[MLn]2+ doubly charged systems: modeling, bonding, life times and unimolecular reactivity

Abstract

Doubly charged species in the gas phase have been an oddity for many years, but the possibility of generating and detecting them with the new available experimental techniques has faced the scientific community with challenging questions regarding their stability, bonding and reactivity. In this paper we analyze, mainly from a theoretical perspective, these questions for the particular subset of [ML(n)](2+) dications, where M is a metal and L an organic or inorganic ligand. Special attention is devoted to the challenges associated with their theoretical description, in particular as far as their bonding and their life times are concerned. A survey of their unimolecular reactivity is also presented as well as a discussion of the information available on dication affinities, and how they correlate with proton affinities or monocation affinities in general.

Experimental Investigation of the Complete Inner Shell Hydration Energies of Ca2+: Threshold Collision-Induced Dissociation of Ca2+(H2O)x Complexes (x = 2–8)

“…Subsequently, Rao et al calculated sequential BDEs at the B3LYP/6-311++G(3d,3p), MP2(full)/6-311++G(3d,3p) and CCSD(T)/6-311++G(d,p) levels of theory using B3LYP/6-311++G(d,p) geometry optimizations along with G3 BDEs . Significantly, there is only one theoretical study of the reaction coordinate for the charge separation pathway from Ca 2+ (H 2 O) 2 to produce CaOH + and H 3 O + , by Beyer et al Examinations of such “Coulomb explosions” is an active area of research with experimental and theoretical studies of other Ca 2+ (ligand) systems. − In this context, the observation of a stable Ca 2+ (H 2 O) complex in the present study is of some interest, although not unexpected because the ionization energy of H 2 O exceeds the second ionization energy of Ca by 0.75 eV (such that dissociation to Ca + + H 2 O + is endothermic by this amount) and the hydroxide anion affinity of H + exceeds that of Ca 2+ by 2.3 ± 0.3 eV , (such that dissociation to CaOH + + H + is endothermic by this amount).…”

HMNTA Complexes of Tetravalent Metal Ions: On the Roles of Carbonyl Oxygen and Amine Nitrogen in the Stabilization of Gas-Phase M(HMNTA)24+Complexes

“…It is well-known that electrospray ionization (ESI) is a powerful technique to generate multiply charged ions in the gas phase, which allows further investigations of their thermochemical properties and structural information in combination with quantum chemical calculations. − Large gas-phase multiply charged ions such as peptides are easy to observe, in general, because the charges are often well separated in the whole system resulting in reduced electrostatic repulsion . In contrast, it is more difficult for highly charged metal complex cations with small or medium ligands where the multiple charges are not well separated to be observed in the gas phase since the strong electrostatic repulsion could result in Coulomb explosion. , Although the Zr­(CH 3 CN) 4+ system was predicted to be metastable by theory, M­(TMOGA) 3 4+ (M = Zr, Hf, Th, U, Np, and Pu, TMOGA = N , N , N ′, N ′-tetramethyl-3-oxaglutaramide) and M­(TMPDA) 3 4+ (M = Zr and Hf, TMPDA = N,N, N ′, N ′-tetramethylpyridine-2,6-dicarboxamide) are the only two categories of gas-phase tetrapositively charged metal complexes that have been observed experimentally.…”

Complexation of Ln3+ with Pyridine-2,6-dicarboxamide: Formation of the 1:2 Complexes in Solution and Gas Phase

“…Electrospray ionization mass spectrometry (ESI-MS) in conjunction with quantum chemical calculation has been employed to acquire this information in the gas phase, which has shed light on their solution chemistry to some extent. , However, the third ionization energies (IEs) of all metals lie well above the IEs of most common simple organic ligands, and the corresponding triply charged metal complexes are prone to charge reduction during the ionization process, which could alter their gas-phase structures and compositions . Despite the difficulty, a series of tripositive transition/lanthanide metal ions M­(L) n 3+ (L = alcohols, CH 3 CN, , DMSO, DMF, or H 2 O, , etc.)…”