Structural and characterization of novel copper(II) azodye complexes

The synthetic methods of novel Cu(II) and adduct complexes, with selective azodyes containing nitrogen and oxygen donor ligands have been developed, characterized and presented. The prepared complexes fall into the stoichiometric formulae of [Cu(Ln)2](A) and [Cu(Ln)2(Py)2](B), where two types of complexes were expected and described. In type [(A) (1:2)] the chelate rings are six-membered/four coordinate, whereas in type [(B) (1:2:2)] they are six-membered/six coordinate. The important bands in the IR spectra and main 1H NMR signals are tentatively assigned and discussed in relation to the predicted assembly of the molecular structure. The IR data of the azodye ligands suggested the existing of a bidentate binding involving azodye nitrogen and C–O oxygen atom of enolic group. They also showed the presence of Py coordinating with the metal ion. The coordination geometries and electronic structures are determined from the framework of the proposed modeling of the formed novel complexes. The complexes (1–5) exist in trans-isomeric [N,O] solid form, while adduct complexes (6–10) exist in trans isomeric (Py) form. The square planar/octahedral coordination geometry of Cu(II)/adduct is made up of an N-atom of azodye, the deprotonated enolic O-atom and two Py. The azo group was involved in chelation for all the prepared complexes. ESR spectra show the simultaneous presence of a planar trans and a nearly planar cis isomers in the 1:2 ratio for all N,O complexes [Cu(Ln)2]. The ligands in the dimmer are stacked over one another. In the solid state of azo-rhodanine, the dimmers have inter- and intramolecular hydrogen bonds. Interactions between the ligands and Cu(II) are also discussed.

Graphical abstractThe plot of g∥ and A∥ × 10−4 cm−1 versus of f gives straight line with increase the value of f decrease the g∥ and increase the A∥ × 10−4 cm−1. This can be explained. The electron withdrawing p-substituent increase the positive charge on the metal ion leading to a increase in f and A∥ × 10−4 cm−1 and subsequently a decrease in g∥.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The coordination geometries and electronic structures of [Cu(Ln)2](A) and [Cu(Ln)2(Py)2](B) are determined from the framework of the proposed modeling of the formed novel complexes. ► The complexes (1–5) exist in trans-isomeric [N,O] solid form, while adduct complexes (6–10) exist in trans isomeric (Py) form. ► ESR spectra show the simultaneous presence of a planar trans and a nearly planar cis isomers in the 1:2 ratio for all N,O complexes [Cu(Ln)2].