Synthesis, crystal structure, and solid-state NMR spectroscopy of (4-HAP)2[Ga4O(PO4)4(H 2O)4] (AP = aminopyridine), a gallophosphate containing discrete double-four-ring units

M. C. Hsien, H. M. Kao, K. H. Lii

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Abstract

A new gallophosphate, (4-HAP)2[Ga4O(PO4)4(H 2O)4] (designated NCUGa-1), has been synthesized in the presence of 4-aminopyridine as the structure-directing agent. The structure consists of discrete Ga4(PO4)4(H2O)4 double-four-ring (D4R) units hosting O2- anions. Charge compensation is achieved by the monoprotonated amine. Each D4R unit is linked to adjacent units and the organic cations via hydrogen bonding. Crystal data: (C5H7N2)2[Ga4O(PO 4)4(H2O)4], orthorhombic, space group Aba2 (no. 41), a = 18.879(4) Å, b = 18.481(4) Å, c = 7.469(1) Å, V = 2606.1(9) Å3, Z = 4, R1 = 0.025, and wR2 = 0.062. 1H MAS NMR confirms that protonation is on the pyridine nitrogen in aminopyridine. The proton-decoupled 31P MAS NMR spectrum exhibits two resonances at 3.8 and 3.4 ppm with an intensity ratio of 1:1, corresponding to two distinct crystallographic 31P sites. The information obtained from 1H → 31P CP/MAS NMR experiments provides insight into the interaction between the hydrogen atoms of the water molecules and/or the amine and the 31P spins, and can be used to correlate 31P resonances with crystallographic sites. In addition, 71Ga MAS NMR confirms the presence of two Ga sites.

Original languageEnglish
Pages (from-to)2584-2588
Number of pages5
JournalChemistry of Materials
Volume13
Issue number8
DOIs
StatePublished - 2001

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