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Computational photochemistry

Molecular motors

We produce guidelines for the design and construction of more efficient molecular motors. Molecular motors are molecules that can perform work by absorbing energy and converting the energy into directed mechanical motion such as rotation around a chemical bond. Because of their ability to execute a number of useful functions, one class of synthetic light-driven molecular motors that have attracted a particular interest in recent years are those developed from sterically overcrowded alkenes by Ben Feringa (co-recipient of the Nobel Prize in Chemistry 2016) and his group. To fully exploit the nanotechnological potential of these motors, which accomplish full 360º rotary motion around a carbon-carbon double bond through sequential photochemical and thermal steps, it is desirable to design and synthesize systems capable of achieving >MHz rotational frequencies under ambient conditions. Using a variety of computational methods, our research in this field aims to provide an atomic- and electronic-level understanding of how this goal can be realized. 

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*Co-first authorship

Photochemical reaction mechanisms

We investigate the mechanisms of organic and enzymatic photoreactions. Whereas ordinary thermal reactions are induced by heat and involve exclusively ground-state species, photoreactions are triggered by light and involve species that during the course of the reaction reside in an excited state. In our research, we explore the mechanistic details of photoreactions by computing the relevant ground and excited-state potential energy surfaces using quantum chemical (ab initio, DFT) and QM/MM methods, and by running non-adiabatic molecular dynamics simulations along these surfaces. A particular focus of our work has been to understand the basic photochemistry underlying the functions of photosensory proteins such as the phytochromes. More recently, we have investigated how the concept of excited-state aromaticity can be exploited for the design of more efficient molecular switches.

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Photosensory proteins

We explore the functions of photosensory proteins. These are ubiquitous signal transduction proteins that employ chromophores to detect light and initiate a physiological response to the prevailing light conditions. As noted above, one family of proteins of current interest is the phytochromes. Another is the rhodopsins. Recently, we presented data indicating that a newly discovered member of this family — Anabaena sensory rhodopsin — is a biological realization of a light-driven molecular motor. Indeed, by performing CASSCF and CASPT2-based QM/MM calculations, we showed that Anabaena sensory rhodopsin not only harbors a retinal chromophore that exhibits light-driven rotary motion, but also shares many features with a synthetic system designed explicitly to accomplish this very behavior.

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*Co-first authorship

Molecular properties

We study how various properties of organic chromophores confer functionality to the chemical systems where the chromophores are present. The functionalities of interest range from color to proton transfer capability, the latter coming into effect through changes in the acidity of the chromophore in an excited state. As an example of this research, we have proposed a mechanism for the >0.50 eV bathochromic shift of the UV-vis absorption of astaxanthin (a carotenoid pigment) in crustacyanin, the carotenoprotein responsible for the characteristic deep-blue coloration of lobster shell. 

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Contact person: Bo Durbeej


Responsible for this page: Mathieu Linares

Last updated: 04/21/21