Syntheses, crystal structures and optical properties of two one-dimensional germanophosphates: HRb 3 Ge 2 (HPO 4 ) 6 and CsGe(HPO 4 ) 2 (OH).

Germanophosphates, as a young class of metal phosphates, have been less reported but might possess more diverse structural types and potential applications. Here, two one-dimensional (1D) alkali-metal germanophosphates (GePOs), namely, hydrogen hexakis(μ-hydrogen phosphato)digermaniumtrirubidium, HRb3 Ge2 (HPO4 )6 (1), and caesium bis(μ-hydrogen phosphato)(μ-hydroxido)germanium, CsGe(HPO4 )2 (OH) (2), have been prepared by the solvothermal method. Compound 1 shows 1D [Ge(HPO4 )6 ]∞ chains along the c axis formed by GeO6 octahedra and PO4 tetrahedra, with Rb+ cations dissociated between the chains. Compound 2 also exhibits 1D [Ge(HPO4 )4 (OH)2 ]∞ chains constructed from adjacent Ge(HPO4 )4 (OH)2 octahedra, with Cs+ cations dissociated between the chains. XRD, TGA, IR and UV-Vis-NIR absorption spectra are presented and discussed for both compounds.