Field-Induced Slow Magnetic Relaxation in Co II Cyclopropane-1,1-dicarboxylates.

New Co II substituted malonate field-induced molecular magnets {[Rb 6 Co 3 (cpdc) 6 (H 2 O) 12 ]∙6H 2 O} n ( 1 ) and [Cs 2 Co(cpdc) 2 (H 2 O) 6 ] n ( 2 ) (where cpdc 2- stands for cyclopropane-1,1-dicarboxylic acid dianions) were synthesized. Both compounds contain mononuclear bischelate fragments {Co II (cpdc) 2 (H 2 O) 2 } 2 - where the quasi-octahedral cobalt environment (CoO 6 ) is complemented by water molecules in apical positions. The alkali metal atoms play the role of connectors between the bischelate fragments to form 3D and 2D polymeric structures for 1 and 2 , respectively. Analysis of dc magnetic data using the parametric Griffith Hamiltonian for high-spin Co II supported by ab initio calculations revealed that both compounds have an easy axis of magnetic anisotropy. Compounds 1 and 2 exhibit slow magnetic relaxation under an external magnetic field (H DC = 1000 and 1500 Oe, respectively).