scholarly journals Fragmentation of benzylpyridinium “thermometer” ions and its effect on the accuracy of internal energy calibration

2010 ◽  
Vol 21 (1) ◽  
pp. 172-177 ◽  
Author(s):  
Konstantin V. Barylyuk ◽  
Konstantin Chingin ◽  
Roman M. Balabin ◽  
Renato Zenobi
Keyword(s):  
Internal Energy ◽  
Energy Calibration ◽  
Thermometer Ions

scholarly journals Unimolecular Fragmentation Properties of Thermometer Ions from Chemical Dynamics Simulations

2020 ◽  
Author(s):  
Abdul Malik ◽  
Riccardo Spezia ◽  
William L. Hase
Keyword(s):  
Internal Energy ◽  
Rate Constants ◽  
Activation Energies ◽  
Bond Dissociation Energies ◽  
Excitation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Thermometer Ions ◽  
Dynamics Simulations ◽  
Threshold Energies

Thermometer ions are widely used to calibrate the internal energy of the ions produced by electrospray ionization in mass spectrometry. Commonly used ions are benzylpyridinium ions with different substituents. More recently benzhydrylpyridinium ions were proposed for their lower bond dissociation energies. Direct dynamics simulations using M06-2X/6-31G(d), DFTB, and PM6-D3 are performed to characterize the activation energies of two representative systems; para-methyl-benzylpyridinium ion (p-Me-BnPy+) and methyl,methylbenzhydrylpyridinium ion (Me,Me-BhPy+). The theoretical bond dissociation energies match closely with the experiment. Simulation results are used to calculate rate constants for the two systems. These rate constants and their uncertainties are used to find the Arrhenius activation energies and RRK fitted threshold energies which give reasonable agreement with calculated bond dissociation energies at the same level of theory. There is only one fragmentation mechanism observed for both systems, which involves C-N bond dissociation via a loose transition state, to generate either benzylium or benzhydrylium ion and a neutral pyridine molecule. For p-Me-BnPy+ using DFTB and PM6-D3 the formation of tropylium ion, from rearrangement of benzylium ion, was observed but only at higher excitation energies and for longer simulation times. These observations suggest that there is no competition between reaction pathways that could affect the reliability of internal energy calibrations.

scholarly journals Unimolecular Fragmentation Properties of Thermometer Ions from Chemical Dynamics Simulations

2020 ◽  
Author(s):  
Abdul Malik ◽  
Riccardo Spezia ◽  
William L. Hase
Keyword(s):  
Internal Energy ◽  
Rate Constants ◽  
Activation Energies ◽  
Bond Dissociation Energies ◽  
Excitation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Thermometer Ions ◽  
Dynamics Simulations ◽  
Threshold Energies

Thermometer ions are widely used to calibrate the internal energy of the ions produced by electrospray ionization in mass spectrometry. Commonly used ions are benzylpyridinium ions with different substituents. More recently benzhydrylpyridinium ions were proposed for their lower bond dissociation energies. Direct dynamics simulations using M06-2X/6-31G(d), DFTB, and PM6-D3 are performed to characterize the activation energies of two representative systems; para-methyl-benzylpyridinium ion (p-Me-BnPy+) and methyl,methylbenzhydrylpyridinium ion (Me,Me-BhPy+). The theoretical bond dissociation energies match closely with the experiment. Simulation results are used to calculate rate constants for the two systems. These rate constants and their uncertainties are used to find the Arrhenius activation energies and RRK fitted threshold energies which give reasonable agreement with calculated bond dissociation energies at the same level of theory. There is only one fragmentation mechanism observed for both systems, which involves C-N bond dissociation via a loose transition state, to generate either benzylium or benzhydrylium ion and a neutral pyridine molecule. For p-Me-BnPy+ using DFTB and PM6-D3 the formation of tropylium ion, from rearrangement of benzylium ion, was observed but only at higher excitation energies and for longer simulation times. These observations suggest that there is no competition between reaction pathways that could affect the reliability of internal energy calibrations.

