The syntheses, structures, and magnetic properties of two mononuclear manganese(II) complexes involving in situ hydrothermal decarboxylation

Two new mononuclear compounds [Mn(3-Br-pydc)(H2O)(3)] (1) and {[Mn(5-Br-pyc)(bipy)(H2O)(Cl)]center dot 2H(2)O (2) (3-Br-H(2)pydc = 3-Br-pyridine-2,6-dicarboxylic acid, 5-Br-Hpyc = 5-Br-pyridine-2-carboxylic acid, bipy = 2,2'-bipyridine) have been synthesized by traditional solution reaction and hydrothermal reaction, respectively. In both compounds, the Mn" center is six-coordinated in a distorted octahedral geometry, formed by one tridentate chelate 3-Br-pydc dianion and three water molecules in 1, while the coordination sphere consists of one bidentate chelate 5-Br-pyc anion, one bipy, one water molecule, and one chloride anion in 2 (MnNO5 for 1 and MnN3O2Cl for 2). O-H center dot center dot center dot O hydrogen bonds, Br center dot center dot center dot O halogen bonds, and/or pi-pi stacking assist in the construction of the three-dimensional (3D) network structures of 1 and 2. Notably, the 5-Br-Hpyc ligand was generated in situ by decarboxylation of the 3-Br-H(2)pydc precursor under hydrothermal conditions. Variable-temperature magnetic susceptibility data in the 2-300 K temperature range indicate weak antiferromagnetic coupling in both 1 and 2.