Coordination complexes of 15-membered pentadentate aza, oxoaza and thiaaza Schiff base macrocycles Old Complexes Offer New Attractions

Two classes of complexes of 15-membered Schiff base macrocycles with a pentadentate (N3X2) cavity (where X = O,N,S) prepared via a metal templated condensation reaction between suitably functionalized 2,6-diacetylpyridine and polyamines are surveyed. The structures and properties of transition metal and lanthanide complexes are presented. Particular emphasis is placed on the unique structural changes accompanying the thermal and light induced spin crossover transition of a [Fe(N3O2)(CN)(2)] complex as well as a detailed exploration of Mn(II) complexes that in addition to their magnetic properties have been investigated for potential applications in biomedical diagnostics, as enzyme mimics for superoxide dismutase as well as for their antimicrobial activity. The remarkable versatility of this family of complexes as building blocks for the self-assembly of discrete and polymeric systems which include clusters, chains and photoswitchable molecule-based magnets is also reviewed. (C) 2015 Elsevier B.V. All rights reserved.