Exploiting Supramolecular Interactions to Control Isomer Distributions in Reduced-Symmetry [Pd2L4]4+ Cages

Roan A.S. Vasdev, Dan Preston, Caitlin A. Casey-Stevens, Vicente Martí-Centelles, Paul J. Lusby, Anna L. Garden, James D. Crowley

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

High-symmetry metallosupramolecular architectures (MSAs) have been exploited for a range of applications including molecular recognition, catalysis, and drug delivery. Recently, there have been increasing efforts to enhance those applications by generating reduced-symmetry MSAs. Here we report our attempts to use supramolecular (dispersion and hydrogen-bonding) forces and solvophobic effects to generate isomerically pure [Pd2(L)4]4+ cage architectures from a family of new reduced-symmetry ditopic tripyridyl ligands. The reduced-symmetry tripyridyl ligands featured either solvophilic polyether chains, solvophobic alkyl chains, or amino substituents. We show using NMR spectroscopy, high-performance liquid chromatography, X-ray diffraction data, and density functional theory calculations that the combination of dispersion forces and solvophobic effects does not provide any control of the [Pd2(L)4]4+ isomer distribution with mixtures of all four cage isomers (HHHH, HHHT, cis-HHTT, or trans-HTHT, where H = head and T = tail) obtained in each case. More control was obtained by exploiting hydrogen-bonding interactions between amino units. While the cage assembly with a 3-amino-substituted tripyridyl ligand leads to a mixture of all four possible isomers, the related 2-amino-substituted tripyridyl ligand generated a cis-HHTT cage architecture. Formation of the cis-HHTT [Pd2(L)4]4+ cage was confirmed using NMR studies and X-ray crystallography.

Original languageEnglish
Pages (from-to)1833-1844
Number of pages12
JournalInorganic Chemistry
Volume62
Issue number5
Early online date23 May 2022
DOIs
Publication statusE-pub ahead of print - 23 May 2022

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