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Kramers–Kronig transformation of experimental electronic circular dichroism: Application to the analysis of optical rotatory dispersion in dimethyl‐ L ‐tartrate
Author(s) -
Polavarapu Prasad L.,
Petrovic Ana G.,
Zhang Peng
Publication year - 2006
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.20310
Subject(s) - chemistry , tartrate , optical rotatory dispersion , wavelength , circular dichroism , dispersion (optics) , excited state , molecular electronic transition , spectral line , atomic electron transition , kramers–kronig relations , molecular physics , analytical chemistry (journal) , atomic physics , crystallography , optics , physics , quantum mechanics , refractive index , chromatography , inorganic chemistry
Abstract When a limited region of the experimental electronic circular dichroism (ECD) spectrum is subjected to Kramers–Kronig (KK) transformation, the resulting optical rotatory dispersion (ORD) may or may not reproduce the experimentally measured ORD in the long‐wavelength nonresonant region. If the KK transform of experimentally measured ECD in a limited wavelength region reproduces the experimentally measured ORD in the long‐wavelength nonresonant region, then that observation indicates that the ORD in the long‐wavelength nonresonant region should be satisfactorily predicted from the correspondingly limited number of electronic transitions in a reliable quantum mechanical calculation. On the other hand, if the KK transform of experimentally measured ECD in a limited region does not reproduce the experimentally measured ORD in the long‐wavelength nonresonant region, then it should be possible to identify the ECD bands in the shorter wavelength region that are responsible for the differences between experimentally observed ORD and KK‐transformed ECD. This approach helps to identify the role of ECD associated with higher energy‐excited states in the nature of ORD in the long‐wavelength nonresonant region. These concepts are demonstrated here by measuring the experimental ECD and ORD for dimethyl‐ L ‐tartrate in different solvents. While ECD spectra of dimethyl‐ L ‐tartrate in different solvents show little variation, ORD spectra in the long‐wavelength nonresonant region show marked solvent dependence. These observations are explained using the difference between experimental ORD and KK‐transformed ECD. Quantum mechanical predictions of ECD and ORD are also presented for isolated ( R , R )‐dimethyl tartrate at the B3LYP/aug‐cc‐pVDZ level. Chirality, 2006. © 2006 Wiley‐Liss, Inc.