Spin-Canted Antiferromagnetic Ordering in Transition Metal-Organic Frameworks Based on Tetranuclear Clusters with Mixed V- and Y-Shaped Ligands.

Four transition metal-organic frameworks were solvothermally synthesized with V-shaped 1,3-bis(1-imidazolyl)benzene (bib) and two Y-shaped carboxylate ligands (1,3,5-benzenetricarboxylic acid (H3btc) and 3,5-pyridinedicarboxylic acid (H2pydc)), namely, {[M2(μ3-OH)(bib)(btc)]·H2O} n (M = Co (1) and Fe (2)) and {[M'2(μ3-OH)(μ2-NO3)(bib)(pydc)]·solvents} n (M' = Co (3) and Ni (4)). All of them are characterized by single-crystal X-ray diffraction, infrared spectrosopy, and powder X-ray diffraction. Both complexes 1 and 2 present two-dimensional (3,8)-connected layer structures, and the point symbol is (3.4²)2(34.46.56.68.7³.8), but Fe2 in 2 is weakly coordinated to O5 as a trigonal bipyramidal geometry compared with the tetrahedral Co2 in 1, while complexes 3 and 4 exhibit three-dimensional "pillar-layer" structures with (3,8)-connected tfz-d net. Interestingly, nitrate anions with a rare μ2-η² coordination mode take part in coordination, and rectangular channels along the c axis exist in 3 and 4. Magnetic studies indicate that 1 and 2 present antiferromagnetic behaviors, while 3 and 4 show the coexistence of spin-canting and long-range magnetic ordering. [ABSTRACT FROM AUTHOR]