Modulation of the structural information in shape-defined heterocyclic strands: the case of a (pyridine-hydrazone)₂pyrazine ligand

Metal ions (Ag$^{+}$, Cd$^{2+}$, Eu$^{3+}$, Sm$^{3+}$) and protons can, through coordination and protonation, modulate in three specific ways the structural information contained in the pyrazine-based heterocyclic strand $L$ (obtained from 2,5-bis(methylhydrazino)pyrazine and 2 equivalents of 2-pyridinecarboxaldehyde), thus generating two linear rod-like conformations and a bent one. This conformational diversity is associated with a structural one that consists of two diprotonated forms ($H_{2}L(PF_{6})_{2}$ and $H_{2}L(CF_{3}SO_{3})_{2}$), a polymeric architecture $[AgL]_{n}(CF_{3}SO_{3})_{n}$, two rack-like complexes $([Eu_{2}H_{2}L_{3}(CF_{3}SO_{3})_{6}](PF_{6})_{2}$ and $[Sm_{2}H_{2}L_{3}(CF_{3}SO_{3})_{6}](PF_{6})_{2})$ and a grid-like structure ($[Cd_{4}L_{4}](CF_{3}SO_{3})_{8}$).