scholarly journals Automated Internal Energy Calibration by OnTheFly for AGR-5/6/7

2021 ◽  
Author(s):  
Edward Reber ◽  
Dawn Scates ◽  
Ryan Fronk
Keyword(s):  
Internal Energy ◽  
Energy Calibration

scholarly journals Unimolecular Fragmentation Properties of Thermometer Ions from Chemical Dynamics Simulations

2020 ◽  
Author(s):  
Abdul Malik ◽  
Riccardo Spezia ◽  
William L. Hase
Keyword(s):  
Internal Energy ◽  
Rate Constants ◽  
Activation Energies ◽  
Bond Dissociation Energies ◽  
Excitation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Thermometer Ions ◽  
Dynamics Simulations ◽  
Threshold Energies

Thermometer ions are widely used to calibrate the internal energy of the ions produced by electrospray ionization in mass spectrometry. Commonly used ions are benzylpyridinium ions with different substituents. More recently benzhydrylpyridinium ions were proposed for their lower bond dissociation energies. Direct dynamics simulations using M06-2X/6-31G(d), DFTB, and PM6-D3 are performed to characterize the activation energies of two representative systems; para-methyl-benzylpyridinium ion (p-Me-BnPy+) and methyl,methylbenzhydrylpyridinium ion (Me,Me-BhPy+). The theoretical bond dissociation energies match closely with the experiment. Simulation results are used to calculate rate constants for the two systems. These rate constants and their uncertainties are used to find the Arrhenius activation energies and RRK fitted threshold energies which give reasonable agreement with calculated bond dissociation energies at the same level of theory. There is only one fragmentation mechanism observed for both systems, which involves C-N bond dissociation via a loose transition state, to generate either benzylium or benzhydrylium ion and a neutral pyridine molecule. For p-Me-BnPy+ using DFTB and PM6-D3 the formation of tropylium ion, from rearrangement of benzylium ion, was observed but only at higher excitation energies and for longer simulation times. These observations suggest that there is no competition between reaction pathways that could affect the reliability of internal energy calibrations.

scholarly journals Mass spectrometry evidence for self-rigidification of π-conjugated oligomers containing 3,4-ethylenedioxythiophene groups using RRKM theory and internal energy calibration

2019 ◽  
Vol 25 (2) ◽  
pp. 239-250
Author(s):  
David Rondeau ◽  
Yves Gimbert ◽  
Károly Vékey ◽  
Laszlo Dráhos ◽  
Mathieu Turbiez ◽  
...  
Keyword(s):  
Transition State ◽  
Internal Energy ◽  
Impact Ionization ◽  
Radical Cations ◽  
Alder Reaction ◽  
Dissociation Rate ◽  
Energy Calibration ◽  
Rrkm Theory ◽  
The Difference ◽  
Dissociation Rate Constants

The self-rigidification of ionized π-conjugated systems based on two combinations of thiophene (T) and 3,4-Ethylenedioxythiophene (E) is investigated using mass-analyzed ion kinetic energy spectrometry (MIKES) of ions produced from electron impact ionization at 70 eV. The m/z 446 radical cations of the two isomers ETTE and TEET lead to detect m/z 418 and 390 daughter ions. The MIKE spectra differ only by the intensities of these fragment ions. As the m/z 418 daughter ion is produced through a same retro-Diels Alder reaction whatever the fragmenting isomer, the difference in daughter ion intensities is interpreted in term of unimolecular dissociation rate constants ( k( Eint)) ratios. Considering that the transition state (TS) of such reaction is attributed to a quinoid form, equivalent vibration modes are assumed for the TS of both dissociating ETTE and TEET radical cations. As a result, by using the Rice–Ramsperger–Kassel–Marcus (RRKM) theory, the difference in daughter ion intensities is interpreted by considering that the fragmenting ion is more or less ordered in its ground state than at the transition state, resulting from the influence of the number of the S…O interactions in the planarization of the TEET ion toward the ETTE charged species. The comparison of this behavior in MIKES experiments is supported by the modeling of ion behavior in mass spectrometer and the calibration in internal energy of the radical cations produced in an EI source.

