Nominally, meso-hydroxyoxochlorins, like known 5-hydroxy-7-oxo-octaethylchlorin (9), its nickel complex [5-hydroxy-7-oxo-octaethylchlorinato]nickel(II) (9Ni), or the novel 5-hydroxy-7,17-dioxo-octaethylbacteriochlorin (10), incorporate an acetylacetonate (acac)-moiety in the enol form in their chromophore structures. X-Ray diffraction...