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

Praseodymium, neodymium and europium complexes of the formula Ln(NCS)(Hmpa)$\text{}_{4}$-(SCN)$\text{}_{2}$-HgCl(SCN) 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, luminescence, excitation and absorption spectra at 6, 77, and 298 K. Probabilities of electronic transitions for Pr$\text{}^{3+}$ ion were examined at 6 K 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 influence on optical properties of active centre was discussed.