In organic chemistry, atoms other than carbon and hydrogen are generally referred to as heteroatoms. The most common heteroatoms are nitrogen, oxygen and sulfur. Now I present to you an article called π-π Stacking interaction in an oxidized CuII-Salen complex with a side-chain indole ring: An approach to the function of the tryptophan in the active site of galactose oxidase, published in 2019, which mentions a compound: 19777-66-3, mainly applied to galactose oxidase active site mimic copper salen complex tryptophan; copper; heterocycles; oxidation; pi interactions; radicals, Quality Control of (S)-Propane-1,2-diamine dihydrochloride.
In order to gain new insights into the effect of the π-π stacking interaction of the indole ring with the CuII-phenoxyl radical as seen in the active form of galactose oxidase, we have prepared a CuII complex of a methoxy-substituted salen-type ligand, containing a pendent indole ring on the dinitrogen chelate backbone, and characterized its one-electron-oxidized forms. The X-ray crystal structures of the oxidized CuII complex exhibited the π-π stacking interaction of the indole ring mainly with one of the two phenolate moieties. The phenolate moiety in close contact with the indole moiety showed the characteristic phenoxyl radical structural features, indicating that the indole ring favors the π-π stacking interaction with the phenoxyl radical. The UV/Vis/NIR spectra of the oxidized CuII complex with the pendent indole ring was significantly different from those of the complex without the side-chain indole ring, and the absorption and CD spectra exhibited a solvent dependence, which is in line with the phenoxyl radical-indole stacking interaction in solution The other physicochem. results and theor. calculations strongly support that the indole ring, as an electron donor, stabilizes the phenoxyl radical by the π-π stacking interaction.
In addition to the literature in the link below, there is a lot of literature about this compound((S)-Propane-1,2-diamine dihydrochloride)Quality Control of (S)-Propane-1,2-diamine dihydrochloride, illustrating the importance and wide applicability of this compound(19777-66-3).
Reference:
Quinoxaline – Wikipedia,
Quinoxaline | C8H6N2 | ChemSpider