The present invention provides a compound of the formula +zM++\u2212xy where x is 3 or 4, y is 2 or 3, x+y is 6, z is 1 or 2, and M++ is selected from the group consisting of iron, cobalt, nickel, copper, zinc, chromium, and manganese, and + is selected from the group consisting of ammonium, sodium, potassium, rubidium and cesium. The torsional damping system has a torsion spring that facilitates transfer of rotary power into a hub. The TFT also has a first part of an etch barrier layer on the active layer, and a source and drain on the first part of the etch barrier layer.