Metals of Transition series influence in proton RMN spectra First of all, Greetings to everyone My question is simple but a bit able to create confusion i can't explain myself right so i'm gonna try... The question is how can the fact of a metal being of the transition serie os periodic table or not influence the H1 RMN spectra? What makes protons in a molecule near Ni more shielded and near Zn for example more unshield? i know that's something about the sigma donation and the transfer of electrons to [tex]\pi*[/tex] of the metal, if anyone can help me on this would be great i will give an example of what i'm talking about, i sintetize ZnTPP and NiTPP and from the spectra resulted in the images, i tryed but my bases on organometallic chemistry are a bit weak i would like to have some lights on this... as i'm confused of how can the transition metals shield more the protons of the porphyrin in this case. my thanks antecipated for who answers this, i didn't put this on homework cause is a fact of the theory that wasn't well assimilated, there are some things i can't relate to this.