Metal assembly in novel dendrimers with porphyrin cores

A series of phenylazozmethine (DPA) dendrimers with a porphyrin core (PnH2) were synthesized by dehydration using TiCl4 from meso-tetrakis(4-aminophenyl)porphyrin and the DPA dendrons. The addition of SnCl2 to a dichloromethane/acetonitrile solution of dendritic cobalt porphyrin resulted in a stepwise spectral change. By using UV-vis spectroscopy to monitor the complexation of the P4CoIIICl until an equimolar amount of SnCl2 has been added, four changes in the position of the isosbestic point were observed during the addition of SnCl2. Titration results suggest that four different complexes are successively formed upon the SnCl2 addition and that the complexation proceeds in, not a random, but a stepwise fashion from the core imines to the terminal imines of P4CoIIICl. The electrochemical study reveals that their dendrimers with Tb ion act as a multielectron mediator in CO2 reduction at high applied potential on the electrode.