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==Characterization of inorganic compounds== | |||
Because of the diverse range of elements and the correspondingly diverse properties of the resulting derivatives, inorganic chemistry is closely associated with many methods of analysis. Older methods tended to examine bulk properties such as the electrical conductivity of solutions, [[melting point]]s, [[solubility]], and [[acidity]]. With the advent of [[Quantum mechanics|quantum theory]] and the corresponding expansion of electronic apparatus, new tools have been introduced to probe the electronic properties of inorganic molecules and solids. Often these measurements provide insights relevant to theoretical models. For example, measurements on the [[Ultra-violet photoelectron spectroscopy|photoelectron spectrum]] of [[methane]] demonstrated that describing the bonding by the two-center, two-electron bonds predicted between the carbon and hydrogen using [[Valence Bond Theory]] is not appropriate for describing ionisation processes in a simple way. Such insights led to the popularization of [[molecular orbital theory]] as fully delocalised orbitals are a more appropriate simple description of electron removal and electron excitation. | |||
Commonly encountered techniques are: | |||
* [[X-ray crystallography]]: This technique allows for the 3D determination of [[molecular structure]]s. | |||
* [[Dual polarisation interferometer]]: This technique measures the [[conformational isomerism|conformation]] and [[conformational change]] of molecules. | |||
* Various forms of [[spectroscopy]] | |||
** [[Ultraviolet-visible spectroscopy]]: Historically, this has been an important tool, since many inorganic compounds are strongly colored | |||
** [[NMR spectroscopy]]: Besides <sup>1</sup>[[Hydrogen|H]] and <sup>13</sup>[[Carbon|C]] many other "good" NMR nuclei (e.g. <sup>11</sup>[[Boron|B]], <sup>19</sup>[[Fluorine|F]], <sup>31</sup>[[Phosphorus|P]], and <sup>195</sup>[[Platinum|Pt]]) give important information on compound properties and structure. Also the NMR of paramagnetic species can result in important structural information. Proton NMR is also important because the light hydrogen nucleus is not easily detected by X-ray crystallography. | |||
** [[Infrared spectroscopy]]: Mostly for absorptions from [[:category:carbonyl complexes|carbonyl ligands]] | |||
** [[Electron nuclear double resonance]] (ENDOR) spectroscopy | |||
**[[Mössbauer spectroscopy]] | |||
** [[Electron-spin resonance]]: ESR (or EPR) allows for the measurement of the environment of [[paramagnetic]] metal centres. | |||
* [[Electrochemical|Electrochemistry]]: [[Cyclic voltammetry]] and related techniques probe the redox characteristics of compounds. | |||
Revision as of 11:18, 5 October 2010
Characterization of inorganic compounds
Because of the diverse range of elements and the correspondingly diverse properties of the resulting derivatives, inorganic chemistry is closely associated with many methods of analysis. Older methods tended to examine bulk properties such as the electrical conductivity of solutions, melting points, solubility, and acidity. With the advent of quantum theory and the corresponding expansion of electronic apparatus, new tools have been introduced to probe the electronic properties of inorganic molecules and solids. Often these measurements provide insights relevant to theoretical models. For example, measurements on the photoelectron spectrum of methane demonstrated that describing the bonding by the two-center, two-electron bonds predicted between the carbon and hydrogen using Valence Bond Theory is not appropriate for describing ionisation processes in a simple way. Such insights led to the popularization of molecular orbital theory as fully delocalised orbitals are a more appropriate simple description of electron removal and electron excitation.
Commonly encountered techniques are:
- X-ray crystallography: This technique allows for the 3D determination of molecular structures.
- Dual polarisation interferometer: This technique measures the conformation and conformational change of molecules.
- Various forms of spectroscopy
- Ultraviolet-visible spectroscopy: Historically, this has been an important tool, since many inorganic compounds are strongly colored
- NMR spectroscopy: Besides 1H and 13C many other "good" NMR nuclei (e.g. 11B, 19F, 31P, and 195Pt) give important information on compound properties and structure. Also the NMR of paramagnetic species can result in important structural information. Proton NMR is also important because the light hydrogen nucleus is not easily detected by X-ray crystallography.
- Infrared spectroscopy: Mostly for absorptions from carbonyl ligands
- Electron nuclear double resonance (ENDOR) spectroscopy
- Mössbauer spectroscopy
- Electron-spin resonance: ESR (or EPR) allows for the measurement of the environment of paramagnetic metal centres.
- Electrochemistry: Cyclic voltammetry and related techniques probe the redox characteristics of compounds.