Experimental and DFT study of UV–vis absorption spectra of azobenzene containing ester groups

Here, we combined experimental measurements and DFT calculations to study UV–vis absorption spectra. DFT calculations of azobenzene and its derivatives proved useful for estimation of experimental spectra with near one-to-one correspondence. Calculation results show that substituents have no obvious effect on the coplanarity of benzene rings and N N bond. Potential energy surfaces were calculated for DHA and DEA. In the ground state, the inversion pathway was found to be preferred. A conical intersection was found between the ground and first excited states along the rotation pathway, indicating that the rotation mechanism is favored in the first excited state for DHA and DEA. UV–vis spectra of DHA and DEA were calculated by TD-DFT. Compared with azobenzene, the calculated wavelength of maximum absorption of DHA- trans and DEA- trans has red shift in UV–vis absorption spectra, which are in reasonable agreement with the experimental data.