Spectroscopic and computational characterization of lanthanide-mediated N–H and C–H bond activation of methylamine

Abstract

Ln (Ln = La and Ce) atom reactions with methylamine are carried out in a pulsed-laser vaporization supersonic molecular beam source. A series of dehydrogenation species are observed with time-of-flight mass spectrometry, and the dehydrogenated Ln-containing species in the formula Ln(NCH3) are characterized by mass-analyzed threshold ionization (MATI) spectroscopy and density functional theory and multiconfiguration spin–orbit coupling computations. The MATI spectrum of La(NCH3) consists of two vibronic band systems that are assigned to the ionization of the 2A1 ground state of the C3v isomer La(N–CH3) and the 2A′ ground state of the Cs isomer La(NH–CH2). The MATI spectrum of Ce(NCH3) also displays two band systems, which are attributed to the ionization of the low-energy spin–orbit coupling states of the C3v isomer Ce(N–CH3). Ln(N–CH3) is formed by the concerted dehydrogenation of the amino group, while La(NH–CH2) is formed by the dehydrogenation of both amino and methyl groups. Ce(NH–CH2) is presumably formed in the reaction based on the computational predictions but not observed by the spectroscopic measurements.

Exploring the structure and hydrogen storage capacity of CeHn0/+ clusters

“…27,[31][32][33][34] The prediction yields a total of 50 generations of structures under symmetric constraints, with each generation comprising 30 structures. The first 50 low-energy isomers among the initial structures are re-optimized using SDD 35,36 and 6-311G++(d,p) 37 base sets for Ce and H atoms at the B3LYP level with Gaussian 09 software. 38 The optimization process considers spin multiplicity and vibration frequency across singlet to sextuple states in order to obtain the actual ground state.…”

Probing La and Ce Excited-State Reactivity with Resonant Two-Photon Ionization Spectroscopy

“…More recently, lanthanide atoms in the ground electronic states have been used to activate C–C/C–H bonds of small hydrocarbons, and the activation reactions were characterized by ionization spectroscopy in the gas phase. − The presence of the 4f electrons and stronger spin–orbit coupling makes the lanthanides different from d-block transition metals. , The compactness of the 4f orbitals makes the lanthanide reactions with minimal reliance on ligands and the ability to undergo rapid ligand exchange. , Despite the recent advancement in the hydrocarbon activation by the ground-state lanthanide atoms and the unique feature of these heavy elements, reports on how their excited states would affect C–H/C bond activations are hard to find in the literature. In this work, we report the reactivity comparison of the initial and excited states of La and Ce atoms using 1-butyne (C 4 H 6 ) as a reaction substrate.…”