Luminol tautomers and their interaction with zinc cation – A DFT treatment

Luminol is a chemiluminescent material having variety of applications. In the present study, its 1,3-proton tautomers have been considered within the restrictions of density functional theory at the level of B3LYP/6-31++G(d,p) and B3LYP/6-311++G(d,p) levels. Also, interaction of luminol tautomers with zinc dication at the level of B3LYP/6-31++G(d,p) is considered. All the structures considered presently are thermally favored and electronically stable at the standard states. The effect of zinc dication on the tautomers of luminol is not drastic but causes some conformational changes and enhancing the hydrogen bond formation in some cases. Some electron population has been transferred from the organic partner of the composite to the zinc cation, thereby lowering the initial formal charge of the cation. Various structural and quantum chemical data have been collected and discussed, including IR and UV-VIS spectra. Also the NICS (0) data have been obtained for the tautomers.