Theoretical Studies On ECD Spectra Of Chiral Polythioanion M(?)bius Strip And Keggin-Type Polyoxometalate Derivatives

Polyoxometalates （POMs） are a unique class of inorganic materials, which are usually formed by early-transition elements in high-oxidation states, such as Mo⁶⁺, W⁶⁺, or V⁵⁺, and mixtures of these elements. POMs have many dramatic applications in various fields such as catalysis, medicine, materials science, and electronic conduction owing to their diverse structures and abundant chemical properties. Chiral materials have attracted much attention, not only because of their potential applications in enantioselective catalysis, materials science, biology, and medicine, but also due to their intriguing variety of architectures and topologies.In this thesis, quantum chemical caculations have been used to study the electronic properties, electronic circular dichorism （ECD） spectra and energy decomposition analysis （EDA） for a series of POMs derivatives. The work focuses on the following three aspects:1. The time-dependent DFT （TD-DFT） method was applied to evaluate the ECD spectra of chiral polythioanion ring cluster [（Mo₂S₂O₂）₄（OH）₆（C₄O₄）（Mo₂O₈）]^4-（1a） and its one-and two-electron reduced forms, [1a]^- and [1a]^2-. The shapes of the ECD bands for the le-/2e-reduced forms of la are similar to those of la, while the rotatory strengths significantly increase. The simulated ECD spectrum of la shows six bands, which originate from the charge transfer from the O and C atoms of the {C₄O₄} unit and S atoms to Mo and Ot atoms. It is proposed that the {C₄O₄} unit plays a role as an optically active chromophore and contributor to the absorptions in the ECD spectrum of la. Aside from the charge transfer from the {C₄O₄} unit to {Mo₂^ⅤO₂S₂} and/or {Mo₂^ⅥO₈} units, the charge transfer transitions from {Mo₂^ⅤO₂S₂} to the{Mo₂^ⅥO₈} unit in the 1e-/2e-reduced forms increase with the addition of electrons.2. The time-dependent DFT （TD-DFT） method was used to investigate the ECD spectra of the complexes [（R, R）-BPEA-PMo₁₁Ⅴ]^3-, which are formed by chiral organic cations modified vanadium derivatives of Keggin-type POM, and its one-electron reduced form. The results show that the reduction mainly occured on V atom, and vanadium （Ⅴ） was reduced to vanadium （Ⅳ）. At short-wavelength absorption band, the charge transfer for [（R, R）-BPEA-PMo₁₁Ⅴ]^3-is mainly from the organic fragments and the oxygen atoms of POM to the metal atoms of POM, For reduced [（R, R）-BPEA-PMo₁₁Ⅴ]^4-, the charge transfer originates from Ⅴ⁴⁺ ions to Mo⁶ ions, and a small part come from the d-d transition of Ⅴ⁴⁺.3. DFT calculations were performed on the star-shaped polyoxoselenitopalladate [Mⁿ⁺Pd₁₅（μ3-SeO₃）₁₀（μ5-O）₁₀]^（10-n）- (M = Li⁺, Na⁺, K⁺, Rb⁺, Mg²⁺, Ca²⁺, Zn²⁺) to investigate their geometrical structures, electronic properties and cation templating effect. The complexation energy and △E_B+△E_solvation for MPd₁₅ （M = Li⁺, Na⁺, K⁺, Rb⁺） decrease as LiPd₁₅>NaPd₁₅>KPd₁₅>RbPd₁₅. The △E_B+△E_solvation for MPd₁₅ (M = Mg²⁺, Ca²⁺, Zn²⁺) are larger because of large △E_elst and △E_orb terms. The bivalent metal cations are favorable to be guest cations in Pd₁₅ cavity rather than univalent cations. The size of Ca²⁺ is similar to that of Na+, but the higher positive charge of Ca²⁺ leads to the stronger interaction with Pd₁₅. These results demonstrate that the smaller size and higher charges are helpful to the guest cations interacting with Pd₁₅, and it is related to the cation templated self-assembly of polyoxopalladate.