Syntheses, crystal structures, and properties of new metal--5-bromonicotinate coordination polymers.

Four metal–5-bromonicotinate (Brnic) coordination polymers [Fe(Brnic) 2 (H 2 O) 2 ] n ( 1 ), [Ni(Brnic) 2 ] n ( 2 ), [Ni(Brnic)(bpy)(H 2 O) 2 ] n · n (Brnic)·4.5 n H 2 O ( 3 ), and [Co 2 (Brnic) 3 (bpy) 2 (OH)] n · n H 2 O ( 4 ) have been synthesized and structurally characterized (bpy=4,4′-bipyridine). Complex 1 has corrugated (4,4) sheets formed by μ-Brnic ligands and planar nodes Fe(II). As for 2 – 4 , they all built up from Brnic-bridged dinuclear subunits, but have very different structure features. Complex 2 is a twin-like polymer with (4,4) layers formed by twin paddle-wheel [Ni 2 (Brnic) 4 ] subunits. Through the bridge coordination of bpy ligands with dinuclear rings [Ni 2 (Brnic) 2 ] and trigons [Co 2 (Brnic) 3 (OH)], 6 3 -topological cationic layers with nanosized grids of 3 and chiral ladder-type double chains of 4 formed, respectively. Notably, halogen-related interactions play an important role in the formation of 3D metallosupermolecules 1 – 4 . The thermostabilities of all compounds have been discussed in detail. Moreover, the magnetic investigations of 2 and 4 indicate that there exist antiferromagnetic interactions in the paddle-wheel [Ni 2 (Brnic) 4 ] and trigon [Co 2 (Brnic) 3 (OH)] cores, respectively. [ABSTRACT FROM AUTHOR]