PhD student position in theoretical chemistry

Job content

Applications of the simplified time-dependent density functional theory (sTD-DFT) and the new eXact integral – sTD-DFT (XsTD-DFT) to evaluate two-photon absorption of large systems

The evaluation of the two-photon (2P) absorption (2PA) of large systems is beyond the reach of current ab initio methods. We recently overcome this limit by implementing the ultra-fast evaluation of 2PA cross-sections (s2PA) with the simplified time-dependent density functional theory (sTD-DFT) as well as by introducing a more accurate scheme: the eXact integral - sTD-DFT (XsTD-DFT). In this PhD project, we will apply both methods to characterize the 2PA of two types of large and challenging systems: fluorescent proteins (FPs) and cocrystals, targeting applications in bio-imaging and 3D optical data storage. A new all-atom quantum chemistry (QC) methodology will be established and design guidelines to improve the experiment will be proposed.

Context

Two-photon absorption is a nonlinear optical (NLO) phenomenon in which a compound absorbs simultaneously two photons. The molecule may reemit one photon at half of the excitation wavelength. It is used in 2P-excited near-infrared-emitting materials (2P-Ms) for applications in bio-imaging, optical data storage, microfabrication, and photodynamic therapy.

2P excitation microscopy (TPEM)1,2 provides high resolution deep tissue imaging. FPs3 can be used as genetically encoded fluorescent tags. A rainbow of FPs with enhanced/tuned biochemical and optical properties are available.4 FP engineering aims to develop bright FPs, with varying color, and providing images with sufficient contrast with respect to the auto-fluorescent background.4

As 2P-excited near-infrared-emitting materials (2P-Ms), organic cocrystals have lately gained attention.5,6 Cocrystallization is an elegant way to fine-tune properties of organic molecules by non-covalent interactions. Usually, large s2PA are obtained by increasing electron delocalization and changing donor-acceptor groups to produce charge transfer (CT) states. In cocrystals, CT states with large s2PA can be obtained via supramolecular architecture.6

Objectives

The Main Objective Of This Project Is For a PhD Student To Develop An Expertise In The Determination Of 2PA Especially With Both STD-DFT And XsTD-DFT Methods For Two Applications

WP1: All-atom QC characterization of the 2PA of FPs

Recently, we proposed a new all-atom QC methodology to compute the second harmonic generation of FPs.7 This was the first time that a NLO property of a system as big as a protein was characterized fully quantum mechanically, thanks to our sTD-DFT implementation.8,9 This study was the first step towards extension to other NLO properties. WP1aims at investigating the 2PA of FPs by both sTD-DFT and XsTD-DFT methods and at developing a new all-atom QC methodology. We will be able to understand their structure/property relationship to provide new insights in order to improve their s2PA for applications in TPEM.

WP2: 2P-induced reversible photodimerization of trans-cinnamic acid, chalcone, and coumarin derivatives cocrystals

Figure 1: The photodimerizations of trans-cinnamic acid.

In the solid state, the [2+2] photodimerizations of trans-cinnamic acid10 (tCA), coumarin11 and chalcone derivatives12 are reversible and can be triggered by 2PA11,13 that increases the yield and the penetration of the light. The reaction cross-section (W2P) is proportional to s2PA. For tCA (Fig.1), two products are formed: the ????-truxillic and ????-truxinic acids. By using cocrystal of tCA with dichlororesorcinol or urea, only ????-truxinic acid is formed. With the possible application as 3D optical data storage, we propose to use both sTD-DFT and XsTD-DFT methods to screen different types of cocrystals to enhance s2PA by manufacturing intermolecular CT states, which increase W2P. Comparisons with experiment will be done in collaboration with Prof. Tom Leyssens at UCLouvain for the experimental part.

Other applications will be considered according to the progress in the field.

PhD supervisor: Marc de Wergifosse

Where

Theoretical chemistry group,

Institute of Condensed Matter and Nanosciences,

Université Catholique de Louvain, Belgium

Duration:4 years

Starting date:October 2022

Funding: Seedfund FSR 2022 grant at UCLouvain

Contact: mdewergifosse@gmail.com

References

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2 H. Myung Kim and B. Rae Cho, Chem. Rev. 115, 5014 (2015).

3 M. Drobizhev, N.S. Makarov, S.E. Tillo, T.E. Hughes, and A. Rebane, Nat. Methods 2011 85 8, 393 (2011).

4 E.A. Rodriguez, R.E. Campbell, J.Y. Lin, M.Z. Lin, A. Miyawaki, A.E. Palmer, X. Shu, J. Zhang, and R.Y. Tsien, Trends Biochem. Sci. 42, 111 (2017).

5 Y. Wang, H. Wu, P. Li, S. Chen, L.O. Jones, M.A. Mosquera, L. Zhang, K. Cai, H. Chen, X.-Y. Chen, C.L. Stern, M.R. Wasielewski, M.A. Ratner, G.C. Schatz, and J.F. Stoddart, Nat. Commun. 2020 111 11, 1 (2020).

6 C. Dai, Z. Wei, Z. Chen, X. Liu, J. Fan, J. Zhao, C. Zhang, Z. Pang, and S. Han, Adv. Opt. Mater. 7, 1900838 (2019).

7 P. Beaujean, B. Champagne, S. Grimme, and M. de Wergifosse, J. Phys. Chem. Lett. 12, 9684 (2021).

8 M. de Wergifosse and S. Grimme, J. Chem. Phys. 149, 024108 (2018).

9 M. de Wergifosse and S. Grimme, J. Phys. Chem. A 125, 3841 (2021).

10 G.M.J. Schmidt, J. Chem. Soc. 2014 (1964).

11 T. Buckup, A. Southan, H.C. Kim, N. Hampp, and M. Motzkus, J. Photochem. Photobiol. A Chem. 210, 188 (2010).

12 J. Träger, S. Härtner, J. Heinzer, H.C. Kim, and N. Hampp, Chem. Phys. Lett. 455, 307 (2008).

13 J. B. Benedict and P. Coppens, J. Phys. Chem. A 113, 3116 (2009).