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On the solid state structure of 4-iodobenzoic acid.
Cara L Nygren1, Chick C Wilson, John F C Turner
1Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996-1600, USA.
The Journal of Physical Chemistry. A
|July 13, 2006
Summary
Variable temperature X-ray diffraction and solid-state NMR reveal a phase transition in 4-iodobenzoic acid at 230.77 K. This transition affects proton placement and molecular interactions in the solid state.
Area of Science:
- Solid-state chemistry
- Crystallography
- Materials science
Background:
- Understanding molecular behavior in the solid state is crucial for materials design.
- 4-iodobenzoic acid is a molecule with potential applications where solid-state properties are important.
Purpose of the Study:
- To elucidate the solid-state structure and phase transition behavior of 4-iodobenzoic acid.
- To investigate the influence of temperature on molecular arrangement and bonding.
Main Methods:
- Variable temperature X-ray diffraction
- Variable temperature solid-state Nuclear Magnetic Resonance (NMR) spectroscopy
- Differential scanning calorimetry (DSC)
Main Results:
- 4-iodobenzoic acid crystallizes in space group P2(1)/n, forming dimers via hydrogen bonds.
- A phase transition was observed at 230.77 K, evidenced by DSC and changes in NMR relaxation times.
- Proton positions within the carboxylate group exhibit temperature-dependent disorder.
Conclusions:
- The solid-state structure is characterized by hydrogen-bonded dimers and van der Waals interactions between iodine atoms.
- The phase transition significantly impacts the molecular structure and dynamics.
- Temperature-dependent studies are essential for fully characterizing the solid-state properties of 4-iodobenzoic acid.