Polytelluride compounds containing distorted nets of tellurium

The propensity of solid state polytelluride compounds to form structures with extended square nets of tellurium and the physicochemical properties of these nets is discussed in view of recent results showing that these square nets of tellurium are in fact average structures. The real structures are strongly modulated, giving rise to patterns within these nets that involve polytelluride oligomers. The patterns are dictated by the average electron-count on the tellurium atoms and often, sophisticated crystallographic techniques (electron diffraction, superstructure, and super spacegroup approaches) are required to elucidate them. In this account we discuss the structural peculiarities observed in KCuCeTe₄, RbCuCeTe₄, Na_0.8Ag_1.2CeTe₄, K_2.5Ag_4.5Ce₂Te₉, K_2.5Ag_4.5La₂Te₉, Cu_0.66EuTe₂, KCu₂EuTe₄, Na_0.2Ag_2.8EuTe₄, and K_0.65Ag₂Eu_1.35Te₄.