Optical Properties and Structure of Ln(NCS)(Hmpa)_{4}-(SCN)_{2}- HgCl(SCN)

Praseodymium, neodymium and europium complexes of the formula Ln(NCS) (Ηmpaa) 4 -(SCΝ) 2 -HgCl(SCΝ) were synthesised from non-aqueous solutions. The structure of neodymium complexes was determined by X-ray diffraction. The crystals of the title compounds crystallise in the space group Cc, where lanthanide ions are coordinated to seven ligand groups: four of Hmpa molecules and three SCN ions. The compounds were characterised by IR, luminnescence, excitation and absorption spectra at 6, 77, and 298 K. Probabilities of electronic transitions for Pr 3+ ion were examined at 6 ^{ and at room temperatures. Vibronic components were observed and analysed on the basis of IR and Raman data. Asymmetric arrangement of Ln ions was found from X-ray analysis and its inflnence on optical properties of active centre was discussed.