Syntheses, crystal structures and optical spectroscopy of Ln2(SO4)3·8H2O (Ln=Ho, Tm) and Pr2(SO4)3·4H2O

The lanthanide sulphate octahydrates Ln2(SO4)3·8H2O (Ln=Ho, Tm) and the respective tetrahydrate Pr2(SO4)3·4H2O were obtained by evaporation of aqueous reaction mixtures of trivalent rare earth oxides and sulphuric acid at 300 K. Ln2(SO4)3·8H2O (Ln=Ho, Tm) crystallise in space group C2/c (Z=4, aHo=13.4421(4) Å, bHo=6.6745(2) Å, cHo=18.1642(5) Å, βHo=102.006(1) Å3 and aTm=13.4118(14) Å, bTm=6.6402(6) Å, cTm=18.1040(16) Å, βTm=101.980(8) Å3), Pr2(SO4)3·4H2O adopts space group P21/n (a=13.051(3) Å, b=7.2047(14) Å, c=13.316(3) Å, β=92.55(3) Å3). The vibrational and optical spectra of Ho2(SO4)3·8H2O and Pr2(SO4)3·4H2O are also reported.