Abstract:

The geometrical strucutres, electronic structures, UV-visible(UV-Vis) absorption and electronic circular dichroism(ECD) spectra of chiral polyoxometalates(POMs) [Se^ⅣMo₆O₂₁(L-alanine)₃]^2-, [Sb^ⅢMo₆O₂₁(L-alanine)₃]^3- and [Bi^ⅢMo₆O₂₁(L-alanine)₃]^3- modified by L-O₂CCHCH₃NH₃(L-alanine) have been explored via the density functional theory(DFT) method. The effect of heteroatoms on optical activities of studied compounds has been determined. The result indicates that the geometrical structures, UV-Vis spectra absorption intensity and peak shape are affected by heteroatoms. The rotational absorption direction and strength of the ECD spectra significantly change from Se^Ⅳ, Sb^Ⅲ to Bi^Ⅲ. The UV-Vis and ECD spectra in the low-energy range are mainly ascribed to the charge-transfer(CT) transitions from the p orbitals of O atoms to the d orbitals of Mo atoms in the POMs, and the both spectra in the high-energy range are mainly from the heteroatoms in the POMs and the p orbitals of the O atoms connecting with heteroatoms to the d orbitals of Mo atoms. These conclusions are significant for understanding the electronic structures and chiral spectroscopy properties of this kind of amino acids modifying POMs.

Key words: Polyoxometalate, Electronic circular dichroism, Chirality, Denstiy functional theory