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Journal Articles

On the role of polymer chains in transducing external mechanical forces to benzocyclobutene mechanophores

Dopieralski, P.*; Anjukandi, P.*; R$"u$ckert, M.*; Shiga, Motoyuki; Ribas-Arino, J.*; Marx, D.*

Journal of Materials Chemistry, 21(23), p.8309 - 8316, 2011/06

The role played by polyethylene-like oligomers in transducing external tensile forces to benzo-cyclobutene mechanophores is investigated computationally. It is demonstrated that the oligomerchains do indeed exert a notable influence on the force-dependence of the activation energies of bothconrotatory and disrotatory ring-opening processes of a $$cis$$ 1,2-disubstituted benzocyclobutene. This opens the doorway to tuning the properties of mechanoresponsive materials not only bychanging the properties of the mechanophore itself, but also by tailoring the force-transducing chain molecules attached to it. Furthermore, it is found that these chains even have a profound impact on the topology of the force-transformed potential energy surface in the vicinity of conrotatory transition states. Hitherto unexpected and most striking is the phenomenon that some of these conrotatory transition states are found to drive the system to disrotatory products.

Journal Articles

On the role of polymer chains in transducing external mechanical forces to benzocyclobutene mechanophores

Dopieralski, P.*; Anjukandi, P.*; R$"u$ckert, M.*; Shiga, Motoyuki; Ribas-Arino, J.*; Marx, D.*

Journal of Materials Chemistry, 21(23), p.8309 - 8316, 2011/06

 Times Cited Count:48 Percentile:80.26(Chemistry, Physical)

The role played by polyethylene-like oligomers in transducing external tensile forces to benzocyclobutene mechanophores is investigated computationally. It is demonstrated that the oligomer chains do indeed exert a notable influence on the force dependence of the activation energies of both conrotatory and disrotatory ring-opening processes of a cis 1,2-disubstitutedbenzocyclobutene. This opens the doorway to tuning the properties of mechanoresponsive materials not only by changing the properties of the mechanophore itself, but also by tailoring the force-transducing chain molecules attached to it.

Journal Articles

Mechanochemical transduction of externally applied forces to mechanophores

Ribas-Arino, J.*; Shiga, Motoyuki; Marx, D.*

Journal of the American Chemical Society, 132(30), p.10609 - 10614, 2010/08

 Times Cited Count:78 Percentile:85.11(Chemistry, Multidisciplinary)

We present a theoretical study on the role played by aliphatic polymer chains in the transduction of external forces to mechanophores. Upon introducing a rigorous approach rooted in catastrophe theory we demonstrate that the rupture force of a cis 1,2 disubstituted benzocyclobutene features a remarkable dependence on the length of attached polymer chains. Not only do our findings highlight the necessity of taking into account the polymer chains explicitly when thinking about mechanochemical manipulation, but they also announce the possibility of tuning the properties of mechanoresponsive polymers by tailoring the force-transducing chain molecules.

Journal Articles

On artificial frequency shifts in infrared spectra obtained from centroid molecular dynamics; Quantum liquid water

Ivanov, S. D.*; Witt, A.*; Shiga, Motoyuki; Marx, D.*

Journal of Chemical Physics, 132(3), p.031101_1 - 031101_4, 2010/01

 Times Cited Count:57 Percentile:89.19(Chemistry, Physical)

Centroid molecular dynamics, CMD, is a popular method to extract approximate quantum dynamics from path integral simulations. Here we provide evidence that for condensed phases, and in particular for liquid water, CMD produces pronounced artificial red-shifts for high-frequency vibrations such as the OH stretching band. This peculiar behavior intrinsic to the CMD method is improved after applying a simple "harmonic curvature correction".

Journal Articles

Unravelling the mechanism of force-induced ring-opening of benzocyclobutenes

Ribas-Arino, J.*; Shiga, Motoyuki; Marx, D.*

Chemistry; A European Journal, 15(48), p.13331 - 13335, 2009/11

 Times Cited Count:40 Percentile:72.14(Chemistry, Multidisciplinary)

By exploring force-transformed potential energy surfaces of both $$cis$$ and $$trans$$ 1,2-disubstitutedbenzocyclobutene molecule, we unravel the mechanism of force-induced ring-opening. The expected conrotatory process of $$cis$$ reactant leading to $$E$$,$$Z$$ product is only observed at very small forces, whereas disrotatory ring-opening yields $$E$$,$$E$$ diene at larger forces, which is shown to be a concerted process.

Journal Articles

On the applicability of centroid and ring polymer path integral molecular dynamics for vibrational spectroscopy

Witt, A.*; Ivanov, S. D.*; Shiga, Motoyuki; Forbert, H.*; Marx, D.*

Journal of Chemical Physics, 130(19), p.194510_1 - 194510_15, 2009/05

 Times Cited Count:159 Percentile:98.75(Chemistry, Physical)

Centroid and Ring Polymer molecular dynamics, CMD and RPMD, are two conceptually distinct extensions of path integral molecular dynamics that are able to generate approximate quantum dynamics of complex molecular systems. Both methods can be used to compute quasi-classical time correlation functions which have direct application in molecular spectroscopy; in particular to infrared spectroscopy via dipole auto-correlation functions. The performance of both methods for computing vibrational spectra of several simple but representative molecular model systems is investigated systematically as a function of temperature and isotopic substitution.

Journal Articles

Understanding covalent mechanochemistry

Ribas-Arino, J.*; Shiga, Motoyuki; Marx, D.*

Angewandte Chemie; International Edition, 48(23), p.4190 - 4193, 2009/04

 Times Cited Count:168 Percentile:95.12(Chemistry, Multidisciplinary)

To control the chemical bond breaking by mechanical forces is a newly growing field called "mechanochemistry", but theoretical background has not been established. Here we suggest a new approach to apply Fukui's intrinsic reaction coordinate concept to molecular motion on adiabatic potential surface distorted by external force. Using this approach we explain the mechanism of forbidden pericyclic reaction in recent ultrasound experiment.

Journal Articles

Quantum effects on vibrational and electronic spectra of hydrazine studied by "on-the-fly" ${it ab initio}$ ring polymer molecular dynamics

Kaczmarek, A.*; Shiga, Motoyuki; Marx, D.*

Journal of Physical Chemistry A, 113(10), p.1985 - 1994, 2009/03

 Times Cited Count:48 Percentile:87.24(Chemistry, Physical)

Structural and spectroscopic properties of hydrazine, N$$_{2}$$H$$_{4}$$, it being a floppy or fluxional molecule in vacuum, are investigated by means of ab initio molecular dynamics, ab initio path integral molecular dynamics, and ab initio ring polymer molecular dynamics simulations in conjunction with on the fly MP2 and CIS(D) electronic structure calculations. This family of methods, combining electronic structure with path integrals, offers a powerful and general computational approach not only to molecular structure determination of floppy or fluxional molecules, but also to evaluation of their electronic and vibrational spectra.

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