Two Related Gadolinium Aquo Carbonate 2-D and 3-D Structures and Their Thermal, Spectroscopic, and Paramagnetic Properties

We report two new extended inorganic materials based on gadolinium. The first, [Gd(CO3)2H2O][NH4], consists of negatively charged 2-D sheets of gadolinium carbonate with one coordinated water molecule and an ammonium cation between the layers. The coordinated water and one carbonate extend into the interlayer space, connecting the layers via an extensive hydrogen bonding network which includes the ammonium ions. The second, a closely related yet more condensed framework structure, [Gd2(CO3)3NH3H2O], is formed at a higher hydrothermal temperature and was characterized by single crystal X-ray diffraction data collected at a synchrotron. This second structure contains layers that are isostructural to the first, bridged together by carbonate, and coordinated by water and ammonia. The properties of these materials were studied by thermogravimetric analysis−mass spectrometry, photoluminescence, electron paramagnetic resonance, and Raman and infrared spectroscopy. The 2-D [Gd(CO3)2H2O][NH4] is stable to about 175 °C, though water and ammonium loss continues through the entire thermogravimetric analysis trace. The 3-D material remains intact until about 325 °C. Both structures exhibit broad luminescence bands in the near-ultraviolet region centered at 354 nm. Electron paramagnetic resonance and magnetic susceptibility show spin−spin coupling between adjacent gadolinium atoms in both structures and confirm that they are paramagnetic. These materials show interesting photoluminescent and paramagnetic properties that could possibly be exploited for chemical sensing or magnetic materials applications.