Tapping the near-infrared spectral region with bacteriochlorin arrays

Bacteriochlorophylls - natural pigments for absorption of near-infrared (NIR) light - underlie light-absorption and energy transduction in photosynthetic bacteria. Capturing and utilizing NIR light is valuable in fields ranging from artificial photosynthesis to photomedicine (photodynamic therapy, imaging, and diagnostics). The desired photochemical features may be best elicited with multicomponent architectures that support efficient excited-state energy and/or electron transfer, yet few such arrays containing bacteriochlorins (the core chromophore of bacteriochlorophylls) are known. This review outlines three synthetic approaches toward bacteriochlorins, surveys all known bacteriochlorin arrays, and compares molecular design strategies for light-harvesting arrays containing bacteriochlorins versus (the better known) porphyrins.