Iodization Threshold in Size-Dependent Reactions of Lead Clusters Pb_n⁺ with Iodomethane

Abstract

Utilizing a magnetron-sputtering (MagS) source in tandem with a multiple-ion laminar flow tube (MIFT) reactor and a customized triple quadrupole mass spectrometer (TQMS), we have prepared clean Pb n + (n = 1–13) clusters and measured their reactivity with iodomethane under high carrier gas pressures. Strong size dependences are found for the reactivity of these cationic Pb n + clusters with CH3I. For the Pb n + with n ≤ 4, iodinated clusters Pb n I+ were found to be the dominant products, in strong contrast to n > 4 where no such products were seen. Quantum chemical studies show that with an increasing number of Pb atoms, the Pb–Pb interatomic interactions become stronger compared with the Pb–I bonding in Pb n I+ clusters. Furthermore, the reactions of Pb1–4 + with CH3I have fairly small transition state energy barriers, in contrast to those for Pb n>4 + clusters which have magnitudes that will prevent reactions under the ambient conditions.

Reactivity of Cobalt Clusters Con±/0 with Dinitrogen: Superatom Co6+ and Superatomic Complex Co5N6+

“…Nowadays, experimental and theoretical studies on metal clusters can be performed at an atomic accuracy, which has attracted researchers’ much more attentions recently in discovery of high catalytic activity and unique selectivity for many significant catalytic reactions. , In most studies, the reactions of small metal clusters with gas molecules display size dependence, showing the possibility of one atom making a difference. Meanwhile, charge states of metal clusters often play a determining role in metal cluster reactivity. − For example, the striking investigation on reactions between aluminum cluster anions and water shows that the chosen Al n – clusters can simply adsorb water molecules while the others give rise to the evolution of hydrogen, shedding light on the complementary Lewis base/acid active sites in controlling the size-selective reactivity . Moreover, by reactions with oxygen or other strong etchants, several interesting metal clusters and metal complexes have been deduced from mass abundances in experimental observations and identified as stable superatoms or magic species. − For example, Castleman, Khanna, and co-workers identified the magic Al 13 – , superatom halogen Al 13 , and superatomic iodide salts (e.g., Al 7 I – , Al 13 I – , Al 13 I 2 – , Al 13 I 4 – , and Al 14 I x – ) .…”

To What Extent Do Iodomethane and Bromomethane Undergo Analogous Reactions?

“…The reactions of Pb n + clusters with iodomethane showed that the small ones are more active in forming the iodinated products Pb n I + , with an iodization threshold at n = 4. This was rationalized that the Pb–Pb interatomic interactions become stronger compared to the Pb–I bonding in Pb n I + clusters with an increasing number of Pb atoms at n ≥ 4, as well as smaller transition-state (TS) energy barriers for the reactions of Pb 1–4 + . Among others, previous studies demonstrated photoinduced reactions of gold clusters with CH 3 Br, where laser irradiation influences the bromine-rich products, shedding light on the photocatalytic methyl radical elimination .…”

“…This was rationalized that the Pb−Pb interatomic interactions become stronger compared to the Pb−I bonding in Pb n I + clusters with an increasing number of Pb atoms at n ≥ 4, as well as smaller transition-state (TS) energy barriers for the reactions of Pb 1−4 + . 13 Among others, previous studies demonstrated photoinduced reactions of gold clusters with CH 3 Br, where laser irradiation influences the bromine-rich products, shedding light on the photocatalytic methyl radical elimination. 14 Also, photoinduced dissociation of CH 3 I was studied, where the first excitation state arising from the electronic transition from the nonbonding 5p-π to C−I antibonding σ* orbital dominates the CH 3 I dissociation.…”

Computational Investigation on Adsorption and Activation of Atmospheric Pollutants CO, NO and SO on Small Cobalt Clusters

“…Meanwhile, the charge states of metal clusters often play a determining role in metal cluster reactivity. [12][13][14] The adsorption and activation of the atmospheric pollutant molecules on the surfaces of metal nanoclusters has been extensively studied over the last two decades. 4,5,9,[15][16][17][18][19][20] The most efficient materials used for such activity are the earth-abundant transition metals, such as, Fe, Co, and Ni, which have versatile catalytic properties for a variety of reactions 3,9,15,[21][22][23] such as, nitrogen fixation/activation, water/ammonia dissociation, and CO/CO2 adsorption.…”