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分子理論化学セミナー（2025年度）

Dr. Ali Hassanali (ICTP in Trieste, Italy)

“Towards the Fundamental Design of Hydrogen-Bond Networks as Fluorescent Optical Probes”

Date: Aug 1, 2025 (Fri) 15:00-
Room: A4-204, Katsura Campus, Kyoto University

Fluorescence takes place throughout the nature world. Most conventional chemical wisdom proposes that in organic molecules, fluorescence occurs in conjugated systems, such as in the aromatics. However, in most biological contexts, the interaction of light with matter occurs in media built up of dense networks of hydrogen bonds (HBNs). Recent experiments suggest that is also possible to observe fluorescence from these networks although the electronic and nuclear components that leads to this emergent phenomena remains an open question. Being able to use these HBNs has the possibility of opening up enormous practical potential paving the way for the design of non-invasive probes.

My talk will be focused on challenging our intuitions on the physics and chemistry behind the notion of a fluorophore. By combining both experiments and state-of-the-art electronic structure and molecular dynamics simulations, I will elucidate our attempts to decipher the origins of intrinsic fluorescence [1,2,3,4]. Certain chemistries that form supramolecular assemblies lend themselves to the formation of more stiff HBNs sometimes leading to proton transfer and the rigidification of vibrational modes both of which can inhibit non-radiative decay. We demonstrate this for a wide class of systems ranging from amyloid proteins to different amino-acids including Glutamine, Cysteine and Lysine.

I will then move on to discussing unpublished work looking at the photophysics and chemistry of aqueous systems including Ice and Liquid Water. If the phenomena of HBN fluorescence is more general, what are the conditions that modulate the photoexcitation and subsequent photochemistry in aqueous solutions. I will discuss recent work on examining the role of topological and ionic defects in modulating the optical properties of Ice [5] and in Liquid Water.

Prof. Tomaz Urbic (University of Ljubljana, Slovenia)

“What can we learn from simple models? From analytical statistical-mechanical modelling to determination of phase diagram by machine learning”

Date: May 15, 2025 (Thu) 16:00-
Room: A2-304, Katsura Campus, Kyoto University

On the simple model with water-like properties, called rose model, we will show how with simple statistical mechanics theory we can reproduce thermodynamics and structure. The analytical model assumes three interaction sites per molecule, where each interaction site is eligible for three types of interactions: hydrogen bonding, vdW contact and no interaction. The results of the analytical model are in good agreement with the results of the computer simulations. The computational efficiency of rose water model also allows us to investigate the properties of water under a wide range of conditions. We have simulated water in the entire phase space to obtain data to construct the phase diagram. Various structural, dynamic and thermodynamic properties were fed to different combinations of unsupervised machine learning methods. The phase diagrams created almost automatically using ML methods match well with the phase diagram created manually.

Prof. Odile Eisenstein

(ICGM Université de Montpellier, CNRS ENSCM Montpellier France Department of Chemistry and Hylleraas Center for Quantum Molecular Sciences, University of Oslo, Norway)

“Searching for the right model: The case of the nucleophilic addition from the Felkin-Anh rule to the Grignard reaction”

Date: April 17, 2025 (Thu) 15:00-
Room: A2-304, Katsura Campus, Kyoto University

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