Synthesis, characterization and single crystal X-ray structure determination of three cadmium(II) complexes derived from picric acid and p-nitrobenzoic acid in the presence and absence of nitrogen donor ligand N-(hydroxyethyl)ethylenediamine.

Cadmium, an extremely toxic heavy metal, is of a major public health concern and its efficient removal from the environment is a real challenge. This work aims for a deep understanding of stable cadmium(II) chelation with a tridentate ligand to form complex salts being stabilized by cation–anion hydrogen bonding non-covalent interactions in addition to electrostatic interactions. Three new Cd(II) complexes, [Cd(H 2 O) 6 ]( pic ) 2 ·2H 2 O 1 , [Cd(N- hyden ) 2 ]( pic ) 2 2 , [Cd(N- hyden ) 2 ]( pnb ) 2 3 , (where N- hyden  = N-(hydroxyethyl)ethylenediamine, H pic  = picric acid and H pnb  = p-nitrobenzoic acid) using the appropriate acids in the absence and presence of the tridentate N- hyden ligand have been synthesized and fully characterized by elemental analyses, thermogravimetric analyses and spectroscopic (FT-IR, NMR) techniques. The exact ionic structures of complexes 1 – 3 have been unambiguously determined using single crystal X-ray diffraction studies. They comprise octahedrally surrounded cationic Cd(II) centers, [Cd(H 2 O) 6 ] 2+ in 1 and [Cd(N- hyden ) 2 ] 2+ in 2 and 3 , together with the counter anions pic / pnb , which are stabilized by a mutual interplay of various hydrogen bonding interactions. [ABSTRACT FROM AUTHOR]