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Study of electronic spectra of free‐base porphin and Mg‐porphin: Comprehensive comparison of variety of ab initio , DFT, and semiempirical methods
Author(s) -
Šeda Josef,
Burda Jaroslav V.,
Leszczynski Jerzy
Publication year - 2005
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.20164
Subject(s) - porphin , chemistry , rydberg formula , excited state , spectral line , free base , basis set , ab initio , ground state , configuration interaction , excitation , atomic physics , porphyrin , computational chemistry , molecular physics , ion , quantum mechanics , physics , density functional theory , ionization , photochemistry , salt (chemistry) , organic chemistry
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