Structure and Fluxionality of B13+ Probed by Infrared Photodissociation Spectroscopy

Abstract

We use cryogenic ion vibrational spectroscopy to characterize the structure and fluxionality of the magic number boron cluster B₁₃⁺. The infrared photodissociation (IRPD) spectrum of the D₂‐tagged all‐¹¹B isotopologue of B₁₃⁺ is reported in the spectral range from 435 to 1790 cm⁻¹ and unambiguously assigned to a planar boron double wheel structure based on a comparison to simulated IR spectra of low energy isomers from density‐functional‐theory (DFT) computations. Born–Oppenheimer DFT molecular dynamics simulations show that B₁₃⁺ exhibits internal quasi‐rotation already at 100 K. Vibrational spectra derived from these simulations allow extracting the first spectroscopic evidence from the IRPD spectrum for the exceptional fluxionality of B₁₃⁺.

A molecular ball bearing: The first spectroscopic evidence for the exceptional fluxionality of the magic number boron cluster B₁₃⁺ is presented. The vibrational spectrum of D₂‐tagged ¹¹B₁₃⁺ is reported and assigned to a planar boron double‐wheel structures based on a comparison to results from density‐functional‐theory computations. The spectral fingerprint of internal quasi‐rotation is identified with the aid of molecular dynamics simulations.