Comment on "Localized and Delocalized States of a Diamine Cation: Resolution of a Controversy".

Since its appearance in [Cheng, X.; Zhang, Y.; Jónsson, E.; Jónsson, H.; Weber, P. M. Nat. Commun. 2016, 7, 11013] and recent re-investigation in [Gałyńska, M.; Ásgeirsson, V.; Jónsson, H.; Bjornsson, R. J. Phys. Chem. Lett., 2021, 12, 1250-1255], the dimethylpiperazine cation (DMP+) has generated considerable discussion and controversy in the scientific literature over the existence of stable, local energy minima in this molecular system. Specifically, prior assumptions that the Rydberg state and radical cation of DMP are similar have led to significant confusion and debate regarding the accuracy of various quantum chemistry methods and the existence of stable configurations of DMP+ itself. The purpose of this Viewpoint is to highlight recent studies that call into question the main findings in the previously mentioned works as well as present new CCSDT (Coupled-Cluster with Single, Double, and Triple excitations) calculations to finally bring closure to this controversy.