Synthesis, structure, and characterization of two photoluminescent zirconium phosphate-quinoline compounds

Two novel zirconium phosphate compounds, |(C(9)H(8)N)(4)(H(2)O)(4)|[Zr(8)P(12)O(40)(OH)(8)F(8)] and |(C(9)H(8)N)(2)|[Zr(2)P(2)O(6)(OH)(4)F(4)], designated as ZrPOF-Q1 and ZrPOF-Q2, respectively, have been synthesized hydrothermally in the presence of quinoline and HF and characterized by elemental and thermogravimetric analyses, UV-vis spectroscopy, and scanning electron microscopy. Their crystal structures were determined from powder X-ray diffraction data using a charge-flipping algorithm. The ZrPOF-Q1 structure [P1, a = 10.7567(1) A, b = 13.8502(1) A, c = 14.8995(1) A, alpha = 109.6(1) degrees, beta = 101.1(1) degrees, and gamma = 100.5(1) degrees] consists of zirconium phosphate layers with quinolinium ions in between. The layers are unusual in that isolated ZrO(2)F(4) octahedra are anchored on both sides of the layer and protrude into the interlayer space. The ZrPOF-Q2 structure [P1, a = 7.7058(1) A, b = 12.3547(1) A, c = 6.5851(1) A, alpha = 97.0(1) degrees, beta = 89.7(1) degrees, and gamma = 101.9(1) degrees] consists of zirconium phosphate chains with an unusual Zr/P ratio of 1.0, interspersed with quinolinium ions. Both materials are stable up to 250 degrees C and exhibit interesting photoluminescence in the UV-vis spectral region. This is attributed to the protonated quinoline molecules, which are an integral part of both structures.