Theoretical Study On Photoisomerization Of Tetrahedrane Derivative

Light-responsive materials are intelligent materials that can produce chemical or physical changes in molecules after absorbing light energy.In addition,light energy has such excellent characteristics as environmental protection,remote control and instantaneity,so more and more attention have been paid to light-responsive materials.The continuous progress and development of modern society,such materials will play a leading role in our daily life.So it is of great significance to study and develop new light-responsive materials.Tetrahedrane and its isomer,cyclobutadiene,have attracted much attention from theoretical and experimental chemists.In addition to their unique bonding properties,they can also be converted to each other by lighting or heating.At the same time,they may have potential applications in light-responsive materials.The successful synthesis of some tetrahedrane derivatives has prompted more and more research on this unique molecule.Moreover,tetrahedrane derivatives can be connected to high polymers by grignard reagent,which is expected to be a candidate of light-responsive polymer materials and of great significance for practical applications.In this paper,the photoisomerization of tetrahedrane derivative was studied by using density functional theory and time-dependent density functional theory.The main contents were summarized as follows:under the light condition with the wavelength greater than 400nm,the chromophore 9,10-dicyanoanthracene is firstly excited from the ground state?S₀?to the S₂ state???*?,which is mainly the local excitation of 9,10-dicyanoanthracene.It assists the perfluoroaryltetrahedrane by losing an electron and of transferring it to 9,10-dicyanoanthracene,and then forms the perfluoroaryltetrahedrane cationic and 9,10-dicyanoanthracene anion.For the electron transfer process,we find the intersection of high-energy local excitation??*state?S₂?and the low-energy charge transfer??*state?S₁?.At the intersection,the local excited state is transformed into charge transfer state,which proves that the electron is transferred.Subsequently,the cationic derivative of tetrahedrane was isomerized to form corresponding cationic derivative of cyclobutadiene.The isomerization barrier is very low,only 6.2kcal/mol,which may lead to the high yield of cyclobutadiene derivative.After isomerization,electron returns from the cyclobutadiene derivative to9,10-dicyanoanthracene,and then it may be vibrationally relaxed back to the ground state.Among them,9,10-dicyanoanthracene has not changed significantly and can be considered as a catalyst for the whole photoisomerization process.The above study of the reaction mechanism is helpful to understand the nature of the transformation between tetrahedrane and cyclobutadiene.It also has a very important guiding significance for the design of new optical control materials.