Study of electronic spectra of free-base porphin and Mg-porphin: Comprehensive comparison of variety of ab initio, DFT, and semiempirical methods
✍ Scribed by Josef Šeda; Jaroslav V. Burda; Jerzy Leszczynski
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 119 KB
- Volume
- 26
- Category
- Article
- ISSN
- 0192-8651
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✦ Synopsis
Abstract
SAC (symmetry adapted cluster)/SAC‐CI and CASPT2 (multiconfigurational second‐order perturbation theory) electron excitation spectra of free‐base porphin and magnesium‐porphin were determined using basis set functions augmented by both the polarization and diffuse functions—6‐31+G(d). Such basis is recommended for correct description of the spectra because diffuse functions play fundamental roles in the formation of Rydberg MOs. The obtained results indicated that already the lowest roots in A~u~, B~1u~, B~2g~, and B~3g~ irreducible representations display Rydberg character. The calculated spectra are in a good agreement with both experimental and recently calculated electronic transitions. It is concluded that the SAC/SAC‐CI level spectral lines are significantly affected by configuration selection when energy thresholds 5.0 × 10^−6^ and 5.0 × 10^−7^ a.u. are used for the determination of ground and excited state properties. © 2004 Wiley Periodicals, Inc. J Comput Chem 26: 294–303, 2005