Redox active [Pd2L4]4+ cages constructed from rotationally flexible 1,1′-disubstituted ferrocene ligands

Two new ferrocene-containing [Pd-2(L-Fc)(4)](4+)(X-)(4) (where X- = BF4- or SbF6-) self-assembled cages (C center dot BF4 and C center dot SbF6) were synthesised from the known, rotationally flexible, 1,1 '-bis(3-pyridylethynyl)ferrocene ligand (L-Fc), and characterised by H-1, C-13 and diffusion ordered (DOSY) NMR and UV-visible absorption spectroscopies, high resolution electrospray ionisation mass spectrometry (HR-ESI-MS), elemental analysis, X-ray crystallography and cyclic voltammetry (CV). The molecular structures confirmed that cage-like systems (C center dot BF4 and C center dot SbF6) were generated. Similar to related [Pd2L4](4+)(X-)(4), C center dot SbF6 was able to interact with a range of neutral and anionic guests, with p-toluenesulfonate showing the strongest association constant. Cyclic voltammetry studies revealed that the cage systems were redox active. However, the redox potential of the cage was unperturbed upon the addition of guests.