Two Metal–Organic Frameworks Constructed from One-Dimensional Cobalt(II) Ferrimagnetic Chains with Alternating Antiferromagnetic/Ferromagnetic and AF/AF/FM Interaction: Synthesis, Structures, and Magnetic Properties

Here, we report two three-dimensional metal–organic
frameworks
of formula [Co2(4-ptz)2(bpp)­(N3)2]n (1) and [Co3(OH)2(bdt)2(bpp)2(H2O)2]n (2), which were synthesized by hydrothermal
reaction from the respective tetrazole ligand (5-(4-pyridyl)­tetrazole
(4-H-ptz) for 1 and 5,5′-(1,4-phenylene)­bis­(1-H-tetrazole) (H2bdt) for 2), long
and flexible pyridyl-containing ligand 1,3-bi­(4-pyridyl)­propane (bpp),
NaN3, and CoCl2. Both 1 and 2 consist of well-isolated one-dimensional cobalt­(II) alternating
chains further linked by the bpp and/or the tetrazole ligand, while
their chain structures are totally different. The chains of 1 are formed by Co2+ ions bridged by single μ-EE-N3 and triple (μ-EO-N3)­(μ-tetrazole)2 alternately, whereas the Co2+ ions are bridged
by μ3–OH to form Co3(OH)2 chains in compound 2. Magnetic measurements demonstrate
that compound 1 contains an alternating antiferromagnetic
(AF)/ferromagnetic (FM) ferrimagnetic chain, while compound 2 exhibits the coexistence of spin canting, slow magnetic
dynamics, and finite-size effect, with alternating AF/AF/FM ferrimagnetic
chains.