Estimation of maximum absorption wavelength of polymethine dyes in visible and near-infrared region based on time-dependent density functional theory

Abstract

Polymethine dyes have been utilized in various applications, including optical functional materials. The maximum absorption wavelength (λmax) of polymethine dyes is the key for designing optical functional materials. However, there have been few theoretical studies on λmax, especially in the near-infrared region. Therefore, using time-dependent density functional theory (TD-DFT), we calculated the excited states of 70 polymethine dyes with λmax ranging in the visible-to-near infrared region. We also compared these calculated λmax values with experimental ones, using linear regression analysis, and confirmed a strong correlation between the experimental and theoretical λmax values when the portion of the Hartree-Fock exchange in exchange–correlation functionals is relatively high. Linear regression analysis revealed that the experimental λmax values of the polymethine dyes can be quantitatively estimated by combining the TD-DFT calculations with the regression curves. Although several polymethine dyes may exhibit different behaviors at λmax, we could categorize these dyes into a few groups and estimate their excitation energies using regression curves suitable for the respective groups.