Hydrothermal syntheses, structures and properties of three cyclic tetranuclear complexes and one 1D chain complex with 3,5-dinitrosalicylate

Abstract

The hydrothermal reactions of Co(OAc) 2 · 4H 2O, 3,5-dinitrosalicylate (3,5-(NO 2) 2sal) and 2,2′-bipyridine (2,2′-bipy) with different reaction periods give metallamacrocycles 1 and 2 with the same chemical formula Co 4(2,2′-bipy) 4{3,5-(NO 2) 2sal} 4. Replacing Co(OAc) 2 · 4H 2O with Zn(NO 3) 2 · 6H 2O, using the same synthetic procedures, results in the formation of compound [Zn(2,2′-bipy){3,5-(NO 2) 2sal}] n ( 3) with a 1D chain structure and the metallamacrocycle compound Zn 4(2,2′-bipy) 4{3,5-(NO 2) 2sal} 4 ( 4). Compounds 1 and 2 crystallize as two different polymorphs of cyclic tetranuclear compounds. Compounds 3 and 4 are polymorphic too. The compounds 1 and 4 are isomorphous. The weak coordination interactions have significant influence on the spacial orientations of the 3,5-(NO 2) 2sal ligand, and may affect the crystallization processes. There are antiferromagnetic interactions in the cyclic tetranuclear cobalt(II) compounds 1 and 2. Compound 3 exhibits weak fluorescent emission in the solid state at room temperature.