Theoretical investigation of fluorescence properties of EDTA and DTPA substituted tetraphenylporphyrin molecules.

The matrix elements of spin-orbit coupling operator (H(SO)) and non-adiabatic coupling operator (Ω) for the H(2)ATPP-EDTA and H(2)ATPP-DTPA molecules were calculated using INDO method. Rate constants of internal conversion and of intersystem crossing were calculated using the values of matrix elements of H(SO) and Ω operators and excitation energies both calculated with the ADC(2) and TDDFT methods and obtained from experimental data. Results of calculations show that the probability of radiationless deactivation in internal conversion channel is greater than the probability of radiationless transition in intersystem crossing channel for considered molecules. Obtained theoretical values of fluorescence quantum yield have good agreement with their experimental values.