Three hybrid tungstosilicates: Confinement of SiW 12 O 40 4− anions in rigid concave surfaces with excellent nonlinear optical performance and interesting magnetic properties

Abstract Three novel polyoxoanion-based organic–inorganic compounds confined by the conjugate organic ligand tris(2-benzimidazylmethyl)amine (NTB) [Co(NTB)] 2 (SiW 12 O 40 )·4H 2 O ( 1 ) [Zn(NTB)] 2 (SiW 12 O 40 )·4H 2 O ( 2 ) and [Ni(NTB)(H 2 O)] 2 (SiW 12 O 40 )(C 2 H 5 OH) 2 ·12H 2 O ( 3 ) have been synthesized successfully by using of hydrothermal synthesis. The penta-coordinate environment of metal ions for compound 1 and compound 2 leads to the formation of trigonal bipyramid, which was less to see in other polyoxoanion-based compounds. All three compounds are constituted of the [SiW 12 O 40 ] 4− unit and M(NTB) unit. The two-photon absorption (TPA) cross section σ value of three compounds are calculated as 1826, 2253 and 1470 GM (1 GM = 10 −50  cm 4  s/photon), respectively. The compound 2 reveals the biggest σ value among the NTB-modified POMs. Furthermore, the compounds 1 and 3 show intriguing paramagnetic performance. The effect of different metal ions on optical property would also be investigated.