The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Mechanisms of photoreactions in solution. XX. Quenching of excited states of benzophenone by metal chelates》. Authors are Hammond, George S.; Foss, Robert P..The article about the compound:Bis(2,2,6,6-tetramethyl-3,5-heptanedionato)nickel(II)cas:14481-08-4,SMILESS:CC(C)(C1=O[Ni+2]2(O=C(C(C)(C)C)[CH-]1)O=C([CH-]C(C(C)(C)C)=O2)C(C)(C)C)C).Recommanded Product: Bis(2,2,6,6-tetramethyl-3,5-heptanedionato)nickel(II). Through the article, more information about this compound (cas:14481-08-4) is conveyed.
Metal chelate compounds containing ligands derived from β-diketones show variable reactivity as quenchers in the photoreduction of benzophenone by benzhydrol. Reactivity varies both as a function of the nature of the central metal atom and of the ligand. There is no correlation between quenching activity and the magnetic properties of the ground states of the chelates. Two possible mechanisms for quenching are discussed but no selection between them is attempted.
In addition to the literature in the link below, there is a lot of literature about this compound(Bis(2,2,6,6-tetramethyl-3,5-heptanedionato)nickel(II))Recommanded Product: Bis(2,2,6,6-tetramethyl-3,5-heptanedionato)nickel(II), illustrating the importance and wide applicability of this compound(14481-08-4).
Reference:
Ester – Wikipedia,
Ester – an overview | ScienceDirect Topics