Theoretical model for optical properties of porphyrin

We propose a simple model to interpret the optical absorption spectra of porphyrin in different solvents. Our model successfully explains the decrease in the intensity of optical absorption at maxima of increased wavelengths. We also prove the dependence of the intensity and peak positions in the absorption spectra on the environment. The nature of the Soret band is supposed to derive from $\pi$ plasmon. Our theoretical calculations are consistent with previous experimental studies.

Figure 1

Illustration of the oblate spheroid modeled for porphyrins; different views.

Figure 2

Absorption spectrum of ${\mathrm{H}}_2\mathrm{TPyP}$ dispersed in water with ${\varepsilon }_{\mathrm{water}}=1.77,{\mathrm{CHCl}}_3$ with ${\varepsilon }_{{\mathrm{CHCl}}_3}=2.07$, and other kinds of solvents as a function of the wavelength of incident light calculated by the Mie theory.

Figure 3

Imaginary and real parts of $\varepsilon \left(\omega \right)$ as a function of $\omega$.

Figure 4

Atomic structure of porphine, with 20 carbon atoms [(green) spheres], 14 hydrogen atoms [small (yellow) spheres], and 4 nitrogen atoms [(brown) spheres], and the reference compound [large (orange) spheres].