Wydział Chemii

Katarzyna Kot

Grażyna Oczko

2018

Polyhedron

146

145-153

10.1016/j.poly.2018.03.004

Naukowa

Angielski

Artykuł

New types of neodymium, samarium and other light lanthanide (Pr) mixed complexes with thiocyanate (NCS) and 1,10-phenanthroline (Phen) were synthesized in solution and as crystals. It was found that these complexes crystallized with the formulae: (phen)·[Nd(phen)₂(NCS)₄] (1) and [Ln(phen)₃(NCS)₃]·EtOH (Ln = Sm(2), Pr(3)). The Pr and Sm complexes are isostructural (space group ), but the Nd compound was different (space group P2₁/n). Compound (1) crystallizes in a monoclinic system with space group P2₁/n and the following unit cell parameters: a = 12.097(2), b = 16.444(3), c = 19.202(3) Å, β = 93.46(2)°.

The optical spectra of these two types of rare-earth compounds were performed at room and low temperatures in order to understand the electrostatic nature of the Ln³⁺N coordination bonds. The high values of absorption spectral intensities at 293 K for Nd³⁺or Pr³⁺ show low symmetries for these metal centres. The absorption spectrum analysis at 4.2 K and the correlation of the results with the IR spectra of the monocrystals of (phen)·[Nd(phen)₂(NCS)₄] and [Pr(phen)₃(NCS)₃]·Et(OH) make it possible to account for vibronic transitions. The observed Stark splitting of f–f transitions for Ln³⁺ ions in the emission spectra at 77 K for Sm³⁺ is in agreement with that predicted by group theory for a single low-symmetry Ln³⁺ ion site. In the absorption spectra, a ‘red shift’ was observed for hypersensitive transitions of lanthanide ions. The variation of the spectroscopic parameters of the title compounds, calculated based on the absorption spectra, the nephelauxetic ratio β, Sinha’s parameter δ and their correlation with the nature of the Ln³⁺N bond, are discussed.

neodymium, atom, Thiocyanate, UV–vis spectroscopy, crystal structure

https://doi.org/10.1016/j.poly.2018.03.004

http://www.elsevier.com