A diruthenium(ii) complex involving the di(terpyridine) ligand 1,2-bis{5-(5″-methyl-2,2′:6′,2″-terpyridinyl)}ethane was synthesised by heating an equimolar ratio of RuCl3 and the ligand under reflux conditions in ethylene glycol for 3 days, realising double-stranded helicate and mesocate forms which were chromatographically separated. The two species were obtained in relatively low yield (each ~7–9%) from the reaction mixture. X-Ray structural studies revealed differences in the cavity sizes of the two structures, with the helicate structure having a significantly smaller cavity. Furthermore, the helicate and mesocate forms pack with notably different arrangements of the structures with the helicate having large solvent and anion filled pores. 1D/2D NMR studies revealed rigidity in the mesocate structure relative to that of the helicate, such that the –CH2CH2– signal was split in the former and appeared as a singlet in the latter. In a manner analogous to the behaviour of the parent [Ru(tpy)2]2+ coordination moiety (tpy=2,2′:6′,2″-terpyridine), photophysical studies indicated that both the helicate and mesocate forms were non-emissive at ~610nm at room temperature, but at 77K in n-butyronitrile, both isomers showed emission at ~610nm (λex 472nm). However, the temporal emission characteristics were very different: time-resolved studies showed the emission of the helicate species decayed with a dominant emission lifetime of ~10 μs (similar to the emissive properties of free [Ru(tpy)2]2+ under the same conditions), whereas for the mesocate the emission lifetime was at least three orders of magnitude lower (~4 ns).

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A series of ligands containing a 1,4-disubstituted 1,2,3-triazole unit have been used for the formation of triple-stranded dinuclear Ru(II) complexes. In contrast to the previously reported complexes of labile metals, the use of inert Ru(II) enabled stereoisomeric mixtures of triple-stranded diruthenium(II) complexes to be accessed. The chromatographic resolution of the enantiomers of a reported helicate containing a more rigid 1,4-xylyl spacer was carried out on cellulose. The ligand spacer was modified and as the flexibility increased the production of isomeric mixtures was detected; the mesocate and helicate forms were separated when an n-propyl spacer was used. This pair of diastereomers was found to exhibit photoconversion, a unique observation for Ru(II) compounds of this type. Partial separation via chromatographic resolution was achieved for compounds containing an n-butyl spacer, and the presence of a mesocate/helicate pair confirmed.

The Front Cover shows the design of triple‐stranded di‐ruthenium(II) complexes from a series of ligands containing a 1,4‐disubstituted 1,2,3‐triazole. Chirality is a common motif in nature, illustrated by a tree in a rainforest, where helical and non‐helical features can arise in the same structure. This is similar to the synthesis of Ru(II) products, where mixtures of helicates and mesocates were observed from the same metal and ligand source. Ligand design played a key role in determining the product distribution, and helicate enantiomers and helicate/mesocate diastereomers were separated for some dinuclear complexes. Interestingly, the mesocate and helicate containing an n‐propyl spacer were found to exhibit extensive photo‐interconversion, a unique observation for Ru(II) compounds of this type. More information can be found in the Research Article by F. R. Keene and co‐workers.