A photoelectron spectroscopic and computational study of the o-dicarbadodecaborane parent anion

Abstract

We report a combined photoelectron spectroscopic and computational study of the o-dicarbadodecaborane (o-carborane) parent anion, (C2B10H12)(-). Previous studies that focused on the electrophilic nature of o-carborane led to tantalizing yet mixed results. In our study, we confirmed that o-carborane does in fact form a parent anion and that it has considerable stability. This anion is an isomer ("Anion iso 2") where unlike in neutral o-carborane, the two carbon atoms are not bound.

The Impact of Huge Structural Changes on Electron Transfer and Measurement of Redox Potentials: Reduction of ortho-12-Carborane

“…It is valuable to compare the results found here with anion photoelectron spectroscopy and computation on 1 by Zhang and Bowen. 4 They reported a broad, ∼1 eV fwhm, photoelectron band centered at 2.26 eV and computations giving two isomers for the anion in some similarity to those described here. From their computations they reported an electron affinity of 1.19 eV for 1, which would translate to a reduction potential of −1.7 V vs Fc, 0.22 V positive of the −1.92 V reduction potential determined here.…”

“…It is valuable to compare the results found here with anion photoelectron spectroscopy and computation on 1 by Zhang and Bowen . They reported a broad, ∼1 eV fwhm, photoelectron band centered at 2.26 eV and computations giving two isomers for the anion in some similarity to those described here.…”

“…Optimization (b3lyp/6-31g*) of 1 and 1 • – in the PCM reaction field for THF found 1 • – to be 2.51 eV more stable than 1 , corresponding to a reduction potential of −1.96 V vs Fc +/0 in agreement with potentials determined by electron transfer. Additional corroboration comes from anion photoelectron spectroscopy by Zhang and Bowen that will be discussed below.…”

“…They are consistent with earlier gas phase results by Zhang and Bowen. 4 Experiments have shown that 5−10 large structural changes produce changes in rate constants for electrochemical ET, 5−7 homogeneous self-exchange ET, 8−12 and heterogeneous bimolecular ET and can markedly alter the appearance of voltammetric waves. 5,6 For crowded ethylene derivatives Evans and co-workers 5−7 found distinct isomers that were roughly planar and perpendicular, with measurable reduction potentials for each.…”