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Unsymmetrical ligands still make one Pd2L4 cage isomer
Steric and geometric ligand design plus solvent polarity steer unsymmetrical dipyridyl ligands into a single cis or trans Pd2L4 cage rather than a statistical isomer mix.
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What architecture do ditopic ligands plus naked Pd(II) typically form here?
Pd2L4 molecular cages.
Source: Conformational control of Pd<sub>2</sub>L<sub>4</sub> assemblies with unsymmetrical ligands · DOI · quote verified
What was the design goal with unsymmetrical ligands?
Form single Pd2L4 cage isomers with high fidelity via steric or geometric control.
Source: Conformational control of Pd<sub>2</sub>L<sub>4</sub> assemblies with unsymmetrical ligands · DOI · quote verified
How was ligand 1 built?
m-Bis(pyridin-3-ylethynyl)aryl motif with a 6-methyl on one pyridine, via successive Sonogashira reactions.
Source: Conformational control of Pd<sub>2</sub>L<sub>4</sub> assemblies with unsymmetrical ligands · DOI · quote verified
What happened when ligand 2 met Pd(II) in d6-DMSO?
A single cage [Pd2(2)4](BF4)4 formed cleanly within 2 h at room temperature.
Source: Conformational control of Pd<sub>2</sub>L<sub>4</sub> assemblies with unsymmetrical ligands · DOI · quote verified
Which isomer of [Pd2(1)4]4+ did DFT prefer, and by how much?
The trans cage, by 6.1 kJ mol−1.
Source: Conformational control of Pd<sub>2</sub>L<sub>4</sub> assemblies with unsymmetrical ligands · DOI · quote verified
How does solvent polarity affect ligand-1 assembly?
MeCN gives trans exclusively; DMSO stabilises the more polar cis isomer.
Source: Conformational control of Pd<sub>2</sub>L<sub>4</sub> assemblies with unsymmetrical ligands · DOI · quote verified
What DFT energy window favoured cis-[Pd2(4)4]4+?
4.4–26.8 kJ mol−1 below the other three isomers.
Source: Conformational control of Pd<sub>2</sub>L<sub>4</sub> assemblies with unsymmetrical ligands · DOI · quote verified
Did ligand 5 converge to one NMR species?
No—even after prolonged heating at 60 °C in d6-DMSO the 1H NMR did not become a single set of signals.
Source: Conformational control of Pd<sub>2</sub>L<sub>4</sub> assemblies with unsymmetrical ligands · DOI · quote verified
What methyl C⋯C distances distinguished cis vs trans for the methyl-clash hypothesis?
3.7 Å (cis) versus 4.6 Å (trans).
Source: Conformational control of Pd<sub>2</sub>L<sub>4</sub> assemblies with unsymmetrical ligands · DOI · quote verified
How was the cis isomer of one assembly proven in the solid state?
Single-crystal X-ray diffraction, with DOSY RH = 8.7 Å and MS supporting Pd2L4.
Source: Conformational control of Pd<sub>2</sub>L<sub>4</sub> assemblies with unsymmetrical ligands · DOI · quote verified
Why run variable-temperature 1H NMR on the simple spectrum?
To check it was one isomer, not several rapidly interconverting species (20 to −30 °C).
Source: Conformational control of Pd<sub>2</sub>L<sub>4</sub> assemblies with unsymmetrical ligands · DOI · quote verified