First copper(II)-cyclophosphato complex with macrocyclic N-donor ligand: Single crystal structure elucidation with Hirshfeld surface analysis, optical, electrochemical and antioxidant properties

Abstract From the system metal-cyclam-condensed phosphate is isolated the first complex of {(H 3 O + ) 2 [Cu(II)(μ-P 4 O 12 )(cyclam)]} n (1) . This complex was characterized by X-ray diffraction (XRD), spectroscopy (diffuse reflectance, UV–Vis and FT-IR) and thermal analysis (DTA/TGA). The solved molecular structure of 1 revealed one rare 1D-anionic polymeric copper(II)-complex, {[Cu(II)(μ-P 4 O 12 )(cyclam)] 2- } n , involving two distinct ring ligands (cyclam / cyclotetraphosphate), in which a new coordination mode of the P 4 O 12 4 − was observed. The counterions (H 3 O + ) ensure the connection between 1D-polymers by acting as donor in a strong "charge-assisted" hydrogen bonds with P 4 O 12 rings leading to 2D-supramolecular frameworks arranged in -A-B-A- fashion. The 2D-supramolecular network is stabilized by O/N-H…O interactions whereas the van der Waals contacts play a key role in the consolidation of the 3D packing as verified by Hirshfeld surface analysis in combination with 2D fingerprint plots. The biochemical properties of 1 was also evaluated via DDPH, ABTS, hydroxyl radical scavengers and ferric reducing power (FRP) showing promising antioxidant activities which has been clarified by means of the cyclic voltammetric study.