Structurally varied Cu(II) complexes involving kinetin and its derivatives: Synthesis, characterization and evaluation of SOD-mimic activity

Three new structural types of Cu(II) complexes of kinetin and its purine- and/or furan-substituted derivatives (HLn), involving acetato-bridges (Ac) or mixed N-donor ligands, are reported. Complexes of the compositions [Cu2(μ3-L1)2(μ2-Ac)2]n (1), [Cu2(μ3-L2)2(μ2-Ac)2]n (2), [Cu2(μ3-L3)2(μ2-Ac)2]n (3), [Cu2(μ2-Ac)4(HL5)2] (4), [Cu2(μ2-Ac)4(HL6)2] (5), [Cu(H2O)2(L3)2(phen)] (6) and [Cu(H2O)2(L4)2(phen)]·2H2O (7), with kinetin (N6-furfuryladenine, HL1) and its derivatives N6-(5-methylfurfuryl)adenine (HL2), 2-chloro-N6-furfuryladenine (HL3), 2-chloro-N6-(5-methylfurfuryl)adenine (HL4), 2-chloro-N6-furfuryl-9-isopropyladenine (HL5) and 2-chloro-N6-(5-methylfurfuryl)-9-isopropyladenine (HL6) (phen = 1,10-phenanthroline), have been fully characterized by elemental analyses, FTIR, electronic spectroscopy, conductivity, temperature dependent magnetic susceptibility measurements, thermogravimetric (TG) and differential thermal (DTA) analyses. The geometry around the Cu(II) centers is square pyramidal in the two structural groups involving the acetato bridges (1–3, and 4, 5) and octahedral in the mononuclear 6 and 7. This was confirmed by single crystal X-ray analysis for the dimeric complexes 4 and 5, with each Cu(II) atom five-coordinated by four O atoms from the acetato bridges and one N7 atom from the adenine moiety of HLn. The length of the Cu⋯Cu separation present in the dimers 4 and 5 is equal to 2.6508(6) and 2.6523(4) Å, respectively. The anti-radical activity of the presented complexes was evaluated by an in vitro SOD-mimic assay and the best results were found for 4 with IC50 equal to 57.4 μM.

Polymeric [Cu2(μ3-Ln)2(μ2-Ac)2]n (1–3), dimeric [Cu2(μ2-Ac)4(HLn)2] (4, 5) and mononuclear [Cu(H2O)2(Ln)2(phen)] (6, 7) Cu(II) complexes involving the combination of kinetin and its derivatives (HLn) and acetato bridges or 1,10-phenanthroline, were synthesized, thoroughly characterized, and tested for their in vitro SOD-like activity.Figure optionsDownload as PowerPoint slide