Lanthanide triple-stranded helical complexes with a substituted 2,6-pyridinedicarboxylateElectronic supplementary information (ESI) available: analytical, IR and luminescence data, contact and dipolar shifts, calculated Cartesian co-ordinate for the EuIII complex, plots of chemical shifts for protons H8, H9 versus the chemical shift of proton H2. See http://www.rsc.org/suppdata/dt/b1/b104448f/