Multidimensional molecular-based magnets are the focus of considerable current research effort from both fundamental and device-related perspectives. [1] Two-or three-dimensional (2-D, 3-D) homometallic magnetic systems can behave as ferromagnetic, antiferromagnetic, or as metamagnetic materials depending on the nature of the spin coupling. [1b, 2] However, an example of a 3-D homometallic system with ferrimagnetic behavior has not yet been reported because the conditions for the noncompensation of the individual spin moments are difficult to achieve in these systems. In this communication we report the synthesis, crystal structure, and magnetic behavior of a 3-D homometallic ferrimagnet that orders magnetically at 6 K. To the best of our knowledge, this is the first 3-D homometallic molecular ferrimagnet.
Hydrothermal treatment of Ni(NO 3 ) 2 ยฅ 6 H 2 O with disodium fumarate (Na 2 (CO 2 CH CHCO 2 ); Na 2 (fum)) in water at 170 8C leads to the formation of the complex [Ni 3 (fum) 2 -(m 3 -OH) 2 (H 2 O) 4 ] n ยฅ (2 H 2 O) n 1. The X-ray analysis shows a 3-D structure [3] formed by chains of fused Ni II octahedral units. These chains, in which all the metal atoms are coplanar, include two crystallographically independent ions: A symmetry related pair Ni(1) and Ni(1') separated by 3.017(1) รค that alternates with Ni(2), located on a center of symmetry. The Ni(1)รNi(2) and Ni(1')รNi(2) distances are 3.661(1) and 3.557(1) รค, thus forming a figure close to an isosceles triangle. The three metal atoms share an edge of their octahedron, being capped by the hydroxyl oxygen O(5), alternatively above and below the chain but slightly displaced by 0.55 รค (Figure 1). The fumarate carboxylate groups bridge the longest edges of the metal triangle, completing the coordination sphere of Ni(2), whereas the hexacoordination about
[*] Prof.