Preferential formation of mixed dimers in aluminium containing porphyrin-phthalocyanine systems: A photophysical study

The interaction of chloroaluminium phthalocyanine and aluminium porphyrin in solution was studied using UV-visible and fluorescence techniques. The spectra of the porphyrin alone exhibited new bands attributed to aggregates and a value of −12.6 kJ mol−1 for the enthalpy of dimerization was obtained. A small dimerization constant of 5.8 × 103 M−1 was found for phthalocyanine homodimers and preferential formation of mixed dimers over porphyrin homodimers was observed experimentally and supported by molecular modelling. kd and ΔH values of 5.7 × 104 M−1 and −21.1 kJ mol−1 were found in the mixed system, along with an enhancement in phthalocyanine fluorescence.