Probing the geometry reorganization from solution to gas-phase in putrescine derivatives by IRMPD, H-1-NMR and theoretical calculations

Author(s)

Correra, Thiago Carita ; Fernandes, Andre Santos ; Reginato, Marcelo Mota ; Ducati, Lucas Colucci ; Berden, Giel ; Oomens, Jos

• Document type: Journal article
• Source: Physical Chemistry Chemical Physics; v. 19, n. 35, p. 24330-24340, SEP 21 2017.
• Web of Science Citations: 4

Abstract

Single and double protonated (E)-1,4-diamine-2-butenes were evaluated as a model system to probe isomerization during the ESI processes employing infrared multiple-photon dissociation (IRMPD) spectroscopy and density function theory (DFT) calculations, including implicit and explicit solvation models. Our results show that the preferential protonation takes place at the amines for singly protonated species and that the double bond is not protonated even under double protonation, as expected from known pK(a) values. This behavior was shown to reflect the (E)-(Z) interconversion rate, as no interconversion was observed nor predicted by implicit solvation model based on density (SMD) calculations even by the olefin protonation pathway. Explicit solvent calculations show that the singly protonated (E) configuration observed in the gas phase is also the most stable configuration in solution due to molecular interactions with the solvent that are absent for the (Z) configuration. The explicit solvation calculation reverts the supposed gas-phase stability of the (Z) configuration in comparison to (E) from -9 kcal mol (-1) (in relative Gibbs free energy) in the gas phase to +89 kcal mol(-1) (in total potential energy) as depicted by explicit Monte Carlo (MC) simulations. Together with previous results for the saturated 1,4-diamines from Morton and coworkers that show the (Z) configuration related conformation to be the most stable geometry in the gas-phase due to intermolecular hydrogen bonding, our experiments clearly show that conformational reorganizations can take place during the ESI process. These results suggest that gas-phase experiments and vacuum calculations may not be valid as evidence for conformations in solution without prior testing to check for isomerization during the ESI process. (AU)

• FAPESP's process: 15/08541-6 - Nuclear magnetic resonance spectroscopy: beyond molecular structure assignment
• Grantee: Claudio Francisco Tormena
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 15/11769-9 - Isolation of Sharpless reaction intermediates epoxidation and characterization of these species by theoretical calculations
• Grantee: André Santos Fernandes
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 15/08539-1 - Multi-User Equipment approved in grant 2014/15962-5: ion trap mass spectrometer modified to perform infrared vibrational spectroscopy (IRMPD)
• Grantee: Thiago Carita Correra
• Support Opportunities: Multi-user Equipment Program
• FAPESP's process: 14/21930-9 - Study of the solvent effect on the spin spin coupling constant 1JPt-Tl in heavy metal complexes by ab initio molecular dynamics
• Grantee: Lucas Colucci Ducati
• Support Opportunities: Scholarships abroad - Research
• FAPESP's process: 14/15962-5 - Reaction mechanism of asymmetric catalysts by mass spectrometry and gas-phase vibrational ion spectroscopy
• Grantee: Thiago Carita Correra
• Support Opportunities: Research Grants - Young Investigators Grants