolamine (H(2)mdea) and 3,5-dinitrobenzoic acid (Hdnbz) as principal building blocks and azide as an ancillary ligand. The obtained products 1-3 were isolated as air-stable microcrystalline solids and fully characterized. Single-crystal X-ray diffraction studies reveal similar type of molecular units [Fe(6)Ln(4)(mu(4)-O)(2)(mu(3)-OH)(2)(mdea)(6)(dnbz)(8)(N-3)(4)]center dot 2MeCN center dot xH(2)O center dot CH2Cl2 \Ln = Y (1), Gd (2), Dy (3); x = 4, 6, 10, respectively\. Topological analysis of 1-3 was performed following a method for high nuclearity coordination clusters. The [Fe(6)Ln(4)(mu-O)(10)(mu(3)-O)(4)(mu(4)-O)(2)] cores were identified in all structures and further simplified to graph topological skeletons, which were classified as pentanodal 2,3,3,5,6-connected motifs with the unique topology. The magnetic behavior of 1-3 was investigated in detail. The magnetic studies and magnetocaloric measurements reveal that the tetranuclear gadolinium centers of 2 exhibit a high cryogenic magnetocaloric effect (MCE) that reaches 13.66 J.kg(-1).K-1 (25.18 mJ.cm(-3).K-1) for Delta H = 90 kOe at 4.5 K. Among all the compounds, only 3 shows the ac-signals (ac, alternating current) and slow-relaxation behavior, which is a peculiar characteristic of a single-molecule magnet (SMM), giving a value of U-eff = 19.5(4) K. The present work thus contributes to the design of topologically unique discrete crystalline materials with notable functional properties. |
