Theoretical study on phthalocyanine, pyrazinoporphyrazine and their complexation with Mg²⁺ and Zn²⁺ 

Abstract

We have studied the UV–vis absorption spectra of metal-free phthalocyanine (H₂Pc), metal-free pyrazinoporphyrazine (H₂PyzPz) and their complexes with Mg^2 +  and Zn^2 +  using semiempirical Zerners intermediate neglect of differential overlap and time-dependent density functional theory methods. The predicted absorption spectra of H₂Pc and their complexes are in agreement with a previous experiment report. The calculated results show that the Q band absorption peaks of H₂PyzPz and their complexes are blue-shifted by 40 nm as compared with those of H₂Pc and their complexes, respectively. The frontier molecular orbitals (HOMO and LUMO) of H₂Pc, H₂PyzPz and their metal complexes were investigated as well. The nitrogen atoms in the pyrazine rings stabilise the HOMO more than the LUMO, and the deprotonation of the pyrrole rings induced by the metal coordination destabilises the LUMO more than the HOMO. Because of the increased band gap, the absorption bands of H₂PyzPz and the metal-coordinated compounds are blue-shifted.

Keywords:

• phthalocyanine
• pyrazinoporphyrazine
• metal complex
• ZINDO
• TDDFT
• UV–vis absorption spectra

Acknowledgements

This study was supported by Grant No. 10031803 from the Industrial Source Technology Development Programs and a grant from the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy, Republic of Korea. We thank Accelrys Korea for support with the modelling software.