Coordination structures of lithium-methylamine clusters from infrared spectroscopy and ab initio calculations

Abstract

Spectra of clusters formed between lithium atoms and methylamine molecules are reported for the first time. Mass-selective infrared spectra of Li͑NH 2 CH 3 ͒ n have been recorded in both the N-H and C-H stretching fundamental regions. The infrared spectra are broadly in agreement with ab initio predictions, showing redshifted N-H stretching bands relative to free methylamine and a strong enhancement of the N-H stretching fundamentals relative to the C-H stretching fundamentals. The ab initio calculations suggest that, for n = 3, the methylamine molecules bunch together on one side of the lithium atom to minimize repulsive interactions with the unpaired electron density. The addition of a fourth methylamine molecule results in closure of the inner solvation shell and, thus, Li͑NH 2 CH 3 ͒ 5 is forced to adopt a two-shell coordination structure. This is consistent with neutron diffraction studies of concentrated lithium/methylamine solutions, which also suggest that the first solvation shell around the lithium atom can contain a maximum of four methylamine molecules.

Infrared spectroscopy in superfluid helium droplets

“…Moreover, the Ag shell around the Et core does not show any metallic behavior in the IR spectra of Et, thereby confirming that Ag atoms do not coagulate into a single compact cluster. Other composite clusters of metal atoms and small hydrocarbon molecules have been studied in helium droplets [121,[135][136][137].…”

A New Perspective on the Role of A‐Site Cations in Perovskite Solar Cells

“…LM + is again difficult to be synthesized, though its spectra were observed from experiments. [33] This is however also investigated to understand what kind of molecular type is useful to reduce the e-ph coupling.…”

Electron Solvation and the Unique Liquid Structure of a Mixed‐Amine Expanded Metal: The Saturated Li–NH3–MeNH2 System

“…All metallic metal amines share the trait of being highly structured liquids,13, 14, 15, 16 with distinct M (solv) –M (solv) correlations. In both Li–NH 3 and Li–MeNH 2 solutions, Li is found to be four‐coordinate, which has subsequently been found to be the case in the gas phase,17, 18, 19 and through computational investigation 1, 19, 20, 21. The volumetric expansion of these liquid metals across their insulator–metal transition is also accompanied by the appearance of void spaces, which is presumably linked to the conduction electron density.…”

“…[13,14] All metallic metal amines share the trait of being highly structured liquids, [13][14][15][16] with distinct M (solv) -M (solv) correlations.I nb oth Li-NH 3 and Li-MeNH 2 solutions,L ii s found to be four-coordinate,w hich has subsequently been found to be the case in the gas phase, [17][18][19] and through computational investigation. [1,[19][20][21] Thevolumetric expansion of these liquid metals across their insulator-metal transition is also accompanied by the appearance of void spaces,which is presumably linked to the conduction electron density.I nLi-NH 3 these voids take the form of channels between Li(NH 3 ) 4 units, [13] whereas in Li(MeNH 2 ) 4 the voids are spatially isolated. [14] This is concordant with magnetic measurements that suggest electronic conduction in Li(MeNH 2 ) 4 is via rapid migration of electrons between these polaronic voids,w hich begin to localize in the solid state.…”