Discovery of <i>β</i>-HIO<sub>3</sub>: A Metastable Polymorph of HIO<sub>3</sub>

• 作者: Daniel K. Unruh Dylan K. Smith Michelle L. Pantoya
• 来源期刊: 材料物理与化学进展(英文)
• 学科: 化学
• 关键词: X-Ray Diffraction IODATES Acids Crystal Structure Oxides
• 年，卷（期）: 2018,（5）
• 页码范围: 246-256
• 页数: 11页
• 分类号: O6

摘要

The β-HIO3 polymorph, previously difficult to detect and whose existence was questioned, has been structurally characterized. The crystal structure of β-HIO3 was solved in the same space group as α-HIO3 (P212121);however, it was found that the unit cell axes were all different by about 1 Å. Similar to that of α and γ phases, the unit cell contains only a single HIO3 molecule in the asymmetric unit with I-O bond lengths ranging from 1.786(5) to 1.903(7) Å. The I(V) atom is further coordinated by three oxygen atoms of neighboring acid molecules forming a distorted octahedral with a range of I-O distances (2.498(6) - 2.795(7) Å). The one structural difference that separates the β phase from the α and γ phases is that the hydroxyl group is bridging between two I(V) atoms, resulting in a smaller hydrogen bonding distance (O-O distance: 2.559 Å(β), 2.665 Å(γ) and 2.696 Å(α)) and presumably a different crystalline energy. Similar to γ-HIO3, β-HIO3 is metastable and slowly converts to α-HIO3. It is hypothesized that β-HIO3 is a transition step in the formation of α-HIO3 and β-HIO3 is a result of trapped water inside particles during crystallization.