Synthesis,crystal structure and magnetism of a 1-D polymeric manganese(II) complex with pyrazine-2-carboxylate as bridging ligand

A one-dimensional chain complex {[Mn(pyz)(SCN)(H₂O)₂] · H₂O} (pyz = pyrazine-2-carboxylic anion) has been synthesized and its crystal structure determined by X-ray crystallography. In the complex each Mn ion is located in a distorted octahedral environment with two oxygen atoms O(3), O(4) from terminal ligands of two water molecules, another oxygen atom O(1) from the carboxylate group of pyz, and three nitrogen atoms N(1), N(2A) from two different pyz units and N(3) from the terminal ligand thiocyanate anion, in which a chelated five-membered ring is formed by coordination of O(1) and N(1) to the Mn(1) atom. Thus, an infinite zigzag chain consisting of Mn and pyz is constructed and the chains are linked together by hydrogen bonding from coordinated and uncoordinated water molecules, the sulfur atom of thiocyanate and the carboxylate oxygen of pyz. The variable-temperature magnetic susceptibility of the complex was measured in the 4–300 K range. The magnetic coupling parameter is consistent with an antiferromagnetic exchange between the two manganese(II) centers and the data fit a binuclear magnetic exchange model based on the Hamiltonian operator (H = –2JS₁S₂, S₁ = S₂ = 5/2), giving the antiferromagnetic coupling parameter of 2J = –0.17 cm^–1. This is the first pyrazine-2-carboxylic anion bridging complex dealing with the magnetic interaction study.