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Armstrong BI, Willans M, Pearson EL, Becker T, Hackett MJ, Raiteri P. Revisiting the Conformational Isomerism of Dihaloethanes: A Hybrid Computational and Experimental Laboratory for the Undergraduate Curriculum. ACS Phys Chem Au 2023; 3:157-166. [PMID: 36968445 PMCID: PMC10037444 DOI: 10.1021/acsphyschemau.2c00055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 12/20/2022] [Accepted: 12/22/2022] [Indexed: 01/13/2023]
Abstract
The conformational isomerism of disubstituted ethanes is a well-known concept that is part of every chemistry curriculum. Due to the species' simplicity, studying the (free) energy difference between the gauche and anti isomers has been the testing ground of experimental and computational techniques, such as Raman and IR spectroscopy, quantum chemistry, and atomistic simulations. While students normally receive formal training in spectroscopic techniques during their early undergraduate years, computational methods often receive less attention. In this work, we revisit the conformational isomerism of 1,2-dichloroethane and 1,2-dibromoethane and design a hybrid computational and experimental laboratory for our undergraduate chemistry curriculum with a focus on introducing computational techniques as a complementary research tool to experimentation. We show how commonly available Raman spectrometers and atomistic simulations performed on desktop computers can be combined to study the conformational isomerism of disubstituted ethanes while discussing the advantages and limitations of the different approaches.
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Affiliation(s)
- Blake I. Armstrong
- School of Molecular and Life Sciences and Curtin Institute for Computation, Curtin University, PO Box U1987, Perth, Western Australia6845, Australia
| | - Meg Willans
- School of Molecular and Life Sciences and Curtin University, PO Box U1987, Perth, Western Australia6845, Australia
| | - Emma L. Pearson
- School of Molecular and Life Sciences and Curtin University, PO Box U1987, Perth, Western Australia6845, Australia
| | - Thomas Becker
- School of Molecular and Life Sciences and Curtin University, PO Box U1987, Perth, Western Australia6845, Australia
| | - Mark J. Hackett
- School of Molecular and Life Sciences and Curtin University, PO Box U1987, Perth, Western Australia6845, Australia
| | - Paolo Raiteri
- School of Molecular and Life Sciences and Curtin Institute for Computation, Curtin University, PO Box U1987, Perth, Western Australia6845, Australia
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Bawden JC, Francis PS, DiLuzio S, Hayne DJ, Doeven EH, Truong J, Alexander R, Henderson LC, Gómez DE, Massi M, Armstrong BI, Draper FA, Bernhard S, Connell TU. Reinterpreting the Fate of Iridium(III) Photocatalysts─Screening a Combinatorial Library to Explore Light-Driven Side-Reactions. J Am Chem Soc 2022; 144:11189-11202. [PMID: 35704840 DOI: 10.1021/jacs.2c02011] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Photoredox catalysts are primarily selected based on ground and excited state properties, but their activity is also intrinsically tied to the nature of their reduced (or oxidized) intermediates. Catalyst reactivity often necessitates an inherent instability, thus these intermediates represent a mechanistic turning point that affords either product formation or side-reactions. In this work, we explore the scope of a previously demonstrated side-reaction that partially saturates one pyridine ring of the ancillary ligand in heteroleptic iridium(III) complexes. Using high-throughput synthesis and screening under photochemical conditions, we identified different chemical pathways, ultimately governed by ligand composition. The ancillary ligand was the key factor that determined photochemical stability. Following photoinitiated electron transfer from a sacrificial tertiary amine, the reduced intermediate of complexes containing 1,10-phenanthroline derivatives exhibited long-term stability. In contrast, complexes containing 2,2'-bipyridines were highly susceptible to hydrogen atom transfer and ancillary ligand modification. Detailed characterization of selected complexes before and after transformation showed differing effects on the ground and excited state reduction potentials dependent on the nature of the cyclometalating ligands and excited states. The implications of catalyst stability and reactivity in chemical synthesis was demonstrated in a model photoredox reaction.
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Affiliation(s)
- Joseph C Bawden
- School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia
| | - Paul S Francis
- School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia
| | - Stephen DiLuzio
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - David J Hayne
- Institute for Frontier Materials, Deakin University, Geelong, Victoria 3220, Australia
| | - Egan H Doeven
- School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia
| | - Johnny Truong
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Richard Alexander
- Centre for Regional and Rural Futures, Deakin University, Geelong, Victoria 3220, Australia
| | - Luke C Henderson
- Institute for Frontier Materials, Deakin University, Geelong, Victoria 3220, Australia
| | - Daniel E Gómez
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Massimiliano Massi
- School of Molecular and Life Sciences, Curtin University, Bentley, Western Australia 6102, Australia
| | - Blake I Armstrong
- School of Molecular and Life Sciences, Curtin University, Bentley, Western Australia 6102, Australia
| | - Felicity A Draper
- School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia
| | - Stefan Bernhard
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Timothy U Connell
- School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia
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Malajczuk CJ, Armstrong BI, Stachura SS, Mancera RL. Mechanisms of Interaction of Small Hydroxylated Cryosolvents with Dehydrated Model Cell Membranes: Stabilization vs Destruction. J Phys Chem B 2021; 126:197-216. [PMID: 34967634 DOI: 10.1021/acs.jpcb.1c07769] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The mechanism by which cryosolvents such as alcohols modify and penetrate cell membranes as a function of their concentration and hydration state remains poorly understood. We conducted molecular dynamics simulations of 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayers in the presence of aqueous solutions of four common penetrating hydroxylated cryosolvents (methanol, ethylene glycol, propylene glycol, and glycerol) at varying concentration ranges and across three different hydration states. All cryosolvents were found to preferentially replace water at the bilayer interface, and a reduction in hydration state correlates with a higher proportion of cryosolvent at the interface for relative concentrations. Minor differences in chemical structure had a profound effect on cryosolvent-membrane interactions, as the lone methyl groups of methanol and propylene glycol enhanced their membrane localization and penetration, but with increasing concentrations acted to destabilize the membrane structure in a process heightened at higher hydration states. By contrast, ethylene glycol and glycerol promoted and retained membrane structural integrity by forming hydrogen-bonded lipid bridges via distally located hydroxyl groups. Glycerol exhibited the highest capacity to cross-link lipids at relative concentrations, as well as promoted a bilayer structure consistent with a fully hydrated bilayer in the absence of cryosolvent for all hydration states investigated.
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Affiliation(s)
- Chris J Malajczuk
- Curtin Medical School, Curtin Health Innovation Research Institute and Curtin Institute for Computation, Curtin University, GPO Box U1987, Perth WA 6845, Australia
| | - Blake I Armstrong
- Curtin Medical School, Curtin Health Innovation Research Institute and Curtin Institute for Computation, Curtin University, GPO Box U1987, Perth WA 6845, Australia
| | - Sławomir S Stachura
- Curtin Medical School, Curtin Health Innovation Research Institute and Curtin Institute for Computation, Curtin University, GPO Box U1987, Perth WA 6845, Australia
| | - Ricardo L Mancera
- Curtin Medical School, Curtin Health Innovation Research Institute and Curtin Institute for Computation, Curtin University, GPO Box U1987, Perth WA 6845, Australia
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