Carbazole-based N4-donor Schiff base macrocycles: obtained metal free and as Cu(ii) and Ni(ii) complexes
Stuart J Malthus1, Rajni K Wilson1, A Vikas Aggarwal1
1Department of Chemistry and MacDiarmid Institute for Advanced Materials and Nanotechnology, PO Box 56, Dunedin 9054, New Zealand. sbrooker@chemistry.otago.ac.nz.
Abstract:
The very different multi-step routes to the closely related pair of diformyl-carbazole head units, 1,8-diformyl-3,6-di-tert-butyl-9H-carbazole (1tBu) and 1,8-diformyl-9H-carbazole (1H), are detailed and compared. The first examples of Schiff base macrocycles derived from diformyl-carbazole head units are reported. Specifically, the direct cyclisation of 1tBu or 1H with diethylenetriamine gives the two metal-free [1 + 1] Schiff base macrocycles HLH and HLtBu in high yields. Four carbazole-based macrocyclic complexes, [CuIIL(OH2)]OAc and [NiIIL]OAc, where L = LH or LtBu, were accessed either by metallation of these macrocycles, or by metal templated reaction of the macrocycle components. [CuIILtBu(OH2)]OAc·0.5(Ether) and [NiLH]OAc·EtOH, were structurally characterised, confirming the nickel(ii) complexes are square planar (both show diamagnetic NMR spectra) and that the copper(ii) complexes are square pyramidal with a water molecule bound in the axial site. Like porphyrins, both of these N4-donor macrocycles, which differ only in the R group present at the 3 and 6 positions (H or tBu), impose a strong ligand field.
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