A novel left-handed double helicate constructed from l-tartrate bridged molybdenum(vi) and gadolinium(iii) atomsElectronic supplementary information (ESI) available: crystallographic data, TGA, powder X-ray patterns, ORTEP structure and molar susceptibility plot for compound 1. See http://www.rsc.org/suppdata/cc/b3/b301542d/

The one-dimensional double helicate, [NH4][Mo2O4Gd(H2O)6(L-C4H2O6)2] x 4H2O (1), which was synthesized by the reaction of GdCl3, L-tartaric acid and ammonium molybdate in acidified water solution, is built up by two heft-handed single-helical chains, linked up further by eight-coordinated GdIII pieces in an enantiopure left-handed double helical configuration, of which each helix is formed by L-tartrate bridged six-coordinated MoVI atoms.