A ligand strand that displays anion-dependant reactivity with acetonitrile; formation of either a mononuclear complex or head-to-tail circular helicate.

The ligand L-2,L-2 contains two bidentate domains separated by a 3,3-diamino-2,2 '-biphenyl spacer unit and with Cu(ClO4)(2) a mononuclear species is formed (e.g. [Cu(L-2,L-2)](2+)). Upon coordination with Cu(triflate)(2) the ligand undergoes reaction with an acetonitrile solvent, producing a different ligand with unsymmetrical bidentate and tridentate domains (L-2,L-3). This new ligand results in the formation of a tetranuclear head-to-tail circular helicate [Cu-4(L-2,L-3)(4)](8+) showing that in the presence of the triflate anion the ligand denticity is changed.