Chiral properties of peridinin-chlorophyll-protein (PCP) light-harvesting complexes are studied in terms of vibronic dimer theory previously applied to study certain structural aspects of α-crustacyanin pigments. On the base of CD spectra it is shown that the peridinin dimer acts as a chiral group in PCP complexes and its geometrical structure is such that the peridinin monomers cannot be coplanar. Certain observations concerning the energy transfer process in PCP complexes in vivo are also made.
Model calculations are reported for an (E+E)∗e system including linear and quadratic Jahn-Teller and Herzberg-Teller vibronic interactions. The effects of these interactions on magnetic circular dichroism and absorption spectra are compared with experimental observations on CoF^{3-}_{6} salts.
The infrared reflection spectra of the organic quasi-one-dimensional semiconductor triethylammonium (TCNQ)_{2} between 80 and 300 K are reported. Characteristic changes in the temperature dependencies of the bands assigned to the donor vibrations are observed. An interpretation of the electron-molecular vibration coupling in terms of the dimer theory is discussed. It is concluded that the thermal evolution of the spectrum corroborates the semiconductor-semiconductor type of phase transition attributed to the cation disorder.
An interpretation of the IR polarized spectra of the organic quasi-one--dimensional semiconductor triethylammonium (TCNQ)_{2}, between 80 and 300 K, is discussed in terms of the dimer and tetramer theories. It is concluded that the dimer model is acceptable only for describing high-T phase of TEA(TCNQ)_{2}. The tetramer model is more adequate for an interpretation of the IR spectra of the salt within the large temperature range. It is also shown that the phase transition influences distinctly neither vibronic (electron-molecular vibration coupled) modes nor conformity of the experimental spectra with calculated ones according to the dimer or tetramer theory.
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