Two coordination polymers based on conjugated pyrazine aromatic carboxylic acid ligands: Structural and magnetic research.

• Two 3D coordination polymers based on the 5-(pyrazin-2-yl) isophthalic acid ligand have been purposefully synthesized by solution-diffusion synthesis method. • Studies of magnetic properties show that compounds 1 and 2 have weak antiferromagnetic behavior. • The TGA reveals that compounds 1 and 2 possess a better thermal stability. Two new coordination polymers [M(L)(H 2 O) 2 ] n (M=Co (1) and Mn (2)) (H 2 L=5-(pyrazin-2-yl) isophthalic acid) were synthesized by hydrothermal method and systematically characterized. The two compounds were analyzed in depth by x-ray single crystal diffraction, elemental analysis, IR spectroscopy, PXRD and thermal analysis. The x-ray single crystal diffraction results indicate that compound 1 is a 3D framework structure. Through the carboxyl oxygen atoms and pyrazine nitrogen atoms on different L2− ligands, two interesting infinitely extended right helix chains are formed along the c -axis, and the two helix chains are combined to form a 3D framework structure of 1. In compound 2 , the adjacent Mn2+ is bridged with four carboxyl oxygen groups in the ligand to form a binuclear structure unit {Mn 2 O 4 }. Each {Mn 2 O 4 } is linked to six organic ligands, and each ligand is linked to three {Mn 2 O 4 }, which together form a (3,6) linked 3D coordination polymer material. It is noteworthy that the interconnections between the layers form a lantern-like structure when viewed from the b -axis direction. Additionally, compounds 1 and 2 demonstrated temperature-dependent magnetic susceptibility (dc) and negative values of θ (equal to -10.59 K and -6.38 K), which are indicates the presence of weak antiferromagnetic interactions in both compounds 1 and 2. [Display omitted] [ABSTRACT FROM AUTHOR]