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Computer design of a bio-mimetic single-molecule molecular motor

Objective

Recently much attention has been paid to the construction of different prototypes of molecular motors powered by chemical, electrochemical and photochemical reactions. However, the task of designing bio-mimetic molecular devices capable to achieve an efficient photo driven rotary motion is still far from complete. The objective of the present research project is to demonstrate, through a series of theoretical-computational studies that is possible to approach a rational design of a bio-mimetic device. In particular the ultimate target of the research is the first-principle design of a bio-mimetic single-molecule molecular motor based on the 4-cyclopent-2 ' -enylidene-3 , 4-dihydro-2H-pyrrole framework or its higher homologous. To our knowledge, compounds based on this framework have never been investigated/synthesized and can thus potentially lead to a new class of molecular devices. The design strategy proposed in the present project is based on the successful development of computer tools that allow for an accurate and systematic description of the photochemical reaction paths in organic molecules. The major target is to define the size of the substituents and the pattern of substitution that allow for peak unidirectional efficiency for both the Z->E and E->Z rotary motion. We will employ abinitio MCSCF and multireference-MP2 (MR-MP2) methods to construct torsional analytic force field controlling the photoisomerization of the target chromophores, superior homologues and the corresponding chiral derivatives along their photoisomerization paths. Additionally, we will use the MCSCF and MR-MP2 computations to predict the most likely photoinduced decomposition pathways for aforementioned compound, as well as to evaluate the time scale of the photoisomerization event and the prevalency of unidirectional rotary motion on the excited state. We believe that the above project will provide a formative experience in the field of advanced computational chemistry. During the research work the applicant will learn how to use different advanced computational chemistry packages for the search and characterization of organic reaction mechanisms and conformational analysis. In particular, the applicant will have the opportunity, through the proposed research, to become an expert in the field of computational investigation of photochemical reactivity. More importantly the applicant will have the chance to acquire skill in the use of high level abinitio data for the construction non-standard torsional analytic force fields to be used in the design of novel bio-mimetic materials and/or for tackling mechanistic problems in photochemistry. The group of Prof. Massimo Olivucci has long been involved in the investigation of the photophysical and photochemical properties of biological chromophores. Thus, the new computational strategies, the development of which is part of the proposed project, and the integration of different computational tools, shall be of fundamental importance in further studies of chromophores photostability.

Funding Scheme

RGI - Research grants (individual fellowships)

Coordinator

UNIVERSITÀ DEGLI STUDI DI SIENA
Address
Via Aldo Moro
53100 Siena
Italy