Synthesis and photophysical properties of porphyrin-phthalocyanine heterodimer linked by piperazine

A porphyrin-phthalocyanine heterodimer linked by piperazine has been synthesized and characterized by spectroscopic methods. UV-visible absorption spectra indicated the presence of weak intramolecular interaction between the two chromophores. Selective excitation of the porphyrin moiety leads to energy transfer process to the phthalocyanine subunit. Furthermore, on the bases of the solvent-dependent fluorescence data, a competing electron transfer reaction is shown to occur in this heterodimer. The efficiency of both photophysical processes depends strongly on solvent polarity and is related to the separation distance of the two chromophores and their relative orientation. The value of Delta G(ET)(0) obtained using the Rehm-Weller equation clearly indicates that the heterodimer exists preferably in the "boat form" upon excitation in good agreement with the experimental results of co-occurence of energy and electron transfer process observed for the heterodimer.