Unexpected formation of polymeric silver(I) complexes of azine-type ligand via self-assembly of Ag-salts with isatin oxamohydrazide

Isatin oxamohydrazide (L) reacted with the aqueous solution of silver nitrate at room temperature afforded the polymeric silver(I) nitrato complex, [Ag(2)L′(NO(3))(2)](n), (1) of the azine ligand (L′). Similarly, the reaction of L with silver(I) perchlorate gave the [Ag(2)L′(2)(ClO(4))(2)](n), (2) coordination polymer. Careful inspection of the crystals from the nitrato complex preparation showed the presence of another crystalline product which is found to be [Ag(Isatin-3-hydrazone)NO(3)], (3) suggesting that the reaction between silver(I) nitrate and L proceeds first by the hydrolysis of L to the isatin hydrazone which attacks another molecule of L to afford L′. Testing metal salts such as Ni(2+), Co(2+), Mn(2+), Cu(2+) and Cd(2+) did not undergo any reaction with L either under the same reaction conditions or with heating under reflux up to 24 h. Treatment of the warm alcoholic solution of L with few drops of 1 : 1 (v/v) hydrochloric acid gave the free ligand (L′) in good yield. The [Ag(2)L′(NO(3))(2)](n) complex forms a two-dimensional infinite coordination polymer, while the [Ag(2)L′(2)(ClO(4))(2)](n) forms one-dimensional infinite chains with an alternating silver-azine backbone. Quantitative analysis of the intermolecular interactions in their crystals is made using Hirshfeld surface analysis. Density functional theory studies were performed to investigate the coordination bonding in the studied complexes.