Resolution of Ferrocene and Deuterated Ferrocene Conformations using Dynamic Vibrational Spectroscopy: Experiment and Theory.

Publication date: Available online 17 February 2020Source: Inorganica Chimica ActaAuthor(s): R.M. Trevorah, N.T.T. Tran, D.R.T. Appadoo, F. Wang, C.T. ChantlerAbstractThe signature of molecular vibrations and distortions in dynamic molecules gives a complex fingerprint which is insightful and can substantiate (or otherwise) chemical hypotheses regarding molecular and conformer stability. Using high-accuracy experimental data of ferrocene (Fc) and deuterated ferrocene (dFc, Fc - d10) at temperatures from 7 K through to 388 K, we obtain complex spectral profiles which require an advanced reaction coordinate model to explain. We obtain compelling evidence that the single conformer model (staggered D5d or eclipsed D5h) used to interpret and explain many experimental results on ferrocene is invalid. However we also present compelling evidence that mixed conformer models are invalid, where ferrocene is represented by an effective dihedral angle between the cyclopentadienyl (Cp) rings; or by a mixture of Boltzmann populations of the two conformers. We find no evidence for single or mixed conformer models despite covering almost all conclusions from past literature for gas, solution or solid phase Fc. Some molecular dynamics computations have imputed free rotation at liquid helium temperatures or at room temperature - we find no evidence for either of these hypotheses.We measure and derive point-wise experimental uncertainty of the spectra, enabling quantitative assessment of specifi...

Source: Inorganica Chimica Acta - February 18, 2020 Category: Chemistry Source Type: research