Using ferrocene-based ligand systems, a series of heterobimetallic
architectures of the general formula [Pd
m
L
n
]
x+ were
designed with the aim of installing an opening and closing mechanism
that would allow the release and binding of guest molecules. Palladium
complex formation was achieved through coordination to pyridyl groups,
and using 2-, 3-, and 4-pyridyl derivatives provided access to defined
PdL, PdL2, and Pd2L4 structures,
respectively. The supramolecular complexes were characterized using
nuclear magnetic resonance (NMR) and infrared spectroscopy, mass spectrometry,
and elemental analysis, and for some examples density functional theory
calculations and single-crystal X-ray diffraction analysis. 1H NMR spectroscopy was used to investigate disassembly and reassembly
of the metallosupramolecular structures. The former was induced by
cleavage of the relatively labile Pd–Npyridyl bonds
with the introduction of the competing ligands N,N′-dimethylaminopyridine (DMAP) and Cl– (using tetrabutylammonium chloride) to yield [Pd(DMAP)4]2+ and [PdCl4]2–, respectively.
The process was found to be reversible for several of the heterodimetallic
compounds, with the addition of H+ or Ag+ triggering
complex reassembly. Guest binding studies with several architectures
revealed interactions with the anionic guests p-toluenesulfonate
and octyl sulfate, but not with neutral molecules. Furthermore, the
release of guests was reversibly induced with Cl– ions as a stimulus.