The Mn(Salen) complex, the Jacobsen's catalyst has seen rising interest as a heterogeneous phase catalyst as modern synthesis drives towards environmentally concious practices.  The restricted orentation and mobility of the catalyst deposited onto a solid support is thought to by the cause of the reduced enantioselectivity of the system. Despite this it remains poorly understood eaxctly what parameters account for the behavoir of surface deposited organometalic catalysts. Vibrational sum frequency generation spectroscopy takes advantage of nonlinear optical phenomena to selectively probe the vibrational resonances of molecular interfaces.  Advancements to this technique such, as doubly resonant excitation, heterodyne phase resolution, and polarization analysis, have respectively demonstrated a propensity to probe vibrational and electronic (vibronic) structures of interfacial molecules, the relative phases of molecular resonances, molecular organization, as well as chiral specificity.  We seek to expnad the ways that we can use sum frequency generation spectroscopy to inform us on the interfacial vibronic properties of chiral systems.  Here in we present a study in which chiral doubly resonant internally heterodyne phase resolved sum frequency genration spectroscopy is used to probe the electronic and vibrational sturcture function relation ship for a Jacobsen's catalyst film deposited on crystaline quartz.  We find the ability to discriminate enantiomeres from one another and their racemeate at the interface, as well as the unique ability to probe chiral vibronic coupling in a capaity not shown without chiral specificity. Furthermore,  spectral responses show the ability to probe the vibronic coupling of the ligand to multiple unique electronic excited states in the form phase shifting and resonant enhancement.  We anticipate that this tehcnique will provide a valuable recourse in future application based studies seeking to compare these properties between various systems and derivatives.

Influence of electronic resonances on the phase resolved chiral sum frequency lineshape for a surface confined transition metal catalyst

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.