Uncharged water-soluble metal-bis-porphyrins like molecular tweezers for amino acids

Some new water-soluble bis-porphyrins, constituted of two porphyrin units spaced by means of aliphatic bridges of different lengths, were synthesized and characterized by MALDI-TOF mass spectrometry, H-1 NMR and UV-vis spectroscopy. The hydrosolubility of these uncharged compounds was guaranteed from the presence of six long PEG chains bound on the peripheral positions of the two porphyrins. Cobalt and zinc derivatives were also prepared. In the case of Co-bis-porphyrin, the appearance of induced circular dichroism (ICD) signals in water solution confirmed the formation of stable complexes with some amino acids, in which the bis-porphyrin behaves like molecular tweezers.