Ionothermal synthesis, crystal structure and solid-state NMRspectroscopy of a new organically templated gallium oxalatophosphate: (H2TMPD)0.5[Ga3(C2O4)0.5(PO4)3] (TMPD = N,N,N′,N′-tetramethyl-1,3-propanediamine)

Abstract

A new organically templated gallium oxalatophosphate, (C₇H₂₀N₂)_0.5[Ga₃(C₂O₄)_0.5(PO₄)₃], has been synthesized by using a low-melting-point eutectic mixture of choline chloride and oxalic acid as a solvent and characterized by single-crystal X-ray diffraction, thermogravimetric analysis and solid-state NMR spectroscopy. It is the first example of ionothermal synthesis of organically templated metal oxalatophosphate. The structure contains double 6-ring units of the composition Ga₆(PO₄)₆ which are connected by oxalate ligands and P–O–Ga bonds to form a 3-D framework. The charge-compensating organic ammonium cations which are disordered over two positions are located at the intersections of two types of 8-ring channels. ¹H MAS and ¹³C CPMAS NMR studies confirm the presence of N,N,N′,N′-tetramethyl-1,3-propanediammonium cation. The ⁷¹Ga and ³¹P MAS NMR spectra are also consistent with the crystal structure analysis results.