SYNTHESIS AND PHOTOPHYSICAL EVALUATION OF <i>meso</i>-PHENYL-1,4-DIHYDROPYRIDINE AND PYRIDINE-PORPHYRIN HYBRIDS

Abstract

In the present work, we have synthesized new molecular hybrids consisting of porphyrin ring system connected at the meso positions with phenyl groups and/or, through p-phenylene linkers, with 1,4-dihydropyridine or pyridine moieties. In general, the directed use of dihydropyridine aldehyde, under time-modified Adler–Longo procedures, gave the best overall yields of the following meso-substituted dihydropyridine-porphyrins of general formula A1B3, A2B2, or A4, where A stands for phenyl-dihydropyridine and B for phenyl substituents. The corresponding meso-substituted pyridine-porphyrin hybrids were obtained from oxidation of the dihydropyridineporphyrins with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. The UV-vis spectra bands of the A4 dihydropyridine-porphyrin were unexpectedly red-shifted, having a rhodoporphyrin Q-bands profile. It was also found that an increased production of 1O2 correlates with a higher number of dihydropyridine or pyridine moieties in the hybrid molecule. All porphyrin hybrids were considered adequate candidates to be employed in photodynamic therapy.