In this work

the octaethyl-porphyrins with different central metals (M-OEP

M=Ni

VO

Cu

Co) were used to investigate the ground-state molecular structure

electron distribution and UV-spectra properties on molecular level by density functional theory (DFT). The results showed that the calculation structure parameters of metalloporphyrins agreed well with the experimental value. According to the Natural Bond Orbital (NBO) analysis

the charge distribution of different metalloporphyrins was found that the charge values of the central metal M decreased with the order of VO Ni Co Cu

while the bonding strength between M and the coordinating atom N was VO Ni Co Cu. At the same time

the frontier molecular orbital calculations showed that the SOMO energy of VO (OEP) molecules in the open-shell system was higher than that of Co (OEP) and Cu (OEP)

which means that its UV absorption characteristic peak would be red-shifted. In addition

the IEFPCM model of Time-dependent Density functional theory (TD-DFT) was further utilized to simulate the four substance in toluene solution: Co (OEP)

Ni (OEP)

Cu (OEP) and VO (OEP)

and the Soret band peaks were calculated respectively as: 382 nm

383 nm

391 nm and 401 nm. Furthermore

the quantitative simulation analysis of metalloporphyrins was combined with experimental data. It could be found that the location rules of the four kinds of metalloporphyrins calculated absorption characteristic peaks were consistent with the experimental ones

and the relative errors of each peak were within 3%. These methods used above provide a theoretical path for analyzing and identifying unknown porphyrin compounds in petroleum.