Synthesis, magnetism and spectral studies of six defective dicubane tetranuclear {M4O6} (M = NiII, CoII, ZnII) and three trinuclear CdII complexes with polydentate Schiff base ligands?

Dalton Transactions Pub Date: 2016-05-11 DOI: 10.1039/C6DT00380J

Abstract

A series of NiII, CoII, ZnII and CdII complexes 1–9 with polytopic Schiff base ligands have been synthesized. The single-crystal X-ray crystallography results show that tetranuclear complexes 1–6 have common face-shared defective dicubane cores, whereas trinuclear CdII complexes 7–9 are almost linear entities. Synthesis methods (solvent evaporation and hydrothermal synthesis), reaction conditions (pH, solvents and dosage) and coligands (azide, methanol, chloride and acetate) play vital roles in determining the final structure of the complexes and therefore their magnetic properties. In complexes 1–6, the terminal and central M2+ ions are connected through mixed bridges, μ-phenoxido/μ1,1,1-X and μ-Oalphatic/μ1,1,1-X, while central two M2+ ions are linked by double bridges, μ1,1,1-X (X = azido and methoxido groups for 1 and 2–6 respectively). For complex 1, two central NiII ions are connected through two μ1,1,1-N3? which is relatively less reported. For complexes 7–9, there are two kinds of CdII, the centre CdII ions are eight-coordinated with triangle dodecahedral geometries, while the two side CdII ions are six-coordinated with trigonal prism geometries using chlorides or acetates as terminal ligands. Magnetic susceptibility measurements (χM) for compounds 1–6 have been performed, and they reveal predominant ferromagnetic exchange interactions in CoII and NiII tetramers. The photoluminescence studies show that the ZnII complex 6 and three CdII complexes 7–9 have strong fluorescence, and the lifetimes are measured to be in the 102 nanosecond timescale.

Graphical abstract: Synthesis, magnetism and spectral studies of six defective dicubane tetranuclear {M4O6} (M = NiII, CoII, ZnII) and three trinuclear CdII complexes with polydentate Schiff base ligands
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