Molecular and Polymer Ln₂M₂ (Ln = Eu, Gd, Tb, Dy; M = Zn, Cd) Complexes with Pentafluorobenzoate Anions: The Role of Temperature and Stacking Effects in the Structure; Magnetic and Luminescent Properties

Varying the temperature of the reaction of [{Cd(pfb)(H₂O)₄}⁺_n·n(pfb)⁻], [Ln₂(pfb)₆(H₂O)₈]·H₂O (Hpfb = pentafluorobenzoic acid), and 1,10-phenanthroline (phen) in MeCN followed by crystallization resulted in the isolation of two type of products: 1D-polymers [LnCd(pfb)₅(phen)]_n·1.5nMeCN (Ln = Eu (I), Gd (II), Tb (III), Dy (IV)) which were isolated at 25 °C, and molecular compounds [Tb₂Cd₂(pfb)₁₀(phen)₂] (V) formed at 75 °C. The transition from a molecular to a polymer structure becomes possible because of intra- and intermolecular interactions between the aromatic cycles of phen and pfb from neighboring tetranuclear Ln₂Cd₂ fragments. Replacement of cadmium with zinc in the reaction resulted in molecular compounds Ln₂Zn₂ [Ln₂Zn₂(pfb)₁₀(phen)₂]·4MeCN (Ln = Eu (VI), Tb (VIII), Dy (IX)) and [Gd₂Zn₂(pfb)₁₀(H₂O)₂(phen)₂]·4MeCN (VII). A new molecular EuCd complex [Eu₂Cd₂(pfb)₁₀(phen)₄]·4MeCN (X)] was isolated from a mixture of cadmium, zinc, and europium pentafluorobenzoates (Cd:Zn:Ln = 1:1:2). Complexes II-IV, VII and IX exhibit magnetic relaxation at liquid helium temperatures in nonzero magnetic fields. Luminescent studies revealed a bright luminescence of complexes with europium(III) and terbium(III) ions. View Full-Text