Cover Picture: Water Oxidation with Molecularly Defined Iridium Complexes: Insights into Homogeneous versus Heterogeneous Catalysis (Chem. Eur. J. 40/2012)

Abstract

Water oxidationis a significant and challenging goal. Successfully applied molecularly defined Ir complexes are thought to be converted into Ir-oxo nanoparticles that may also act as catalysts. Thus, the iridium performs “tightrope-walking” between homogeneous and heterogeneous catalysis. New insights have been revealed by XANES, EXAFS, and STEM investigations. For more details, see the Full Paper by M. Beller et al. on page 12749 ff. Diels–Alder Reactions The iminium aza-Diels–Alder reaction (iADA) and the origins, modern developments, mechanistic studies, and synthetic applications of this variation of the DA reaction are presented by M. G. Memeo and P. Quadrelli on page 12554 ff. The inter- and intramolecular versions of the iADA reactions that are conducted in aqueous solutions to generate the reactive dienophile in situ are discussed, and the retro-ADA reaction is presented as an interesting method for the protection of amines.1 Molecular Switching Well-defined aggregate formation of multidomain linear oligomers is described by M. Yamaguchi et al. in their Full Paper on page 12644 ff. Multidomain compounds were designed on the basis of amido and ethynyl oligomers that form dimeric aggregates with properties orthogonal to each other. Four aggregate states and two reversible structural-change processes were obtained by using a single compound.1 π–π Interactions In a series of benzoyl leucine amides of varying electronic character only certain compounds formed homochiral dimers with a stabilizing parallel displaced π–π interaction. All of the 3- and 3,5-disubstituted compounds assembled into homochiral dimers, but no homochiral dimerization was observed in the unsubstituted case and in several 4-substituted cases (shown in yellow). The crystallographic data suggest that local interactions between the dipoles may stabilize the interaction in several of the dimers (shown in red), providing a driving force for homochiral dimerization. For more details, see the Full Paper by J. R. Carey et al. on page 12663 ff.1