trichalcogenides

Trichalcogenides are chemical compounds that contain three chalcogen atoms per formula unit, typically with the general formula MX3, where M is a transition metal (such as Ti, Zr, Ti, Nb, Ta, Mo, W) and X is a chalcogen (S, Se, or Te). They form a diverse family known as transition metal trichalcogenides (TMTCs), including both quasi one-dimensional chain materials and layered structures that can be exfoliated.

In many TMTCs, the crystal structure features MX6 octahedra linking to form one-dimensional MX3 chains or anisotropic two-dimensional layers. This bonding arrangement leads to pronounced structural and electronic anisotropy, with space groups and stacking motifs varying across compounds. Some members are stable in air, while others are more reactive or sensitive to moisture.

Electronic and physical properties span a wide range. Some trichalcogenides are semiconductors, such as titanium trisulfide (TiS3), while others are metallic and display low-dimensional conduction, as seen in niobium triselenide (NbSe3), which can exhibit charge-density waves and temperature-dependent transport. Dimensional reduction, strain, and composition can strongly affect their band structures, optical responses, and excitonic behavior.

Synthesis and applications: TMTCs are typically prepared by high-temperature solid-state reactions, sometimes with methods like chemical vapor transport or direct combination of elements. They attract interest for fundamental low-dimensional physics, anisotropic electronics, and potential uses in nanoelectronics, photonics, and thermoelectrics. Some compounds also serve as precursors for broader families of layered chalcogenides.

Notable examples include TiS3, ZrS3, HfS3, NbSe3, TaS3, and MoS3, among others.