Synthesis and properties of Oxasmaragdyrins containing one Five-membered Heterocycle at Meso-position

The oxasmaragdyrins containing one five membered heterocycle such as pyrrole, thiophene and furan in place of one of the meso-phenyl group were synthesized by acid-catalyzed oxidative coupling reaction of meso-heterocycle substituted dipyrromethane with 16-oxatripyrrane in the presence of catalytic amount of trifluoroacetic acid followed by oxidation with DDQ. The smaragdyrin macrocycles containing one five-membered heterocycle at meso-position were characterized by HR-MS and detailed 1D and 2D NMR studies. The absorption and fluorescence studies revealed that the presence of five membered heterocycle at meso-position of smaragdyrin resulted in bathochromic shifts in absorption and emission bands with slight reduction in quantum yields compared to smraragdyrin macrocycle containing six membered meso-phenyl groups. The electrochemical studies revealed that the meso-heterocycle smaragdyrins are electron deficient compared to meso-phenyl smaragdyrins