OPTICAL-PROPERTIES OF LANTHANIDE SQUARATES

Two types of lanthanide squarate hydrates of formulae Eu(C4O4)(IIC4O4) (II2O)(6) . II2O (compound I) and [Ln(2)(C4O4)(3)(H2O)(8)], where Ln = Eu and Gd (compound II) were investigated. The optical properties of crystals I and selected data of compound II are reported and confronte d with earlier studies of europium complexes type II. Excitation and e mission spectra were measured at 77 K. Effect of polymeric structure o n spectroscopic properties is considered and correlated with the struc tural data. Cooperative intrachain interactions between metal ions cou pled via squarate anions were pointed and cooperative absorption was r ecorded. To check the presence of the Eu2+ traces, the EPR and gamma-i rradiation measurements were applied. Raman spectra of the compound II (where Ln = from Sm to Lu) were measured in the range 50-500 cm(-1). Positions of the bands were considered in function of ionic radius of lanthanide ion. The above, together with the data from excitation spec tra, allows to localize the Ln-O bands. Vibronic components in electro nic spectra were elucidated and assigned.