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Title:INSIGHT INTO THE CHARGE TRANSFER MECHANISMS OF HEAVY ATOM SUBSTITUTED MALDI MATRICES
Author(s):Bridgmohan, Chelsea N
Contributor(s):Kirmess, Kristopher M; Wang, Lichang
Subject(s):Theory and Computation
Abstract:The underlying mechanism of how MALDI matrices work is poorly understood. Experimental literature suggests that the triplet excited state (T$_{1}$) of the matrix plays a significant role in its ability to transfer charge to the analyte effectively. The heavy atom substitution effect predicts that the addition of a heavy atom to an otherwise "dead" matrix, such as 2,4-dihydroxybenzoic acid, would increase the rate of Intersystem Crossing (ISC) to the T$_{1}$ state via spin-orbit coupling. This effect was observed experimentally as there was a visible decay in singlet lifetime and an increase in triplet lifetime, as well as a better matrix performance when compared to its original, unsubstituted partner. To provide insight into the photophysical properties of 2,4-dihydroxybenzoic acid and its halogenated isomers, calculations were performed using \textit{Gaussian09}. Geometry optimizations, frequencies, and IR spectra of all isomers were calculated using Density Functional Theory (DFT) with B3LYP functional and the 6-31G+(d,p) basis set. UV-Vis and fluorescence spectra were generated using Time-Dependent DFT (TDDFT). The following values for the singlet ground state (S$_{0}$), triplet excited state (T$_{1}$), and singlet excited state (S$_{1}$) were tabulated and compared: optimization energies, HOMO-LUMO energies and orbital contours, and bond distances. In addition, the energy values for Proton Affinity (PA) and Gas Phase Acidity (GPA) were determined.
Issue Date:6/21/2017
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:APS
Genre:CONFERENCE PAPER/PRESENTATION
Type:Text
Language:English
URI:http://hdl.handle.net/2142/96966
DOI:10.15278/isms.2017.WI05
Date Available in IDEALS:2017-07-27


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