Two New Noncentrosymmetric Rubidium Titanium Phosphate Phases: Rb2Ti3O2(PO4)2(HPO4)2 and Rb3Ti3O(P2O7)(PO4)3

✍ Scribed by William T.A. Harrison; Thurman E. Gier; Joseph C. Calabrese; Galen D. Stucky

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 559 KB
• Volume: 111
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1994.1226

✦ Synopsis

Two new, noncentrosymmetric, rubidium titanium phosphate phases have been synthesized by hydrothermal and flux methods and structurally characterized by single crystal X-ray diffraction methods. (\mathrm{Rb}{2} \mathrm{Ti}{3} \mathrm{O}{2}\left(\mathrm{PO}{4}\right){2}\left(\mathrm{HPO}{4}\right){2}) (Rb2Ti3P4) consists of a threedimensional framework of vertex-sharing (\mathrm{TiO}{6}, \mathrm{PO}{4}), and (\mathrm{HPO}{4}) polyhedra interconnected via (\mathrm{Ti}-\mathrm{O}-\mathrm{Ti}) and (\mathrm{Ti}-\mathrm{O}-\mathrm{P}) bonds, surrounding large, one-dimensional channels occupied by eight-coordinate "guest" (\mathbf{R b}^{+})cations: these channels propagate along the acrystallographic direction. The framework includes (\left[\mathrm{Ti}{3} \mathrm{O}{16}\right]) units built up from three adjacent (\mathrm{TiO}{6}) octahedra sharing trans- (\mathrm{O}-\mathrm{Ti}-\mathrm{O}) links, crosslinked by the (hydrogen)phosphate groups. (\mathrm{Rb}{3} \mathrm{Ti}{3} \mathrm{O}) (\left(\mathrm{P}{2} \mathrm{O}{7}\right)\left(\mathrm{PO}{4}\right){3}(\mathrm{Rb} 3 \mathrm{Ti3P} 5)) is built up from a network of (\mathrm{TiO}{6}) and (\mathrm{PO}{4}) groups, linked via Ti- (\mathrm{O}-\mathrm{Ti}, \mathrm{Ti}-\mathrm{O}-\mathrm{P}), and (\mathrm{P}-\mathrm{O}-\mathrm{P}) bonds, enclosing channels occupied by the guest rubidium cations. The structural motif of the framework includes isolated (\mathrm{TiO}{6}) and (\left[\mathrm{Ti}{2} \mathrm{O}{11}\right]) groups, interconnected by (pyro)phosphate groups. The (\mathrm{Rb}^{+})cations occupying the one-dimensional channels are eightfold coordinate by oxygen atoms. (\mathrm{Rb}{3} \mathrm{Ti}{3} \mathrm{O}\left(\mathrm{P}{2} \mathrm{O}{7}\right)\left(\mathrm{PO}{4}\right){3}(2) linked octahedra) and (\mathrm{Rb}{\mathrm{a}} \mathrm{Ti}{3} \mathrm{O}{2}\left(\mathrm{PO}{4}\right){2}\left(\mathrm{HPO}{4}\right){2}) (3 linked octahedra) are considered in relation to the nonlinear optical materials (\mathrm{KTiOPO}{4}(\mathrm{KTP})) and (\mathrm{RbTiOPO}{4}) (RbTP) which contain infinite -O-Ti-O-Ti-Ochains. The typical short, "titanyl" (\mathrm{Ti}=\mathrm{O}) bond found in KTP and (\mathrm{RbTP}) is barely apparent in (\mathrm{Rb}{2} \mathrm{Ti}{3} \mathrm{O}{2}\left(\mathrm{PO}{4}\right){2}\left(\mathrm{HPO}{4}\right){2}) and (\mathrm{Rb}{3}) (\mathrm{Ti}{3} \mathrm{O}\left(\mathrm{P}{2} \mathrm{O}{7}\right)\left(\mathrm{PO}{4}\right){3}), and the poor nonlinear response of the title compounds is discussed in relation to the extended (\mathrm{Ti} / \mathrm{O}) chain structure in RbTP. Crystal data: (\mathbf{R b}{2} \mathrm{Ti}{3} \mathrm{P}{4} \mathrm{O}{18} \mathrm{H}{2}, M{\mathrm{r}}=728.5), monoclinic, (P 2_{1}, a=5.1851(4) \AA, b=16.770) (2) (\AA, c=8.4939(6)) (\AA, \beta=90.940(3)^{\circ}, V=738.48 \AA^{3}, Z=2). Final residuals of (R=4.24 %) and (R_{\mathrm{w}}=4.40 %) were obtained for 2331 unique reflections with (I>3 \sigma(I) . \mathrm{Rb}{3} \mathrm{Ti}{3} \mathrm{P}{5} \mathrm{O}{20}, M_{\mathrm{r}}=874.96), orthorhombic, (P c a 2_{1}, a=18.280(1) \AA, b=6.295(1) \AA, c=14.773(1) \AA, V=) (1700.0 \AA^{3}, Z=4, R=4.00 %), and (R_{\mathrm{w}}=3.70 %) for 1498 unique reflections with (I>3 \sigma(I) . \quad 1994) Academic Press, Inc.