Preferential azido bridging regulating the structural aspects in cobalt(III) and copper(II)–Schiff base complexes: Syntheses, magnetostructural correlations and catalytic studies

Preferential azido bridging have resulted dinuclear and polynuclear CoIII and CuII–Schiff base complexes. We report first singly μ1,3-N3 bridged square planar CuII–Schiff base dimer exhibiting unusually strong antiferromagnetic exchange interaction and the high turnover numbers obtained for the CoIII–Schiff base–PhIO system precedes the catalytic activity of other cobalt catalysts for alkene oxidation in homogeneous phase. [Display omitted] ► Azide ions regulate the geometry of the complexes. ► Highest magnitude of J=−252(1)cm−1 was obtained for singly μ1,3-N3 bridged CuII–Schiff base complex. ► CoIII–Schiff base–PhIO system in alkene oxidation results abnormally high t.o.n. A tridentate NNO donor Schiff base ligand [(1Z,3E)-3-((pyridin-2-yl)methylimino)-1-phenylbut-1-en-1-ol=LH] in presence of azide ions coordinates with cobalt(II) and copper(II) ions giving rise to three new coordination complexes [Co2(L)2(μ1,1-N3)2(N3)2] (1), [Cu2(L)2(μ1,3-N3)]·ClO4 (2) and [(μ1,1-N3)2Cu5(μ-OL)2(μ1,1-N3)4(μ1,1,1-N3)2]n (3). The complexes have been characterized by elemental analysis, FT-IR, UV–Vis spectral studies, and single crystal X-ray diffraction studies. These complexes demonstrate that under different synthetic conditions the azide ions and the Schiff base ligand (LH) show different coordination modes with cobalt(II) and copper(II) ions, giving rise to unusual dinuclear and polynuclear species (1, 2 and 3) whose structural variations are discussed. Magneto-structural correlation for the very rare singly μ1,3-N3 bridged CuII–Schiff base dinuclear species (2) has been studied. In addition, the catalytic properties of 1 for alkene oxidation and the general catalase-like activity behavior of 2 have been discussed.