A terahertz absorption spectroscopy study of structural changes in D-penicillaminato CuI8CuII6 clusters induced by water desorption

Structural changes induced by water desorption from D-penicillaminato (D-pen) CuI8CuII6 clusters aggregated into three polymorphic crystal structures ((1) 1D helical, (2) 2D hexagonal sheet, and (3) discrete cubic) were investigated by terahertz (THz) absorption spectroscopy and X-ray diffractometry (XRD), which provided information on the skeletal and crystal structures of the clusters, respectively. The water molecules incorporated into the crystals were removed by evacuation and heating to 100 °C. In the case of crystal 1, the helical structure collapsed upon water evacuation, whereas the skeletal structure of the D-pen CuI8CuII6 clusters did not change. However, the skeletal structures were distorted by the heating process. For crystals 2 and 3, water evacuation did not affect either the skeletal or the sheet and cubic crystal structures of the clusters, which, however, collapsed upon heating. The mechanisms driving these structural changes were discussed in relation to the type and amount of water molecules removed in each process.