Advances in acyclic compartmental ligands and related complexes

Symmetric and asymmetric compartmental acyclic Schiff bases and their reduced polyamine analogues have been considered; they have been classified according to their synthetic procedures, i.e. the condensation ratio between the formyl (or keto) and amine precursors, as [1 + 1] acyclic, [1 + 1] asymmetric end-off, [1 + 2] or [2 + 1] symmetric end-off, [2 + 1] or [1 + 2] side-off asymmetric and [3 + 1] or [1 + 3] systems. Their preparation has been reviewed, together with the physico-chemical and structural properties arising from the different synthetic reactions. The influence of their symmetric or asymmetric nature, their planar or three-dimensional structure on the possibility to obtain the same or different recognition processes at the two adjacent chambers were evaluated. The magneto-structural correlations of the homo- and hetero-dinuclear or -polynuclear complexes, together with the photochemical and photophysical properties resulting from these specific recognition processes, were also considered. The use of specific linkers, capable of forming oligomeric or polymeric complexes or unusual structures (as helicates) with the consequent modification of their properties (especially the magnetic interaction between the metal ions), is also reported. The design and diversification of the two adjacent sites, aimed at enhancing the ability of these ligands to act as selective transfers of specific cations, anions or salts across liquid membranes is considered and the results obtained are adequately discussed. Finally, the specific reactivity and catalytic properties of these systems are discussed. © 2007 Elsevier B.V. All rights reserved.