Spectrophotometric and electrochemical studies of Mg, Zn, Cd, and Hg meso-tetraphenylporphyrins

The axial ligand-addition reactions of (TPP)M where M = Mg(II), Zn(II), Cd(II), and Hg(II) with twenty different nitrogenous bases (L) were investigated by spectrophotometric titration. The stability constant of (TPP)M(L), log K1, increased in the order Zn > Mg > Cd > Hg, and ranged from 0,25 to 5.76 with imidazoles having the highest values. [...]