trisulfur

The S 3 molecule or trisulfur or sulfur trimer or thiozone or triatomic sulfur is an allotrope of sulfur. It occurs as a mixture in liquid and gaseous sulfur and also at cryogenic temperatures as a solid. Under standard conditions it is unstable and self reacts to solid sulfur cyclooctasulfur. The molecule shape is similar to ozone. S 3 is found in sulfur vapour, comprising 10% of vapour species at 713K (440°C; 824°F) and 1,333Pa (10.00mmHg; 0.1933psi). It is cherry red in colour, with a bent structure, similar to ozone, O 3. The bonds between the atoms are not full double bonds (as this would require two fewer electrons, similar to carbon disulfide), and the molecule can be thought of as a resonance between two states, in each of which one of the end atoms has a negative formal charge while the central atom has a positive formal charge.
The molecule has a distance between sulfur atoms of 191.7±.01pm (1.9170±0.0001Å) and angle at the central atom of 7000204831841014054♠117.36°±0.006°. However, cyclic S 3, where the sulfur atoms are arranged in an equilateral triangle with three bonds (similar to cyclic ozone), should in theory be lower in energy than the bent structure actually observed.
The name thiozone was invented by Hugo Erdmann in 1908 who hypothesized that S 3 made up a large proportion of liquid sulfur. However its existence was unproven until the experiments of J. Berkowitz in 1964. Using mass spectrometry, he showed that sulfur vapour contains the S 3 molecule. Above 1,200°C (2,190°F) S 3 is the second most common molecule after S 2 in sulfur gas. In liquid sulfur the molecule is not common until the temperature is high, such as 500°C (932°F). However, small molecules like this contribute to most of the reactivity of liquid sulfur. S 3 has an absorption peak of 6993425000000000000♠425nm with a tail extending into blue light.
S 3 can also be made by photolysis of S 3Cl 2 embedded in a glass or matrix of solid noble gas.