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Palladium(II) Weak-Link Approach Complexes Bearing Hemilabile N-Heterocyclic Carbene–Thioether Ligands

Research paper by Yuan Liu, Zachary S. Kean, Andrea I. d’Aquino, Yashin D. Manraj, Jose Mendez-Arroyo, Chad. A. Mirkin

Indexed on: 10 May '17Published on: 04 May '17Published in: Inorganic Chemistry



Abstract

A new class of palladium(II)-based weak-link-approach complexes bearing hemilabile N-heterocyclic carbene−thioether (NHC,S) ligands can expand and contract in a linear fashion. A tunable linker length between the NHC and thioether moieties enables control over the geometry of the complexes and a change in the length upon switching between the open and closed states. These complexes may be used in the construction of stimuli-responsive supramolecular architectures capable of large changes in geometry.A new class of homoligated palladium(II) weak-link approach (WLA) complexes bearing hemilabile N-heterocyclic carbene (NHC)–thioether ligands is reported that, unlike previous tweezer-like WLA complexes, expand and contract in a linear fashion when switching between configurational states. These complexes can be chemically switched between a trans open state and a trans closed state via the addition or subsequent extraction of Cl–. These bis(NHC) complexes also display unusual isomerization behavior. For example, an NMR spectroscopic investigation into the solution-state configuration of the open complex reveals the presence of interconverting syn,trans and anti,trans isomers, and a kinetic study shows that the barrier is large enough to isolate, store, and study the anti,trans isomer at room temperature. Notably, the linker length between the NHC and thioether moieties can be tailored with additional −CH2– groups, which affords considerable control over the geometric changes imposed by switching. Therefore, this class of complexes may be useful in the construction of allosterically regulated supramolecular assemblies and materials.

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