Synthesis and structure of In(IO3)3 and vibrational spectroscopy of M(IO3)3 (M=Al, Ga, In)

The reaction of Al, Ga, or In metals and H5IO6 in aqueous media at 180 °C leads to the formation of Al(IO3)3, Ga(IO3)3, or In(IO3)3, respectively. Single-crystal X-ray diffraction experiments have shown In(IO3)3 contains the Te4O9-type structure, while both Al(IO3)3 and Ga(IO3)3 are known to exhibit the polar Fe(IO3)3-type structure. Crystallographic data for In(IO3)3, trigonal, space group R3¯, a=9.7482(4) Å, c=14.1374(6) Å, V=1163.45(8) Z=6, R(F)=1.38% for 41 parameters with 644 reflections with I>2σ(I). All three iodate structures contain group 13 metal cations in a distorted octahedral coordination environment. M(IO3)3 (M=Al, Ga) contain a three-dimensional network formed by the bridging of Al3+ or Ga3+ cations by iodate anions. With In(IO3)3, iodate anions bridge In3+ cations in two-dimensional layers. Both materials contain distorted octahedral holes in their structures formed by terminal oxygen atoms from the iodate anions. The Raman spectra have been collected for these metal iodates; In(IO3)3 was found to display a distinctively different vibrational profile than Al(IO3)3 or Ga(IO3)3. Hence, the Raman profile can be used as a rapid diagnostic tool to discern between the different structural motifs.

Al(IO3)3, Ga(IO3)3, and In(IO3)3 have been prepared by reacting the appropriate group 13 metal with H5IO6 in aqueous media at 180 °C. Single-crystal X-ray diffraction has shown that In(IO3)3 contains the Te4O9-type structure in contrast to the Fe(IO3)3-type structure observed previously for Al(IO3)3 and Ga(IO3)3. Raman spectra reveal that Al(IO3)3 and Ga(IO3)3 show similar vibrational profiles due to their isostructural nature, but In(IO3)3 has been found to display a distinctively different vibrational profile. Therefore, Raman spectroscopy can be used as a rapid diagnostic tool to discern the different structural motifs of these two-structure types.Figure optionsDownload as PowerPoint slide