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

The hydrothermal reactions of Co(OAc)2 · 4H2O, 3,5-dinitrosalicylate (3,5-(NO2)2sal) and 2,2′-bipyridine (2,2′-bipy) with different reaction periods give metallamacrocycles 1 and 2 with the same chemical formula Co4(2,2′-bipy)4{3,5-(NO2)2sal}4. Replacing Co(OAc)2 · 4H2O with Zn(NO3)2 · 6H2O, using the same synthetic procedures, results in the formation of compound [Zn(2,2′-bipy){3,5-(NO2)2sal}]n (3) with a 1D chain structure and the metallamacrocycle compound Zn4(2,2′-bipy)4{3,5-(NO2)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-(NO2)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.

Hydrothermal reactions of Co(OAc)2 · 4H2O/Zn(NO3)2 · 6H2O, 3,5-dinitrosalicylate (3,5-(NO2)2sal) and 2,2′-bipyridine (2,2′-bipy) with different reaction times give three cyclic tetranuclear complexes (1, 2 and 4) and complex 3 with a 1D structure. The cobalt complexes 1 and 2 are polymorphic, and the zinc complexes 3 and 4 are polymorphic too. Compounds 1 and 4 form an isomorphous pair.Figure optionsDownload as PowerPoint slide