Molecular and Polymer Ln(2)M(2) (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)(H(2)O)(4)}(+)(n)·n(pfb)(−)], [Ln(2)(pfb)(6)(H(2)O)(8)]·H(2)O (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 [Tb(2)Cd(2)(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 Ln(2)Cd(2) fragments. Replacement of cadmium with zinc in the reaction resulted in molecular compounds Ln(2)Zn(2) [Ln(2)Zn(2)(pfb)(10)(phen)(2)]·4MeCN (Ln = Eu (VI), Tb (VIII), Dy (IX)) and [Gd(2)Zn(2)(pfb)(10)(H(2)O)(2)(phen)(2)]·4MeCN (VII). A new molecular EuCd complex [Eu(2)Cd(2)(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.