Synthesis and studies of -3-pyrrolyl BODIPYnyl porphyrins.

New -substituted porphyrins containing one to four 3-pyrrolyl BODIPY units at the -positions named -3-pyrrolyl BODIPYnyl porphyrins were synthesized in 15-20% yields by condensing -4-formyl phenyl-3-pyrrolyl BODIPY, benzaldehyde, and pyrrole in different molar ratios under acid catalyzed conditions. The identities of -3-pyrrolyl BODIPYnyl porphyrins were confirmed by HR-MS and detailed 1D & 2D NMR spectroscopy. -3-Pyrrolyl BODIPYnyl porphyrins showed a strong Soret band at 427 nm and weak Q-bands in the 500-650 nm region corresponding to the porphyrin unit whereas the 3-pyrrolyl BODIPY unit absorbs strongly in the 500-600 nm region. Thus, the absorption bands of the -3-pyrrolyl BODIPYnyl porphyrins in the Q-band region were significantly enhanced as the number of 3-pyrrolyl BODIPY units increases from one to four at -positions. The -3-pyrrolyl BODIPYnyl porphyrins were stable under both acidic and basic conditions. The steady-state and time-resolved fluorescence studies indicated a possibility of singlet-singlet energy transfer from 3-pyrrolyl BODIPY units to the porphyrin unit and a maximum energy transfer efficiency of 81% was observed for the -tetra 3-pyrrolyl BODIPYnyl porphyrin. DFT and TD-DFT studies were in agreement with the experimental observations.