Synthesis, Structure, and Optical and Redox Properties of Chlorophyll Derivatives Directly Coordinating Ruthenium Bisbipyridine at the Peripheral β-Diketonate Moiety

Symmetrical and Nonsymmetrical Meso-Meso Directly Linked Hydroporphyrin Dyads: Synthesis and Photochemical Properties

A series of a rigid meso-meso directly linked chlorin-chlorin, chlorin-bacteriochlorin, and bacteriochlorin-bacteriochlorin dyads, including free bases as well as Zn(II), Pd(II), and Cu(II) complexes, has been synthesized, and their absorption, emission, singlet oxygen (¹O₂) photosensitization, and electronic properties have been examined. Marked bathochromic shifts of the long-wavelength Q _y absorption band and increase in fluorescence quantum yields in dyads, in comparison to the corresponding monomers, are observed. Nonsymmetrical dyads (except bacteriochlorin-bacteriochlorin) show two distinctive Q _y bands, corresponding to the absorption of each dyad component. A nearly quantitative S₁-S₁ energy transfer between hydroporphyrins in dyads, leading to an almost exclusive emission of hydroporphyrin with a lower S₁ energy, has been determined. Several symmetrical and all nonsymmetrical dyads exhibit a significant reduction in fluorescence quantum yields in solvents of high dielectric constants; this is attributed to the photoinduced electron transfer. The complexation of one macrocycle by Cu(II) or Pd(II) enhances intersystem crossing in the adjacent, free base dyad component, which is manifested by a significant reduction in fluorescence and increase in quantum yield of ¹O₂ photosensitization.

Regioselective addition of amines to the trifluoromethyl-β-diketonate moiety of a chlorophyll derivative

The terminal trifluoroacetyl moiety in a β-diketonate group at the 3 position of a synthetic chlorophyll derivative was reacted with butylamine in dichloromethane to give the hemiaminal-type adduct. Electronic absorption spectra showed the keto carbonyl group at the 3 position of the adduct was converted into the enol type under the basic conditions.