The question of charge localization or delocalization is paramount in chemistry, in general, and in mixed valence (MV) chemistry, especially. A computationally guided approach to the controllable intramolecular charge transfer (ICT) in MV bridged norbornylogous compounds was developed. It based on the combined ab-initio and parametric study with emphasis on the through-bond vs. through-space effects in the ICT.
An analysis of bridge influence on ICT and corresponding charge localization is the goal of proposed approach.
Different kinds of photoinduced processes leading to ICT were discussed as mechanisms suggested for potential molecular devices:
1) Irradiation leading to the ICT excited state;
2) Chemical reaction with ICT transition state;
3) Excited State Intramolecular Proton Transfer (ESIPT). The common features of these processes are the non-radiative transition to the initial state after excitation, with the back transition going through the highly polar charge transfer (CT) area.
Prof. Shmuel Zilberg is a theoretical chemist, interested in spectroscopy, photochemistry, electron and hydrogen transfer processes, unusual molecules etc.
Shmuel Zilberg completed his M.Sc. at Moscow University and Ph.D. at Institute of Organic Chemistry, Academy of Science, Moscow, Russia. He joined the Hebrew University of Jerusalem in 1994, and he became Professor in 2000. Prof. Zilberg joined Ariel University in 2016 and he teaches at the Department of Chemical Sciences at Ariel University..
Electronic structure analysis combined with a qualitative quantum model constitutes the thrust of Zilberg’s research. Zilberg proposed the “Twin states” model interpretation for the Kekule mode upshift for the parent benzene in 1995. An upcoming paper in Accounts of chemical research summarizes the concept “Twin states” for the aromatic molecules. The twin states concept was applied to the analysis of transition state structure of concerted reaction through the spectroscopic study of the bonding excited twin state. This theoretical idea was experimentally confirmed later by H.Quast in 1999.
Aromatic-antiaromatic dichotomy was analyzed through the comparison of the ground and excited states of “Twin states” system. Subsequently, this approach has also been spread on the application of Aromaticity - Antiaromaticity concept to the analysis of Excited States.
Zilberg developed the chemically oriented approach to the analysis of the photoreaction going through the conical intersection (CI). This model based on the extension of the Longuet-Higgins sign-change theorem. It was shown that the Reaction coordinates are the natural CI’s coordinates. In principle, the whole topography of the PES can be reconstructed around the degeneracies since minima and transition states (TSs) are directly accessible from them. Proposed approach provided also the rationalization for the phenomenon of the chemical reaction with two different elementary TSs.
A model accounting for the dual fluorescence of Donor-Acceptor substituted benzene derivatives was proposed by Zilberg in 2002 and modified in 2006. The low-lying electronically excited states are expected for the dual fluorescence's molecules - charge transfer (CT) state and a locally excited (LE) state. This model was verified in different spectroscopic studies and confirmed by D. Pratt in 2013.
The prominent feature of Zilberg’s work is a combination of high level quantum-chemical computations with a qualitative chemically oriented models and concepts. The goal is a development of the chemically oriented approach to the analysis of the ground or excited state PES and its application to the different reactions and unusual chemical species.
Prof. Shmuel Zilberg
Department of Chemical Sciences
Personal website: http://www.ariel.ac.il/sites/shmuel-zilberg