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The development of materials with spectral characteristics of plants is a hot topic in the field of camouflage.Based on the similarity and molecular modifiability of phthalocyanine (Pc) and chlorophyll-porphyrin structures, tetra nitro cobalt phthalocyanine(TNCoPc) with central cobalt ion and alpha position nitro substituted are designed and analysed.Structural optimization of phthalocyanine, cobalt phthalocyanine (CoPc), tetra nitro phthalocyanine (TNPc) and TNCoPc are carried out using the density functional theory B3LYP / 6-31G (d), after which the TD-DFT is used to calculate the UV-Vis spectra. The HOMO-LUMO level comparison diagram of CoPc and Pc molecules and frontier molecular orbital map according to the calculation results of TD-DFT which is based on the optimized geometry are drawn out and compared respectively. The results show that, affected by the d7 electronic structure of cobalt ion and the ligands, 7 electrons of 3d orbitals involved in forming four equivalent dsp2 hybrid orbitals so that the valence electron layer has unpaired single spins, resulting in two kinds of energy gaps of alpha and beta.The energy difference of CoPc is 0.1ev larger than that of Pc so that the blue shift of Q band is observed.The absorption of TNPc is influenced by the electron withdrawing group and the conjugation of the C=O double bond on the nitro group,the energy level difference decreases and the absorption band shifts to longer wavelengths.The absorption of TNCoPc at 652.84nm is mainly the transition of electrons from orbit 188HOMO-1 to 191LUMO+2, and the absorption at 603.19nm is mainly the transition of electrons from orbit 190HOMO to 191LUMO.The results of TNCoPc quantitative calculation provides a reliable and convenient method for the use of phthalocyanines to fit the spectrum of plants.
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