Electron-Withdrawing meso -Substituents Turn On Magneto-Optical Activity in Porphyrins

A series of square planar metalloporphyrins (M(TPP), TPP is 5,10,15,20-tetraphenylporphyrin and M(TPFPP), TPFPP is 5,10,15,20-tetrapentafluorophenylporphyrin; M is Zn2+, Ni2+, Pd2+, or Pt2+) with distinct meso-substituents were prepared and their Magneto-Optical Activity (MOA) was characterized by magnetic circular di-chroism (MCD) and Magneto-Optical Rotary Dis-persion spectroscopy (MORD; also known as Fara-day Rotation spectroscopy). MOA is crucial in the development of next generation magneto-optical devices and quantum computing. The data show that the presence of meso-pentafluorophenyl sub-stituents results in significant increase in MOA in comparison to the homologous phenyl group. Dif-ferences in the MOA of these metalloporphyrins are rationalized using the Gouterman four-orbital mod-el and pave the way for rational design of im-proved and tailorable magneto-optical materials