TY - JOUR
T1 - Fermi resonance as a tool for probing peridinin environment
AU - Kish, Elizabeth
AU - Mendes Pinto, Maria Manuela
AU - Bovi, Daniele
AU - Basire, Marie
AU - Guidoni, Leonardo
AU - Vuilleumier, Rodolphe
AU - Robert, Bruno
AU - Spezia, Riccardo
AU - Mezzetti, Alberto
PY - 2014/6/5
Y1 - 2014/6/5
N2 - In the present paper, we provide an extended study of the vibrational signature of a butenolide carotenoid, peridinin, in various solvents by combining resonance Raman spectroscopy (RRS) with theoretical calculations. The presence of a Fermi resonance due to coupling between the lactonic C-O stretching and the overtone of the wagging of the C-H in the lactonic ring provides a spectroscopic way of differentiating between peridinins lying in different environments. This is a significant achievement, given that simultaneous presence of several peridinins (each with a peculiar photophysical role) in different environments occurs in the most important peridinin containing proteins, the peridinin-chlorophyll proteins (PCPs) and the Chl a-c2-peridinin binding proteins. In RRS, small modifications of solvent polarity can give rise to large differences in the intensity and splitting between the two bands, resulting from the Fermi resonance. By changing the polarity, we can tune the frequency of stretching of the C-O and, while the C-H wagging frequency is almost always constant in different solvents, move the system from a perfect resonance condition to off-resonance ones. We have corroborated our spectroscopic findings with a quasi-classical dynamical model of two coupled oscillators, and DFT calculations on peridinin in different solvents; we have also used calculations to complete the peridinin vibrational mode assignments in the 800-1600 cm-1 region of RRS spectra, corresponding to polyene chain motion. Finally, the presence of Fermi resonance has been used to reinterpret previous vibrational spectroscopic experiments in PCPs.
AB - In the present paper, we provide an extended study of the vibrational signature of a butenolide carotenoid, peridinin, in various solvents by combining resonance Raman spectroscopy (RRS) with theoretical calculations. The presence of a Fermi resonance due to coupling between the lactonic C-O stretching and the overtone of the wagging of the C-H in the lactonic ring provides a spectroscopic way of differentiating between peridinins lying in different environments. This is a significant achievement, given that simultaneous presence of several peridinins (each with a peculiar photophysical role) in different environments occurs in the most important peridinin containing proteins, the peridinin-chlorophyll proteins (PCPs) and the Chl a-c2-peridinin binding proteins. In RRS, small modifications of solvent polarity can give rise to large differences in the intensity and splitting between the two bands, resulting from the Fermi resonance. By changing the polarity, we can tune the frequency of stretching of the C-O and, while the C-H wagging frequency is almost always constant in different solvents, move the system from a perfect resonance condition to off-resonance ones. We have corroborated our spectroscopic findings with a quasi-classical dynamical model of two coupled oscillators, and DFT calculations on peridinin in different solvents; we have also used calculations to complete the peridinin vibrational mode assignments in the 800-1600 cm-1 region of RRS spectra, corresponding to polyene chain motion. Finally, the presence of Fermi resonance has been used to reinterpret previous vibrational spectroscopic experiments in PCPs.
UR - http://www.scopus.com/inward/record.url?scp=84902007714&partnerID=8YFLogxK
U2 - 10.1021/jp501667t
DO - 10.1021/jp501667t
M3 - Article
C2 - 24754506
AN - SCOPUS:84902007714
VL - 118
SP - 5873
EP - 5881
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
SN - 1520-6106
IS - 22
ER -