Self-Assembled Cationic Heterochiral Honeycomb-Layered Metal Complexes with the in Situ Generated Pyrimidine-2-carboxylato Bisdidentate Ligand. Hydrothermal Synthesis, Crystal Structures, Magnetic Properties, and Theoretical Study of [M₂(μ-pymca)₃]OH·H₂O (M = Fe<sup

The hydrothermal reaction of 2-cyanopyrimidine and either CoCl2·6H2O or FeCl2·4H2O affords 2D isostructural coordination polymers [M2(μ-pymca)3]OH·H2O ((M = CoII (1) and FeII (2) pymca = pyrimidine-2-carboxylato). The bisdidentate ligand (pymca) that can be considered an intermediate between bipyrimidine and oxalato is generated in situ from the hydrolysis of 2-cyanopyrimidine. The structure of 1 and 2 consists of heterochiral (6,3) honeycomb layers, crystal water molecules, and OH- anions, the latter playing a template and balancing charge role in the structure. Both compounds exhibit antiferromagnetic interactions between metal ions through the pyrimidine-2-carboxylate bridging ligand. Compound 1 is a spin-canted antiferromagnet leading to weak ferromagnetism at Tc < 10 K with a coercitive field of 580 Oe, whereas compound 2 is an antiferromagnet with TN = 21 K. Fit of the variable-temperature magnetic susceptibility data of 2 to the empirical equation for a regular honeycomb with S = 1 derived from Monte Carlo simulations leads to the following parameters: J = −4.57(2) cm-1 and g = 2.300(4). Density functional calculations have been used to explain the magnetic coupling in 2.