Resonance Raman Spectra and Electronic Transitions in Carotenoids: A Density Functional Theory Study

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2014-03, Vol.118 (10), p.1817-1825
• Main Authors: Macernis, Mindaugas, Sulskus, Juozas, Malickaja, Svetlana, Robert, Bruno, Valkunas, Leonas
• Format: Article
• Language: English
• Subjects: Band spectra; Carotenoids; Carotenoids - chemistry; Computer Simulation; Conjugation; Density functional theory; Electricity; Electronics; Isomerization; Linear Models; Mathematical analysis; Models, Molecular; Polyenes - chemistry; Raman spectra; Spectrum Analysis, Raman
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp406449c

Raman and electronic absorption spectra corresponding to the S0–S2 electronic transition of various carotenoid and polyene molecules are theoretically analyzed using the density functional theory (DFT) approach. The results demonstrate the linear dependence between the frequency of the so-called ν1 band corresponding to the CC stretching modes in the Raman spectra and the S0–S2 electronic transition for molecules of different conjugation lengths. From these calculations the following relationship have been identified: (i) the effective conjugation length shortens in conformers of carotenoids containing β-rings whereas it increases in polyene upon s-cis isomerization at their ends, (ii) methyl groups connected to the conjugated chain of carotenoids induce a splitting of the ν1 band in the Raman spectra, (iii) the effective conjugation lengths of all-trans-polyenes and corresponding all-trans-carotenoids are the same as follows from the Raman ν1 frequency, but they are different as defined from S0–S2 electronic transition energies. The results well correlate with the experimental observations.