Energy-Resolved Collision-Induced Dissociation Studies of 1,10-Phenanthroline Complexes of the Late First-Row Divalent Transition Metal Cations: Determination of the Third Sequential Binding Energies

Abstract

The third sequential binding energies of the late first-row divalent transition metal cations to 1,10-phenanthroline (Phen) are determined by energy-resolved collision-induced dissociation (CID) techniques using a guided ion beam tandem mass spectrometer. Five late first-row transition metal cations in their +2 oxidation states are examined including: Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+). The kinetic energy dependent CID cross sections for loss of an intact Phen ligand from the M(2+)(Phen)3 complexes are modeled to obtain 0 and 298 K bond dissociation energies (BDEs) after accounting for the effects of the internal energy of the complexes, multiple ion-neutral collisions, and unimolecular decay rates. Electronic structure theory calculations at the B3LYP, BHandHLYP, and M06 levels of theory are employed to determine the structures and theoretical estimates for the first, second, and third sequential BDEs of the M(2+)(Phen)x complexes. B3LYP was found to deliver results that are most consistent with the measured values. Periodic trends in the binding of these complexes are examined and compared to the analogous complexes to the late first-row monovalent transition metal cations, Co(+), Ni(+), Cu(+), and Zn(+), previously investigated.