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Two modifications of a KH2PO4.HF adduct
Radmila Krupková1, Jan Fábry, Premysl Vanek
1Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 182 21 Prague 8, Czech Republic.
Summary
This study determined the crystal structures of two potassium dihydrogenphosphate-hydrofluoric acid modifications. Differences were found in the arrangement of dihydrogenphosphate anions and short hydrogen bonds.
Area of Science:
- Crystallography
- Solid-state chemistry
- Hydrogen bonding
Background:
- Potassium dihydrogenphosphate-hydrofluoric acid (KH(2)PO(4).HF) exists in multiple crystalline forms.
- Understanding these structures is crucial for solid-state chemistry and materials science.
Purpose of the Study:
- To determine the crystal structures of two distinct modifications of KH(2)PO(4).HF.
- To elucidate the differences in anion arrangement and hydrogen bonding between these modifications.
Main Methods:
- Single-crystal X-ray diffraction was used to determine the structures.
- Structures were solved and refined at various temperatures (e.g., 250 K, 150 K, 292 K).
- Difference Fourier maps were utilized for hydrogen atom localization.
Main Results:
- Two modifications, (I) and (II), were characterized, crystallizing at different temperatures.
- Modification (I) features looped dimeric and tetrameric dihydrogenphosphate units.
- Modification (II) exhibits two types of looped tetrameric dihydrogenphosphate units.
- Both structures contain very short F-H.O hydrogen bonds (2.38-2.40 Å).
- Potassium ions (K+) are coordinated by oxygen and fluorine atoms in both modifications.
Conclusions:
- The two modifications of KH(2)PO(4).HF exhibit distinct arrangements of dihydrogenphosphate anions.
- The presence of short F-H.O hydrogen bonds is a key feature in both structures.
- The coordination environment of potassium ions is similar across both determined modifications.