The colours of simple salts of the violurate anion
摘要:
Salts of the violurate anion with the alkali and alkaline earth metals, the d10 ions Zn2+ and Cd2+, Mn2+, Pb2+, Ag+ and the lanthanides show a variety of spectacular colours in the solid state. The metal ions have no intrinsic absorption in the visible region (apart from the weak spin-forbidden bands of Mn2+) and do not normally show charge-transfer absorption. The colours are ascribed to the n --> pi* transition of the violurate anion. As confirmation of this assignment the visible absorption of the K+ salt is shown to be polarized perpendicular to the plane of the violurate anion. Low temperature (approximately 20 K) absorption spectra of the Na+, K+ and Rb+ salts are reported.