Long-range electronic connection in picket-fence like ferrocene–porphyrin derivatives

Abstract

The effects of a direct connection between ferrocene and porphyrin units have been thoroughly investigated by electrochemical and spectroscopic methods. These data not only reveal that substitution of the porphyrin macrocycle by one, two, three or four ferrocenyl groups strongly affects the electronic properties of the porphyrin and ferrocenyl moieties, they also clearly demonstrate that the metallocene centres are "connected" through the porphyrin-based electronic network. The dynamic properties of selected ferrocene-porphyrin conjugates have been investigated by VT NMR and metadynamic calculations. 1,3-Dithiolanyl protecting groups have been introduced on the upper rings of the ferrocene fragments to allow a straightforward and easy access to redox active picket-fence porphyrins. X-ray diffraction analyses of the zinc(II) 5-[1'-[2-(1,3-dithiolanyl)]ferrocenyl]-10,15,20-tri(p-tolyl)porphyrin and 5,15-bis[1'-[2-(1,3-dithiolanyl)]ferrocenyl]-10,20-bis(p-tolyl)porphyrin complexes reveal the existence of S-Zn bonds involved in supramolecular arrays. The solid state analysis of the trans-5,15-di-(1'-(formyl)ferrocenyl)-10,20-di-(p-tolyl)-porphyrinatozinc(II) complex, obtained by deprotection of the dithiolane substituted analog, is conversely found in the crystal lattice as a monomer exhibiting a hexacoordinated zinc metal centre.