Kalender
TALK: Ab initio mechanochemistry in condensed phase
Freitag, 2. Dezember, 14:30 » 16:00
Website-Termin
Mechanochemistry is a field with a long history going back at least to year 1892. But only about a decade ago it was transferred from macroscopic milling-type experiments down to the molecular level due to advances in molecular force probes.
I will start with one slide-explanation of a constant-force approach code implemented in the Car-Parrinello Molecular Dynamics (CPMD), to extensively discuss the usage of this technique together with metadynamics and thermodynamic integration.
Ultimately, the computational tensile force approach was applied to deliver explanation to experimentally observed a mechanochemical “switch” around 0.5 nN during reduction of the disufide bridge in aqueous solution. Successful application of metadynamics and thermodynamic integration with a series of constant tensile forces result in understanding of the experimentally observed unexpected change in reaction rate. [1, 2]
It is also turned out that some reaction paths compete with each other under certain forces,
(e.g. path of substitution on the sulfur atom with path of heterolytic breaking of the C-S bond
at 2.0 nN) and others converge to single reaction path - such as the substitution path on a‑carbon about 1.25 nN collapses into the C-S bond cleavage pathway.
The computational mechanochemistry of b-elimination reaction[3] exposed that forces greater than 1 nN transform free energy surface of the reaction, such that a second channel is formed in which the order of the reaction steps is inversed! Further research on disulfide bridges involved the use of a large model and another attacking agent have shown that non-covalent chalcogen-chalcogen S···O type 1,5 interactions control the mechanochemical reactivity of disulfides at very low forces. [4]
At the end I will present our computational contribution to the subject of the ring opening of the triazole [5] – where other authors have shown in controversial experimental research, that the cycloreversion of 1,2,3—triazole is mechanochemically reversible.
[1] P. Dopieralski, J. Ribas-Arino, P. Anjukandi, M. Krupicka, J. Kiss, D. Marx, Nat. Chem. 2013, 5, 685–691.
[2] P. Dopieralski, J. Ribas-Arino, P. Anjukandi, M. Krupicka, D. Marx, Nat. Chem. 2017, 9, 164–170.
[3] P. Dopieralski, J. Ribas-Arino, P. Anjukandi, M. Krupicka, D. Marx, Angew. Chem. Int. Ed. 2016, 55, 1304–1308.
[4] P. Dopieralski, M. Zoloff-Michoff, D, Marx, Phys. Chem. Chem. Phys. 2020, 22, 25112–25117.
[5] Martin Krupicka , P. Dopieralski. D. Marx, Angew. Chem. Int. Ed. 2017, 56, 7745–7749.
I will start with one slide-explanation of a constant-force approach code implemented in the Car-Parrinello Molecular Dynamics (CPMD), to extensively discuss the usage of this technique together with metadynamics and thermodynamic integration.
Ultimately, the computational tensile force approach was applied to deliver explanation to experimentally observed a mechanochemical “switch” around 0.5 nN during reduction of the disufide bridge in aqueous solution. Successful application of metadynamics and thermodynamic integration with a series of constant tensile forces result in understanding of the experimentally observed unexpected change in reaction rate. [1, 2]
It is also turned out that some reaction paths compete with each other under certain forces,
(e.g. path of substitution on the sulfur atom with path of heterolytic breaking of the C-S bond
at 2.0 nN) and others converge to single reaction path - such as the substitution path on a‑carbon about 1.25 nN collapses into the C-S bond cleavage pathway.
The computational mechanochemistry of b-elimination reaction[3] exposed that forces greater than 1 nN transform free energy surface of the reaction, such that a second channel is formed in which the order of the reaction steps is inversed! Further research on disulfide bridges involved the use of a large model and another attacking agent have shown that non-covalent chalcogen-chalcogen S···O type 1,5 interactions control the mechanochemical reactivity of disulfides at very low forces. [4]
At the end I will present our computational contribution to the subject of the ring opening of the triazole [5] – where other authors have shown in controversial experimental research, that the cycloreversion of 1,2,3—triazole is mechanochemically reversible.
[1] P. Dopieralski, J. Ribas-Arino, P. Anjukandi, M. Krupicka, J. Kiss, D. Marx, Nat. Chem. 2013, 5, 685–691.
[2] P. Dopieralski, J. Ribas-Arino, P. Anjukandi, M. Krupicka, D. Marx, Nat. Chem. 2017, 9, 164–170.
[3] P. Dopieralski, J. Ribas-Arino, P. Anjukandi, M. Krupicka, D. Marx, Angew. Chem. Int. Ed. 2016, 55, 1304–1308.
[4] P. Dopieralski, M. Zoloff-Michoff, D, Marx, Phys. Chem. Chem. Phys. 2020, 22, 25112–25117.
[5] Martin Krupicka , P. Dopieralski. D. Marx, Angew. Chem. Int. Ed. 2017, 56, 7745–7749.
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