Carbazole-based N4-donor Schiff base macrocycles: obtained metal free and as Cu(ii) and Ni(ii) complexes. Issue 10 (27th January 2017) - Malthus, Stuart J.
Abstract : Practical multi-step routes to 1, 8-diformylcarbazole head units, and the first examples of Schiff base macrocycles derived from them, are reported. Like porphyrins, both macrocycles are shown to impose a strong ligand field. 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-9 H -carbazole (1 t Bu ) and 1, 8-diformyl-9 H -carbazole (1 H ), are detailed and compared. The first examples of Schiff base macrocycles derived from diformyl-carbazole head units are reported. Specifically, the direct cyclisation of1 t Bu or1 H with diethylenetriamine gives the two metal-free [1 + 1] Schiff base macrocycles HL H and HL t Bu in high yields. Four carbazole-based macrocyclic complexes, [Cu II L (OH2 )]OAc and [Ni II L ]OAc, whereL =L H orL t Bu, were accessed either by metallation of these macrocycles, or by metal templated reaction of the macrocycle components. [Cu II L t Bu (OH2 )]OAc·0.5(Ether) and [NiL H ]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 t Bu), impose a strong ligand field.