Substitution effects on optical properties of iminonitroxide- substituted iminonitroxide diradical

Abstract

Absorption spectra of iminonitroxide-substituted iminonitroxide diradical (IN-IN) are calculated by means of time-dependent density functional theory. Since IN-IN has two different conformations with small singlet–triplet gaps, the statistical average of the absorption spectrum is compared with the experimental one. We also investigate the substitution effects of CN, OMe, and NH₂ groups and found that the introduction of OMe and NH₂ groups results in the redshift of the longer wavelength region due to the delocalisation of the lowest unoccupied molecular orbital over lone pair of OMe from the analyses on molecular orbitals of an IN monomeric unit instead of IN-IN. On the other hand, there is no explicit difference in the short-wavelength region in spite of the introduction of these functional groups.

Keywords:

• absorption spectra of (di)radicals
• time-dependent density functional theory
• substitution effects

Acknowledgements

Theoretical calculations are partly performed using Research Center for Computational Science, Okazaki, Japan.

Additional information

Funding

This study is supported by a Fellowship for the doctor course students [KAKENHI No. 12J01481] from the Japan Society for the Promotion of Science (JSPS). This is also partly supported by a Grant-in-Aid for Young Scientists (A) [KAKENHI No. 22685003] from JSPS and by a Grant-in-Aid for the innovative area ‘Computics’ and ‘Dynamic ordering of biomolecular systems for creation of integrated systems’ [KAKENHI Nos 25104716 and 26102525] from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.