Design of Near-Infrared Dyes Based on π-Conjugation System Extension. Theoretical Evaluation of Arylimidazole Derivatives of Perylene Chromophore

To design the near-infrared (NIR) dyes, the electronic absorption spectra of arylimidazole-introduced 3,4,9,10-perylenetetracarboxylic dianhydride and its imide derivatives (PTCAIs) have been theoretically elucidated by using the molecular orbital (MO) calculation. An arylimidazole introduction causes a longer shift of the absorption wavelength (bathochromic shift) by destabilization of the HOMO level. The HOMO level of aryl groups (e.g., benzene and naphthalene) is close to the energy of PTCAI's HOMO; therefore, new orbitals which are characterized as a mixture of each orbital's features are generated by this large orbital interaction. The absorption wavelength shift depends not only on a HOMO level of the aryl group (π-conjugation size), but also on its pattern. With the bathochromic shift of the absorption spectrum, the transition is characterized as more intense of the charge-transfer (CT) property rather than the π−π* excitation on the perylene moiety.