Influence of fluorination on UV spectra of polyurethane structural fragments

Results of TDDFT calculations of the characteristics for excited singlet states of fluorinated urethanes containing from one to six fluorine atoms were presented. The influence of the number and location of the fluorine atoms in the urethane structure on the formation of its UV absorption spectrum was analyzed. It was established that fluorination of a phenyl group in the ortho-positions led to steric hindrance in the urethane structure and to rotation of the urethane group by a significant angle (of about 20A degrees). The rotation angle of the urethane group could reach 60A degrees and more with additional fluorination of the amine. Such changes in the urethane structure were accompanied by characteristic significant bathochromic shifts of the long-wavelength absorption bands.