Study of the suppression of porphyrin emission upon addition of rare earthions

A topic of constant investigation in recent decades has been the study of e lectron and/or energy transfer reactions in supramolecular systems. The ene rgy transfer between donor-acceptor depends on the influence of the substit uent in the intersystem crossing. The competition between the radiative and non-radiative processes also depends on other factors such as temperature, solvent and energy gap. In this work, we have studied the suppression of t he emission of monocarboxyphenyl porphyrins after addition of rare earth io ns (RE(III)). The porphyrin emission decreases with the addition of RE(III) , no matter which ion is present. When Eu(III) was used, the emission of th is ion was not observed either. This suppression happens due to the effect of the heavy atom and not due to the energy transfer through electronic lev els between the porphyrin and the RE(III). After the addition of RE(III), t he lifetime for MCTPPH2 started to decay biexponentially, indicating the fo rmation of a new species (MCTPPH2-RE(III)) of a shorter lifetime. The prese nce of NO2 groups in the ortho mesoaryl positions of MCTNPPH2 and the prese nce of Zn(II) in Zn(MCTPP) decreased both the porphyrin lifetime and emissi on due to an increase in the spin-orbit coupling.