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

Abstract

Two new ferrocene-containing [Pd2(LFc)4]4+(X−)4 (where X− = BF4− or SbF6−) self-assembled cages were synthesised from the known, rotationally flexible, 1,1′-bis(3-pyridylethynyl)ferrocene ligand (LFc). The cages were shown to bind neutral and anionic guest molecules and displayed reversible redox activity.

Self‐Assembly of a Redox Active, Metallosupramolecular [Pd3L6]6+ Complex Using a Rotationally Flexible Ferrocene Ligand

“…This indicated that there is no electronic communication between the Fc units within C ⋅ BF 4 (Supporting Information). The electrochemical data was consistent with our previous work on the related [Pd 2 ( L 3EFc ) 4 ] 4+ system [15] …”

“…Two BF 4 − counterions were found to reside in the cavity of the structure. The Pd–N bond lengths ranged from 1.98(2) to 2.07(2) Å, similar to our previously reported [Pd 2 ( L 3EFc ) 4 ] 4+ ferrocene cage [15] and other [Pd n (L) 2n ] n+ systems [17–19] . The thin needles of C ⋅ SbF 6 again gave modest diffraction but the structure was solved in the rhombohedral space group and showed the presence of the [Pd 3 ( L 4EFc ) 6 ] 6+ double‐walled triangle molecular architecture (Supporting information).…”

“…Initial attempts to obtain the structural data using a Cu Kα X‐ray source were unsuccessful with only very weak diffraction observed. The related C ⋅ SbF 6 was generated, following our previously published procedure, [15] in an attempt to obtain superior quality crystals but this system also only displayed very weak diffraction. However, the use of synchrotron radiation enabled the molecular structures of both C ⋅ BF 4 and C ⋅ SbF 6 to be determined.…”

“…We have recently shown that the rotationally flexible 1,1′‐bis(3‐pyridylethynyl)ferrocene ( L 3EFc ) ligand can quantitively form a discrete [Pd 2 ( L 3EFc ) 4 ] 4+ cage architecture when exposed to Pd(II) ions [15] . In contrast to the free 1,1′‐bis(3‐pyridylethynyl)ferrocene ligand, which adopts a syn π‐stacked conformation, all four 1,1′‐ferrocene units within the cage structure adopted the anti ‐configuration with the “arms” of the linker ligands averaging 150° apart.…”

Oxidation triggers guest dissociation during reorganization of an FeII4L6twisted parallelogram

“…Among such motifs, metallocenes [35][36][37][38][39][40][41][42][43][44] can display conformational isomerism by rotation of the cyclopentadiene ligands with respect to one another. The different eclipsed and staggered conformations of metallocenes offer a large range of possible dihedral angles between covalently-connected substituents, rendering such building blocks attractive in the synthesis of low-symmetry metal-organic assemblies.…”