Theoretical studies on oxidation-switchable second-order nonlinear optical responses of Metallosalen-Keggin polyoxometalate derivatives

Abstract

To explore the effect of one-electron oxidation on nonlinear optical (NLO) responses, the frontier molecular orbitals, second-order NLO responses and electronic transition properties of three metallosalen-polyoxometalate compounds {SiW 11 O 39 [O(SiR) 2 M]} 4À (R ¼ (CH 2 ) 3 N-CH(2-OPh); M ¼ Pd, Ni and Co) (M-salen-POM) and their one-electron oxidized species were systematically investigated by density functional theory (DFT). Fukui function analysis shows that the M-salen is the oxidized center in M-salen-POM compounds. In addition, four functionals have been taken to confirm the switching behavior of the NLO properties by the one-electron oxidation. The b tot value of oxo-Pd-salen-POM is 98 times larger than that of Pd-salen-POM, indicating that the first hyperpolarizability is enhanced by one-electron oxidation. Time dependent (TD) DFT calculations show that the charge transfer from POM to M-salen, and intramolecular charge transfer within M-salen in oxidized species are beneficial to reduce the transition energy and improve the static first hyperpolarizabilities. The M-salen-POM may be a potential class of switchable nonlinear optical materials by one-electron oxidized processes.

Synthesis, structure, and characteristics of a hexa-Ti-oxo-cluster-added Keggin-type polyoxometalate

“…NLO materials have aroused wide attention due to their potential applications in optical computing, optical data storage, telecommunications, and optical information processing [43][44][45]. The relationship between the microstructure of NLO crystals and the macroscopic nonlinear effect of the crystals under strong light irradiation is important for optimizing and creating NLO crystal materials with enhanced properties and functions [46,47]. The most basic property of NLO crystals is the noncentrosymmetric space group in their crystal structures.…”