Compounds that contain several different metal atoms — heteromultimetallic complexes — have recently caught the interest of researchers hoping to exploit their properties in fields as diverse as homogeneous catalysis and information storage. Of particular interest are those containing carbon-rich π-conjugated ligands because these form complexes with rigid rod structures that enable electrons to flow through them. By using a benzene ring functionalized with three alkynes (1,3,5 triethynylbenzene), these systems can be extended in three directions.

Now, Heinrich Lang and colleagues from the Chemnitz University of Technology in Germany have used this strategy1 to create a complex that contains seven different metal atoms. At the centre of the complex is an unsymmetrical platinum unit: both sides are bonded to triethynylbenzene groups, which are each joined to two different metal complexes. Three of these four metals are bonded to ethynyl groups, but the other — copper — is connected through the two nitrogen atoms of a bipyridyl group. At each extremity, ruthenium and copper atoms are linked to a ferrocene or titanocene group, respectively. Ferrocene is connected to the ruthenium atom by diphenylphosphine ligands, and titanocene to the copper by more π-conjugated ligands — in this case, side-on ethynyl groups.

Perhaps surprisingly, the orange compound is stable in the solid state, but does decompose relatively quickly when solutions of it are exposed to air. Lang and co-workers have illustrated the efficiency of the strategy by creating compounds with anywhere between four and seven metal atoms.