Elucidation of the electronic structure of water-soluble quaternized meso-tetrakis(3-pyridyl)bacteriochlorin derivatives by experimental and theoretical methods

Three water-soluble quaternized metal-free tetra-(3-pyridyl)bacteriochlorins were synthesized and characterized by UV-vis, MCD, and NMR spectroscopy as well as elemental analysis. DFT calculations are indicative of the ΔHOMO < ΔLUMO relationship, which correlates well with the experimentally observed by MCD spectroscopy for all bacteriochlorins “reversed” sign sequence in the Vis-NIR region. TDDFT calculations also correctly predict large splitting between the Qx and Qy bands as well as splitting of the Soret band observed experimentally in all bacteriochlorins.