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Supramolecular chemistry of 1, 1’ - disubstituted ferrocene amides

It is well known that 1, 1’ – amino acid disubstituted ferrocenes form well defined secondary structures which often mimic β or -turns. They are important for biological function and thus attractive for research [1]. When two chiral ferrocene pendant chains are hydrogen bonded, the free rotation of the ferrocene rings is hindered, and the ferrocene moiety becomes helically chiral, providing a CD signal in the visible region of the spectra which enables characterisation by chirooptic methods. Inspired by our previous work in enantioselective hydrogenation catalysis [2], we have prepared a small series of 1, 1’ - disubstitued ferrocene amides and their monosubstituted analogues (Figure 1). The prepared compounds are model systems for the precatalytic Rh complexes in our previous work, and they will hopefully provide additional insight into supramolecular enantioselective catalysis. In addition, they are also interesting in their own right, as they exhibit hydrogen bonding and other types of noncovalent interactions. We have applied different spectroscopic techniques (NMR, IR, UV-Vis, CD, XRD, MS) and DFT calculation to these systems in order to elucidate their structure in solution and characterise interesting supramolecular phenomena, such as the solvent induced chirality inversion, which occur in these systems.

Ferrocene ; hydrogen bond ; secondary structure ; chirality ; backdoor induction ; amides

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