Theoretical Study On Molecular Isomerization Of 4-azobenzenesulfonamide And Its Derivatives

Azobenzene and its derivatives have always been a hot topic in chemical research due to the unique and efficient reversible cis-trans isomerization process.Recently,the isomerization of azobenzene derivative aggregates has also received attention.In order to better understand the interaction between azobenzene compounds and assembly,in this paper,density functional theory is used to study the cis-trans isomerization mechanism of 4azobenzenesulfonamide and its derivatives.The research work mainly includes the following aspects:1.Using density functional theory to explore the cis-trans isomerism of 4azobenzenesulfonamide and its three derivatives at the calculation level ofωB97XD/6-3 1 g(d)//6-311+G(d,p),two isomerization pathways were discovered:(1)by connecting the nitrogen atom(N1)of benzene or three other substituted benzenes;(2)by connecting the nitrogen atom(N2)of benzenesulfonamide,the products are the anti-enantiomer structures respectively.The isomerization free energy barriers of N1 and N2 inversion are 28.4 and 25.26 kcal/mol,respectively,so N2 inversion is the more favorable path.At the same time,it is found that the two isomerism pathways are closely related to the withdrawing and donating electron ability of the substituents on the benzene ring connected with the N1 atom.The results show that the stronger the withdrawing electron ability of the substituent,the lower the electron density of the directly connected benzene ring,which in turn makes the substituted benzene and N1 The smaller the atom’s lone pair electron repulsion,the easier the N1 inversion.2.Under the calculation level of ωB97XD/6-31 g(d),the isomerization mechanism of single molecule and its three derivatives and bimolecular 4Azobenzenesulfonamide propyltrioxy group on silicon substrate was studied.It is found that there are two inversion mechanisms for the single-molecule 4azobenzenesulfonamide propyl triethoxy group on the silicon substrate,N1 and N2 inversion,and N2 inversion is the more dominant path.It was found that the bimolecular 4-Azobenzenesulfonamide triethoxy group on silicon substrate can undergo order isomerization.The isomerization of the first molecule is similar to that of a single molecule,and the second molecule is different from that of a single molecule,when the first molecule undergoes N2 inversion,the second molecule undergoes N1 inversion is the most favorable path.The free energy barriers of two isomerization mechanism are 26.88 and 13.99 kcal/mol,respectively.3.Because 4-Azobenzenesulfonamide propyl trioxyethyl silane can be assembled on a silicon substrate,the B3LYP/6-311+G(d,p)method was used to study thermal and force induced isomerization mechanism of 4Azobenzenesulfonamide propyl trioxyethyl silane and its three derivatives.Thermal isomerization can occur through N1 inversion and N2 inversion.The electron energy barrier of N2 inversion isomerization is lower,which is 21.03kcal/mol.Finally,the magnitude of the applied force is simulated by the size of the molecular structure deformation.When the cis structure is subjected to an external force,it will be transformed into a high-energy and unstable intermediate F.After the external force is removed,the energy of intermediate F will drop rapidly and isomerization occurs in two pathway.