Metal-ion-induced shape switching: Stereoselective formation of a dinuclear Hg(II) double helicate from a hydrazonobis(acylhydrazone) ligand

Construction of bis-, tris- and tetrahydrazones by addition of azoalkenes to amines and ammonia

Exhaustive Michael-type alkylations of amines and ammonia with azoalkenes (generated from α-halohydrazones) were demonstrated as an efficient approach to poly(hydrazonomethyl)amines - a novel class of polynitrogen ligands. An intramolecular cyclotrimerization of C=N bonds in tris(hydrazonomethyl)amine to the respective 1,4,6,10-tetraazaadamantane derivative was demonstrated.

Hydrazone-based switches, metallo-assemblies and sensors

The hydrazone functional group has been extensively studied and used in the context of supramolecular chemistry. Its pervasiveness and versatility can be attributed to its ease of synthesis, modularity, and most importantly unique structural properties, which enable its integration in different applications. This review provides an overview of the utilization of hydrazones in three supramolecular chemistry related areas: molecular switches, metallo-assemblies and sensors. These topics were chosen because they highlight the diversity of hydrazones, and emphasize their uniqueness vis-à-vis the imine functional group. Discussion entails (i) chemical and light activated switching of hydrazones, and how this can be used in controlling the properties of self-assembled systems, (ii) the use of hydrazones in the formation of dynamic and stimuli responsive metallogrids, and (iii) the use of hydrazones in detecting metal cations (Zn(2+), Cu(2+), Hg(2+), etc.), anions (F(-), CN(-), P2O7(4-), etc.) and neutral molecules (amines, water, Cys, etc.).