Figure 5 Simulated Absorption Spectrum of Heterocyclic and Amino-ethyl-amino Modified Dyes Obtained by ωB97XD/6-311G(d,p) Calculation in Dichloromethane
The MTPADP-Pyc molecule is a conjugate, so its maximum absorption peak position undergoes a significant red shift, and a new absorption peak appears, extending the absorption spectrum towards 800 nm. In the absorption spectrum of MTPAQL-Pyc molecule, a new absorption peak appeared near the maximum absorption peak, and the absorption intensity was higher than the maximum absorption peak, broadening the entire absorption spectrum, and the maximum absorption peak was red-shifted. The HOMO and LUMO of the MTPABD-Pyc molecule overlap to a greater extent, exhibiting the hyper-conjugation of the entire molecule, and thus its absorption spectrum has a significant red shift. The absorption spectrum of MTPAPA-Pyc molecule is similar to that of MTPABT-Pyc molecule in shape, but the maximum absorption peak is red-shifted and the absorption band is slightly wider. In summary, the absorption spectra of MTPADP-Pyc, MTPAQL-Pyc, and MTPABD-Pyc molecules all showed a new absorption peak near the maximum absorption peak, which broadened the absorption spectrum to some extent and improved the absorption characteristics of dye molecules.
After the introduction of amino-ethyl-amino group, the intensity of the maximum absorption peak of all dyes is lower than that of MTPA-Pyc, which will affect the light absorption efficiency of such dyes at the maximum absorption wavelength. However, the maximum absorption peaks of MTPADP-APyc, MTPAQL-APyc, MTPABD-APyc and MTPAPA-APyc molecules are significantly red-shifted compared with that of MTPA-Pyc.