Ligands and complexes of 1,8-diformylcarbazole and 2,2’-iminobisbenzaldehyde derivatives

Abstract

The project detailed in this thesis was a successful attempt to prepare diphenylamine- and carbazole-based dialdehyde units; a handful of metal-free [2+2] macrocycles; and a selection of complexes which represent a first step towards generating new series of potential catalysts. In addition, the preparation of diphenylamine- and carbazole-based anion receptors was briefly explored.

Chapter 1 is split into two major sections. The first moves from considering naturally occurring porphyrins through to the use of various dialdehydes in the literature, their downfalls and the subsequent realisation of diphenylamine and carbazole dialdehydes as building blocks with a lot of potential. This is followed by a comprehensive review of the synthesis of (110) related ligands and (320) metal complexes thereof, as well as of their properties and structural parameters (55 complexes) where relevant.

Chapter 2 details the optimisation of the literature syntheses of 2,2’-iminobisbenzaldehyde (HU1) and 1,8-diformyl-9H-carbazole (HU2). Given the poor availability of 1,8-diformyl-9H-carbazole derivatives (multiple steps, low yields), an alternative, robust, and flexible route to such compounds was developed. The carbazole derivatives HU2, 1,8-diformyl-3,6-di-tert-butyl-9H-carbazole (HU3) and 1,8-diformyl-3,6-bis(dodecyl)-9H-carbazole (HU4) were prepared using this general strategy in moderate overall yields. Nine of the compounds in this chapter were structurally characterised.

Chapter 3 details the metal-free synthesis of analytically clean imine [2+2] macrocycles resulting from the condensation of HU1 with 1,2-diaminoethane, 1,3-diaminopropane and 1,4-diaminobutane, H2L1EtI, H2L1PrI and H2L1BuI respectively, in very good yields. The preparation of the corresponding reduced amine macrocycles is also described. Attempts were made to prepare analogous imine macrocycles from HU2 and HU3, but resulted in a complex mixture of products. The three imine and three amine macrocycles derived from HU1 were structurally characterised.

Chapter 4 details the preparation of various mono- and di-metallic complexes derived from H2L1EtI, H2L1PrI and H2L1BuI. The dicopper(II) acetate and tetrafluoroborate complexes were prepared in good yields, and four were structurally characterised, [CuII2L1EtI(OAc)2], [CuII2L1PrI(OAc)2] · 1.5MeOH · 0.5H2O, [CuII2L1BuI(OAc)2] · 3MeOH and [CuII2L1PrI(DMF)4](BF4)2· 0.5H2O. The electrochemistry of these complexes was investigated. In addition, an attempt to prepare the dicopper(II) tetrafluoroborate [2+2] macrocyclic complex derived from HU3 and 1,2-diaminoethane by a metal-templated approach resulted instead in the formation of an acyclic complex, which was structurally characterised, [Cu2(2HU3+3en)(DMF)4](BF4)2. One attempt was made to prepare the macrocyclic complex by a “purification-by-complexation” approach. It was only partially successful, but did allow the structural characterisation of the intended complex, [Cu2(OAc)2L2PrI]·2H2O · 0.5MeOH. A series of nickel, copper and zinc complexes of H2L1EtI, H2L1PrI and H2L1BuI were also prepared, but all contained less than two metal ions per macrocycle.

Chapter 5 steps through the attempted development of some diphenylamine- and carbazole-based anion receptors. One bis-amide receptor, which was structurally characterised, was prepared but showed no binding affinity for the anions tested. Attempts to prepare a bis-urea analogue by a Curtius rearrangement resulted instead in a benzimidazolone product. Finally, a preliminary attempt to rectify this problem by a protecting group strategy was investigated.