Theoretical exploration to the substituting effect on second-order nonlinear optical properties for lacunary γ-Keggin polyoxometalates

Theoretical study of new push–pull molecules based on transition metals for NLO applications and determination of ICT mechanisms by DFT calculations

This study is based on the valuation of a few model molecules. The objective of this research is focussed on the nonlinear optical (NLO) improvement of four organometallic molecules and one organic molecule. These molecules have been subjected to several calculations by different functionals: CAM–B3LYP, LC–BLYP, LC–wPBE, wB97X, M11, M06–2X, M08–HX and M08–SO. These functionals gave three orders of classification of the [Formula: see text] parameters. The CAM–B3LYP functional recorded very good agreement between [Formula: see text] parameters and gaps ([Formula: see text]. Significant first hyperpolarizabilities ([Formula: see text] have been obtained around 880 * 10[Formula: see text][Formula: see text]esu. The mechanisms of intramolecular charge transfer (ICT) have shown energetic passages from donor groups to acceptors and vice versa. The substitution of metals influences the location of [Formula: see text] electrons at the level of the chromophores. Finally, the lengthening of the aromatic chains between the acceptor and donor groups shows significant NLO improvements. The first and second hyperpolarizabilities ([Formula: see text] and ([Formula: see text] for a chain of several benzene rings are of the order of 21,663.16 * 10[Formula: see text][Formula: see text]esu and 16,464.65 * 10[Formula: see text][Formula: see text]esu, respectively.

Theoretical exploration on switchable NLO response induced by redox properties of polyoxometalates [XNbW11O40]n-/(n+1)- (X = Al, Si, P, S, Ga, Ge, As, Se)

Calculations based on density functional theory (DFT) have been performed to investigate the relationship between redox properties and second-order nonlinear optical (NLO) responses of Keggin-type anions [XNbW₁₁O₄₀]^n- (X = Al, Si, P, S, Ga, Ge, As, Se) and their corresponding heteropoly blues. The frontier molecular orbitals, NLO responses and electronic transition properties of fully oxidized anions and heteropoly blues were discussed. It is noticeable that the second-order NLO behaviors can be switched by reduced electrons for these Keggin-type anions. The calculated β₀ value of heteropoly blues [XNbW₁₁O₄₀]^(n+1)- (X = P, As, S) are 21-23 times as large as those of fully oxidized anions [XNbW₁₁O₄₀]^n- (X = P, As, S) according to CAM-B3LYP/6-31G* (LANL2DZ basis sets for metal atom) calculations in CH₃CN. The aim of this work is to combine the attractive redox properties and NLO response of polyoxometalates to obtain the switchable NLO materials.

Theoretical exploration to the cation effect on the second-order nonlinear optical properties of Strandberg-type polyoxometalates

The combination of cations with octahedral coordinated d0 transition metal ions has been proved to be an effective way for designing new polar materials. So we investigate the second-order nonlinear optical (NLO) properties of Strandberg-type polyoxometalates (POMs) with alkali metal cations M 6 Mo 5 X 2 O 23 ( M = K +, Rb +, Cs +; X = P , As ) and M 4 M o5 X 2 O 21 ( M = K +, Rb +, Cs +; X = S , Se , Te ) by density functional theory (DFT) method. The calculated results show that this kind of Strandberg-type POMs possesses remarkably large molecular second-order NLO polarizability, especially for the Cs 6 Mo 5 P 2 O 23 (system Ic), which has a computed β0 value of 12526 a.u. and might be an excellent second-order NLO material. Moreover, the cations have important impact on the second-order NLO polarizabilities. Therefore, a careful choice of appropriate cations may allow the control of the second-order NLO response on these Strandberg-type POMs, which may provide a new route to design efficient NLO materials.