What is the smallest molecule
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The Smallest Molecule: An Overview
Definition and Context of Small Molecules
Small molecules are organic compounds with low molecular weight, typically less than 500 Daltons (Da) . These molecules are fundamental in various fields, including drug discovery and material science, due to their diverse chemical properties and biological activities .
Smallest Molecule in Quantum Chemistry: Hydrogen Molecule
In the realm of quantum chemistry, the hydrogen molecule (H₂) is often considered the smallest molecular system. It consists of just two hydrogen atoms and serves as a fundamental model for studying molecular properties and quantum mechanical behavior . Recent advancements in quantum computing have enabled precise calculations of the hydrogen molecule's energy spectrum, demonstrating its significance in both theoretical and practical applications .
Smallest Neutral Molecule with Noble-Gas Atoms: HXeOXeH
A notable example of a small neutral molecule containing noble-gas atoms is HXeOXeH. This molecule, identified through infrared spectroscopy, is composed of two xenon atoms and one oxygen atom, making it the smallest known neutral molecule with two noble-gas atoms . The formation of HXeOXeH involves UV photolysis of water in solid xenon, followed by annealing at low temperatures . This discovery is significant for understanding noble-gas chemistry and has potential implications for addressing the "missing xenon" problem on Earth .
Smallest Supramolecular Helix: Diethylamine
Diethylamine is recognized as the smallest and simplest molecule that forms a supramolecular helix in its lowest energy aggregate. Structural studies and simulations have shown that the helical arrangement of diethylamine is more stable compared to other small hydrogen-bonding molecules, which typically form cyclic structures . This unique property highlights the diverse structural possibilities even among the smallest molecules .
Smallest Molecular Switch: Benzene-Dithiolate
Benzene-dithiolate (BDT) molecules on a gold surface represent the smallest two-terminal molecular switches discovered to date. These molecules exhibit bistable electrical properties, switching between strongly and weakly conducting states when manipulated by a scanning tunneling microscope (STM) tip . This finding underscores the potential of small molecules in developing nanoscale electronic devices .
Conclusion
The study of the smallest molecules spans various fields, from quantum chemistry to material science. The hydrogen molecule serves as a fundamental model in quantum studies, while HXeOXeH and diethylamine illustrate the unique properties and structural diversity of small molecules. Additionally, benzene-dithiolate's role as a molecular switch highlights the technological potential of these tiny entities. Understanding and exploring these smallest molecules continue to provide valuable insights and innovations across scientific disciplines.
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