From AgTeO2F and Ag2(TeO2F2) to Ag3F3(TeF6)(TeO2)12: the first silver tellurite oxyfluorides with linear and nonlinear optical properties

The first examples of silver fluorotellurites, namely, AgTeO2F and Ag-2(TeO2F2), and the first silver fluoride tellurite, Ag3F3(TeF6)(TeO2)(12), have been obtained successfully under mild hydrothermal conditions. AgTeO2F displays a new 2D structure composed of a 2D silver oxide layer strengthened by 1D [TeO2F](infinity) chains. Ag-2(TeO2F2) exhibits a new 3D construction consisting of a 3D silver oxyfluoride framework with 1D polyhedral ring channels occupied by the isolated TeO2F2 groups. Ag3F3(TeF6)(TeO2)(12) features the first 3D neutral [TeO2](infinity) open framework with 8- and 4-MPR channels along the a-, b- and c-axes. AgTeO2F and Ag-2(TeO2F2) crystallize in the centrosymmetric space group while Ag3F3(TeF6)(TeO2)(12) is in a non-centrosymmetric space group. Ag3F3(TeF6)(TeO2)(12) shows a unique nonlinear optical property with an SHG intensity of about 70% that of commercial KH2PO4, while AgTeO2F and Ag-2(TeO2F2) present an apparent linear optical property and their birefringence is calculated as 0.078 and 0.032@1064 nm, respectively. This work further confirms that fluorination in tellurium(iv) oxides can greatly enrich the structural chemistry and optical properties of metal tellurites.