A water soluble macromolecular nanobox having porphyrinic walls as a large host for giant guests

Cyclic tetra{5,15‐di‐[ p (ω‐methoxypolyethyleneoxy)phenyl]‐10,20‐[ p ‐oxyphenyl] methylen porphyrin}, cy‐[O‐(H 2 ‐PTPEG 2 )‐O‐CH 2 ‐] 4 , a water soluble macromolecule consisting of four porphyrin units [each with two long ω‐methoxypolyethyleneoxy (PEG) branches bound on its peripheral positions] linked by means of four methylenoxy bridges, was prepared by an interfacial etherification reaction. Structural and spectroscopic characterization of cy‐[O‐(H 2 ‐PTPEG 2 )‐O‐CH 2 ‐] 4 and of its cobalt‐derivative {cy‐[O‐(Co‐PTPEG 2 )‐O‐CH 2 ‐] 4 } was performed by means of MALDI‐TOF mass spectrometry, NMR, UV–vis, and circular dichroism spectroscopy. The data obtained from the cy‐[O‐(Co‐PTPEG 2 )‐O‐CH 2 ‐] 4 /Gramicidin‐S mixture showed that some evident spectral changes were compatible with the formation of a supramolecular structure between the porphyrinic nanobox and the Gramicidin S (a polypeptide having a relevant pharmacological importance). These preliminary data highlight how cy‐[O‐(H 2 ‐PTPEG 2 )‐O‐CH 2 ‐] 4 and/or its metalled derivatives, for their both chemical composition and structural arrangement, have promising properties for applications as a drug carrier in aqueous media.