Cooperative Effect of a Classical and a Weak Hydrogen Bond for the Metal-Induced Construction of a Self-Assembled beta-Turn Mimic

A novel metal-induced template for the self-assembly of two independent phosphane ligands by means of unprecedented multiple noncovalent interactions (classical hydrogen bond, weak hydrogen bond, metal coordination, pi-stacking interaction) was developed and investigated. Our results address the importance and capability of weak hydrogen bonds (WHBs) as important attractive interactions in self-assembling processes based on molecular recognition. Together with a classical hydrogen bond, WHBs may serve as promoters for the specific self-assembly of complementary monomeric phosphane ligands into supramolecular hybrid structures. The formation of an intermolecular C-H center dot center dot center dot N hydrogen bond and its persistence in the solid state and in solution was studied by X-ray crystal analysis, mass spectrometry and NMR spectroscopy analysis. Further evidence was demonstrated by DFT calculations, which gave specific geometric parameters for the proposed conformations and allowed us to estimate the energy involved in the hydrogen bonds that are responsible for the molecular recognition process. The presented template can be regarded as a new type of self-assembled beta-turn mimic or supramolecular pseudo amino acid for the nucleation of beta-sheet structures when attached to oligopeptides.