The coordination-driven self-assembly of four different trigonal prisms from three equivalents of one of four different tetrapyridyl star connectors and six equivalents of a platinum linker dication in nitromethane is presented. This face-directed approach affords high yield without template assistance. The prisms have been characterized by multinuclear and DOSY NMR and dual ESI-FT-ICR mass spectrometry. The use of a conformationally chiral star connector leads to a conformationally chiral prism when connector arm ends attached to a vertex have a strongly correlated twist sense and chirality is communicated across polyhedral faces, edges and vertices. Molecular mechanics results suggest that in the smallest prism 3d collective effects dominate and the all-P and all-M conformers are strongly favored. NMR data prove that the two edges of the pyridine rings in the triflate salts of 3a -3d are distinct. An Eyring plot of rates obtained from lineshape analysis and 1-D EXCHSY NMR yields an activation enthalpy ΔH ‡ of ∼12 kcal/mol and activation entropy ΔS ‡ of ∼-15 cal/mol.K for the edge interconversion process, compatible with pyridine rotation around the Pt-N bond. For 3c, this behavior is observed only up to ∼318 K. At higher temperatures, the Eyring plot is again linear but follows a very different straight line, with ΔH ‡ of ∼35 kcal/mol and ΔS ‡ of ∼60 cal/mol.K. This highly unusual result is further investigated and discussed in the following companion paper.
The coordination-driven self-assembly of discrete 2D macrocyclic species from ambidentate pyridyl-carboxylate-based donor ligands and platinum-containing acceptors is presented. All these species are characterized by electrospray ionization mass spectrometry (ESIMS), multinuclear NMR, and in one example, X-ray crystallography. In each case only one isomeric assembly is selectively formed in high yield, despite the potential for more than one product as a consequence of differences in connectivity.
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