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

Abstract

The reaction of Al, Ga, or In metals and H 5IO 6 in aqueous media at 180 °C leads to the formation of Al(IO 3) 3, Ga(IO 3) 3, or In(IO 3) 3, respectively. Single-crystal X-ray diffraction experiments have shown In(IO 3) 3 contains the Te 4O 9-type structure, while both Al(IO 3) 3 and Ga(IO 3) 3 are known to exhibit the polar Fe(IO 3) 3-type structure. Crystallographic data for In(IO 3) 3, trigonal, space group R 3 ¯ , 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>2 σ( I). All three iodate structures contain group 13 metal cations in a distorted octahedral coordination environment. M(IO 3) 3 ( M=Al, Ga) contain a three-dimensional network formed by the bridging of Al 3+ or Ga 3+ cations by iodate anions. With In(IO 3) 3, iodate anions bridge In 3+ 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(IO 3) 3 was found to display a distinctively different vibrational profile than Al(IO 3) 3 or Ga(IO 3) 3. Hence, the Raman profile can be used as a rapid diagnostic tool to discern between the different structural motifs.