scholarly journals Internal Energy Deposition in Dielectric Barrier Discharge Ionization is Significantly Lower than in Direct Analysis in Real-Time Mass Spectrometry

2017 ◽  
Vol 70 (11) ◽  
pp. 1219 ◽  
Author(s):  
Morphy Dumlao ◽  
George N. Khairallah ◽  
W. Alexander Donald
Keyword(s):  
Mass Spectrometry ◽  
Internal Energy ◽  
Energy Deposition ◽  
Barrier Discharge ◽  
Direct Analysis ◽  
Ion Source ◽  
Dielectric Barrier ◽  
Internal Energy Deposition ◽  
Thermometer Ions ◽  
Dielectric Barrier Discharge Ionization

The extent of internal energy deposition using three different plasma-based ionization mass spectrometry (MS) methods, atmospheric pressure chemical ionization (APCI), direct analysis in real time (DART), and active capillary dielectric barrier discharge ionization (DBDI), was investigated using benzylammonium ‘thermometer’ ions. Ions formed by DBDI were activated significantly less than those that were formed by DART and APCI under these conditions. Thermal ion activation by DART can be reduced slightly by positioning the DART source further from the capillary entrance to the MS and reducing the heat that is applied to metastable atoms exiting the DART source. For example, the average ion internal energy distribution decreased by less than 10 % (166.9 ± 0.3 to 152.2 ± 1.0 kJ mol−1) when the distance between the DART source and the MS was increased by 250 % (10 to 25 mm). By lowering the DART temperature from 350 to 150°C, the internal energy distributions of the thermometer ions decreased by ~15 % (169.93 ± 0.83 to 150.21 ± 0.52 kJ mol−1). Positioning the DART source nozzle more than 25 mm from the entrance to the MS and decreasing the DART temperature further resulted in a significant decrease in ion signal. Thus, varying the major DART ion source parameters had minimal impact on the ‘softness’ of the DART ion source under these conditions. Overall, these data indicate that DBDI can be a significantly ‘softer’ ion source than two of the most widely used plasma-based ion sources that are commercially available.

scholarly journals Unimolecular Fragmentation Properties of Thermometer Ions from Chemical Dynamics Simulations

2020 ◽  
Author(s):  
Abdul Malik ◽  
Riccardo Spezia ◽  
William L. Hase
Keyword(s):  
Internal Energy ◽  
Rate Constants ◽  
Activation Energies ◽  
Bond Dissociation Energies ◽  
Excitation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Thermometer Ions ◽  
Dynamics Simulations ◽  
Threshold Energies

Thermometer ions are widely used to calibrate the internal energy of the ions produced by electrospray ionization in mass spectrometry. Commonly used ions are benzylpyridinium ions with different substituents. More recently benzhydrylpyridinium ions were proposed for their lower bond dissociation energies. Direct dynamics simulations using M06-2X/6-31G(d), DFTB, and PM6-D3 are performed to characterize the activation energies of two representative systems; para-methyl-benzylpyridinium ion (p-Me-BnPy+) and methyl,methylbenzhydrylpyridinium ion (Me,Me-BhPy+). The theoretical bond dissociation energies match closely with the experiment. Simulation results are used to calculate rate constants for the two systems. These rate constants and their uncertainties are used to find the Arrhenius activation energies and RRK fitted threshold energies which give reasonable agreement with calculated bond dissociation energies at the same level of theory. There is only one fragmentation mechanism observed for both systems, which involves C-N bond dissociation via a loose transition state, to generate either benzylium or benzhydrylium ion and a neutral pyridine molecule. For p-Me-BnPy+ using DFTB and PM6-D3 the formation of tropylium ion, from rearrangement of benzylium ion, was observed but only at higher excitation energies and for longer simulation times. These observations suggest that there is no competition between reaction pathways that could affect the reliability of internal energy calibrations.

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