Panchromatic Photosensitizers Based on Push-Pull, Unsymmetrically Substituted Porphyrazines

A series of five push-pull porphyrazines of A₃ B type, in which unit B is an isoindole 4-carboxylic acid, has been prepared. The units A have been endowed with thioether, amine, ether and alkyl functions, either directly attached to the β-position of the pyrrolic units, or connected to the porphyrazine core through p-substituted phenyl groups. Attaching the electron-donor functions to the porphyrazine periphery produces strong perturbations in the electronic and redox properties of the dyes. Their HOMO and LUMO energies, estimated from the optical and redox data, as well as with DFT calculations, raise upon functionalization with amines, while the corresponding frontier orbital energetic levels lower upon functionalization with thioethers, p-methoxyphenyl or p-tert-butylphenyl groups. The effective interaction of peripheral substitution with the macrocycle produces chromophores with panchromatic absorption between 300 and 750-850 nm.