1,4-Phenylene-di(N-l-alanylaminomethylphosphonate) a new diaminophosphonate peptide receptor for lysine and arginine

New diaminophosphonate peptide receptor composed of two aminomethylphosphonic acid fragments attached to phenyl ring in para position was described. Intermolecular interactions between such host molecule and unprotected cationic forms of lysine and arginine (guest molecules) were studied by means of NMR spectroscopy and ESI-MS spectrometry in both methanol and water solutions. Unfortunately, no complexation induced shifts in NMR spectra were observed for these host–guest systems in water solution. However, the performed studies have shown that in methanol complexes in host to guest ratio of 1:1 and 1:2 are formed and they precipitate from the solution, while in water 1:1 complexes are only seen and supramolecular interactions between host and guest discovered using 1H- and 31P NMR T1 relaxation method suggest that they are present as ionic pairs in aqueous solution. The supramolecular studies were supported by DFT theoretical studies performed for free receptor and its molecular complexes with Lys and Arg.