Gas Phase Electronic Spectroscopy of Several Aryl Boronate Esters

<p>Covalent organic frameworks (COFs) are an important class of polymers. However, from a physical chemistry perspective, these types of species have not been investigated in detail. One important class of molecules used as a building block in some COFs are aryl boronate esters. Even these relatively small molecules have not garnered in-depth spectroscopic studies. The aryl boronate ester of interest for this study, 2-phenyl-1,3,2-benzodioxaborole (compound <strong>1</strong>), is planar with two aromatic moieties and is an interesting target for high resolution electronic spectroscopy for two reasons. First, understanding this constituent can have application in understanding the electronic structure of the larger COF material. Second, there are very few boronate molecules of this type studied and thus they are an interesting target for general understanding of this class of compounds. In this work we have applied Resonance Enhanced Multiphoton Ionization (REMPI) and Zero Electron Kinetic Energy (ZEKE) laser techniques to measure high resolution, jet cooled spectra of compound <strong>1</strong> and three substituted derivatives. We were able to demonstrate that the π electrons from two aromatic rings are localized and show two distinct electronic states, which are only separated by 240 cm_-1. Such findings may play an important role in understanding the electronic structure of COF materials containing these species. Computational calculations were performed to complement the experimental data and provide further insight.</p>