Due to their intrinsic long wavelength absorption and emission, bacteriochlorins have become a highly targeted class of photosensitizers in areas like photomedicine and artificial light harvesting. Presented here is the first synthesis of novel meso-tetraarylbacteriochlorin analogues in which both pyrrolidines of a bacteriochlorin are formally replaced by morpholino moieties. Oxidative cleavage (sNaIO4 on silica gel) of the two vic-diols of meso-tetraaryl-2,3,12,13-tetraolbacteriochlorins 1 , followed by an acid induced ring closure of the corresponding secobacteriochlorin aldehyde afforded the meso-tetraaryl-bis-(dimethoxymorpholino)-bacteriochlorin 2 , in a single step. Further treatment of 2  with acid causes a unidirectional double ring-fusion to form the bis-phenyl-fused bismorpholinobacteriochlorin 3 . Bacteriochlorin analogues 2   (?max = 790 nm) and 3   (?max = 735 nm) possess strongly bathochromically shifted UV-vis spectra compared to the starting tetraol 1   (?max = 708 nm). The double ring expansion also resulted in a dramatic distortion to the macrocycle conformation, as determined by single crystal X-ray diffraction.

Expanded bacteriochlorins

243rd National Meeting (2012)

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