Nanocluster crystals of lacunary polyoxometalates as structure-design-flexible, inorganic nonlinear materials

Abstract

Lacunary polyoxometalates, large inorganic, structure-design-flexible, nanocluster crystals are found to have higher optical nonlinearity than KH2PO4 by the powder second-harmonic-generation method. Moreover, the capability of generating ultraviolet radiation down to around 300 nm is found. The basic criteria to design the high nonlinearity are also discovered by the reduction of the molecular symmetry.

Chirality in Polyoxometalate Chemistry

“…Thus, the point of view of crystallographers and chemists differ in the entity under consideration (crystal structure vs. molecule) and in the symmetry restrictions (noncentrosymmetric vs. lack of mirror, reflection, inversion through a point, rotoinversion). Noncentrosymmetry in a crystal can result from disorder, as shown by Murakami for a series of Keggin‐type compounds with interesting nonlinear optical properties 34. In this paper, we adopt the position of the chemists and consider the absolute configuration of a molecular entity in the crystal.…”

How Do the Different Defect Structures and Element Substitutions Affect the Nonlinear Optical Properties of Lacunary Keggin Polyoxometalates? A DFT Study

“…The results indicate some common trends, which are in agreement with the qualitative predictions of Murakami and co-workers on the NLO response of nanostructured materials made from lacunary POMs. [4] First, the trivacant Keggin complexes (IIa, IIb, and IIc) have larger β 0 values than the monovacant structure (I): all the β 0 values of IIa, IIb, and IIc are above 1100 a.u. whereas the present calculations predict the β 0 value of I to be just 794.0 a.u.…”

“…The present DFT calculations predict the β 0 value of system IIIc to be 2071.0 a.u., whereas the predicted second-order polarizability of Au 20 is 1655.3 a.u. [9] All these complexes have high transparency in the visible area [4] therefore, in view of the merit of this class of inorganic complexes, they could be an excellent material for use in the second-order NLO field. , and Ta V ).…”

“…They also defined design criteria to obtain a large NLO response. [4] This experi- mental result inspired us to further investigate the electronic and NLO properties of lacunary α-Keggin derivatives by a DFT method. In the past decade, DFT has been shown to be able to successfully predict the properties of molecules and materials, including the NLO properties.…”

“…In order to synthesize novel POMs with predicted structures, an approach widely used is to treat lacunary POM precursors with transition metal ions or organometallic fragments as lacunary structures possess a reactive nucleophilic polyoxygenated site. Different transition metal ions can partly or wholly fill these vacancies to give rise to compounds with magnetism or catalysts, [2] such as PW 9 4 . They also defined design criteria to obtain a large NLO response.…”