Athugun á hvarfgöngum uppleystra ljósnæmra járn-komplexa: fjölskala reiknilíkan sem nýtir hnikað teygjuband, NEB - verkefni lokið

Fréttatilkynning verkefnisstjóra

18.7.2024

Í doktorsverkefninu var orkudreifni tveggja ítarlega rannsakaðra sameinda, rannsakað, IrDimen og PtPOP. Báðir flokkar innihalda tvo hliðarmálma og sýna ríka dýnamík í örvuðu rafeindaástandi. Einstakt tækifæri til samvinnu við leiðandi tilraunahópa á þessu sviði, frá SLAC/Stanford og DTU kom upp til að rannsaka þessar sameindir leystar upp í annaðhvort vatni eða asetónítríl. Með þróun á bættri útgáfu af hnikuðu teygjubands (NEB) aðferðinni fyrir leit að lágmarksorkuferli, tengt við blandaða hermunaraðferð, svokallaða skammtafræði/sameindafræði (QM/MM), voru viðamiklar hermanir framkvæmdar á grunnástandsbyggingu og dýnamík í örvuðu rafeindaástandi. Rásir orkudreifni voru greindar og mismunur á milli upplausnar í vatni eða asetónítríl útskýrður út frá víxlverkun leysis sameinda við hliðarmálmsatóm flókanna tveggja. Einnig var díamín hringsameind DMP rannsökuð til að greina jafnvægið milli staðbundins og óstaðbundins rafeindaástands, fyrir örvað Rydberg ástand og samsvarandi katjón.

English:

The excitation of a molecule by the absorption of a photon has wide applicability, for example
in sensitizers for systems driven by energy obtained from light. A key issue there are the various
channels through which the energy can dissipate. In the PhD project, the dissipation channels of two widely studied molecules were studied, IrDimen and PtPOP. Both contain two transition metals and show rich dynamics in the excited electronic state. A unique opportunity for close collaboration with leading experimental groups in the field at SLAC/Stanford and DTU on studies of these molecules dissolved either in water or acetonitrile arose. By developing an improved implementation of the nudged elastic band (NEB) method for finding minimum energy paths of transitions, coupled to a hybrid simulation approach, so-called quantum mechanics / molecular mechanics (QM/MM), extensive simulations could be carried out for the ground state structure and the dynamics in the electronic excited state. The energy dissipation pathways were identified and the difference between solvation in water and acetonitrile explained in terms of the interaction of the solvent molecules with the transition metal atoms in the complexes. Also, a diamine ring molecule, DMP was studied to identify the balance between localized and delocalized electronic states both for the Rydberg excited state and the corresponding cation.

Information on how the results will be applied:
The results from the theoretical study of IrDimen revealed that to obtain the two ground
state conformers the addition of a dispersion correction is necessary to obtain both conformers.
This will help in future QM/MM calculations to simulate the selective excitation of either ground
state conformer. For PtPOP solvated in water and acetonitrile it was shown that the main
pathway of energy transfer between solute and solvent is mediated through the non-Coulombic
force term, showing the importance of system specific non-Coulombic force terms. Additionally,
the novel application of the energy flux of a solvated molecule to a multiscale model will help
with gaining a deeper knowledge of the interactions between solute and solvent in future
QM/MM simulations. The results will be applied to help interpret high-level X-ray based
experiments carried out in accelerators, for example SLAC. Ultimately, the improved knowledge
of energy dissipation channels will help develop improved photosensitizers for various
applications driven by energy coming from light.

A list of the project’s outputs:
An improved implementation of the widely used nudged elastic band (NEB) method has been
developed and is made available, in particular, in the ORCA software. This new implementation
has significantly better performance than previous implementations. An article on this method
and tests of over 100 molecular reactions has already been published (and has received 150
citations in less than 3 years, illustrating the high relevance of this work).
Another article has been accepted in JACS (Journal of The American Chemical Society), a very
high impact journal (impact factor 15.0). It describes a joint experimental and theoretical study
of the IrDimen complex dissolved in acetonitrile.
Furthermore, a manuscript reporting the results from extensive QM/MM calculations of the
photoexcitation of the PtPOP complex in water and acetonitrile, introducing a novel approach to
map energy transfer between quantum and mechanistic models, is near completion and will be
submitted within the next couple of months.
Finally, an article on localized and delocalized states of a diamine ring molecule, DMP, and the
issue of whether photoexcitation brings the system to a temporary localized state befor
equilibrating in a delocalized state is nearly complete and will be submitted for publication later
this year.
A PhD defence is scheduled at the end of summer.

Heiti verkefnis: Athugun á hvarfgöngum uppleystra ljósnæmra járn-komplexa: fjölskala reiknilíkan sem nýtir hnikað teygjuband, NEB - Exploring the Reaction Paths of Solvated Iron Photosensitizers: a Multiscale Nudged Elastic Band Strategy
Verkefnisstjóri: Benedikt Orri Birgisson, Háskóla Íslands
Tegund styrks: Doktorsnemastyrkur
Styrktímabil: 2020-2022
Fjárhæð styrks kr. 19.800.000
Tilvísunarnúmer Rannsóknasjóðs: 207014