Three-Dimensional Co- and Mn-MOFs Containing a C_2h-Symmetric Terphenyl-3,3′-dicarboxylate Linker and Their Magnetic Properties

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• 作者：Hyun-Chul Kim ; Ja-Min Gu ; Youngmee Kim ; Do Nam Lee and Seong Huh
• 刊名：European Journal of Inorganic Chemistry
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：2016
• 期：30
• 页码：4891-4897
• 全文大小：1900K
• ISSN：1099-0682c

文摘

We report herein two new isostructural, three-dimensional (3D) MOFs with the general formula [M(3,3′-tpdc)(dmf)] [M = Co^II (I), Mn^II (II)] resulting from the assembly of a metal ion and the C_2h-symmetric ditopic bridging ligand terphenyl-3,3′-dicarboxylate (3,3′-tpdc). Both isostructural MOFs crystallize in the monoclinic space group C2/c. The metal ion is coordinated by four O_carboxylate (η¹:η¹:µ₂) and two µ₂-O_dmf atoms in a distorted octahedral geometry. The metal centers are interconnected through bridging 3,3′-tpdc and dmf ligands to form a 1D chain. The resulting 1D metal chains are further interconnected by 3,3′-tpdc ligands to form 3D frameworks without porosity. The thermolabile dmf bridging ligands were easily removed by heating at 180 °C under vacuum for 5 h. The activated MOFs I and II exhibited very low gas uptake of N₂, CO₂, and H₂ after removal of the dmf bridging ligands. The encapsulation of iodine guest molecules by the activated I and II was also investigated. The crystal structure of iodine-encapsulated II was also elucidated. The coordination environment of the Mn^II atom in II changed as a result of the loss of dmf bridging ligands. The as-prepared MOFs I and II exhibit weak antiferromagnetic interactions in their 1D metal chains; these magnetic interactions should mainly occur between the metal ions bridged by the short carboxylate-based ligand and dmf oxygen atoms. Thermal removal of the bridging dmf molecules led to a change in the Mn···Mn distances in the 1D chains of II that also affected its magnetic properties.