Synthesis, structure and properties of CsHSi3O7, a layered silicate with a chiral structure

Abstract

The chiral layered silicate CsHSi 3 O 7 has been synthesized by hydrothermal techniques, and its structure determined by single crystal X-ray diffraction. The compound crystallizes in the space group P 2 1 2 1 2 1 . The silicate single layer consists of both four- and three-connected SiO 4 tetrahedra and may be considered as a member of a series of layer structures with the general formula (Si 4 O 9 ) m (Si 2 O 5 ) n . Strong hydrogen bonds occur between the terminal OH − and O 2− ions of neighboring layers. The Cs + cations can be ion-exchanged by protons to give a phase of composition H 2 Si 3 O 7 ·H 2 O with a water molecule occupying the original Cs position, as confirmed by single crystal X-ray diffraction data. The water molecule in H 2 Si 3 O 7 ·H 2 O can be readily removed without collapse of the crystal structure. Both CsHSi 3 O 7 and H 2 Si 3 O 7 ·H 2 O show SHG (second harmonic generation) efficiencies comparable to that of quartz, and both are not phase-matchable materials.