Lone-Pair-π Bond Strength Unveiled by a Combined Experimental and Computational Study.

A series of naphthalene-diimide (NDI) and perylene-diimide (PDI) connected bis-N-heterocyclic carbene complexes of iridium(III) have been prepared and fully characterized. The analysis of their NMR spectroscopic features, together with their molecular structures show that these species display lone-pair-π interactions between the chloride ligands of the Ir(III) complex and the heterocycles of the NDI/PDI moieties. The detection of this type of interaction in solution is due to the formation of two atropisomers, which are formed as a result of the restricted rotation about the Ir-C bond imposed by the (Cl)lp⋅⋅⋅π interaction.

A redox-switchable catalyst with an 'unplugged' redox tag.

Two bis-(propyl-imidazolium)-napthalenediimide (NDI) salts were prepared and used as N-heterocyclic carbene (NHC) precursors for the preparation of dimetallic complexes of rhodium and iridium. Infrared spectroelectrochemical studies indicate that the metals are sensitive to changes in the electronic state of the NDI moiety. The catalytic behavior of the rhodium and iridium complexes was tested in the cycloisomerization of alkynoic acids, where the complexes showed effective redox-switching properties.